INTERNATIONAL TELECOMMUNICATION UNION

CCITT Q.767
THE INTERNATIONAL
TELEGRAPH AND TELEPHONE
CONSULTATIVE COMMITTEE
SPECIFICATIONS
OF SIGNALLING SYSTEM No. 7
APPLICATION OF THE ISDN USER PART
OF CCITT SIGNALLING SYSTEM No. 7 FOR
INTERNATIONAL ISDN INTERCONNECTIONS
Recommendation Q.767
Geneva, 1991
FOREWORD
The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the
International Telecommunication Union (ITU). CCITT is responsible for studying technical, operating and tariff
questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide
basis.
The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves
Recommendations prepared by its Study Groups. The approval of Recommendations by the members of CCITT between
Plenary Assemblies is covered by the procedure laid down in CCITT Resolution No. 2 (Melbourne, 1988).
Recommendation Q.767 was prepared by Study Group XI and was approved under the Resolution No. 2
procedure on the 15th of February 1991.
___________________
CCITT NOTE
In this Recommendation, the expression Administration is used for conciseness to indicate both a
telecommunication Administration and a recognized private operating agency.
ITU 1991
All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the ITU.
Recommendation Q.767 1
Recommendation Q.767
Recommendation Q.767
APPLICATION OF THE ISDN USER PART OF CCITT SIGNALLING SYSTEM No. 7
FOR INTERNATIONAL ISDN INTERCONNECTIONS
1 Introduction
ISDN international interconnections have to be realized between non homogeneous ISDNs that differ in
terms of services supported, national network signalling system and national access protocol.
In order to perform such international ISDN interconnections, it is required to specify unambiguously and
without options:
the service capabilities of the international signalling system;
the international signalling interface, i.e., the signalling information elements and messages sent and
received on the international signalling section and the related procedures;
all additional information, which is not specifically signalling system related, but which is needed to
absorb the potential differences between the national networks.
Section 2 of this Recommendation describes the list of services supported by the ISUP international interface.
Section 3 contains the definition of the international ISUP signalling specification, in terms of
exceptions/clarifications to the existing Blue Book ISUP text.
Section 4 contains additional information to ease international ISDN interconnections. This Guidelines
section should be understood as a user's guide for international ISDN interconnection. One of the objectives is to
highlight possible areas of difficulty and propose standard solutions, that should be applied as far as possible by
international operators.
The Annexes A to E contain the complete revised Blue Book text. Sections 1 to 4 have precedence over the
content of Annexes A to E.
Blue Book SDLs have not been revised and are therefore not applicable to Recommendation Q.767.
2 Recommendation Q.767
2 Services supported
The following services are supported by the first version of the ISUP international interface, specified in
Recommendation Q.767. The services supported by the international interface have not to be fully supported in a
national network.
The relevant CCITT Recommendations are indicated per service, with the possible
modifications/simplifications applied for international operation of the service.
2.1 Bearer services
The following bearer services are supported by the international interface:
64 kbits/s unrestricted (Recommendation I.231.1);
Speech (Recommendation I.231.2);
3.1 kHz audio (Recommendation I.231.3).
Semi permanent switched connections are considered as non ISUP controlled, and are, therefore, outside the
scope of this document.
2.2 Teleservices
The following teleservices are supported:
Telephony (Recommendation I.241.1);
Teletex (Recommendation I.241.2);
Telefax Gr 4 (Recommendation I.241.3);
Mixed mode (Recommendation I.241.4);
Videotex (Recommendation I.241.5);
Telefax Gr 2/3.
2.3 Supplementary services
The following supplementary services are supported:
CLIP/CLIR as described in Recommendation I.251.3/4;
COLP/COLR as described in Recommendation I.251.5/6;
CUG as described in Recommendation I.255.1;
UUS 1 implicit as described in Recommendation I.257.1.
Recommendation Q.767 3
Direct Dialling In and Multiple Subscriber Number are without significance to the international interface.
Subaddressing and terminal portability are implicitly supported, as part of the basic Q.767 procedures.
2.4 Interworking between ISDN and PSTN/IDN
Interworking between ISDN and PSTN/IDN is supported for the following services:
telephony;
voice band data;
digital connectivity.
3 Exceptions and clarification to the Blue Book ISUP Recommendations
3.1 General
The objective of this section is to specify the exceptions to CCITT Recommendations:
Q.761 (Functional description of the ISDN User Part of CCITT Signalling System No. 7);
Q.762 (General functions of CCITT Signalling System No. 7 ISDN User Part Messages and
parameters);
Q.763 (Formats and codes of CCITT Signalling System No. 7 ISDN User Part Messages and
parameters);
Q.764 (Signalling procedures for CCITT Signalling System No. 7 ISDN User Part);
Q.730 (ISDN supplementary services),
with deletions, clarifications etc., for international application. The following information is presented as an exceptions
document which should be read in conjunction with Recommendations Q.761 to Q.764 and Q.730. Annexes A to E
contain the complete revised text.
Those parts of the CCITT Recommendation which have not been listed as exceptions and are not relevant to
international interconnection should only be used as additional information to aid understanding. Although this
Recommendation applies only to the international signalling section, the specification of functions, formats and codes
of messages and signals, and actions performed at originating and destination local exchanges is retained.
4 Recommendation Q.767
An international gateway mainly performs functions like a normal transit exchange in all cases where the
national ISDN User Part implementation is the same as the implementation of the ISDN User Part for the international
signalling section. In the case where a national signalling system behaves differently, the international gateway
exchange has to support both the concerned national and the international network and the services and equipments
supported by both the concerned national and the international network.
3.2 Exceptions and clarifications to Recommendation Q.761
Table 1/Q.767 contains three columns as follows:
the first column marked Section identifies the relevant section of Recommendation Q.761;
the second column marked Title identifies the relevant subject of Recommendation Q.761;
the third column marked Remarks identifies the deviations from Recommendation Q.761 as
appropriate for the international signalling section.
No remark is made against national options. It is assumed that they will not occur on an international relation.
All subsections are the same as in Recommendation Q.761 unless indicated otherwise in Table 1/Q.767
below.
TABLE 1/Q.767
Q.761
Section
Title Remarks
1 General 4th paragraph:
SCCP is not used
2 Services supported by the ISDN User Part The list of services and supplementary services is
contained in Rec. Q.767, 2.
3.2.4 Status a) Delete in the 1st paragraph, 1st sentence:
a) "or the ISDN User part at the destination is
a) unavailable"
b) The note to Table 1/Q.761 reads:
b) "The cause parameter can assume one value:
b) signalling network congested."
4 End-to-end signalling Not applicable
Recommendation Q.767 5
3.3 Exceptions and clarifications to Recommendation Q.762
Table 2/Q.767 contains three columns as follows:
the first column marked Section identifies the relevant section of Q.762;
the second column marked Title identifies the relevant subject of Q.762;
the third column marked Remarks identifies the deviations from Q.762 as appropriate for the
international signalling section.
All subsections are the same as in Recommendation Q.762 unless indicated otherwise in Table 2/Q.767
below.
The remark Not used in the table means that a message, parameter or indicator should not be generated at
an outgoing or incoming gateway exchange towards the international signalling network and if such a message,
parameter or indicator is received by an international exchange the procedures defined in Recommendation Q.764,
2.10.5 in combination with the remarks listed in the 3.5 of Recommendation Q.767 against 2.10.5 of
Recommendation Q.764 are invoked.
The remark Default value is used in the table means that an indicator is seen on the international interface,
but only one value is allowed to be sent.
The remark Default coding is used in the table means that a parameter is seen on the international interface,
but only one coding is allowed to be sent.
No remark is made against messages and parameters marked For national use. It is assumed that they will
not appear on an international relation.
Paragraph 3.3.1 contains definitions for additional messages, parameters and indicators.
6 Recommendation Q.767
TABLE 2/Q.767 (sheet 1 of 4)
Q.762
section
Title Remarks
1.5 Call modification completed message (CMC) Not used
1.6 Call modification reject message (CMRJ) Not used
1.7 Call modification request message (CMR) Not used
1.16 Circuit group query message (CQM) Not used
1.17 Circuit group query response message (CQR) Not used
1.18 Confusion message (CFN) Not used
1.23 Facility accepted message (FAA) Not used
1.24 Facility rejected message (FRJ) Not used
1.25 Facility request message (FAR) Not used
1.27 Information message (INF) Not used
1.28 Information request message (INR) Not used
1.32 Pass-along message (PAM) Not used
1.33 Release message (REL) Delete last sentence "In case the call..."
1.42 User to user information message (USR) Not used
2.2 Address presentation restricted indicator Last sentence changed
It is also used to indicate the non-availability of the
address
2.5 Call forwarding may occur indicator Default value is used
2.6 Call identity Not used
2.7 Call reference Not used
Recommendation Q.767 7
TABLE 2/Q.767 (sheet 2 of 4)
Q.762
section
Title Remarks
2.12 Calling party address request indicator Not used
2.13 Calling party address response indicator Not used
2.14 Calling party number incomplete indicator Default value is used
2.16 Calling partys category request indicator Not used
2.17 Calling partys category response indicator Not used
2.18
item a)
item b)
item c)
item d)
item e)
item f)
Cause value
Normal class
Resource unavailable class
Service or option not available class
Service or option not implemented class
Invalid message (e.g. Parameter out of range)
class
Protocol error (e.g. unknown message) class
Cause 2 not used
Cause 22: delete 2nd and 3rd sentences
Additional definition for cause 44 (see 3.3.1 of
Rec. Q.767)
Cause 50 not used
Causes 69 and 70 not used.
Cause 87 redefined (see 3.3.1 of
Rec. Q.767); cause 91 not used
Cause 102 is added (see 3.3.1 of Rec. Q.767);
Causes 97, 99, 103 not used.
2.24 Circuit state indicator Not used
2.27 Coding standard Default value is used
2.29 Connection request Not used
2.32 Credit Not used
2.33 Diagnostic Not used
2.35 End-to-end information indicator Default value is used
2.36 End-to-end method indicator Default value is used
2.38 Event presentation restriction indicator Default value is used
8 Recommendation Q.767
TABLE 2/Q.767 (sheet 3 of 4)
Q.762
section
Title Remarks
2.40 Facility indicator Not used
2.49 Local reference Not used
2.52 Modification indicator Not used
2.55 Numbering plan indicator Default value is used
2.57 Original called number Not used
2.58 Original redirection reason Not used
2.59 Point code Not used
2.60 Protocol class Not used
2.61 Protocol control indicator Whether a bit or a bit combination contained in the
PCI has history or control characteristic is specified
in the definitions of the individual bits or bit
combinations.
2.63 Recommendation indicator Not used
2.64 Redirecting indicator Not used
2.65 Redirecting number Not used
2.66 Redirecting reason Not used
2.67 Redirecting counter Not used
2.68 Redirection number Not used
2.71 SCCP method indicator Default value is used
2.74 Solicited information indicator Not used
2.81 User to user indicators Default value is used
2.AA Connected line identity request indicator See 3.3.1 of Rec. Q.767
2.BB Network discard indicator See 3.3.1 of Rec. Q.767
Recommendation Q.767 9
TABLE 2/Q.767 (sheet 4 of 4)
Q.762
section
Title Remarks
Table
1/Q.762
Table 1/Q.762 is replaced by the following
Table 3/Q.767. The following remarks apply:
Messages and parameters not used are not
included.
Subfields included in used parameters and
optional parameters included in used
messages that are marked as "default value is
used" are marked with bold type characters.
Subfields included in used parameters and
optional parameters included in used
messages that are marked as "default coding
is used" are marked with underlined bold
type characters.
10 Recommendation Q.767
TABLE 3/Q.767 (Sheet 1 of 5)
Mandatory or optional parameters in the ISDN user part messages
Message Group
Forward
set-up
Gen
sup.
Backward
set-up
Call
supervision
Circuit supervision
Circuit grp.
supervision
Parameter field Subfield
Type
Q.763

IAM SAM COT ACM CON CPG ANM FOT REL RLC
CCR
RSC
BLO
UBL
BLA
UBA
SUS
RES
CGB
CGU
CGB
A-C
GUA
GRS
GRA
Message type 2.1 M M M M M M M M M M M M M M M M M
Access transport
3.2 O O O O O
Automatic congestion
level
3.3 O
Backward call
indicators
Charge indicator
Called party's status indic.
Called party's category ind.
End to end method ind.
Interworking ind.
End to end information ind.
ISDN user part ind.
Holding indicator
ISDN access indicator
Echo control device ind.
SCCP method ind.
3.4 M M O O
Called party number Odd/even indicator
Nature of address
Internal network number ind.
Numbering plan ind.
Address signals
3.7 M
Bold characters means "default value is used".
M = Mandatory
O = Optional
Recommendation Q.767 11
TABLE 3/Q.767 (Sheet 2 of 5)
Mandatory or optional parameters in the ISDN user part messages
Message Group
Forward
set-up
Gen
sup.
Backward
set-up
Call
supervision
Circuit supervision
Circuit grp.
supervision
Parameter field Subfield
Type
Q.763

IAM SAM COT ACM CON CPG ANM FOT REL RLC
CCR
RSC
BLO
UBL
BLA
UBA
SUS
RES
CGB
CGU
CGB
A-C
GUA
GRS
GRA
Called party number Odd/even indicator
Nature of address
Number incomplete ind.
Numbering plan ind.
Address pres. restricted ind.
Screening ind.
Address signals
3.8 O
Calling party's category 3.9 M
Cause indicators Coding standard
Location
Cause value
3.10 O M
Circuit group
supervision message
type ind.
Type indicator
3.11 M M
CUG interlock code Network identity
Binary code
3.13 O
Connected number Odd/even indicator
Nature of address
Numbering plan ind.
Address pres. restricted ind.
Screening ind.
Address signals
3.14 O O
Bold characters means "default value is used".
12 Recommendation Q.767
TABLE 3/Q.767 (Sheet 3 of 5)
Mandatory or optional parameters in the ISDN user part messages
Message Group
Forward
set-up
Gen
sup.
Backward
set-up
Call
supervision
Circuit supervision
Circuit grp.
supervision
Parameter field Subfield
Type
Q.763

IAM SAM COT ACM CON CPG ANM FOT REL RLC
CCR
RSC
BLO
UBL
BLA
UBA
SUS
RES
CGB
CGU
CGB
A-C
GUA
GRS
GRA
Continuity indicators Continuity indicators 3.16 M
Even indicators
Event indicator
Event pres. restricted ind.
3.18 M
Forward call ind. National/international ind.
End to end method ind.
Interworking ind.
End to end information ind.
ISDN user part ind.
ISDN user part preference ind.
ISDN access ind.
SCCP method ind.
3.20 M
Nature of
connection ind.
Satellite ind.
Continuity check ind.
Echo control device ind.
3.23 M
Optional backward
call ind.
In-band information ind.
Call forwarding may occur ind.
3.24 O O M
Optional forward
call ind.
CUG call ind.
Connected line id. reg. ind.
3.25 O
Bold characters means "default value is used".
Recommendation Q.767 13
TABLE 3/Q.767 (Sheet 4 of 5)
Mandatory or optional parameters in the ISDN user part messages
Underlined, bold characters means "default coding is used".
Message Group
Forward
set-up
Gen
sup.
Backward
set-up
Call
supervision
Circuit supervision
Circuit grp.
supervision
Parameter field Subfield
Type
Q.763

IAM SAM COT ACM CON CPG ANM FOT REL RLC
CCR
RSC
BLO
UBL
BLA
UBA
SUS
RES
CGB
CGU
CGB
A-C
GUA
GRS
GRA
Range and status Range
Status
3.27 M M M
Subsequent number Odd/even ind.
Address signals
3.32 M
Suspend/resume ind. 3.33 M
Transmission medium
requirement
3.35 M
User service
information
Coding standard
Information transfer capabil.
Transfer mode
Information transfer rate
Structure
Configuration
Establishment
Symmetry
User information protocols
3.36 O
User-to-user indicators Type
Service 1
Service 2
Service 3
Network discard indicator
3.37 O O
User-to-user
information
3.38 O O O O O O
14 Recommendation Q.767
Abreviations relatives to Tables 3/Q.767 (Sheet 5 of 5)
ACM Address complete message
ANM Answer message
BLA Blocking acknowledgement message
BLO Blocking message
CCR Continuity check request message
CGB Circuit group blocking message
CGBA Circuit group blocking acknowledgement message
CGU Circuit group unblocking message
CGUA Circuit group unblocking acknowledgement message
CON Connect message
COT Continuity message
CPG Call progress message
FOT Forward transfer message
GRA Circuit group reset acknowledgement message
GRS Circuit group reset message
IAM Initial address message
REL Release message
RES Resume message
RLC Release complete message
RSC Reset circuit message
SAM Subsequent address message
SUS Suspend message
UBA Unblocking acknowledgement message
UBL Unblocking message
Recommendation Q.767 15
3.3.1 Additional definitions
3.3.1.1 connected line identity request indicator
Information sent in the forward direction indicating a request for the connected party number to be returned.
3.3.1.2 network discard indicator
This indicator indicates that user to user information included in the call control message has been discarded
by the network.
3.3.1.3 cause 44 Requested circuit/channel not available
This cause is returned when the circuit or channel indicated by the requesting entity cannot be provided by
the other side of the interface.
3.3.1.4 cause 87 Called user not member of CUG
This cause indicates that the called user for the incoming CUG call is not member of the specified CUG or
that the calling user is an ordinary subscriber calling a CUG subscriber, respectively.
3.3.1.5 cause 102 Recovery on timer expiry
This cause indicates that a procedure has been initiated by the expiry of a timer in association with error
handling procedures.
16 Recommendation Q.767
3.4 Exceptions and clarifications to Recommendation Q.763
Table 4/Q.767 contains three columns as follows:
the first column marked Section identifies the relevant section of Recommendation Q.763;
the second column marked Title identifies the relevant subject of Recommendation Q.763;
the third column marked Remarks identifies the deviations from Recommendation Q.763 as
appropriate for the international signalling section.
All subsections are the same as in Recommendation Q.763 unless indicated otherwise in Table 4/Q.767
below.
The remark Not used in the table means that a message, parameter or indicator should not be generated at
an outgoing or incoming gateway exchange towards the international signalling network and if such a message,
parameter or indicator is received by an international exchange the procedures defined in Recommendation Q.764
2.10.5 in combination with the remarks listed in 3.5 of Recommendation Q.767 against 2.10.5 of
Recommendation Q.764 are invoked.
All spare bits are reserved and not used. All code values marked Reserved or Spare are reserved and not
used. All codings allocated by CCITT to messages, parameters and indicators which are marked as Not used in the
table below may only be reintroduced for the CCITT specified purpose.
No remark is made against messages, parameters and parameter values marked For national use. It is
assumed that they will not appear on an international relation.
Recommendation Q.767 17
TABLE 4/Q.767 (sheet 1 of 6)
Q.763
Section
Title Remarks
1 General The Note is not applicable
1.2 Circuit identification code See 4.1.11 of Rec. Q.767
1.4 Formatting principles Additional sentence: Between parameters there
should be no unused (i.e. dummy) octets.
1.6 Mandatory variable part 2nd paragraph, 3rd sentence is replaced by :
If the message type indicates that an optional part is
possible (reflected by the presence of an "end of
optional parameter octet" in Tables 5/Q.767
through 28/Q.767), but there is no optional part
included in this particular message than a pointer
field containing all zeros will be used.
Add the following paragraph at the end of 1.6:
If there are no mandatory variable parameters, but
optional parameters are possible, the start of
optional parameters pointer (coded all '0's if no
optional parameter is present and coded '0000001'
if any optional parameter is present) will be
included.
1.8 End of optional parameters octet Additional sentence : If no optional parameter is
present an "end of optional parameter" octet is not
transmitted.
1.11 National message types and parameters Not used
2.1 Message type codes
Table 3/Q.763
The following message types are not used:
Call modification completed
Call modification reject
Call modification request
Circuit group query
Circuit group query response
Confusion
Facility accepted
Facility request
Facility reject
Information
Information request
Pass along
User-to-user information
18 Recommendation Q.767
TABLE 4/Q.767 (sheet 2 of 6)
Q.763
Section
Title Remarks
3.1 Parameter names
Table 4/Q.763
The following parameters are not used:
Call modification indicators
Call reference
Circuit state indicator
Connection request
Facility indicator
Information indicators
Information request indicators
Original called number
Redirecting number
Redirection information
Redirection number
3.2 Access transport For the contents and the length of the Access
Transport Parameter, see 4.3.2 of
Rec. Q.767.
3.4 Backward call indicators BA: is used
Note The interpretation of these bits depends only
on the originating exchange.
DC= 10: not used
HG= 00: is used only
J = 1: is not used
L = 1: is not used
PO = 00: is used only
3.5 Call modification indicators Not used
3.6 Call reference Not used
3.7
item b)
Nature of address indicator Only 000 0011 and 000 0100 are used
3.7
item d)
Numbering plan indicator 001 is used only
3.8 Figure 10/Q.763 Delete note
3.8
item b)
Nature of address indicator 000 0100 is used only
Delete note
3.8
item c)
Calling party number incomplete indicator (NI) 1 is not used
3.8
item d)
Numbering plan indicator 001 is used only
3.8
item e)
Address presentation restricted indicator 10 is not used for calling party number
delete note
Recommendation Q.767 19
TABLE 4/Q.767 (sheet 3 of 6)
Q.763
Section
Title Remarks
3.8
item f)
Screening indicator Only 01 and 11 are used
Delete note
3.9 Calling partys category 00000000 not used
3.10 Cause indicators Only octets 1 and 2 will be supported
Coding standard: only 00 is used; delete note
Location: 0001 and 0010 are not used
Recommendation: not used
Cause value: 2, 5, 50, 69, 70, 91, 97, 99, 103 are
not used
Diagnostic: not used
Cause 87 is redefined
Cause 102 "Recovery on timer expiry" is used in
addition
3.12 Circuit state indicator not used
3.13 Closed user group interlock code Add sentence: "Only international interlock codes
shall be used"
3.14
item b)
item c)
item e)
Connected number
Nature of address indicator
Numbering plan indicator
Screening indicator
Only 0000000 and 0000100 are used
Only 000 and 001 are used
00 and 10 not used
3.15 Connection request Not used
3.18 Event information 0000100-0000110 not used
Event presentation restricted indicator is always set
to 0
3.19 Facility indicator Not used
3.20 Forward call indicators CB = 00: is used only
E = 1: is not used
KJ = 00: is used only
3.21 Information indicators Not used
3.22 Information request indicators Not used
3.24 Optional backward call indicators B = 0: is used only
20 Recommendation Q.767
TABLE 4/Q.767 (sheet 4 of 6)
Q.763
Section
Title Remarks
3.25 Optional forward call indicators
Additional indicator:
Connected line identity request indicator
Bit H:
H = 0: not requested
H = 1: requested
3.26 Original called number Not used
3.27 Range and status a) Range:
Range code 0: is not used
b) Status:
The minimum number of status bits in the
status subfield is 2
Query messages are not used
3.28 Redirecting number Not used
3.29 Redirection information Not used
3.30 Redirection number Not used
3.35 Transmission medium requirements 0000 0000, 0000 0010, 0000 0011 are used only
3.36 User service information for further information see 4.3 of
Rec. Q.767
3.37 User-to-user indicators
Additional indicator:
Network discard indicator
A = 1: is used only
CB = 00, ED = 00, GF = 00 are used only
Bit H:
H = 0: no information
H = 1: UUI discarded by the network
H = 1 is used only
Table 5 Message type :
Address complete
a) The following parameters are not used:
Call reference
Connected number
b) length of cause indicators is 4
c) length of User to User information is 3-131;
delete reference and note a)
Recommendation Q.767 21
TABLE 4/Q.767 (sheet 5 of 6)
Q.763
Section
Title Remarks
Table 6 Message type :
Answer
a) The following parameters are not used:
Optional backward call indicator
Call reference
User to User indicators
b) length of User to User information is 3-131;
delete reference and note a)
Table 7 Message type:
Call progress
a) The following parameters are not used:
Call reference
Cause indicators
Redirection number
User to user indicators
b) length of User to User information is 3-131;
delete reference and note a)
Table 8 Message type:
Circuit group query response
Not used
Table 10 Message type:
Confusion
Not used
Table 11 Message type:
Connect
a) The following parameters are not used:
Optional backward call indicator
Call reference
b) length of User to User information is 3-131;
delete reference and note a)
Table 13 Message type:
Facility reject
Not used
Table 14 Message type:
Information
Not used
Table 15 Message type:
Information request
Not used
Table 16 Message type:
Initial address
a) The following parameters are not used:
Call reference
Connection request
Original called number
Redirecting number
Redirection information
User to User indicators
b) Note c) is not applicable
c) length of User to User information is 3-131;
delete reference and note b)
22 Recommendation Q.767
TABLE 4/Q.767 (sheet 6 of 6)
Q.763
Section
Title Remarks
Table 17 Message type:
Release
a) The following parameters are not used:
Access transport
Redirection information
Redirection number
b) length of User to User information is 3-131;
delete reference and note b)
c) length of cause indicators is 3
Table 18 Message type:
Release complete
cause indicators: not used
Table 20 Message type :
User to user information
Not used
Table 21 Message type :
Forward transfer
Call reference is not used
Table 22 Message type :
Suspend
Resume
Call reference is not used
Table 24 Message type :
Call modification completed
Call modification request
Call modification reject
Not used
Table 26 Message type :
Circuit group reset
Circuit group query
Circuit group query: not used
Table 27 Message type :
Facility accepted
Facility request
Not used
Table 28 Message type :
Pass-along
Not used
Annex A For action on spare codes refer to 4.1.1 of
Rec. Q.767.
Recommendation Q.767 23
3.4.1 Additional formats and codes
3.4.1.1 Connected line identity request indicator
See 3.25 in Table 4/Q.767.
3.4.1.2 Network discard indicator
See 3.37 in Table 4/Q.767.
3.4.1.3 Cause 102 Recovery on timer expiry
See 3.10 in Table 4/Q.767.
3.5 Exceptions and clarifications to Recommendation Q.764
Table 5/Q.767 contains three columns as follows:
the first column marked Section identifies the relevant section of Recommendation Q.764;
the second column marked Title identifies the relevant subject of Recommendation Q.764;
the third column marked Remarks identifies the deviations from Recommendation Q.764 as
appropriate for the international signalling section.
All subsections are the same as in Recommendation Q.764 unless indicated otherwise in
Table 5/Q.767 below.
The remark Not applicable in the table means that a procedure described in Recommendation Q.764 is not
available in the international signalling network and is therefore not used on the international signalling links.
No remark is made against procedures marked For national use. It is assumed that they will not be invoked
on an international relation.
24 Recommendation Q.767
TABLE 5/Q.767 (sheet 1 of 7)
Q.764
Section
Title Remarks
1.3 Address signalling Note The use of en-bloc or overlap signalling is
based on bi-lateral agreements.
1.5 Signalling methods 1st paragraph, replace first sentence with:
"One signalling method is used in this
Recommendation"
Delete 2nd hyphenated item
2nd paragraph, delete last sentence
1.6 Layout of Recommendation. Q.764 Delete 2nd and last sentence
2.1.1.1
item a)
item c)
item d)
Actions required at the originating exchange
Circuit selection
Initial address message
Transfer of information not included in the initial
address message
a) n
*
64 kbit/s connections are not supported
b) Connection types "alternate speech/64 kbit/s
unrestricted" and "alternate 64 kbit/s
unrestricted/speech" are not supported
c) The sentence "the first value of bearer
information received will be used to set the
initial mode of the connection." is not
applicable
a) 3rd paragraph item i) reads:
" The only type of end to end method..."
and delete " 3"
b) Delete at the end of the paragraph starting
with "The ISDN UP preference indicator..."
the last sentence starting with "In addition...".
c) At the end of the section items (i) and (iii) are
not applicable
Not applicable
Recommendation Q.767 25
TABLE 5/Q.767 (sheet 2 of 7)
Q.764
Section
Title Remarks
2.1.1.2
item a)
item b)
Actions required at an intermediate exchange
Circuit selection
Parameters in the initial address message
1st paragraph, delete sentences starting with:
"Within a network..." to "...connection type"
a) Delete in 2nd sentence: "end to end method
indicator"
b) Delete 3rd sentence: " A change..."
2.1.1.3 Actions required at the destination exchange 2nd paragraph is not applicable
2.1.2.1
item a)
item c)
item d)
Actions required at the originating exchange
Circuit selection
Content of initial and subsequent address Messages
Transfer of information not included in the Initial
Address Message
a) n
*
64 kbit/s connections are not supported
b) Connection types "alternate speech/64 kbit/s
unrestricted" and "alternate 64 kbit/s
unrestricted/speech" are not supported
c) The sentence "the first value of bearer
information received will be used to set the
initial mode of the connection." is not
applicable
2nd sentence in the 1st paragraph reads "The
contents of the initial address message is the same
as described in 2.1.1.1 c) taking into account the
remarks against 2.1.1.1 c) given in this
recommendation."
Not applicable
2.1.2.2
item a)
item b)
Actions required at an intermediate exchange
Circuit selection
Parameters in the initial address message
Delete 2nd paragraph
a) Delete in 2nd sentence: "end to end method
indicator"
b) Delete 3rd sentence: " A change..."
26 Recommendation Q.767
TABLE 5/Q.767 (sheet 3 of 7)
Q.764
Section
Title Remarks
2.1.2.3 Actions required at the destination exchange 2nd paragraph is not applicable
2.1.3 Calling party number The only method is to send this information within
the IAM
2.1.4.9 Return of subaddress information in ACM, CON or
CPG
Not applicable for ACM and CPG; subaddress
information can only be returned in ANM or CON;
for the detailed procedure see
Recommendation Q.767, 4.
2.1.5 Call progress CPG can only be sent after ACM
2.1.6 Information messages Not applicable
2.1.7 Answer message See Rec. Q.767, 4 for the handling of subaddress
2.1.8 Continuity-check a) Add the following text after the third
paragraph:
"When an initial address message is received
with a request for continuity check (either on
this circuit or on a previous circuit), timer T8 is
started. On receipt of a continuity message,
timer T8 is stopped.
If timer T8 expires, the connection is cleared.
If an indication of continuity check failure is
received in a continuity message, timer T27 is
started awaiting a continuity recheck request.
Also, the connection to the succeeding
exchange is cleared, if any. Timer T27 is
stopped when the continuity check request
message is received and timer T36 is started
awaiting a continuity or release message.
If either timer T27 or T36 expires, a reset
circuit message is sent to the preceding
exchange. On reception of the release
complete message, the circuit is set to idle.
b) "inherent fault indication" is replaced by
"fault indication according to
Recommendation Q.33" in the second line of
the fifth paragraph (after the Note).
c) Replace item i) with the following:
"when initial address messages with a
continuity check request indication are
received".
Recommendation Q.767 27
TABLE 5/Q.767 (sheet 4 of 7)
Q.764
Section
Title Remarks
2.1.12 Forward transfer message Procedures are not supported by all network
operators
2.2.1 Unsuccessful call set-up
Actions at exchange initiating a release message
Replace second sentence with:
"The exchange sends a release message to the
preceding exchange and timers T1 and T5 are
started to ensure that a release complete message is
received from the preceding exchange (expiration
of timers T1 and T5 is covered in 2.10.6)."
2.2.2 Action at intermediate exchange Replace 2nd sentence with:
"Timers T1 and T5 are started to ensure that a
release complete message is received from the
preceding exchange (expiration of timers T1 and
T5 is covered in 2.10.6)."
2.2.5 Address incomplete Add the following text as a new 2.2.5:
"The determination that proper number of digits
has not been received can be made at once if the
end of pulsing signal is received.
When overlap working is used, and the end of
pulsing signal has not been received, the release
message with cause 28 (address incomplete) will be
sent 15-20 seconds (T35) after receipt of the latest
digit and before receipt of the minimum or fixed
number of digits for forward routing of the call."
2.3.1
item a)
item b)
item d)
Release initiated by a calling party
Actions at the originating exchange
Actions at an intermediate exchange
Charging
Replace 2nd sentence with:
"A release message is sent to the succeeding
exchange and timers T1 and T5 are started to
ensure that a release complete message is received
from the succeeding exchange (expiration of timers
T1 and T5 is covered in 2.10.6)."
Replace 2nd sentence of item ii) with:
"Timers T1 and T5 are started to ensure that a
release complete message is received from the
succeeding exchange (expiration of timers T1
and T5 is covered in 2.10.6)."
National matter
28 Recommendation Q.767
TABLE 5/Q.767 (sheet 5 of 7)
Q.764
Section
Title Remarks
2.5.1.1
item a)
Suspend initiated by a calling party
Actions at originating exchange
The suspend request controlling exchange is within
the network of the suspend initiating user
add "or notification" after "suspend request"
2.5.1.2 Suspend initiated by a called party The suspend request controlling exchange is within
the network of the suspend initiating user
2.5.3 Expiration of timer T2 or timer T6 Cause value # 102 is used in the release message
2.7 In-call modification Not applicable
2.8.3.1 Echo control procedure
Actions at the destination exchange
a) Remove "or call progress" from the second
hyphenated item
b) Replace "nature of connection indicators field
not being set" with "backward call indicators
parameter field" in the last paragraph
2.8.3.2 Echo control procedure
Actions at an intermediate exchange
a) Remove "or call progress" from the first
sentence
2.9.2.3 Abnormal blocking and circuit group blocking
procedures
a) In item iv) replace the end of the 1st sentence
with:
"...group blocking message, then the
maintenance system should be notified for the
circuits concerned."
b) In item v) and vii) replace "a circuit group
unblocking message will be sent" with "the
maintenance system should be notified".
c) Editorial, renumber 2nd item iv) with vi)
d) In item vi) and viii) replace "a circuit group
blocking message will be sent" with "the
maintenance system should be notified".
e) In item ix) replace "may" with "shall" in the
last line
f) In item xii) replace "an unblocking message
will be sent" with "the maintenance system
should be notified".
g) In item xiii) replace "a blocking message will
be sent" with "the maintenance system should
be notified".
Recommendation Q.767 29
TABLE 5/Q.767 (sheet 6 of 7)
Q.764
Section
Title Remarks
2.9.3 Circuit group query Not applicable
2.10.1.4 Actions to be taken on detection of dual seizure Last sentence is not applicable
2.10.3.1 Reset circuit message a) The 4-15 s timer is T16
b) The 1 min timer is T17
c) Replace in item f) 2nd sentence with:
The circuit shall be made available for service
after receipt of the appropriate
acknowledgement message
2.10.3.2 Circuit group reset message a) The 4-15 s timer is T22
b) The 1 min timer is T23
2.10.4 Failure in the blocking/unblocking sequence a) The 4-15 s timer is T12 for blocking message,
T14 for unblocking message, T18 for circuit
group blocking message, T20 for circuit group
unblocking message.
b) The 1 min timer is T13 for blocking message,
T15 for unblocking message, T19 for circuit
group blocking message, T21 for circuit group
unblocking message
2.10.5.1 Handling of unexpected messages a) In item c) the last sentence is not applicable
b) Item e) is not applicable
2.10.5.2 General requirements on receipt of unrecognized
signalling information messages and parameters
Not applicable
For further information, see Rec. Q.767,
4.1.1
Table 1 Minimum messages recognized and parameters Not applicable
For further information, see Rec. Q.767,
4.1.1
2.10.5.3 Procedures for handling of the unrecognized
messages or parameters
Not applicable
For further information, see Rec. Q.767,
4.1.1
2.10.6 Failure to receive a "release complete" message Replace "retransmitting" with "transmitting" in the
1st sentence of 2nd paragraph.
2.10.7 Failure to receive a response to an INR Not applicable
30 Recommendation Q.767
TABLE 5/Q.767 (sheet 7 of 7)
Q.764
Section
Title Remarks
2.10.8.2 Call-failure Replace 1st sentence with:
The call failure indication (cause #31) is sent in a
release message whenever a call attempt fails and
other specific cause value do not apply
2.10.8.3 Abnormal release conditions a) Replace "T6" by "T9"
b) Add the following item to b) and c):
" on failure to receive an address message
before 15-20 seconds (T35) after receipt of the
latest address message and before the
minimum or fixed number of digits have been
received."
2.10.8.4 Message loss during end-to-end transfer Not applicable
2.10.8.5 SCCP supervision timer Not applicable
2.10.10 Temporary trunk blocking before release of call Not applicable
2.12 Automatic congestion control a) The parameter should be recognized.
b) If this procedure is not implemented the ACC
parameter is not acted upon and discarded as
normal
3 End-to-end signalling Neither the pass-along method nor the SCCP
method is applicable, only the link-by-link method
is supported
Table A Timers in Recommendation Q.764 See the following Table 6/Q.767
Recommendation Q.767 31
TABLE 6/Q.767 (sheet 1 of 6)
Timers in Recommendation Q.764
Symbol
Time-out
value
Signi-
ficance
Cause for initiation Normal termination At expiry Section
T1 4-15
seconds
Local When release message is sent At the receipt of release
complete message
Re-transmit release
message and start timer
T1
2.2 - 2.3.1
2.10.6
T2 3 min Dual When suspend request
controlling exchange receives
suspend (user) message
At the receipt of resume
(user) message at
controlling exchange
Initiate release
procedure
2.5.1.1
2.5.2.1
2.5.3
T3 Not used on the international
interface
2.6
T4 Not used on the international
interface
2.7.1
2.7.2
T5 1 min Local When initial release message is
sent
At receipt of release
complete message
Send reset circuit
message, alert
maintenance personnel
and remove the circuit
from service, stop T1
start T17; Procedure
continues until
maintenance
intervention occurs.
2.2
2.3.1
2.10.6
T6 Covered in
Rec. Q.118
Dual When controlling exchange
receives suspend (network)
At the receipt of resume
(network) message
Initiate release
procedure
2.5.1.3
2.5.2.3 -
2.5.3
32 Recommendation Q.767
TABLE 6/Q.767 (sheet 2 of 6)
Timers in Recommendation Q.764
Symbol Time-out
value
Signifi-
cance
Cause for initiation Normal termination At expiry Section
T7 20-30 s Dual When the latest address
message is sent
When the condition
for normal release of
address and routing
information is met
(receipt of ACM, CON
messages)
Release all equipment
and connection (send
release message)
2.1.1.1
2.1.2.1 f)
2.1.4.4
2.1.4.8
2.10.8.3
T8 10-15 s Local When transit or incoming
international exchange
receives initial address
message requiring continuity
check on this circuit, or
indicates that continuity check
has been performed on a
previous circuit
At receipt of
continuity message
Release all equipment
and connection into
national network (send
release message)
2.1.8
2.10.8.3
T9 Interval
specified in
Rec. Q.118
Dual When national controlling or
outgoing international
exchange receives ACM
At the receipt of
answer
Release connection
and send back release
message
2.1.4.4
2.1.7.2
2.1.7.3
2.10.8.3
T10 4-6 s Dual When last digit is received in
interworking situations
At the receipt of fresh
information
Send address complete
message
2.1.2.1 e)
2.1.4.8
T11 15-20 s Dual When latest address message
is received in interworking
situations
When ACM is sent Send address complete
message
2.1.4.8
T12 4-15 s Local When blocking message is
sent
At receipt of blocking
acknowledgement
Re-transmit blocking
message and start T12
2.10.4
Recommendation Q.767 33
TABLE 6/Q.767 (sheet 3 of 6)
Timers in Recommendation Q.764
Symbol
Time-out
value
Signifi-
cance
Cause for initiation Normal termination At expiry Section
T13 1 min Local When initial blocking
message is sent
At receipt of blocking
acknowledgement
Transmit blocking
message, alert
maintenance personnel
and start T13; stop
T12. Procedure
continues until
maintenance
intervention occurs.
2.10.4
T14 4-15 s Local When unblocking message is
sent
At receipt of
unblocking
acknowledgement
Re-transmit
unblocking message
and start T14
2.10.4
T15 1 min Local When initial unblocking
message is sent
At receipt of
unblocking
acknowledgement
Re-transmit
unblocking message
and alert maintenance
personnel, start T15
and stop T14.
Procedure continues
until maintenance
intervention occurs.
2.10.4
T16 4-15 s Local When reset circuit message is
sent not due to the expiry of
Timer T5
At the receipt of the
acknowledgement
(RLC message)
Re-transmit reset
circuit message start
T16
2.10.3.1
T17 1 min Local When initial reset circuit
message is sent
At the receipt of the
acknowledgement
Alert maintenance
personnel, re-transmit
reset circuit message,
start T17 and stop
T16. Procedure
continues until
maintenance
intervention occurs.
2.10.3.1
T18 4-15 s Local When group blocking
message is sent
At receipt of group
blocking
acknowledgement
Re-transmit group
blocking message and
start T18
2.10.4
34 Recommendation Q.767
TABLE 6/Q.767 (sheet 4 of 6)
Timers in Recommendation Q.764
Symbol
Time-out
value
Signifi-
cance
Cause for initiation Normal termination At expiry Section
T19 1 min Local When initial group blocking
message is sent
At receipt of group
blocking
acknowledgement
Re-transmit group
blocking message,
alert maintenance
personnel, start T19
and stop T18.
Procedure continues
until maintenance
intervention occurs.
2.10.4
T20 4-15 s Local When group unblocking
message is sent
At receipt of group
unblocking
acknowledgement
Re-transmit group
unblocking message
and start T20
2.10.4
T21 1 min Local When initial group
unblocking message is sent
At the receipt of group
unblocking
acknowledgement
Re-transmit group
unblocking message,
alert maintenance
personnel, start T21
and stop T20.
Procedure continues
until maintenance
intervention occurs.
2.10.4
T22 4-15 s Local When circuit group reset
message is sent
At the receipt of the
acknowledgement
Re-transmit circuit
group reset message,
start T22
2.10.3.2
T23 1 min Local When initial circuit group
reset message is sent
At receipt of the
acknowledgement
Alert maintenance
personnel and start
T23, re-transmit
circuit group reset
message, stop T22.
Procedure continues
until maintenance
intervention occurs.
2.10.3.2
Recommendation Q.767 35
TABLE 6/Q.767 (sheet 5 of 6)
Timers in Recommendation Q.764
Symbol
Time-out
value
Signifi-
cance
Cause for initiation Normal termination At expiry Section
T24 < 2 s Local When check tone is sent At the receipt of
backward check tone
Send continuity message
with failure indication
and:
a) start T25 if
continuity check was asked in an IAM
b) start T26 if
continuity check was asked in a CCR
Rec. Q.724
7.4.1
T25 1-10 s Local When initial continuity
check failure is detected
Send CCR message and
repeat continuity check
Rec. Q.724
7.3
T26 1-3 min Local When second or subsequent
continuity check failure is
detected
Send CCR message and
repeat continuity check
Rec. Q.724
7.3
T27 4 min Local When continuity check
failure indication is
received
At receipt of continuity
check request message
Send reset circuit
message; start T16 and
T17
2.1.8
T28 Not used on the
international interface
2.9.3.2
T29 300-600
ms
Local Congestion indication
received when T29 not
running
New congestion
indication will be taken
into account
2.11.2
T30 5-10 s Local Congestion indication
received when T29 not
running
Restore traffic by one
step if not yet at full load
and start T30
2.11.2
36 Recommendation Q.767
TABLE 6/Q.767 (sheet 6 of 6)
Timers in Recommendation Q.764
3.6 Exceptions and clarifications to Recommendation Q.730
Supplementary services relevant to this Recommendation are listed below:
User to User Signalling (Q.730, 2);
Closed User Group (Q.730, 3);
Calling Line Identification Presentation/Restriction (Q.730, 4);
Direct Dialling In (Q.730, 5);
Connected Line Identification Presentation/Restriction (not in Q.730);
Symbol
Time-out
value
Signifi-
cance
Cause for initiation Normal termination At expiry Section
T31 Not used on the international
interface
3.7.2
3.7.3
3.7.4
T32 Not used on the international
interface
3.7.5
T33 Not used on the international
interface
2.1.6.2
2.10.7
T34 Not used on the international
interface
2.9.3.2
T35 15-20 s Dual At receipt of the latest digit (<
>ST) and before the minimum
or fixed number of digits have
been received
At receipt of ST or
when the minimum or
fixed number of digits
have been received
Send release message
(cause 28)
2.2.5
2.10.8.3
T36 10-15 s Local When transit or incoming
international exchange
receives continuity check
request message
At receipt of
continuity or release
message
Release all equipment,
sent reset circuit
message, start T16 and
T17
2.1.8
Recommendation Q.767 37
Subaddressing (not in Q.730);
Multiple Subscriber Number (not in Q.730);
Terminal Portability (not in Q.730).
Direct Dialling In and Multiple Subscriber Number are supported but are without relevance to the
international interface.
Subaddressing and Terminal Portability are implicitly supported, as part of the basic Q.764 procedures (see
Recommendations Q.767, 4.1.9 and 4.1.8).
This section contains the following subsections:
exceptions and clarifications for ISDN supplementary services in Recommendation Q.730;
ISDN supplementary services not in Recommendation Q.730.
3.6.1 Exceptions and clarifications for ISDN supplementary services in Recommendation Q.730
Table 7/Q.767 contains three columns as follows:
the first column marked Section identifies the relevant section of Q.730;
the second column marked Title identifies the relevant subject of Q.730;
the third column marked Remarks identifies the deviations from Q.730 as appropriate for the
international signalling section.
All subsections are the same as in Recommendation Q.730 unless indicated otherwise in Table 7/Q.767
below.
The remark Not applicable in the table means that a procedure described in Q.730 is not available in the
international signalling network and is therefore not used on the international signalling links.
38 Recommendation Q.767
TABLE 7/Q.767 (sheet 1 of 6)
Q.730
section
Title Remarks
Sec. 1 General
1.1 (untitled) References to TCAP, SCCP, and TC are not
applicable.
1.2 Information request/ response Not applicable
1.4 Layout of Rec. Q.730 "Close" should be "closed".
Call forwarding, DDI, the time-out table, and the
note are not applicable
Sec. 2 User-to-User Signalling service
2.1 General description
ISUP, SCCP SCCP is not used
2.1.1 Services
Maximum length of UUI
Only Implicit Service 1 is supported
In the last paragraph, the sentence
"The 128 octets" reads:
"The 128 octets do not include the parameter name,
the length octet and the protocol discriminator."
2.1.2 Service request Service 1 is requested implicitly in an IAM.
2.1.3 Service response The paragraph replaced by:
The discard of user-to-user information by the
network except in the case of PSTN interworking
or terminating access non ISDN is explicitly
notified by the user-to-user indicator parameter in
the appropriate backward message. Bit H is coded
"UUI discarded by the network" and bits CB are
coded "no information".
No notification is given if the called user does not
understand the service or cannot support the
service.
Recommendation Q.767 39
TABLE 7/Q.767 (sheet 2 of 6)
Q.730
section
Title Remarks
2.1.4 Flow control Not applicable
2.2 Procedures for user to user signalling associated
with circuit switched call
Delete last sentence
2.2.1 UUS Service 1
2.2.1.1 UUS # 1 General characteristics Replace the last sentence with "If for any reason
the combination of the basic plus supplementary
services information causes the overall maximum
length of the messages to be exceeded or if
128 octets of user-to-user information cannot be
supported in the IAM, then the user-to-user
information parameter is discarded
and a user-to-user indicator parameter is sent in the
first appropriate backward message (e.g., ACM or
CON). No truncation of user-to-user information is
performed".
2.2.1.2 User to user in the call set-up phase Delete in the last paragraph 1st sentence the words
"or network"
Add a 5th paragraph reading;
"If no UUS information is sent in the IAM, the
incoming (outgoing) national network should
prevent the transmission of UUS in the backward
(forward) direction.
2.2.1.3 Interworking Delete last sentence
2.2.1.4 Rejection of implicit service request Networks that cannot provide the requested service
will return a reject indication in the user-to-user
indicator parameter in the first appropriate
backward message. Bit H is coded "UUI discarded
by the network" and bits CB are coded "no
information".
2.2.2.1 Call forwarding services Not applicable
2.2.2.2 Call waiting service Not applicable
40 Recommendation Q.767
TABLE 7/Q.767 (sheet 3 of 6)
Q.730
section
Title Remarks
Sec. 3 Closed user group (CUG)
3.1 General The administration of CUG data is considered as a
national matter.
The last two paragraphs are deleted
3.2 Call set-up procedure with decentralized
administration of CUG data
The title is expanded to read: "Call set-up
procedure with decentralized or centralized
administration of CUG data".
3.2.2 Transit exchange The first eight words of the first paragraph are
deleted.
The last sentence of the second paragraph
terminates with the words:
"...at the gateway exchange". The remainder of that
sentence is deleted.
The first sentence of the third paragraph, the word
"incoming" precedes the words "gateway
exchange". In the last sentence replace cause "88"
by "87".
3.2.3 Destination exchange Delete "called" in the definition of cause "87".
Delete reference to "cause # 88".
3.3 Call set-up procedure with centralized
administration of CUG data
Not applicable.
Table 1 Action at the gateway with a network without CUG
capability
The title is expanded to read: "Action at the
incoming gateway with a network without CUG
capability".
Replace "cause # 88" with "cause # 87"
Table 2 Handling of a CUG call at destination exchange Replace "cause # 88" with "cause # 87"
3.4 ASE for CUG Not used in the international network.
Figures 3, 4
and 5
Flows for a CUG call with centralized
administration of CUG data
Not applicable.
Recommendation Q.767 41
TABLE 7/Q.767 (sheet 4 of 6)
Q.730
section
Title Remarks
Tables 3
and 4
Validation check of CUG call concerning the
calling/called user
Not applicable
3.5 Interactions with other supplementary services Add the following new paragraph
There are no known interactions with
supplementary services applicable at the
international interface
Sec. 4 General description of the CLIP and CLIR services In the first and second paragraphs the words
"possibly with additional address information
(i.e. sub-address)" are replaced by "with additional
address information (e.g. calling party subaddress)
if any".
The first sentence of third paragraph : replace
"I.254" with "I.251".
4.1 Description of the CLIP service Second paragraph is replaced by: "The Calling
Line Identity is the ISDN number of the calling
party (with additional address information, e.g.
calling party subaddress, if any) which may be
provided by the network or partly by the calling
party".
Third paragraph is not applicable.
Fourth paragraph is replaced by: "In the case where
a calling party is an ISPBX the network sends the
ISDN number including the DDI digits of the
extension as the CLI if the latter is provided by the
calling party, or the network provided default
number if the extension number is not provided.
4.1.1 Call set-up procedure Systematic inclusion in the IAM is the only method
used when the CLI is available.
42 Recommendation Q.767
TABLE 7/Q.767 (sheet 5 of 6)
Q.730
section
Title Remarks
4.1.1.1 The CLI is included in the IAM The second paragraph including items a) and b) is
not applicable.
Concerning item b) the release of restricted CLIs
across international boundaries is decided by
bilateral agreement. If any agreement requires
restricted CLIs not to be passed then the originating
gateway shall ensure that no such CLIs are sent
(Note this bilateral agreement may depend on the
application of override categories in the destination
network, see 4.2.2.1 and 4.2.2.2 of
Recommendation Q.730).
The last three paragraphs are replaced by:
"If no address signals are to be sent, then the
Calling Party Number parameter shall not be sent".
When interworking with signalling systems which
do not support calling line identity (e.g. No. 5) or
from which calling line identity is not immediately
available (e.g. TUP), the Calling Party Number
parameter is not sent.
Only complete calling party numbers are sent."
4.1.1.2 The CLI is not included in the IAM The entire section is replaced by:
"If no Calling Party Number parameter is received
in the Initial Address Message, then it is a function
of the user-network interface not to present the
calling party subaddress, if received, to the user."
Figures 6, 7
and 8
CLIP/R message flows Figures 6-8 are replaced by Figures 1/Q.767-
3/Q.767.
4.2 Description of CLIR service In the second paragraph, the words "possibly with
additional address information" are replaced by
"with additional address information (e.g. calling
party subaddress) if present."
4.2.1 Normal case Information message is not applicable
4.2.2.3 Interworking with non-ISDN or via non-ISDN Second paragraph is replaced by "If CLIR is
applicable and the restriction indicator cannot be
conveyed on the next signalling section the
interworking exchange will not send the CLI and
any additional address information provided by the
calling party (e.g. calling party subaddress)."
Recommendation Q.767 43
TABLE 7/Q.767 (sheet 6 of 6)
Q.730
section
Title Remarks
4.2.2.4 Restriction of additional address information Replace "i.e. subaddress" by "e.g. calling party
subaddress".
4.4.2 Call Forwarding Not applicable.
4.4.3 Call Waiting Not applicable.
4.4.5 Direct Dialling In Not applicable
4.4.7 Other services Add the following section:
"There are no known interactions with
supplementary services applicable to the
international interface other than those listed"
4.5.2 Call Forwarding Not applicable.
4.5.3 Call Waiting Not applicable.
4.5.4 CUG Replace text with: "No interaction".
4.5.5 Direct Dialling In Not applicable
4.5.7 Other services Add the following paragraph:
"There are no known interactions with
supplementary services applicable to the
international interface other than those listed"
Figures
9-13
Nodal signalling functions for CLIP/R Figures 10 and 11 are replaced by Figures 4/Q.767
and 5/Q.767.
Figures 9, 12, and 13 are not applicable.
5 Direct Dialling In (DDI) Not relevant (no impact on the international
interface)
6 Call forwarding Not applicable
7 Time-out table Not applicable
Annex A Signalling procedures for the explicit invocation of
user to user signalling services 1, 2 and 3.
Not applicable
44 Recommendation Q.767
T1148080-92/d01
Set-up IAM IAM Set-up
Calling
user
Originating
exchange
Transit
exchange
Terminating
exchange
Called
user
Calling Party Number
(user provided/verified)
Set-up IAM IAM Set-up
Calling Party Number
not provided
"Calling Party Number
parameter" omitted
(CLI)
PR = 00
SI = 01
a) CLI
provided
in the
IAM
b) CLI not
provided
in the
IAM
PR
SI
Presentation restricted
Screening indicator
FIGURE 1/Q.767
Calling Line Identification Presentation
Presentation allowed CLI provided by the calling user
(CLI)
PR = 00
SI = 01
T1148090-92/d02
a)
b)
PR
SI
Presentation restricted
Screening indicator
FIGURE 2/Q.767
Calling Line Identification Presentation
Presentation allowed CLI provided by the originating node
a) Cli
provided
in the
IAM
b) CLI not
provided
in the
IAM
Calling
user
Originating
exchange
Transit
exchange
Terminating
exchange
Called
user
Set-up
Set-up
IAM
IAM
IAM
IAM Set-up
Set-up
PR = 00
SI = 00
PR = 00
SI = 00
Calling Party Number
(networtk provided)
Calling Party Number
not provided
Calling Party Number
parameter
amited
Recommendation Q.767 45
T1148100-92/d03
Set-up IAM IAM Set-up
Calling
user
Originating
exchange
Transit
exchange
Terminating
exchange
Called
user
Calling Party Number
not provided
Set-up IAM IAM Set-up
Calling Party Number
not provided
"Calling Party Number
parameter" omitted
a) CLI
provided
in the
IAM
b) CLI not
provided
in the
IAM
PR
SI
Presentation restricted
Screening indicator
FIGURE 3/Q.767
Calling Line Identification Restriction
Presentation allowed CLI provided by the calling user
(CLI)
(presentation
restricted)
(CLI)
(presentation
restricted)
PR = 01
SI = 01
PR = 01
SI = 01
46 Recommendation Q.767
T1148110-92/d04
Idle
Set-up
IAM
CL
identity
present
Note 1
Yes
No
No
Number
Complete
Omit "calling
party number
parameter field"
from IAM
Presentation
allowed
Yes
No
Yes
Yes
Special
agreement
on PR
International
number
Yes
No
No
Delete trunk prefix
(if any)
Add originating
country code
Set nature of
address indicator
to "International
Number"
Omit calling
party number
parameter
from IAM
Keep PR and SI
as provided by the
incoming network
Note 2
IAM
Idle
CL
PR
SI
NI
Calling line
Presentation restriction
Screening indicator
Number incomplete indicator
Note 1 This flow assumes that there is no restriction on passing non-restricted CLIs across the international
boundary. If no such agreement exists then any CLI in the incoming IAM will be removed.
Note 2 Allowed values for the international section are
PR = 00 or 01
SI = 01 or 11
NI = 0
FIGURE 4/Q.767
Nodal signalling functions for CLIP and CLIR
Outgoing international gateway
Recommendation Q.767 47
T1148120-92/d05
Idle
Set-up
IAM
CL
identity
present
Add international
prefix (optional)
Keep PR and SI
as provided
IAM
Idle
CL
PR
SI
Calling line
Presentation restriction
Screening indicator
FIGURE 5/Q.767
Nodal signalling function for CLIP and CLIR
Destination international gateway exchange
Yes
No
48 Recommendation Q.767
3.6.2 ISDN supplementary services not in Recommendation Q.730
3.6.2.1 General Description of the Connected Line Identification Presentation and Restriction Service
Connected Line Identification Presentation (COLP) is a supplementary service offered to the calling party
which provides the connected partys ISDN number, with additional address information (e.g. connected party sub-
address) if any, to the calling party at the call establishment phase.
Connected Line Identification Restriction (COLR) is a supplementary service offered to the connected party
to restrict presentation of the connected partys ISDN-number, with additional address information (e.g. connected
party sub-address) if any, to the calling party.
The Stage 1 CCITT definitions for the COLP and COLR services are given in Recommendations I.251.5 and
I.251.6 respectively. The Stage 2 CCITT descriptions are contained in Recommendations Q.81, 5 and Q.81, 6
respectively. This stage 3 description of COLP and COLR uses the ISDN User Part protocol as defined in the
Recommendations Q.761-Q.764 and Q.766.
3.6.2.1.1 Description of the Connected Line Identification Presentation (COLP) Service
Connected Line Identity Presentation (COLP) is a user facility that enables a user to be informed, on outgoing
calls, of the address of the connected party. When provided the facility applies to all outgoing calls except for when the
connected party has the Connected Line Identity Restriction (COLR) facility active [see 3.6.1.2 below].
The Connected Line Identity (COL) is the ISDN number of the connected party (with additional address
information, e.g. connected party sub-address, if any) which may be provided by the network or by the connected party
or partially by the network with the rest provided by the connected party.
Only full international number, including the country code, should be passed across the international
boundary.
Moreover, the information on the COL may include address information generated by the connected user and
transparently transported by the network. The sub-address is subject to a maximum of 20 octets (the length of the
subaddress is not checked at international gateways). The network is not responsible for the content of this additional
address information.
The destination exchange shall deliver the COL only if it was requested at call set-up. However, if it is
received in the Answer of Connect message when it has not been requested it should not be considered as a protocol
error and the call should be allowed to continue.
Recommendation Q.767 49
In the case where a connected party is a DDI ISPBX extension, the network sends the ISDN number and the
DDI number of the extension as the COL if the extension digits are provided by the connected party. If the extension
digits are not provided the network sends the ISDN default number. The default number is stored within the network
but the value is agreed between the Administration and the customer concerned.
When the COL is provided by the user or ISPBX it is verified or screened for validity by the network i.e. the
COL provided by the user is within the known number range for that user.
i) If the user provided COL is valid the Connected Number parameter field contains the COL in the
address signals with the screening indicator set to user provided verified and passed.
ii) If the user provided COL is not valid or screened the destination exchange inserts the default number for
the address signals with the screening indicator set to network provided.
When the COL is provided by the network the terminating exchange includes the stored COL set against the
connected party and sets the screening indicator to network provided.
Information indicating that a subscriber has the user access to the COLP facility is available in the exchange
to which the subscriber is connected.
The destination gateway can remove the COL digits and indicate that connected line identity is not available.
3.6.2.1.1.1 Call set-up procedure
The call control procedure and the information included in call control messages vary depending on whether
the calling party has indicated, in the optional forward call indicator in the IAM, a request to use the COLP facility for
this call.
3.6.2.1.1.2 The request of COLP facility is included in the initial address message
When the calling party user has subscribed to the COLP facility the originating exchange, if the Connected
Line Identification is supported by the network, must include in the IAM an indication to request the COLP facility.
50 Recommendation Q.767
The Connected Line Identification is determined by the destination exchange. If the connected party number
is received from the connected user, the information is verified and passed to the originating exchange. If no
information is received from the connected user, the destination exchange shall generate the connected party number.
The information is conveyed by the network in the Connected Number parameter field of the Answer (ANM)
or Connect (CON) message. The service has no impact on the signalling procedures.
Optionally a Connected party Sub-address may be included, if received from the called party user, in the
Connected Sub-address information element which is added to the ATP (Access Transport parameter) of these
messages.
Both parameters, ATP and Connected Number are sent to the originating exchange.
If the COL cannot be transferred (because its presentation is restricted or because the national network cannot
provide the number) then the Connected Number parameter should be included in the ANM or CON messages with the
indication Presentation restricted or Address not available set as appropriate in the Address Presentation Restriction
Indicator.
In the case of Connected Number Presentation Restriction, the COL with the presentation restriction
indication will be forwarded to the originating exchange but not presented to the calling party (unless the national
option of the override category is invoked).
In the case of interworking between ISDNs the destination network can restrict the presentation of the COL.
If this option is invoked the COL shall be marked as not available.
No particular actions are required at intermediate exchanges.
At the international boundary, the destination gateway can remove the Connected Number digits if it cannot
be released to the originating network and a COL not available indication will be passed to the originating network
(Address presentation restricted indicator set to address not available).
At the originating exchange, when a Connected Party Number is received in the answer or connect message,
the originating exchange determines if the information may be presented to the user.
Note If no Connected Party Number parameter or a restricted connected number is received in the answer or
connect message, then it is a function of the user-network interface not to present the connected party subaddress, if
received, to the user.
3.6.2.1.1.3 COLP Facility not requested by the calling party user
When the calling party user has not subscribed to the COLP facility no particular actions are required. When
a request for the COL is not included in the IAM the Connected Number Parameter should not be included in either the
answer or connect message. However, if it is included under these circumstances it should not be considered as a
protocol error and the call should continue.
Recommendation Q.767 51
3.6.2.1.1.4 Message sequence diagrams for COLP
Figure 6/Q.767 describes the message flows for COLP.
T1148130-92/d06
Set-up IAM IAM Set-up
Calling
user
Originating
exchange
Transit
exchange
Terminating
exchange
Called
user
Alerting ACM ACM Alerting
a) COL
provided by
the called
user
b)
FIGURE 6/Q.767
Connected line identification presentation
Connected number
+ Subaddress
(optional)
COLP-request
(Note 1)
COLP-request
Connect ANM/CON Connect ANM/CON
Connected number
+ Subaddress
(if provided
PR = 00
SI = 01)
Connected number
+ Subaddress
(optional)
Connected number
+ Subaddress
(if provided
PR = 00
SI = 01)
(Note 2)
COL not
provided by
the called
user or
provided
but no valid
or screened
Set-up IAM IAM Set-up
Alerting ACM ACM Alerting
Connected number
COLP-request
Connect ANM/CON Connect ANM/CON
Connected number
PR = 00
SI = 11
COLP-request
Connected number
PR = 00
SI = 11
Note 1 This service is subscribed by the calling user and the request is included by the originating exchange.
Note 2 The connect message is appropriate only if the answer condition is detected prior to the return of the address complete message.
52 Recommendation Q.767
3.6.2.1.2 Description of the Connected Line Identity Restriction (COLR Service)
Connected Line Identification Restriction (COLR) is a user facility offered to restrict the presentation of the
COL to the calling party. The information that the called subscriber has the COLR facility is available at the call
terminating exchange.
When COLR is applicable and activated the destination exchange provides the originating node with a
notification that the connected users ISDN number and any sub-address information is not allowed to be presented to
the calling user. In this case no connected party number is included in the call connected information sent to the calling
user.
The presentation restriction function does not influence the forwarding of the connected number within the
network as part of the basic service procedure.
The passing of restricted Connected Number parameters across international boundaries is decided by
bilateral agreements. If any agreement requires restricted Connected Number parameters not to be passed, then the
terminating gateway shall ensure that no such Connected Number parameters are sent.
Note This bilateral agreement may depend on the application of override categories in the originating
network (see 3.6.2.1.2.2).
The restriction service is applied universally for all services for a particular customer.
3.6.2.1.2.1 Call set up procedure
When the calling party user has subscribed to the COLP facility the originating exchange includes in the IAM
an indication to request the COL. If the called party user has subscribed to the COLR facility, the destination exchange
will send the Connected Line Identity to the originating exchange, with an indication that the presentation is restricted
(address presentation restricted indicator set to presentation restricted).
This information is conveyed by the network in the Connected Number parameter field of the ANM or CON
messages. The service has no impact on the signalling procedures.
No particular actions are required at intermediate exchanges.
At the international boundary, the destination gateway can remove the COL if it cannot be released to the
originating network and change the address presentation restricted indicator, set to presentation restricted, into address
not available.
At the originating exchange, when a Connected Party Number is received in the ANM or CON message with
the indication that the presentation is restricted, the originating exchange must not present the COL to the user.
Recommendation Q.767 53
3.6.2.1.2.2 Override category
i) Override category within an ISDN
As a national option the originating exchange can override the Presentation Restriction Indication and
the COL is then presented to the calling subscriber for specific calling partys categories (e.g. Police).
ii) Override category between ISDNs
When a call originates in one ISDN network and terminates in another ISDN network and COLR is
applicable, the rules and regulations of the originating (host) network should apply.
For example, if an override category is not available in the destination network but is available in the
originating network. The originating network can still override the presentation restriction whenever
COL is available at this network.
As a national option the destination network can restrict the COL to the originating network if COLR is
applicable.
3.6.2.1.2.3 Interworking with non-ISDN or via non-ISDN
On calls from or via non-ISDN networks, it cannot be guaranteed that the COLR indication will be carried to
the originating network.
If COLR is applicable and the restriction indicator cannot be conveyed on the preceding signalling section the
interworking exchange will not send the COL.
If the originating network receives a Connected Line Identity without any indication of presentation allowed
or restricted, the originating network will act according to its rules and regulations.
3.6.2.1.2.4 Restriction of additional address information
Any additional address information provided by the connected party, e.g. connected party sub-address, will
also be subject to the COLR supplementary service as indicated in the Address Presentation Restriction Indicator in the
Connected Number parameter.
3.6.2.1.2.5 Message sequence diagrams for COLR
Figure 7/Q.767 describes the message flow for COLR.
54 Recommendation Q.767
T1148140-92/d07
Set-up IAM IAM Set-up
Calling
user
Originating
exchange
Transit
exchange
Terminating
exchange
Called
user
Alerting ACM ACM Alerting
a) COL
provided by
the called
user
b)
FIGURE 7/Q.767
Connected line identification restriction
COLP-request
(Note 1)
COLP-request
Connect ANM/CON Connect ANM/CON
Connected number
+ Subaddress
(if provided
PR = 01
SI = 01)
Connected number
+ Subaddress
(optional)
Connected number
+ Subaddress
(if provided
PR = 01
SI = 01)
(Note 3)
COL not
provided by
the called
user or
provided
but no valid
or screened
Set-up IAM IAM Set-up
Alerting ACM ACM Alerting
COLP-request
Connect ANM/CON Connect ANM/CON
Connected number
PR = 01
SI = 11
COLP-request
Connected number
PR = 01
SI = 11
Note 1 This service is subscribed by the calling user and the request is included by the originating exchange.
Note 3 This service is subscribed by the called user and stored at the destination exchange.
Note 2 The connect message is appropriate only if the answer condition is detected prior to the return of the address complete message.
(Note 2)
3.6.2.1.3 Nodal signalling function SDLs for COLP and COLR
Nodal signalling function procedures for COLP and COLR are described in Figures 8/Q.767 to 11/Q.767.
Recommendation Q.767 55
2
3
1
T1148150-92/d08
2
3
1
Idle
CON or ANM
Was
COL requested
on this call
Is COL
to be provided
anyway
No
COL
available
Yes
Yes
No
Yes
Yes
Yes
No
No
No
Set PR = 10
SI = 11
COL
supplied by
connected
user
Verification
of COL
Add missing
part of COL
COL = default
number
(Note)
Set SI = 11 Set SI = 01
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
Note The default number is a network supplied default number.
FIGURE 8/Q.767 (sheet 1 of 2)
Nodal signalling functions for COLP and COLR terminating local exchange
(This figure is not applicable for the international interface and provided for information only)
56 Recommendation Q.767
1
2 3
1
2
3
T1148160-92/d09
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
FIGURE 8/Q.767 (sheet 2 of 2)
Nodal signalling functions for COLP and COLR terminating local exchange
Idle
CON or ANM
Set nature of address
and incomplete
number indication
Omit connected party
number parameter
field from
CON or ANM
Set PR = 01 Set PR = 00
Any
presentation
restriction
No
Yes
Recommendation Q.767 57
2
3
4 1
1
4
3
2
T1148170-92/d10
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
FIGURE 9/Q.767 (sheet 1 of 2)
Idle
CON or ANM
Has
COL been
requested
No
Is COL
to be provided
anyway
COL
present
Presentation
allowed
Special
agreement on
PR
No
No
No
Note
Yes
No
Yes
Yes
Note This flow assumes that there is no restriction on passing non-restricted COL's across the international boundary
if no such agreement exists then any COL in the incoming CON or ANM will be removed and the PR indicator set
to 10. "COL not available".
Nodal signalling function for COLP and COLR incoming international gateway
Yes
58 Recommendation Q.767
T1148180-92/d11
1
3 4 2 3, 4, 2
1
FIGURE 9/Q.767 (sheet 2 of 2)
Nodal signalling function for COLP and COLR incoming international gateway
International
number
Delete trunk
prefix (if any)
Add terminating
country code
Set nature of
address indicator to
"International number"
Set PR = 10
Set SI = 11
Keep PR and SI
as provided by
the I/C network
Omit COL
Set PR = 01
Set SI = 11
Omit connected
party number
parameter field
from CON or ANM
CON or ANM
Idle
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
No
Yes
Recommendation Q.767 59
T1148190-92/d12
FIGURE 10/Q.767
Nodal signalling functions for COLP and COLR originatiog international gateway exchange
Omit connected
party number
parameter field
from CON or ANM
COL
PR
Si
Connectd line identity
Presentation restriction
Screening indicator
Idie
CON or ANM
Has
COL been
requested
Maintain
PR = 10
SI = 11
Add international
prefix (optional)
Keep PR and Si
as provided
CON or ANM
Idie
No
No
Yes
CL
Iidentity
present
Yes
60 Recommendation Q.767
T1148200-92/13
Idle
CON or ANM
COLP
subscription
or provided by
default
COL
identity
available
Any
presentation
restrictions
No information
about the connected
party is sent to
the calling party
No
Yes
No
Yes
Yes
No
Address information
will not be presented
to the calling party
Set PR = 00
Keep SI as
provided
Note 1
Note 3
Set PR = 10
Set SI = 11
Note 2
CON or ANM
Idle
Nodal signalling functions for COLP and COLR originating local exchange
(This figure is not applicable for the international interface and provided for information only)
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
Note 1 Presentation may be restricted due to national requirements or presentation restriction. Presentation restriction
may be overridden due to calling partys category (e.g. Police).
Note 2 In the case where the address information is indicated as not available due to interworking, etc. Only the indicators
are presented to the user.
Note 3 The "Connected Party Number parameter" is not included in the incoming CON or ANM.
FIGURE 11/Q.767
Recommendation Q.767 61
3.6.2.1.4 Interaction of COLP with other supplementary services
3.6.2.1.4.1 Calling Line Identification Presentation
No interaction.
3.6.2.1.4.2 Calling Line Identification Restriction
If a user has Calling Line Identification Restriction (CLIR) activated then COLR will also be activated.
Therefore the number of the user will not be available for presentation on both incoming and outgoing calls.
3.6.2.1.4.3 Connected Line Identification Restriction
The Connected Line Identification will not be presented if the connected user has an arrangement to inhibit
the presentation of his number to the calling party.
3.6.2.1.4.4 Closed user group
No interaction.
3.6.2.1.4.5 User to user information
No interaction.
3.6.2.1.5 Interaction of COLR with other supplementary services
3.6.2.1.5.1 Calling Line Identification Presentation
If a user has COLR activated then CLIR will also be activated. Therefore the number of the user will not be
available for presentation on both incoming and outgoing calls.
3.6.2.1.5.2 Calling Line Identification Restriction
No interaction.
3.6.2.1.5.3 Connected Line Identification Presentation
COLR will take precedence over COLP.
The only occasion when a user subscribing to Connected Line Identification Presentation can take precedence
over Connected Line Identification Restriction is when the user has override category. This is a national option.
62 Recommendation Q.767
3.6.2.1.5.4 Closed user group
No interaction.
3.6.2.1.5.5 User to user information
No interaction.
4 Guidelines for ISDN international interconnections
4.1 Clarifications to ISUP basic call control procedures
4.1.1 Handling of unrecognized signalling information
All signalling information not described in the Blue Book ISUP signalling specifications as amended by the
exceptions contained in 3 of this Recommendation, is considered as unrecognized signalling information. The
following section intends to recommend, as far as possible, standard reactions to the receipt of such unrecognized
signalling information (unrecognized messages, parameters and parameter values).
4.1.1.1 In international ISUP transit situations
Unrecognized messages and parameters should be discarded without disrupting normal call handling. As far
as unrecognized signalling information is concerned, the following principles are applied:
fields/bits marked as not used in 3 of this Recommendation are passed on unchanged;
spare values are passed on unchanged;
spare fields/bits are passed on unchanged or reset to zero;
fields/bits marked as national use are passed on unchanged or reset to zero.
Unrecognized parameter values should be handled as indicated below:
Default: handle as if the default value was received; the default value is sent.
Ignore: the value is don't care; the received value may be passed on unchanged or reset to zero.
No Default: value received passed on unchanged.
Recommendation Q.767 63
TABLE 8/Q.767 (sheet 1 of 4)
Q.763
Section
Title Action
3.2 Access Transport parameter No Default (see 4.3 of Rec Q.767)
3.3 Automatic congestion level Discard parameter
3.4 Backward call indicators
Charge indicators
Bits B A
Called party status indicators
Bits D C
Called party category indicator
Bits F E
End to end method indicator
Bits H G
End to end information indicator
Bit J
Holding indicator (national use)
Bit L
SCCP method indicator
Bits P O
No Default
No Default
No Default
No Default
No Default
Ignore
No Default
3.7 Called party number
Nature of address indicator
Numbering plan indicator
Spare
Address signals
Filler
Release with cause value 28
Release with cause value 28
Ignore
Release with cause value 28 (Note)
Default: 0000
3.8 Calling party number
Nature of address indicator
Number incomplete indicator
Numbering plan indicator
Presentation restricted indicator
Screening indicator
Address signals
Filler
No Default
No Default
No Default
No Default
No Default
No Default
Ignore
64 Recommendation Q.767
TABLE 8/Q.767 (sheet 2 of 4)
Q.763
Section
Title Action
3.9 Calling partys category No Default
3.10 Cause indicators
Coding standard
Spare
Location
Cause value
No Default
Ignore
No Default
No Default
3.11 Circuit group supervision message type indicator
Bits B A
Bits C-H: Spare
Discard message
Ignore
3.13 CUG interlock code No Default
3.14 Connected number
Nature of address indicator
Spare
Numbering plan indicator
Presentation restricted indicator
Screening indicator
Address signals
Filler
No Default
Ignore
No Default
No Default
No Default
No Default
Ignore
3.16 Continuity indicators
Bits B-H: spare Ignore
3.18 Event information
Event indicator
Bits GFEDCBA
No Default
3.20 Forward call indicator
End to end method indicator
Bits C B
End to end information indicator
Bit E
ISUP preference indicator
Bits H G
SCCP method indicator
Bits K J
Spare: Bit L
Bits M-P (national use)
No Default
No Default
Release with cause 111
No Default
Ignore
Ignore
Recommendation Q.767 65
TABLE 8/Q.767 (sheet 3 of 4)
Q.763
Section
Title Action
3.23 Nature of connection indicators
Satellite indicator
Bits B A
Continuity indicator
Bits D C
Spare
Bits F-H
Default: 10 "two satellites in the connection"
Default: 00 "continuity check not required"
unless required on the outgoing circuit
Ignore
3.24 Optional backward call indicators
Bit B: Call forwarding may occur
Bits C-D: spare
Bit E-H (national use)
No Default
Ignore
Ignore
3.25 Optional forward call indicator
Closed user group call indicator
Bits B A
Spare
Bits C-G
No Default
Ignore
3.27 Range and status See Rec. Q.764, 2.10.3 and 2.9.2
3.32 Subsequent Number
Spare
Bits 1-7
Address signal
Filler
Ignore
Release with cause 28 (Note)
Default: 0000
3.33 Suspend/Resume indicators
Spare
Bits B-H Ignore
3.35 Transmission medium requirement Release with cause 65
66 Recommendation Q.767
TABLE 8/Q.767 (sheet 4 of 4)
Note Evaluated as far as needed for routing.
4.1.1.2 In incoming/outgoing gateway or in interworking situations
Unrecognized messages and parameters should be discarded without disrupting normal call handling.
Unrecognized parameter values should be handled as indicated below:
Default: handle as if the default value was received.
Ignore: the value is don't care; the received value may be passed on unchanged or reset to zero.
No Default: value passed on unchanged.
Q.763
Section
Title Action
3.36 User Service Information No Default (see 4.3 of Rec. 767)
3.37 User to User indicators
Type
Bit A
Service 1
Bits C B
Service 2
Bits E D
Service 3
Bits G F
Network discard indicator Bit H
No Default
No Default
No Default
No Default
No Default
Recommendation Q.767 67
TABLE 9/Q.767 (sheet 1 of 4)
Q.763
Section
Title Action
3.2 Access Transport parameter No Default (see 4.3 of Rec. Q.767)
3.3 Automatic congestion level Discard parameter
3.4 Backward call indicators
Charge indicators
Bits B A
Called party status indicators
Bits D C
Called party category indicator
Bits F E
End to end method indicator
Bits H G
End to end information indicator
Bit J
Holding indicator (national use)
Bit L
SCCP method indicator
Bits P O
Default: 10 "charge"
Default: 00 "no indication"
Default: 00 "no indication"
Default: 00 "no end to end method available"
Default: 0 "no end to end info available"
Ignore
Default: 00 "no indication"
3.7 Called party number
Nature of address indicator
Numbering plan indicator
Spare
Address signals
Filler
Release with cause value 28
Release with cause value 28
Ignore
Release with cause value 28 (Note)
Default: 0000
68 Recommendation Q.767
TABLE 9/Q.767 (sheet 2 of 4)
Q.763
Section
Title Action
3.8 Calling party number
Nature of address indicator
Number incomplete indicator
Numbering plan indicator
Presentation restricted indicator
Screening indicator
Address signals
Filler
Discard parameter
Discard parameter
Discard parameter
Default: 01 "presentation restricted"
Discard parameter
No Default
Default: 0000
3.9 Calling partys category Default: 0000 1010
" ordinary subscriber"
3.10 Cause indicators
Coding standard
Spare
Location
Cause value
Default: 00 "CCITT"
Ignore
Default: 0111 "International network"
Default: "Unspecified within class XXX"
3.11 Circuit group supervision message type indicator
Bits B A
Bits C-H: Spare
Discard message
Ignore
3.13 CUG interlock code No Default
3.14 Connected number
Nature of address indicator
Spare
Numbering plan indicator
Presentation restricted indicator
Screening indicator
Address signals
Filler
Discard parameter
Ignore
Discard parameter
Default: 01 "presentation restricted"
Discard parameter
No Default
Default: 0000
3.16 Continuity indicators
Bits B-H: spare Ignore
Recommendation Q.767 69
TABLE 9/Q.767 (sheet 3 of 4)
Q.763
Section
Title Action
3.18 Event information
Event indicator
Bits G F E D C B A
No Default
3.20 Forward call indicator
End to end method indicator
Bits C B
End to end information indicator
Bit E
ISUP preference indicator
Bits H G
SCCP method indicator
Bits K J
Spare: Bit L
Bits M-N (national use)
Default: 00 "no end to end method available"
Default: 0 " no end to end info available
Release with cause 111
Default: 00 "no indication"
Ignore
Ignore
3.23 Nature of connection indicators
Satellite indicator
Bits B A
Continuity indicator
Bits D C
Spare
Bits H-F
Default: 10 "two satellites in the connection"
Default: 00 "continuity check not required"
Ignore
3.24 Optional backward call indicators
Bit B: Call forwarding may occur
Spare: Bits C-D
Bits E-H (national use)
Default: 0 " no indication"
Ignore
Ignore
70 Recommendation Q.767
TABLE 9/Q.767 (sheet 4 of 4)
Note Evaluated as far as needed for routing.
Q.763
Section
Title Action
3.25 Optional forward call indicators
Closed user group call indicator
Bits B A
Spare
Bits C-G
Default: 00 "Non CUG call"
Ignore
3.27 Range and status See Rec. Q.764, 2.10.3 and 2.9.2
3.32 Subsequent number
Spare
Bits 1-7
Address signal
Filler
Ignore
Release with cause 28 (Note)
Default: 0000
3.33 Suspend/Resume indicators
Spare
Bits B-H
Ignore
3.35 Transmission medium requirement Release with cause 65
3.36 User Service Information No Default (see 4.3 of Rec. Q.767)
3.37 User to User indicators
Type
Bit A
Service 1
Bits C B
Service 2
Bits E D
Service 3
Bits G F
Bit H
Default: 1 "response"
Default: 00 "no information"
Default: 00 "no information"
Default: 00 "no information"
Default: 1 " Network discard"
Recommendation Q.767 71
4.1.1.3 Format errors
The following are considered as message format errors:
The message length is less than the number of octets required for the fixed mandatory part, the
mandatory variable pointers and the start of optional parameters pointer.
A mandatory variable or start of optional parameter's pointer points beyond the message length.
A mandatory variable or optional parameter's length indicator causes the overall message length to be
exceeded.
When a message format error is detected, the message shall be discarded.
Note A format error can only be detected when the message type is recognized.
For the purpose of format error detection, the message length may be interpreted as either:
i) the received message length, or
ii) the maximum message length (SIF = 272 octets).
Interpretation i) is preferred as it will detect errors which may not be found by interpretation ii). However it is
not contained in the MTP Recommendation that the received message length is passed to its users by the MTP.
4.1.2 Cause values
The list of causes supported and the code values are listed in Q.763 amended by the exceptions (see
Table 4/Q.767). This section contains clarification of the usage of cause values, the handling of location indicators, the
relation to relevant Q.764/Q.730 procedures. Some guidance to the correspondence with other signalling systems
failure signals is also given.
72 Recommendation Q.767
4.1.2.1 Usage of causes
Table 10/Q.767 indicates the usage of cause values for the international interface.
a) meaning of notes:
*location: see item b) handling of location indicators
b) used abbreviations:
U: user
PRN: private network serving the remote user
TN: transit network
INT:international network
RN: public network serving the remote user
Setting causes 18 and 19, and using location public or private network serving the remote user or any other
cause with location user or private network serving the remote user should imply that the call has reached the called
party, i.e end to end fields have been transmitted.
National networks should make sure, to avoid public network misuse, that the following locations are not
generated on the access:
public, international, transit network and beyond an interworking point.
The cause value sent is the one of the latest occurred event (e.g. retransmitting of the release message).
Recommendation Q.767 73
TABLE 10/Q.767 (sheet 1 of 3)
Cause Definition Q.762 Location Reference Notes
1 Unallocated number .......................
........................................................
........................................................
... U, PRN............
... RN
... TN, INT...........
...Q.931
... ............................. ... no route by digit analysis
3 No route to destination................... ... U, PRN............ ...Q.931
4 Send special information tone ... ......................... ...(Q.931: no proc) .. ... see Rec. Q.35 7
16 Normal call clearing....................... ... U, PRN............ ...Q.931
17 User busy........................................ ... U, PRN, RN.... ...Q.931
18 No user responding......................... ... RN................... ...Q.931
19 User alerting no answer..................
........................................................
........................................................
........................................................
... RN...................
... INT..................
... .........................
... .........................
...Q.931
...Q.767 (D.2.1.4.4),
...Q.767 (D.2.10.8.3)
... .............................
...] expiry of waiting ANM timer (T9)
...] (generated by international outgoing
...] exchanges)
21 Call rejected.................................... ... U, PRN............ ...Q.931
22 Number changed............................. ... U, PRN............ ...Q.931
27 Destination out of order.................. ... RN................... ...Q.931
28 Address incomplete ........................
........................................................
........................................................
........................................................
........................................................
... U, PRN, RN....
... TN,INT............
... .........................
... .........................
... .........................
...Q.931
...Q.767 (D.2.1.1),......
...Q.767 (D.2.1.2.1),...
...Q.767 (D.2.10.8.3)..
...Q.767 (D.2.2.5).......
...] the called party number is not in a
...] valid format or is not complete.
...]
...]
29 Facility rejected ..............................
........................................................
... RN, U, PRN....
... TN, INT...........
...(Q.931: no proc)
... ............................. ...inability to provide a requested
...signalling capability.
74 Recommendation Q.767
TABLE 10/Q.767 (sheet 2 of 3)
Cause Definition Q.762 Location Reference Notes
31 Normal, unspecified .......................
........................................................
........................................................
........................................................
........................................................
........................................................
........................................................
........................................................
........................................................
........................................................
... RN...................
... TN, INT...........
... .........................
... .........................
... .........................
... .........................
... .........................
... .........................
... .........................
... .........................
...Q.931
...Q.767 (D.2.1.1.1).
...Q.767 (D.2.1.2.1).
...Q.767 (D.2.9.1),...
...Q.767 (D.2.9.2.1).
...Q.767 (D.2.9.2.2).
...Q.767 (D.2.10.3),.
...Q.767 (D.2.10.6),.
...Q.767 (D.2.10.8.2)
...Q.767 (D.2.10.8.3)
...] call failure information indicating
...] the failure of a call due to the lapse
...] of a timeout or a fault not covered
...] by specific causes
...] (examples: expiry of timers Q.764
...] not covered by specific causes,
...] release of interconnected ] circuit, . .
.)
...]
34 No circuit available ........................
........................................................
........................................................
........................................................
... U, PRN, RN....
... TN, INT...........
... .........................
... .........................
...Q.931
... .............................
... .............................
... .............................
...] circuit congestion encountered on
...] an international exchange or in
...] the national destination network.
38 Network out of order ...................... ... ......................... ...(Q.931: no proc)
41 Temporary failure........................... ... U, PRN, RN.... ...Q.931
42 Switching equipment congestion ... ... RN, TN, INT
44 Q.931 (requested channel not
available) ........................................ ... U, PRN............ ...Q.931
47 Resource unavailable, unspecified. ... ......................... ...(Q.931: no proc)
55 Incoming calls barred within
CUG................................................ ... RN................... ...Q.767 (E.3.2.3)
57 bearer capability not authorized
58 Bearer capability not presently
available
Recommendation Q.767 75
TABLE 10/Q.767 (sheet 3 of 3)
Cause Definition Q.762 Location Reference Notes
63 Service/option not available,
unspecified
65 Bearer capability not
implemented................................... ...TN, INT ......... ... .............................. ... inability to provide a requested
... TMR
79 Service/option not implemented,
unspecified
87 User not member of CUG.............. ...RN, INT......... ... Q.767 (E.3.2.3, and
... E 3.2.2)
88 Incompatible destination................ ...U, PRN........... ... Q.931
95 Invalid message, unspecified
102 Recovery on timer expiry...............
........................................................
........................................................
........................................................
........................................................
........................................................
........................................................
...RN..................
...........................
...........................
...........................
...INT.................
...........................
...........................
... Q.767 (D.2.5.1.1), ..
... Q.767 (D.2.5.1.2), ..
... ................................
... Q.767 (D.2.5.3) ......
... Q.767 (D.2.5.1.3), ..
... Q.767 (D.2.5.3) ......
... ................................
... ] expiry of waiting RES(user)
... ] timer
... ]
... ] expiry of waiting RES
... ] (network) timer
... ] (not generated by international
... ] transit exchanges)
111 Protocol error, unspecified............. ...RN.................. ... Q.931
127 Interworking, unspecified
76 Recommendation Q.767
4.1.2.2 Handling of location indicators
If the event causing the sending of the cause indicators parameter takes place in the international exchange
(i.e. incoming or outgoing gateway or international transit exchange), the location will be set to 0111 International
network.
If interworking is encountered in the international exchange and if a message containing the cause indicators
parameter is sent because of the receipt of a message of the other signalling system, the location will be set 1010
Beyond an interworking point (BI).
The location public network serving the local user or private network serving the local user should not be
sent on the international section. The conversion from public network serving the local user to public network
serving the remote user or private network serving the local user to private network serving the remote user shall
take place in the national network generating the cause.
In all other cases the international exchange will pass on the received location.
Using this solution, it is impossible to distinguish a national location transit network from a location
transit network beyond the international boundary.
The real location where the event was generated is lost when interworking: for example CGC and NNC in
TUP are coded 34,BI. In spite of that, the limitations of this solution are accepted, because they are considered as
acceptable for this international ISUP version.
4.1.2.3 Interworking
In Table 11/Q.767 some guidelines can be found for the handling of cause values in the case of interworking
with some other CCITT signalling systems in an international exchange.
Recommendation Q.767 77
TABLE 11/Q.767 (sheet 1 of 3)
TUP
Signal Cause #
ACB Access barred 88 Incompatible destination
ADI Address incomplete 28 Address incomplete
CGC Circuit group congestion 34 No circuit available
DPN Digital path not provided 65 Bearer capability not
implemented
LOS Line out of service 27 Destination out of order
NNC National network congestion 34 No circuit available
RSC Reset circuit
CFL Call failure
GRS Circuit Group reset
31 Normal unspecified
SEC Switching equipment congestion 42 Switching equipment congestion
SSB Subscriber busy 17 User busy
SST Send special information tone 4 Send special information tone
UNN Unallocated number 1 Unallocated number
CLF Clear forward 16 Normal call clearing
Call failure due to the expiry of timer according
to Rec. Q.118, 4.3.3 at the incoming gateway
102 Recovery on timer expiry
Information indicating the failure of a call due
to expiry of timer or a fault not covered
elsewhere
127 Interworking unspecified
78 Recommendation Q.767
TABLE 11/Q.767 (sheet 2 of 3)
R2
N 5
Signal Cause #
A4/B4 Congestion in the national network 34 No circuit available
A15 Congestion in an international
exchange or at its output
34 No circuit available
A3+B2 Send special information tone 4 Send special information tone
A3+B3 Subscribers line busy 17 User busy
A3+B5 Unallocated number 1 Unallocated number
A3+B8 Subscribers line out of order 27 Destination out of order
Clear forward 16 Normal call clearing
Call failure due to the expiry of timer according
to Rec. Q.118, 4.3.3 at the incoming gateway
102 Recovery on timer expiry
Information indicating the failure of a call due
to expiry of timer or a fault not covered
elsewhere
127 Interworking unspecified
(Note)
Note In case of R2 signals B9-B15, see Recommendations Q.400, Q.441, Q.474 and
Q.480.
Event Cause #
Clear forward 16 Normal call clearing
Busy flash F2 34 No circuit available
Information indicating the failure of a call due
to expiry of timer or a fault not covered
elsewhere
127 Interworking unspecified
Recommendation Q.767 79
TABLE 11/Q.767 (sheet 3 of 3)
CCITT No. 6
Signal Cause #
ADI Address incomplete 28 Address incomplete
CGC Circuit group congestion 34 No circuit available
LOS Line out of service 27 Destination out of order
NNC National network congestion 34 No circuit available
RSC Reset circuit
CFL Call failure
RSB Reset band
31 Normal unspecified
SEC Switching equipment congestion 42 Switching equipment congestion
SSB Subscriber busy 17 User busy
SST Send special information tone 4 Send special information tone
UNN Unallocated number 1 Unallocated number
CLF Clear forward 16 Normal call clearing
Call failure due to the expiry of timer according
to Rec. Q.118, 4.3.3 at the incoming gateway
102 Recovery on timer expiry
Information indicating the failue of a call due to
expiry of timer or a fault not covered elsewhere
127 Interworking unspecified
80 Recommendation Q.767
4.1.3 Charging
Charging indicators are basically defined for national use. Therefore, unless bilateral agreement, the decision
to charge a call or not, or to start international accounting will not be decided upon reception of these indicators.
4.1.4 Operator services
4.1.4.1 Forward transfer
The support of the FOT message in the international interface does not impose that the related functions are
implemented in each gateway (e.g. language assistance).
4.1.4.2 Called part number for operator calls
International gateways should support access to operators equipment as specified in Recommendation Q.101.
The sending sequence of specific forward address information to be sent for calls to operators (incoming,
delay or particular delay operator) is shown below. The other informations of the IAM are coded as the ones for an
automatic call IAM (nature of connection indicator, TMR, etc.).
4.1.4.2.1 International transit operator call
* Called party number: nature of address indicator: 0000100 international number
address: * country code: I
1
, I
1
I
2
, I
1
I
2
I
3
* extra digit designating the incoming international exchange N
1
(see Note 1)
* access to operator's position: Code 11 or Code 12 or special number (see
* Note 2)
* number of a particular position: x
1
(x
2
x
3
...)
* sending finished: ST
Note 1 The extra digit (N
1
) designating the incoming international exchange is used in cases where more
than one incoming international exchange can be reached in the country of destination. The insertion of the extra digit
is not mandatory (see Recommendation Q.107).
Recommendation Q.767 81
Note 2 The incoming operator or the delay operator may be obtained by using a special number (see
Recommendation Q.101).
* Calling party's category:
00000001 operator, language French
00000010 operator, language English
00000011 operator, language German
00000100 operator, language Russian
00000101 operator, language Spanish
4.1.4.2.2 International terminal operator call
* Called party number: nature of address indicator: 0000011 national (significant) number
address: * extra digit designating the incoming international exchange N
1
(see Note 1,
* 4.1.4.2.1)
* access to operator's position: Code 11 or Code 12 or special number (see
* Note 2, 4.1.4.2.1)
* number of a particular position: x
1
(x
2
x
3
...)
* sending finished: ST
* Calling party's category:
00000001 operator, language French
00000010 operator, language English
00000011 operator, language German
00000100 operator, language Russian
00000101 operator, language Spanish
82 Recommendation Q.767
4.1.5 Test Calls
4.1.5.1 Called number for calls to testing and measuring devices
This section only describes the standard sending sequence of forward address information in the case of calls
to testing and measuring devices.
* Called party number: nature of address indicator: 0000011 national (significant) number
address: * access code for a particular testing or measuring device: XY (as given in
* Recommendation Q.107 Blue Book)
* sending finished: ST
* Calling party's category: 00001101 test call
Note The principles in Recommendation Q.107 (Blue Book) are not always applicable to the international
network.
4.1.5.2 Called number for test calls
This section only describes the sending sequence of forward address information in the case of test calls
based on bilateral agreements.
* Called party number: nature of address indicator: 0000011 national (significant) number
address: * access code N
1
...N
n
based on bilateral agreements.
* sending finished: ST
* Calling party's category: 00001101 test call
4.1.5.3 Accounting of test calls
In international accounts, tests should be deducted according to CCITT Recommendation D.390-R 7.
4.1.6 Continuity Check
As a minimum requirement, international gateways should support the continuity check procedure, initiated
by the reception of a CCR message or of a continuity check indicator in the IAM, by providing a check loop on 4 wire
circuits, on a call by call basis. This procedure is described in Recommendation Q.764, 2.1.8, and in
Recommendation Q.724, 7 and in 3.5 of this Recommendation.
Recommendation Q.767 83
International gateways should support the continuity check procedure on previous circuit as described in
Recommendation Q.764, ( 2.1.8 as amended by Table 5/Q.767), and Recommendation Q.724, 7.
If in an interworking situation with any non No. 7 Signalling System or a national Signalling System No. 7
not performing continuity check, a continuity check has to be performed on one or more of the circuits involved in the
connection preceding the interworking point, appropriate measures (e.g. digit dragging) must be taken to prevent
alerting of the called party until the continuity of such circuits has been verified.
4.1.7 Application of Recommendation Q.118 for suspend/resume (network)
The suspend (network) message in the ISDN UP can be generated by the network in response to a clearback
indication from an interworking node or an on-hook condition from an analogue called party.
When an outgoing gateway receives the suspend (network) message,this gateway starts a timer (1-2 minutes)
according to Recommendation Q.118, 4.3.2. If this timer expires, the release procedure is initiated on both sides.
When an incoming gateway sends the suspend (network) message, this gateway starts a timer (2-3 minutes)
according to Recommendation Q.118, 4.3.3, unless this function is already provided in the national network. If this
timer expires, the release procedure is initiated on both sides.
4.1.8 Terminal Portability
The Terminal Portability supplementary service allows a calling as well as a called user to move a terminal
from one socket to another during the established state of a call. It is also possible to replace a terminal by another
compatible terminal or to suspend and resume the call without changing the terminal or the socket.
The user initiated suspend and resume procedures as described in Recommendation Q.764, 2.5, are applied.
The suspend/resume indicator in the suspend and resume messages are set to ISDN subscriber initiated.
If interworking with a network or a signalling system not supporting remote user notification of call
suspension/resumption occurs, user initiated suspend/resume messages received will be discarded. If the clearback
signal is not needed in the national network, it is recommended that no mapping, e.g. to clearback should be performed.
84 Recommendation Q.767
4.1.9 Subaddress
During call set-up, the called party subaddress provided by the calling party is transported from the
originating to the destination exchange, in the IAM.
The calling party may also provide its own subaddress to complement the calling line identification, as
provided in the CLI service. This subaddress is transported from the originating to destination exchange, in the IAM.
The called party may also provide its own subaddress to complement the connected line identification as
provided in the COL service. This subaddress is transported from the destination to originating exchange, in the ANM
or CON.
Up to 20 octets of subaddress information can be conveyed. Calling and called party subaddress information
is conveyed in the ATP parameter of the IAM. Connected line subaddress information is conveyed in the ATP
parameter in the ANM or CON.
No notification of delivery or non delivery of subaddress information is sent to the subaddress sending user.
On interworking with a network or a signalling system which does not support the transfer of the received
subaddress (due to a shorter length or no subaddress at all), the whole subaddress information element is discarded. No
notification of non delivery is provided.
4.1.10 MTP pause/resume
On reception of a MTP pause primitive, ISUP takes the following action:
If the affected destination is not a destination (SP) known by ISUP (not connected by circuits to the
exchange), no action takes place.
If the affected destination is a destination (SP) known by the ISUP, the circuits connected to the
inaccessible SP will be prohibited for new outgoing calls. If no other circuits are available to route these
calls, they are released with the appropriate cause (34 no circuit available).
Recommendation Q.767 85
All other procedures (blocking, unblocking, reset and continuity check) to be started on these circuits, and all
procedures and calls already started before the MTP pause reception, are handled as usual. The local and remote ISUP
will not receive answers to the messages sent; message repetition, reset procedures or normal call release procedures on
time out will be initiated, depending on the duration of the SP inaccessibility.
On reception of a MTP resume primitive, ISUP takes the following action:
If the affected destination is not a destination (SP) known by ISUP (not connected by circuits to the
exchange), no action takes place.
If the affected destination is a destination (SP) known by the ISUP, the circuits connected to the
previously inaccessible SP can be used again for calls to that direction. The pending procedures that
were running during the signalling relation unavailability, are completed as messages can be again
exchanged between the two SPs. As a result of the time supervision mechanism for responses to the
messages sent in each relevant procedure, the circuits affected by the signalling relation unavailability
are restored to a normal state when the signalling relation becomes available.
4.1.11 CIC allocation
The following rules should apply for the allocation of CIC codes to circuits in the international network:
the CIC should be coded according to the traffic circuit number between two switching units;
the basis for the traffic circuit numbering should be the Recommendation M.140, Blue Book (switching
unit related traffic circuit numbering);
the CIC will be the binary code of the traffic circuit number without the letter Z or B.
4.2 Clarifications to ISUP supplementary services
The following summarizes the action taken by a national network not supporting a given supplementary
service, and provides also consideration for international transit operation.
4.2.1 Gateway (incoming/outgoing) reactions for supplementary services not supported in the national network
As national networks may not fully support the basic services and supplementary services supported by this
version of the international ISUP signalling system, it is essential to standardize the gateways reaction when receiving
signalling information on the international section relevant to a service or supplementary service not provided or
partially provided in the national network. Bilateral agreements are necessary before opening between two networks, a
service supported by the international signalling system. It may happen however, that no service screening on a route
basis is performed/feasible in the outgoing gateway; and therefore a service request for a national supplementary
service not supported, may be received in an international gateway.
86 Recommendation Q.767
TABLE 12/Q.767
Supplementary
service
Reaction in international gateway Remarks
UUS 1
implicit
Incoming gateway:
Reject UUS information received in IAM using
user to user indicator bit H = 1 "Network discard"
in ACM or CON
Incoming/Outgoing gateway
UUS information received in other messages is
discarded without notification by the
outgoing/incoming gateway
If no UUS information is sent in the IAM, the
incoming (outgoing) national network should
prevent the transmission of UUS in the backward
(forward) direction
CLIP Incoming gateway:
Discard Calling Party Number
No notification is given
CLIR Incoming gateway:
Discard Calling Party Number if unable to handle
or convey the restriction indication
No notification is given
CUG See 3.6 of Rec. Q.767
COLP Outgoing gateway:
Discard Connected Number
Incoming gateway:
Send Connected Number parameter with indication
address not available in ANM or CON
Connected number should be received only on
request
No notification is given
COLR Outgoing gateway:
Discard Connected Number if unable to handle or
convey the restriction indication
No notification is given
Subaddressing Discard subaddress The national network shall discard the received
subaddress
No notification is given
Terminal
portability
Discard suspend/resume (user initiated) messages No notification is given
Recommendation Q.767 87
4.2.2 Transit considerations
In ISUP international transit working, all basic services and supplementary services defined for this version
of the ISUP applicable for international ISDN interconnection should be supported in international transit operation, i.e.
all related parameters should be transited unchanged.
If this is not possible, the same reaction as for an incoming/outgoing (or interworking) gateway should apply,
as described in 4.2.1.
4.3 Handling of access information
4.3.1 General
For a certain period of time, national ISDNs may not guarantee the support of all supplementary services and
information elements contained in access protocol standards. It is, however, essential, in order to allow international
ISDN communication, that a minimum common profile for the various services supported (see 2) is defined.
These profiles for bearer capability (BC), high layer compatibility (HLC), low layer compatibility (LLC) are
given as typical examples to allow gateways to perform necessary mapping, if needed (e.g. national network does not
support the fully transparent transfer or handling of HLC, BC, LLC).
There is no intention however to restrict the sending of any further codings on the international section (but
the result is not guaranteed). Checks on the codings sent/received are not mandatory in a gateway.
4.3.2 Content of Access Transport parameter (ATP)
No check should be made on the content of ATP, with reference to the table below. The maximum length
should only be limited by the message length, as the content of ATP will probably evolve in the future. If maximum
message length is exceeded, the user to user information (UUI) should be the first information discarded.
88 Recommendation Q.767
TABLE 13/Q.767
Note Two progress indicators may be sent in a message.
It is not recommended to perform any check in the gateway, unless required, on the presence and validity
(coding/ max length) of the information elements received in the ATP, in particular subaddress.
4.3.3 Coding of USI (BC), HLC, LLC
4.3.3.1 General
This section identifies the ISUP parameters and Q.931 information elements (Blue Book) that may be present
with various services. It also proposes specific codings for the User Service Information (USI) parameter, high layer
compatibility (HLC) information element and low layer compatibility (LLC) information element, which may be
present at the international interface. The HLC, LLC information elements are included in the Access Transport
parameter.
4.3.3.2 Relationship between services and signalling information
Table 14/Q.767 below identifies the relationship between services and the presence of USI(BC), HLC and
LLC signalling information in the ISUP IAM.
Message Forward Backward Information element
ACM X Progress indicator
ANM X Progress indicator
Connected party subaddress
LLC
CPG X Progress indicator
CON X Progress indicator
LLC
Connected party subaddress
IAM X Progress indicator
Calling party subaddress
Called party subaddress
LLC
HLC
Recommendation Q.767 89
TABLE 14/Q.767
Note 1 All teleservices operate at 64 kbits/s as specified in Recommendation I.241.
Note 2 LLC will be included if provided by the user. Guidelines for the application of LLC can be found in
Annex L of Recommendation Q.931.
Note 3 Analogue subscriber connected to an ISDN local exchange are treated as analogue subscribers in
the PSTN, i.e. no USI, HLC or LLC, respectively is contained in the ISUP IAM.
Any USI parameter received not conforming to this section might result in the call being failed.
Transport of codings specified should at least be guaranteed across the international interface.
Services Parameter/info elements
O
R
I
Teleservice
(Note 1)
Bearer Service USI HLC LLC
G
I
N
A
T
I
N
G
N
E
T
W
O
I
S
D
N
Note 3
Telephony
Facsimile G2/G3
Facsimile G4
Mixed mode
Teletex
Videotex
64 kbit/s
unrestricted
3.1 kHz audio
Speech
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
Note 2
Note 2
Note 2
Note 2
Note 2
Note 2
Note 2
Note 2
Note 2
R
K
P
S
T
N
Telephony/Voice band data
Digital connectivity
No
No
No
No
No
No
90 Recommendation Q.767
4.3.3.2.1 Teleservices
Key:
x possibly examined at certain gateway and may be coded 0 or 1
. it has no significance to the international network (e.g. coded according to network/user specific rules)
a) Telephony
User Service Information parameter
High layer compatibility information element
1 0 0 0 0 0 0 0
1 0 0 1 0 0 0 0
1 0 1 0 0 0 1 x
Octet 1 Coding standard and information
transfer capability (speech)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
(Rec. G.711 A/ law)
0 1 1 1 1 1 0 1
0 0 0 0 0 0 1 0
1 0 0 1 0 0 0 1
1 0 0 0 0 0 0 1
Octet 1 HLC information element identifier
2 Length (2 octets)
3 Coding standard, interpretation and presentation
method of protocol profile
4 High layer characteristics identification (telephony)
Recommendation Q.767 91
b) Facsimile G2/G3
User Service Information parameter
High layer compatibility information element
1 0 0 1 0 0 0 0
1 0 0 1 0 0 0 0
1 0 1 0 0 0 1 x
Octet 1 Coding standard and information transfer capability
(3.1 kHz audio)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
(Rec. G.711 A/ law)
0 1 1 1 1 1 0 1
0 0 0 0 0 0 1 0
1 0 0 1 0 0 0 1
1 0 0 0 0 1 0 0
Octet 1 HLC information element identifier
2 Length (2 octets)
3 Coding standard interpretation and presentation
method of protocol profile
4 High layer characteristics identification (fax G2/G3)
92 Recommendation Q.767
c) Facsimile Group 4
User Service Information parameter
Note Octet 3 and 3a are used only when rate adaptation is applied.
High layer compatibility information element
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 0 1
1 0 0 0 1 1 1 1
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
protocol (V.110 rate adaptation)
3a Synchronous; 56 kbit/s
0 1 1 1 1 1 0 1
0 0 0 0 0 0 1 0
1 0 0 1 0 0 0 1
1 0 1 0 0 0 0 1
Octet 1 HLC information element identifier
2 Length (2 octets)
3 Coding standard, interpretation and presentation
method of protocol profile
4 High layer characteristics identification (fax group 4)
Recommendation Q.767 93
d) Mixed mode
User Service Information parameter
Note Octet 3 and 3a are used only when rate adaptation is applied.
High layer compatibility information element
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 0 1
1 0 0 0 1 1 1 1
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
protocol (V.110 rate adaptation)
3a Synchronous; 56 kbit/s
0 1 1 1 1 1 0 1
0 0 0 0 0 0 1 0
1 0 0 1 0 0 0 1
1 0 1 0 0 1 0 0
Octet 1 HLC information element identifier
2 Length (2 octets)
3 Coding standard, interpretation and presentation
method of protocol profile
4 High layer characteristics identification (mixed
mode)
94 Recommendation Q.767
e) Teletex
User Service Information parameter
Note Octet 3 and 3a are used only when rate adaptation is applied.
High layer compatibility information element
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 0 1
1 0 0 0 1 1 1 1
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
protocol (V.110 rate adaptation)
3a Synchronous; 56 kbit/s
0 1 1 1 1 1 0 1
0 0 0 0 0 0 1 0
1 0 0 1 0 0 0 1
1 0 1 1 0 0 0 1
Octet 1 HLC information element identifier
2 Length (2 octets)
3 Coding standard, interpretation and presentation
method of protocol profile
4 High layer characteristics identification (teletex)
Recommendation Q.767 95
f) Videotex
User Service Information parameter
Note Octet 3 and 3a are used only when rate adaptation is applied.
High layer compatibility information element
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 0 1
1 0 0 0 1 1 1 1
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
protocol (V.110 rate adaptation)
3a Synchronous; 56 kbit/s
0 1 1 1 1 1 0 1
0 0 0 0 0 0 1 0
1 0 0 1 0 0 0 1
1 0 1 1 0 0 1 0
Octet 1 HLC information element identifier
2 Length (2 octets)
3 Coding standard, interpretation and presentation
method of protocol profile
4 High layer characteristics identification (videotex)
96 Recommendation Q.767
4.3.3.2.2 Bearer services
a) 64 kbit/s unrestricted
i) Synchronous 64 kbit/s working
User Service Information parameter
ii) Synchronous 56 kbit/s working with V.110/X.30 rate adaptation and no NIC
User Service Information parameter
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbit/s)
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 0 1
1 0 0 0 1 1 1 1
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
protocol (V.110 rate adaptation)
3a Synchronous; 56 kbit/s
Recommendation Q.767 97
iii) Synchronous rates less than 56 kbit/s with V.110/X.30 rate adaptation
User Service Information parameter
Low layer compatibility information element
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbits/s)
0 1 1 1 1 1 0 0
0 0 0 0 0 1 0 1
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 0 1
0 0 0 user rate
1 0 0 x x 0 0 0
Octet 1 LLC information element identifier
2 Length (5 octets)
3 Coding standard and information transfer capability
(64 kbit/s)
4 Transfer mode and information transfer rate
(64 kbit/s)
5 Layer identification and user information layer 1
protocol (V.110 rate adaptation)
5a Synchronous; user rate
5b Intermediate rate, with/without NIC and no flow control
on Tx & Rx
98 Recommendation Q.767
iv) Synchronous 64 kbit/s working with X.25 protocol
User Service Information parameter
Low layer compatibility information element
Note 1 Octet 5 is omitted when working at 64 kbit/s. The presence of the layer 2 and 3 information in octet 6
and 7 is identified by bits 7 and 6 of those octets being coded "10" and "11" respectively.
Note 2 Octets 6 and 7 could also be coded as: 11001101 and 11100111, signifying X.75 SLP Layer 2 protocol
and ISO 8208 Layer 3 protocol, respectively.
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbit/s)
0 1 1 1 1 1 0 0
0 0 0 0 0 1 0 0
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
1 1 0 0 0 1 1 0
1 1 1 0 0 1 1 0
Octect 1 LLC information element identifier
2 Length (4 octets)
3 Coding standard and information transfer capability
(64 kbit/s)
4 Transfer mode and information transfer rate
(64 kbit/s)
6 Layer 2 identification and user information layer 2
protocol (X.25 link level)
7 Layer 3 identification and user information
layer 3 protocol (CCITT X.25 packet layer)
Recommendation Q.767 99
v) Synchronous 56 kbit/s with V.110/X.30 rate adaptation and X.25 protocol
User Service Information parameter
Low layer compatibility information element
Note Octets 6 and 7 could also be coded as: 11001101 and 11100111, signifying X.75 SLP Layer 2 protocol
and ISO 8208 Layer 3 protocol, respectively.
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 0 1
1 0 0 0 1 1 1 1
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
protocol (V.110 rate adaptation)
3a Synchronous; 56 kbit/s
0 1 1 1 1 1 0 0
0 0 0 0 0 1 1 0
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 0 1
1 0 0 0 1 1 1 1
1 1 0 0 0 1 1 0
1 1 1 0 0 1 1 0
Octet 1 LLC information element identifier
2 Length (6 octets)
3 Coding standard and information transfer capability
(64 kbit/s)
4 Transfer mode and information transfer rate
(64 kbit/s)
5 Layer identification and user information layer 1
protocol (V.110 rate adaptation)
5a Synchronous; 56 kbit/s
6 Layer 2 identification and user information layer 2
protocol (CCITT X.25 link level)
7 Layer 3 identification and user information layer 3
protocol (X.25 packet layer)
100 Recommendation Q.767
vi) Synchronous rates less than 56 kbit/s with V.110/X.30 rate adaptation and X.25 protocol
User Service Information parameter
Low layer compatibility information element
Note Octets 6 and 7 could also be coded as: 11001101 and 11100111, signifying X.75 SLP Layer 2 protocol
and ISO 8208 Layer 3 protocol, respectively.
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbit/s)
0 1 1 1 1 1 0 0
0 0 0 0 0 1 1 1
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 0 1
0 0 0 user rate
1 0 0 x x 0 0 0
1 1 0 0 0 1 1 0
1 1 1 0 0 1 1 0
Octet 1 LLC information element identifier
2 Length (7 octets)
3 Coding standard and information transfer capability
(64 kbit/s)
4 Transfer mode and information transfer rate
(64 kbit/s)
5 Layer identification and user information layer 1
protocol (V.110 rate adaptation)
5a Synchronous; user rate
5b Intermediate rate, with/without NIC and no flow
control on Tx & Rx
6 Layer 2 identification and user information layer 2
protocol (X.25 link level)
7 Layer 3 identification and user information layer 3
protocol (X.25 packet layer)
Recommendation Q.767 101
vii) Asynchronous rates with V.110 rate adaptation
User Service Information parameter
Low layer compatibility information element
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
Octet 1 Coding standard and information transfer capability
(64 kbit/s)
2 Transfer mode and information transfer rate
(64 kbit/s)
0 1 1 1 1 1 0 0
0 0 0 0 0 1 1 1
1 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 0 1
0 1 0 user rate
0 0 0 0 0 x x 0
0 x x x x x x x
1 x . . . . . .
Octet 1 LLC information element identifier
2 Length (7 octets)
3 Coding standard and information transfer capability
(64 kbit/s)
4 Transfer mode and information transfer rate
(64 kbit/s)
5 Layer identification and user information layer 1
protocol (V.110 rate adaptation)
5a Asynchronous; user rate (user rates up to 19.2 kbit/s
possible)
5b Intermediate rate, without NIC and with/without flow
control on Tx & Rx
5c Number of stop bits, number of data bits, parity
5d Half/Full duplex, modem type
102 Recommendation Q.767
b) 3.1 kHz audio
i) 3.1 kHz audio with A/ law
User Service Information parameter
ii) Voice band data modem
User Service Information parameter
1 0 0 1 0 0 0 0
1 0 0 1 0 0 0 0
1 0 1 0 0 0 1 x
Octet 1 Coding standard and information transfer capability
(3.1 kHz audio)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
protocol (Rec. G.711 A/ law)
1 0 0 1 0 0 0 0
1 0 0 1 0 0 0 0
1 0 1 0 0 0 1 x
Octet 1 Coding standard and information transfer capability
(3.1 kHz audio)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
protocol (Rec. G.711 A/ law)
Recommendation Q.767 103
Low layer compatibility information element
c) Speech
User Service Information parameter
0 1 1 1 1 1 0 0
0 0 0 0 0 1 1 1
1 0 0 1 0 0 0 0
1 0 0 1 0 0 0 0
0 0 1 0 0 0 1 x
0 x 0 user rate
0 0 0 x x x x 0
0 x x x x x x x
1 x ......
Octet 1 LLC information element identifier
2 Length (7 octets)
3 Coding standard and information transfer capability
(3.1 kHz audio)
4 Transfer mode and information transfer rate
(64 kbit/s)
5 Layer identification and user information layer 1
protocol (G.711 A/)
5a Synchronous/asynchronous: user rate
5b Intermediate rate, with/without NIC and with/without
flow control on Tx & Rx
5c Number of stop bits, number of data bits, parity
5d Half/full duplex, modem type
1 0 0 0 0 0 0 0
1 0 0 1 0 0 0 0
1 0 1 0 0 0 1 x
Octet 1 Coding standard and information transfer capability
(speech)
2 Transfer mode and information transfer rate
(64 kbit/s)
3 Layer identification and user information layer 1
(Rec. G.711 A/ law)
104 Recommendation Q.767
4.4 Clarifications for practical interconnections
4.4.1 Start up procedures
The start up procedure for ISUP circuits is a manually controlled procedure. It is initiated by each gateway
exchange for its outgoing circuits. Bidirectional circuits are tested by both sides.
During the process of placing circuits into service, unacknowledged circuit supervision messages will most
likely be reported to maintenance systems. In order to minimize this impact, it is recommended that coordination take
place between exchanges and established procedures for placing circuit into service be followed. Lack of coordination
may result in inefficient use of exchange and maintenance resources.
Before the test itself, some exchanges, named exchanges of type A do not require anything before the test
call, and only respond to a received GRS (RSC) with a GRA (RLC/BLO) message. Other exchanges, named exchanges
of type B, do require a GRS/GRA (or RSC/RLC) cycle before the continuity check or the conversation test is
performed.
The start up procedure necessary for exchanges of type B is intended both for unidirectional and bidirectional
circuits in accordance with 4.4.1.1 and 4.4.1.2.
Possible relations are:
A - - - - - > A
A - - - - - > B
B - - - - - > A
B - - - - - > B
4.4.1.1 Initial procedure for putting the first circuits into service
a) exchange A - - - - - > exchange A
No initial procedure required
b) exchange A - - - - - > exchange B
< - - - - - GRS - - - - - >
< - - - - - GRA - - - - - >
c) exchange B - - - - - > exchange A
< - - - - - GRS - - - - - >
< - - - - - GRA - - - - - >
d) exchange B - - - - - > exchange B
< - - - - - GRS - - - - - > < - - - - - GRS - - - - - >
< - - - - - GRA - - - - - > < - - - - - GRA - - - - - >
or
< - - - - - GRS - - - - - > < - - - - - GRS - - - - - >
< - - - - - GRA - - - - - > < - - - - - GRA - - - - - >
Note It is also possible to have individual reset circuit messages. The diagrams do not intend to cover all
possible exchange of messages (see Recommendation Q.764).
Recommendation Q.767 105
4.4.1.2 Initial procedure for putting additional circuits into service
a) exchange A - - - - - > exchange A
No initial procedure required
b) exchange A - - - - - > exchange B
< - - - - - RSC - - - - - >
< - - - - - RLC - - - - - >
c) exchange B - - - - - > exchange A
< - - - - - RSC - - - - - >
< - - - - - RLC - - - - - >
d) exchange B - - - - - > exchange B
< - - - - - RSC - - - - - > < - - - - - RSC - - - - - >
< - - - - - RLC - - - - - > < - - - - - RLC - - - - - >
or
< - - - - - RSC - - - - - > < - - - - - RSC - - - - - >
< - - - - - RLC - - - - - > < - - - - - RLC - - - - - >
4.4.1.3 Test procedures
This section describes two different test procedures (named A and B) for the initial testing of circuit. As a
minimum, it is required that an international exchange can actively perform one of these test procedure and respond to
the other procedure.
Each exchange checks its own circuits. Bidirectional circuits are checked by both ends.
a) Procedure using a conversation test
< - - - -Test IAM- - - - >
< - - - - - ACM - - - - - >
< - - - - - ANM - - - - - >
Conversation test
< - - - - - REL - - - - - >
< - - - - - RLC - - - - - >
106 Recommendation Q.767
b) Procedure using the continuity check procedure
The continuity check procedure is used for the start up procedure, even if no continuity check is required
during normal operation of the circuits.
exchange A or B> - - - - - - - - - - >exchange A or B
test initiating exchange
< - - - - - CGB - - - - - >
< - - - - - CGBA - - - - >
1) < - - - - - CCR - - - - - >
2)
tone
>
|
loop
evaluation
<
|
3) If the test is OK
- - - - - - REL - - - - - >>
< - - - - - RLC - - - - - >
4) the circuit is in the idle state blocked
5) perform the CCR, REL, RLC sequence for all remaining trunks that are to be brought into service.
6)
< - - - - - CGU - - - - >
< - - - - - CGUA - - - >
7) The trunks are in service
8) If the test is not OK
9)
< - - - - COT (F) - - - >
10)
< - - - - - CCR - - - - - >
11)
tone
>
|
loop
evaluation
<
|
Recommendation Q.767 107
12) If the test is OK, continue as in 3)
13) If the test is not OK, report CIC, do not unblock trunk for outgoing traffic and continue CCR on the
trunk then continue in 5).
Note It is also possible to have individual blocking messages. The diagrams do not intend to cover all
possible exchange of messages (see Recommendation Q.764).
4.4.2 Interconnection test
4.4.2.1 Validation tests
See Recommendations Q.780, Q.784 and Q.785.
4.4.2.2 Compatibility tests
See Recommendations Q.780, Q.784 and Q.785.
4.4.2.3 Terminal to terminal tests (operational test calls)
The aim of ISDN operational test calls is to verify, before opening ISDN services between countries, that
these services are working properly from the user point of view. These calls are to be established as normal calls from
real terminals in a country, to called numbers (corresponding to ISDN or non ISDN subscribers) provided by the other
country, aiming to verify that:
calls are correctly set up and compatible called terminals are selected, or calls are correctly rejected if no
compatible called terminal exists;
the data or voice transmission is possible with a normal quality;
calls can be correctly released by the calling or called user.
4.4.3 Routing
See Recommendation E.172.
108 Recommendation Q.767
ANNEXES
(to Recommendation Q.767)
ISDN User Part of Signalling System No. 7
for international interconnections
Used conventions
sections which are not applicable are replaced with:
(this section is not applicable to the international interface)
paragraphs or sentences in a section which are not applicable are:
struck out
added sections, paragraphs or sentences are:
underlined
changed text is:
IN SMALL ITALIC CAPITALS
Contents
Annex A: Recommendation Q.761
Annex B: Recommendation Q.762
Annex C: Recommendation Q.763
Annex D: Recommendation Q.764
Annex E: Recommendation Q.730
Recommendation Q.767 109
ANNEX A
(to Recommendation Q.767)
Functional description of the ISDN User Part
of Signalling System No. 7
for international interconnections
A.1 General
The ISDN User Part is the Signalling System No. 7 protocol which provides the signalling functions required
to support basic bearer services and supplementary services for voice and non-voice applications in an integrated
services digital network.
The ISDN User Part is also suited for application in dedicated telephone and circuit switched data networks
and in analogue and mixed analogue/digital networks. In particular the ISDN User Part meets the requirements defined
by CCITT for worldwide international semiautomatic and automatic telephone and circuit switched data traffic.
The ISDN User Part is furthermore suitable for national applications. Most signalling procedures, information
elements and message types specified for international use are also required in typical national applications. Moreover,
coding space has been reserved in order to allow national administrations and recognized private operating agencies to
introduce network specific signalling messages and elements of information within the internationally standardized
protocol structure.
The ISDN User Part makes use of the services provided by the Message Transfer Part (MTP) and in some
cases by the Signalling Connection Control Part (SCCP) for the transfer of information between ISDN User Parts.
THE ISDN USER PART PROTOCOL FOR INTERNATIONAL INTERCONNECTIONS WHICH SUPPORTS THE BASIC BEARER
SERVICE IS DESCRIBED IN 3.2 AND ANNEX A TO 3.5 AND ANNEX D, AND Q.766. A GENERAL DESCRIPTION OF ISDN USER PART
SIGNALS AND MESSAGES IS PROVIDED IN 3.3 AND ANNEX B. MESSAGE FORMATS AND MESSAGE FIELD CODINGS ARE DEFINED IN
3.4 AND ANNEX C, WHILE THE SIGNALLING PROCEDURES ARE DESCRIBED IN 3.5 AND ANNEX D. RECOMMENDATION Q.766
DEALS WITH ISDN USER PART PERFORMANCE OBJECTIVES.
ISDN USER PART PROTOCOL ELEMENTS WHICH SUPPORT SUPPLEMENTARY SERVICES ARE DESCRIBED IN 3.6 AND
ANNEX E.
Note The message set, message formats and procedures specified in this version of the ISDN User Part
protocol are not in complete alignment with those of the 1984 version (Red Book). The two versions of the protocol are
therefore not compatible in all aspects.
110 Recommendation Q.767
A.2 Services supported by the ISDN User Part
The ISDN User Part protocol supports the basic bearer service, i.e. the establishment, supervision and release
of 64 kbit/s circuit switched network connections between subscriber line exchange terminations.
THE ISDN USER PART SUPPORTS THE FOLLOWING SERVICES:
BEARER SERVICES:
64 kbit/s UNRESTRICTED
SPEECH
3.1 kHz AUDIO
TELESERVICES:
TELEPHONY
TELETEX
TELEFAX GR 4
MIXED MODE
VIDEOTEX
TELEFAX GR 2/3
SUPPLEMENTARY SERVICES:
CALLING LINE IDENTIFICATION PRESENTATION (CLIP)
CALLING LINE IDENTIFICATION RESTRICTION (CLIR)
CONNECTED LINE IDENTIFICATION PRESENTATION (COLP)
CONNECTED LINE IDENTIFICATION RESTRICTION (COLR)
CLOSED USER GROUP (CUG)
USER TO USER SERVICE 1 IMPLICITLY REQUESTED (UUS1)
DIRECT DIALING IN (DDI)
MULTIPLE SUBSCRIBER NUMBER (MSN)
SUBADDRESSING (SUB)
TERMINAL PORTABILITY (TP)
Recommendation Q.767 111
A.3 Services assumed from the Message Transfer Part (MTP)
A.3.1 General
This section describes the functional interface presented by the Message Transfer Part to the ISDN User Part.
In accordance with the description techniques defined by the open system interconnection (OSI) model, information is
transferred to and from the MTP in the form of parameters carried by primitives.
The general syntax of a primitive is as follows:
where:
X designates the function providing the service (the MTP, in this case),
the generic name describes an action by X,
the specific name indicates the purpose of the primitive, i.e. whether it conveys a request for service, an
indication that service related information has been received, a response to a service request or a
confirmation that the requested service has been performed, and
the parameters contain the elements of supporting information transferred by the primitive.
X Generic name Specific name Parameter
112 Recommendation Q.767
A.3.2 Description of primitives
The following paragraphs describe the primitives used across the ISDN User Part Message Transfer Part
functional interface. The primitives together with the parameters carried by each primitive are also shown in
Table A-1/Q.767.
A.3.2.1 Transfer
The MTP-TRANSFER service primitives are used either by the ISDN User Part to access the signalling
message handling function of the Message Transfer Part or by the latter to deliver signalling message information to the
ISDN User Part.
A.3.2.2 Pause
The MTP-PAUSE primitive is sent by the Message Transfer Part to indicate its inability to transfer messages
to the destination specified as a parameter.
A.3.2.3 Resume
The MTP-RESUME primitive is sent by the Message Transfer Part to indicate its ability to resume
unrestricted transfer of messages to the destination specified as a parameter.
Recommendation Q.767 113
A.3.2.4 Status
The MTP STATUS primitive is sent by the Message Transfer Part to indicate that the signalling route to a
specific destination is congested or the ISDN user part at the destination is unavailable. The affected destination and the
congestion indication are carried as parameters (see Table A-1/Q.767) in the primitive.
TABLE A-1/Q.767
Message Transfer Part service primitives
A.4. End-to-end signalling
(This section is not applicable to the international interface.)
A.5 Future enhancements
Requirements for additional protocol capabilities, such as the ability to support new supplementary services,
will result from time to time in the need to add to or modify existing protocol elements and thus to create a new
protocol version.
Primitives
Parameters
Generic name Specific name
MTP-TRANSFER Request
Indication
OPC
DPC
SLS
SIO
INF
MTP-PAUSE Indication Affected DPC
MTP-RESUME Indication Affected DPC
MTP-STATUS Indication Affected DPC
Cause (see Note)
OPC Originating point code
DPC Destination point code
SLS Signalling link selection code
SIO Service information octet
Note The cause parameter can assume one value:
signalling network congested (level), Where level is included only if national options with congestion
priorities and multiple signalling states without congestion priorities (see Recommendation Q.704) are
implemented.
emote user unavailable
114 Recommendation Q.767
In order to ensure adequate service continuity, the insertion of a new protocol version into one part of a
network should be transparent to the remainder of the network. Compatible interworking between protocol versions is
optimized by adhering to the following guidelines when specifying a new version:
1) Existing protocol elements, i.e. procedures, messages, parameters and codes, should not be changed
unless a protocol error needs to be corrected or it becomes necessary to change the operation of the
service that is being supported by the protocol.
2) The semantics of a message, a parameter or of a field within a parameter should not be changed.
3) Established rules for the formatting and encoding messages should not be modified.
4) The addition of parameters to the mandatory part of an existing message should not be allowed. If
needed, a new message should be defined containing the desired set of existing and new mandatory
parameters.
5) A parameter may be added to an existing message as long as it is allocated to the optional part of the
message.
6) The addition of new octets to an existing mandatory fixed length parameter should be avoided. If
needed, a new optional parameter should be defined containing the desired set of existing and new
information fields.
7) The sequence of fields in an existing variable length parameter should remain unchanged. New fields
may be added at the end of the existing sequence of parameter fields. If a change in the sequence of
parameter fields is required, a new parameter should be defined.
8) The all zeros code point should be used exclusively to indicate an unallocated (spare) or insignificant
value of a parameter field. This avoids an all zeros code, sent by one protocol version as a spare value, to
be interpreted as a significant value in another version.
ANNEX B
(to Recommendation Q.767)
General function of messages and signals
THIS RECOMMENDATION DESCRIBES THE ELEMENTS OF SIGNALLING INFORMATION USED BY THE ISDN USER PART
PROTOCOL FOR INTERNATIONAL INTERCONNECTIONS AND THEIR FUNCTION. THE ENCODING OF THESE ELEMENTS, THE FORMAT
OF THE MESSAGES IN WHICH THEY ARE CONVEYED AND THEIR APPLICATION IN THE ISDN USER PART SIGNALLING PROCEDURES
ARE DESCRIBED IN 3.4 AND ANNEX C, AND 3.5 AND ANNEX D. TABLE B-1/Q.767 GIVES THE MANDATORY OR OPTIONAL
PARAMETERS IN THE ISDN USER PART MESSAGES AND TABLE B-2/Q.767 THE LIST OF ABBREVIATIONS OF THESE MESSAGES.
Recommendation Q.767 115
TABLE B-1/Q.767 (Sheet 1 of 4)
Mandatory or optional parameters in the ISDN user part messages
Bold characters means "default value is used".
M Mandatory
O Optional
Message Group
Forward
set-up
Gen
sup.
Backward
set-up
Call
supervision
Circuit supervision
Circuit grp.
supervision
Parameter field Subfield
Type
Q.763
Annex
C

IAM SAM COT ACM CON CPG ANM FOT REL RLC
CCR
RSC
BLO
UBL
BLA
UBA
SUS
RES
CGB
CGU
CGB
A-C
GUA
GRS
GRA
Message type 2.1 M M M M M M M M M M M M M M M M M
Access transport 3.2 O O O O O
Automatic congestion
level
3.3 O
Backward call
indicators
Charge indicator
Called party's status indic.
Called party's category ind.
End to end method ind.
Interworking ind.
End to end information ind.
ISDN user part ind.
Holding indicator
ISDN access indicator
Echo control device ind.
SCCP method ind.
3.4 M M O O
Called party number Odd/even indicator
Nature of address
Internal network number ind.
Numbering plan ind.
Address signals
3.7 M
116 Recommendation Q.767
TABLE B-1/Q.767 (Sheet 2 of 4)
Mandatory or optional parameters in the ISDN user part messages
Bold characters means "default value is used".
Message Group
Forward
set-up
Gen
sup.
Backward
set-up
Call
supervision
Circuit supervision
Circuit grp.
supervision
Parameter field Subfield
Type
Q.763
Annex
C

IAM SAM COT ACM CON CPG ANM FOT REL RLC
CCR
RSC
BLO
UBL
BLA
UBA
SUS
RES
CGB
CGU
CGB
A-C
GUA
GRS
GRA
Calling party number Odd/even indicator
Nature of address
Number incomplete ind.
Numbering plan ind.
Address pres. restricted ind.
Screening ind.
Address signals
3.8 O
Calling party's
category
3.9 M
Cause indicators Coding standard
Location
Cause value
3.10 O M
Circuit group
supervision
message type ind.
Type indicator 3.11 M M
CUG interlock code Network identity
Binary code
3.13 O
Connected number Odd/even indicator
Nature of address
Numbering plan ind.
Address pres. restricted ind.
Screening ind.
Address signals
3.14 O O
Recommendation Q.767 117
TABLE B-1/Q.767 (Sheet 3 of 4)
Mandatory or optional parameters in the ISDN user part messages
Bold characters means "default value is used".
Message Group
Forward
set-up
Gen
sup.
Backward
set-up
Call
supervision
Circuit supervision
Circuit grp.
supervision
Parameter field Subfield
Type
Q.763
Annex
C

IAM SAM COT ACM CON CPG ANM FOT REL RLC
CCR
RSC
BLO
UBL
BLA
UBA
SUS
RES
CGB
CGU
CGB
A-C
GUA
GRS
GRA
Continuity indicators Continuity indicators 3.16 M
Event indicators Event indicator
Event pres. restricted ind.
3.18 M
Forward call ind. National/international ind.
End to end method ind.
Interworking ind.
End to end information ind.
ISDN user part ind.
ISDN user part preference ind.
ISDN access ind.
SCCP method ind.
3.20 M
Nature of connection
ind.
Satellite ind.
Continuity check ind.
Echo control device ind.
3.23 M
Optional backward call
ind.
In-band information ind.
Call forwarding may occur ind.
3.24 O O M
Optional forward call
ind.
CUG call ind.
Connected line id. reg. ind.
3.25 O
118 Recommendation Q.767
TABLE B-1/Q.767 (Sheet 4 of 4)
Mandatory or optional parameters in the ISDN user part messages
Underlined, bold characters means "default coding is used".
Bold characters means "default value is used".
Message Group
Forward
set-up
Gen
sup.
Backward
set-up
Call
supervision
Circuit supervision
Circuit grp.
supervision
Parameter field Subfield
Type
Q.763
Annex
C

IAM SAM COT ACM CON CPG ANM FOT REL RLC
CCR
RSC
BLO
UBL
BLA
UBA
SUS
RES
CGB
CGU
CGB
A-C
GUA
GRS
GRA
Range and status Range
Status
3.27 M M M
Subsequent number Odd/even ind.
Address signals
3.32 M
Suspend/resume ind. 3.33 M
Transmission medium
requirement
3.35 M
User service
information
Coding standard
Information transfer capabil.
Transfer mode
Information transfer rate
Structure
Configuration
Establishment
Symmetry
User information protocols
3.36 O
User-to-user
indicators
Type
Service 1
Service 2
Service 3
Network discard indicator
3.37 O O
User-to-user
information
3.38 O O O O O O
Recommendation Q.767 119
TABLE B-2/Q.767
ISDN User Part message acronyms
English French Spanish
ACM
ANM
BLA
BLO
CCR
CFN
CGB
CGBA
CGU
CGUA
CMC
CMR
CMRJ
CON
COT
CPG
CRG
CQM
CQR
DRS
FAA
FAR
FOT
FRJ
GRA
GRS
IAM
INF
INR
LPA
OLM
PAM
REL
RES
RLC
RSC
SAM
SUS
UBL
UBA
UCIC
USR
ACO
REP
BLA
BLO
CCD
ICO
BLG
BGA
DBG
DGA
MAE
MAD
MAR
CON
CCP
PRG
TAX
IGD
IGR
LID
SUAC
SUDM
IOP
SURF
RZA
RZG
MIA
INF
IND
BOA
SUR
FAP
LIB
RPR
LIT
RZC
MSA
SUS
DBO
DBA
CINE
UAU
MDC
RST
AEB
BLO
PPC
CFN
BGC
ARBG
DGC
ARDG
MLC
PLM
RFA
CNX
CON
PRL
TAS
IGC
RIG
LID
FAA
PFA
INT
RFA
ARRG
RGC
MID
INF
PIN
AEB
SBC
MDP
LIB
REA
LIC
RCI
MSD
SUS
DBL
ARD
CICN
IUU
Address complete
Answer
Blocking acknowledgement
Blocking
Continuity check request
Confusion
Circuit group blocking
Circuit group blocking ack.
Circuit group unblocking
Circuit group unblocking ack.
Call modification completed
Call modification request
Call modification reject
Connect
Continuity
Call progress
Charge information
Circuit group query
Circuit group query response
Delayed release
Facility accepted
Facility request
Forward transfer
Facility rejet
Circuit group reset ack.
Circuit group reset
Initial address
Information
Information request
Loop back acknowledgement
Overload
Pass along
Release
Resume
Release complete
Reset circuit
Subsequent address
Suspend
Unblocking
Unblocking acknowledgement
Unequipped circuit identifica.
User-to-user information
120 Recommendation Q.767
B.1 Signalling messages
B.1.1 Address complete message (ACM)
A message sent in the backward direction indicating that all the address signals required for routing the call to
the called party have been received.
B.1.2 Answer message (ANM)
A message sent in the backward direction indicating that the call has been answered. In semiautomatic
working this message has a supervisory function. In automatic working this message is used in conjunction with
charging information in order to:
start metering the charge to the calling subscriber (see Recommendation Q.28), and
start measurement of call duration for international accounting purposes (see Recommendation E.260).
B.1.3 Blocking message (BLO)
A message sent only for maintenance purposes to the exchange at the other end of a circuit, to cause an
engaged condition of that circuit for subsequent calls outgoing from that exchange. When a circuit is used in the
bothway mode of operation an exchange receiving the blocking message must be capable of accepting incoming calls
on the concerned circuit unless it has also sent a blocking message. Under certain conditions, a blocking message is
also a proper response to a reset circuit message.
B.1.4 Blocking acknowledgement message (BLA)
A message sent in response to a blocking message indicating that the circuit has been blocked.
B.1.5 Call modification completed message (CMC)
(This section is not applicable to the international interface.)
B.1.6 Call modification reject message (CMRJ)
(This section is not applicable to the international interface.)
B.1.7 Call modification request message (CMR)
(This section is not applicable to the international interface.)
B.1.8 Call progress message (CPG)
A message sent in the backward direction indicating that an event has occurred during call setup which
should be relayed to the calling party.
Recommendation Q.767 121
B.1.9 Charge information message (CRG) (national use)
(This section is not applicable to the international interface.)
B.1.10 Circuit group blocking message (CGB)
A message sent to the exchange at the other end of an identified group of circuits to cause an engaged
condition of this group of circuits for subsequent calls outgoing from that exchange. An exchange receiving a circuit
group blocking message must be able to accept incoming calls on the group of blocked circuits unless it has also sent a
blocking message. Under certain conditions, a circuit group blocking message is also a proper response to a reset circuit
message.
B.1.11 Circuit group blocking acknowledgement message (CGBA)
A message sent in response to a circuit group blocking message to indicate that the requested group of
circuits has been blocked.
B.1.12 Circuit group reset message (GRS)
A message sent to release an identified group of circuits when, due to memory mutilation or other causes, it is
unknown whether for example, a release or release complete message is appropriate for each of the circuits in the
group. If at the receiving end a circuit is remotely blocked, reception of this message should cause that condition to be
removed.
B.1.13 Circuit group reset acknowledgement message (GRA)
A message sent in response to a circuit group reset message and indicating that the requested group of circuits
has been reset. The message also indicates the maintenance blocking state of each circuit.
B.1.14 Circuit group unblocking message (CGU)
A message sent to the exchange at the other end of an identified group of circuits to cause cancellation in that
group of circuits of an engaged condition invoked earlier by a blocking or circuit group blocking message.
B.1.15 Circuit group unblocking acknowledgement message (CGUA)
A message sent in response to a circuit group unblocking message to indicate that the requested group of
circuits has been unblocked.
B.1.16 Circuit group query message (CQM)
(This section is not applicable to the international interface.)
122 Recommendation Q.767
B.1.17 Circuit group query response message (CQR)
(This section is not applicable to the international interface.)
B.1.18 Confusion message (CFN)
(This section is not applicable to the international interface.)
B.1.19 Connect message (CON)
A message sent in the backward direction indicating that all the address signals required for routing the call to
the called party have been received and that the call has been answered.
B.1.20 Continuity message (COT)
A message sent in the forward direction indicating whether or not there is continuity on the preceding
circuit(s) as well as of the selected circuit to the following exchange, including verification of the communication path
across the exchange with the specified degree of reliability.
B.1.21 Continuity check request message (CCR)
A message sent by an exchange for a circuit on which a continuity check is to be performed, to the exchange
at the other end of the circuit, requesting continuity checking equipment to be attached.
B.1.22 Delayed release message (DRS) (national use)
(This section is not applicable to the international interface.)
B.1.23 Facility accepted message (FAA)
(This section is not applicable to the international interface.)
B.1.24 Facility reject message (FRJ)
(This section is not applicable to the international interface.)
B.1.25 Facility request message (FAR)
(This section is not applicable to the international interface.)
B.1.26 Forward transfer message (FOT)
A message sent in the forward direction on semiautomatic calls when the outgoing international exchange
operator wants the help of an operator at the incoming international exchange. The message will normally serve to
bring an assistance operator (see Recommendation Q.101) into the circuit if the call is automatically set up at the
exchange. When the call is completed via an operator (incoming or delay operator) at the incoming international
exchange, the message should preferably cause this operator to be recalled.
Recommendation Q.767 123
B.1.27 Information message (INF)
(This section is not applicable to the international interface.)
B.1.28 Information request message (INR)
(This section is not applicable to the international interface.)
B.1.29 Initial address message (IAM)
A message sent in the forward direction to initiate seizure of an outgoing circuit and to transmit number and
other information relating to the routing and handling of a call.
B.1.30 Loop back acknowledgement message (LPA) (national use)
(This section is not applicable to the international interface.)
B.1.31 Overload message (OLM) (national use)
(This section is not applicable to the international interface.)
B.1.32 Pass along message (PAM)
(This section is not applicable to the international interface.)
B.1.33 Release message (REL)
A message sent in either direction to indicate that the circuit is being released due to the reason (cause)
supplied and is ready to be put into the idle state on receipt of the release complete message. In case the call was
forwarded or is to be rerouted, the appropriate indicator is carried in the message together with the redirection address
and the redirecting address.
B.1.34 Release complete message (RLC)
A message sent in either direction in response to the receipt of a released message, or if appropriate to a reset
circuit message, when the circuit concerned has been brought into the idle condition.
B.1.35 Reset circuit message (RSC)
A message sent to release a circuit when, due to memory mutilation or other causes, it is unknown whether
for example, a release or a release complete message is appropriate. If, at the receiving end, the circuit is remotely
blocked, reception of this message should cause that condition to be removed.
B.1.36 Resume message (RES)
A message sent in either direction indicating that the calling or called party, after having been suspended, is
reconnected.
124 Recommendation Q.767
B.1.37 Subsequent address message (SAM)
A message that may be sent in the forward direction following an initial address message, to convey
additional called party number information.
B.1.38 Suspend message (SUS)
A message sent in either direction indicating that the calling or called party has been temporarily
disconnected.
B.1.39 Unblocking message (UBL)
A message sent to the exchange at the other end of a circuit to cancel, in that exchange, the engaged condition
of the circuit caused by a previously sent blocking or circuit group blocking message.
B.1.40 Unblocking acknowledgement message (UBA)
A message sent in response to an unblocking message indicating that the circuit has been unblocked.
B.1.41 Unequipped circuit identification code message (UCIC) (national use)
(This section is not applicable to the international interface.)
B.1.42 User-to-user information message (USR)
(This section is not applicable to the international interface.)
B.2 Signalling information
B.2.1 Access transport
Information generated on the access side of a call and transferred transparently in either direction between
originating and terminating local exchanges. The information is significant to both users and local exchanges.
B.2.2 Address presentation restricted indicator
Information sent in either direction to indicate that the address information is not to be presented to a public
network user, but can be passed to another public network. IT IS ALSO USED TO INDICATE THE NON AVAILABILITY OF THE
ADDRESS.
B.2.3 Address signal
An element of information in a network number. The address signal may indicate digit values 0 to 9, code 11
or code 12. One address signal value (ST) is reserved to indicate the end of the called party number.
Recommendation Q.767 125
B.2.4 Automatic congestion level
Information sent to the exchange at the other end of a circuit to indicate that a particular level of congestion
exists at the sending exchange.
B.2.5 Call forwarding may occur indicator
Information sent in the backward direction indicating that call forwarding may occur, depending on the
response received (or lack thereof) from the called party.
Only the default value is allowed to be sent on the international interface.
B.2.6 Call identity
(This section is not applicable to the international interface.)
B.2.7 Call reference
(This section is not applicable to the international interface.)
B.2.8 Called party number
Information to identify the called party.
B.2.9 Called partys category indicator
Information sent in the backward direction indicating the category of the called party, e.g. ordinary subscriber
or payphone.
B.2.10 Called partys status indicator
Information sent in the backward direction indicating the status of the called party, e.g. subscriber free.
B.2.11 Calling party number
Information sent in the forward direction to identify the calling party.
B.2.12 Calling party address request indicator
(This section is not applicable to the international interface.)
B.2.13 Calling party address response indicator
(This section is not applicable to the international interface.)
B.2.14 Calling party number incomplete indicator
Information sent in the forward direction indicating that the complete calling party number is not included.
Only the default value is allowed to be sent on the international interface.
126 Recommendation Q.767
B.2.15 Calling partys category
Information sent in the forward direction indicating the category of the calling party and, in case of
semiautomatic calls, the service language to be spoken by the incoming, delay and assistance operators.
B.2.16 Calling partys category request indicator
(This section is not applicable to the international interface.)
B.2.17 Calling partys category response indicator
(This section is not applicable to the international interface.)
B.2.18 Cause value
Information sent in either direction indicating the reason for sending the message (e.g. release message).
Definitions for each cause value are listed below.
a) Normal class
Cause 1 Unallocated (unassigned) number
This cause indicates that the called party cannot be reached because, although the called party number is
in a valid format, it is not currently allocated (assigned).
Cause 2 No route to specified transit network
(This cause is not applicable to the international interface.)
Cause 3 No route to destination
This cause indicates that the called party cannot be reached because the network through which the call
has been routed does not serve the destination desired. This cause is supported on a network-dependent
basis.
Cause 4 Send special information tone
This cause indicates that the called party cannot be reached for reasons that are of long-term nature and
that the special information tone should be returned to the calling party.
Cause 5 Misdialled trunk prefix
(This cause is not applicable to the international interface.)
Cause 16 Normal call clearing
This cause indicates that the call is being cleared because one of the users involved in the call has
requested that the call be cleared. Under normal situation, the source of this cause is not the network.
Cause 17 User busy
This cause is used when the called party has indicated the inability to accept another call. It is noted that
the user equipment is compatible with the call.
Recommendation Q.767 127
Cause 18 No user responding
This cause is used when a called party does not respond to a call establishment message with either an
alerting or connect indication within the prescribed period of time.
Cause 19 No answer from user (user alerted)
This cause is used when the called party has been alerted but does not respond with a connect indication
within the prescribed period of time.
Cause 21 Call rejected
This cause indicates that the equipment sending this cause does not wish to accept this call, although it
could have accepted the call because the equipment sending this cause is neither busy nor incompatible.
Cause 22 Number changed
This cause is returned to a calling party when the called number indicated by the calling party is no
longer assigned. The new called number may optionally be included in the diagnostic field. If a network
does not support this capability, cause number 1 shall be used.
Cause 27 Destination out of order
This cause indicates that the destination requested by the user cannot be reached because the interface to
the destination is not functioning correctly. The term not functioning correctly indicates that a
signalling message was unable to be delivered to the remote party; e.g. a physical layer or data link layer
failure at the remote party, user equipment off-line, etc.
Cause 28 Address incomplete
This cause indicates that the called party cannot be reached because the called party number is not in a
valid format or is not complete. This condition may be determined in the incoming international
exchange (or in the national destination network):
immediately after reception of an ST signal, or
on timeout after the last received digit.
Cause 29 Facility rejected
This cause is returned when a supplementary service requested by the user cannot be provided by the
network.
Cause 31 Normal, unspecified
This cause is used to report a normal event only when no other cause in the normal class applies.
128 Recommendation Q.767
b) Resource unavailable class
Cause 34 No circuit available
This cause indicates that there is no appropriate circuit presently available to handle the call.
Cause 38 Network out of order
This cause indicates that the network is not functioning correctly and that the condition is likely to last a
relatively long period of time, e.g. immediately re-attempting the call is not likely to be successful.
Cause 41 Temporary failure
This cause indicates that the network is not functioning correctly and that the condition is not likely to
last a long period of time, e.g. the user may wish to try another call attempt almost immediately.
Cause 42 Switching equipment congestion
This cause indicates that the switching equipment generating this cause is experiencing a period of high
traffic.
Cause 44 Requested circuit / channel not available
This cause is returned when the circuit or channel indicated by the requesting entity cannot be provided
by the other side of the interface.
Cause 47 Resource unavailable, unspecified
This cause is used to report a resource unavailable event only when no other cause in the resource
unavailable class applies.
c) Service or option not available class
Cause 50 Requested facility not subscribed
(This cause is not applicable to the international interface.)
Cause 55 Incoming calls barred within CUG
This cause indicates that although the called party is a member of the CUG for the incoming CUG call,
incoming calls are not allowed within this CUG.
Cause 57 Bearer capability not authorized
This cause indicates that the user has requested a bearer capability which is implemented by the
equipment which generated this cause but the user is not authorized to use.
Recommendation Q.767 129
Cause 58 Bearer capability not presently available
This cause indicates that the user has requested a bearer capability which is implemented by the
equipment which generated this cause but which is not available at this time.
Cause 63 Service or option not available, unspecified
This cause is used to report a service or option not available event only when no other cause in the
service or option not available class applies.
d) Service or option not implemented class
Cause 65 Bearer capability not implemented
This cause indicates that the equipment sending this cause does not support the bearer capability
requested.
Cause 69 Request facility not implemented
(This cause is not applicable to the international interface.)
Cause 70 Only restricted digital information bearer capability is available
(This cause is not applicable to the international interface.)
Cause 79 Service or option not implemented, unspecified
This cause is used to report a service or option not implemented event only when no other cause in the
service or option not implemented class applies.
e) Invalid message (e.g. parameter out of range) class
Cause 87 Called user not member of CUG
This cause indicates that the called user for the incoming CUG call is not a member of the specified
CUG or that the calling user is an ordinary subscriber calling a CUG subscriber, respectively.
Cause 88 Incompatible destination
This cause indicates that the equipment sending this cause has received a request to establish a call
which has low layer compatibility or high layer compatibility or other compatibility attributes (e.g. data
rate) which cannot be accommodated.
Cause 91 Invalid transit network selection
(This cause is not applicable to the international interface.)
Cause 95 Invalid message, unspecified
This cause is used to report an invalid message event only when no other cause in the invalid message
class applies.
130 Recommendation Q.767
f) Protocol error (e.g. unknown message) class
Cause 97 Message type nonexistent or not implemented
(This cause is not applicable to the international interface.)
Cause 99 Parameter not existent or not implemented discarded
(This cause is not applicable to the international interface.)
Cause 102 Recovery on timer expiry
This cause indicates that the procedure has been initiated by the expiry of a timer in association with
error handling procedure.
Cause 103 Parameter nonexistent or not implemented passed on
(This cause is not applicable to the international interface.)
Cause 111 Protocol error, unspecified
This cause is used to report a protocol error event only when no other cause in the protocol error class
applies.
g) Interworking class
Cause 127 Interworking, unspecified
This cause indicates that there has been interworking with a network which does not provide causes for
actions it takes; thus, the precise cause for a message which is being sent cannot be ascertained.
B.2.19 Charge indicator
Information sent in the backward direction indicating whether or not the call is chargeable.
B.2.20 Charge information request indicator (national use)
(This section is not applicable to the international interface.)
B.2.21 Charge information response indicator (national use)
(This section is not applicable to the international interface.)
B.2.22 Circuit group supervision message type indicator
Information sent in a circuit group blocking or unblocking message, indicating whether blocking
(unblocking) is maintenance oriented or hardware oriented.
B.2.23 Circuit identification code
Information identifying the physical path between a pair of exchanges.
Recommendation Q.767 131
B.2.24 Circuit state indicator
(This section is not applicable to the international interface.)
B.2.25 Closed user group call indicator
Information indicating whether or not the concerned call can be set up as a closed user group call and, if a
closed user group call, whether or not outgoing access is allowed.
B.2.26 Closed user group interlock code
Information uniquely identifying a closed user group within a network.
B.2.27 Coding standard
Information sent in association with a parameter (e.g. cause indicators) identifying the standard in which the
parameter format is described.
Only the default value is allowed to be sent on the international interface.
B.2.28 Connected number
Information sent in the backward direction to identify the connected party.
B.2.29 Connection request
(This section is not applicable to the international interface.)
B.2.30 Continuity check indicator
Information sent in the forward direction indicating whether or not a continuity check will be performed on
the circuit(s) concerned or is being (has been) performed on a previous circuit in the connection.
B.2.31 Continuity indicator
Information sent in the forward direction indicating whether or not the continuity check on the outgoing
circuit was successful. A continuity check successful indication also implies continuity of the preceding circuits and
successful verification of the path across the exchange with the specified degree of reliability.
B.2.32 Credit
(This section is not applicable to the international interface.)
132 Recommendation Q.767
B.2.33 Diagnostic
(This section is not applicable to the international interface.)
B.2.34 Echo control device indicator
Information indicating whether or not a half echo control device is included in the connection.
B.2.35 End-to-end information indicator
Information sent in either direction indicating whether or not the sending exchange has further call
information available for end-to-end transmission. In the forward direction, an indication that end-to-end information is
available will imply that the destination exchange may obtain the information before alerting the called party.
Only the default value is allowed to be sent on the international interface.
B.2.36 End-to-end method indicator
Information sent in either direction indicating the available methods, if any, for end-to-end transfer of
information.
Only the default value is allowed to be sent on the international interface.
B.2.37 Event indicator
Information sent in the backward direction indicating the type of event which caused a call progress message
to be sent to the originating local exchange.
B.2.38 Event presentation restricted indicator
Information sent in the backward direction indicating that the event should not be presented to the calling
party.
Only the default value is allowed to be sent on the international interface.
B.2.39 Extension indicator
Information indicating whether or not the associated octet has been extended.
B.2.40 Facility indicator
(This section is not applicable to the international interface.)
B.2.41 Holding indicator (national use)
(This section is not applicable to the international interface.)
Recommendation Q.767 133
B.2.42 Hold provided indicator (national use)
(This section is not applicable to the international interface.)
B.2.43 In band information indicator
Information sent in the backward direction indicating that inband information or an appropriate pattern is now
available.
B.2.44 Internal network number indicator
Information sent to the destination exchange indicating whether or not the call is allowed should the called
party number prove to be an internal network number (e.g. mobile access point).
B.2.45 Interworking indicator
Information sent in either direction indicating whether or not Signalling System No. 7 is used in all parts of
the network connection.
B.2.46 ISDN access indicator
Information sent in either direction indicating whether or not the access signalling protocol is ISDN.
B.2.47 ISDN User Part indicator
Information sent in either direction to indicate that the ISDN User Part is used in all preceding parts of the
network connection. When sent in the backward direction, the preceding parts are those towards the called party.
B.2.48 ISDN user preference indicator
Information sent in the forward direction indicating whether or not the ISDN User Part is required or
preferred in all parts of the network connection.
B.2.49 Local reference
(This section is not applicable to the international interface.)
B.2.50 Location
Information sent in either direction indicating where an event (e.g. release) was generated.
134 Recommendation Q.767
B.2.51 Malicious call identification request indicator (national use)
(This section is not applicable to the international interface.)
B.2.52 Modification indicator
(This section is not applicable to the international interface.)
B.2.53 National/international call indicator
Information sent in the forward direction indicating in the destination national network whether the call has to
be treated as an international call or as a national call.
B.2.54 Nature of address indicator
Information sent in association with an address indicating the nature of that address, e.g. ISDN international
number, ISDN national significant number, or ISDN subscriber number.
B.2.55 Numbering plan indicator
Information sent in association with a number indicating the numbering plan used for that number (e.g. ISDN
number, telex number).
Only the default value is allowed to be sent on the international interface.
B.2.56 Odd/even indicator
Information sent in association with an address, indicating whether the number of address signals contained
in the address is even or odd.
B.2.57 Original called number
(This section is not applicable to the international interface.)
B.2.58 Original redirection reason
(This section is not applicable to the international interface.)
B.2.59 Point code
(This section is not applicable to the international interface.)
B.2.60 Protocol class
(This section is not applicable to the international interface.)
Recommendation Q.767 135
B.2.61 Protocol control indicator
Information consisting of the end-to-end method indicator, the interworking indicator, the end-to-end
information indicator, the SCCP method indicator and the ISDN User Part indicator. The protocol control indicator is
contained in both the forward and backward call indicators parameter field and describes the signalling capabilities
within the network connection.
Whether a bit or a bit combination contained in the PCI has history or control characteristic, is specified in
the definitions of the individual bits or bit combinations.
B.2.62 Range
Information sent in a circuit group supervision message (e.g. circuit group blocking) to indicate the range of
circuits affected by the action in the message.
B.2.63 Recommendation indicator
(This section is not applicable to the international interface.)
B.2.64 Redirecting indicator
(This section is not applicable to the international interface.)
B.2.65 Redirecting number
(This section is not applicable to the international interface.)
B.2.66 Redirecting reason
(This section is not applicable to the international interface.)
B.2.67 Redirection counter
(This section is not applicable to the international interface.)
B.2.68 Redirection number
(This section is not applicable to the international interface.)
B.2.69 Routing label
Information provided to the message transfer part for the purpose of message routing (see Recom-
mendation Q.704, 2.2).
B.2.70 Satellite indicator
Information sent in the forward direction indicating the number of satellite circuits in the connection.
136 Recommendation Q.767
B.2.71 SCCP method indicator
Information sent in either direction indicating the available SCCP methods, if any, for end-to-end transfer of
information.
Only the default value is allowed to be sent on the international interface.
B.2.72 Screening indicator
Information sent in either direction to indicate whether the address was provided by the user or network.
B.2.73 Signalling point code (national use)
(This section is not applicable to the international interface.)
B.2.74 Solicited information indicator
(This section is not applicable to the international interface.)
B.2.75 Status
Information sent in a circuit group supervision message (e.g. circuit group blocking) to indicate the specific
circuits, within the range of circuits stated in the message, that are affected by the action specified in the message.
B.2.76 Suspend/resume indicator
Information sent in the suspend and resume messages to indicate whether suspend/resume was initiated by an
ISDN subscriber or by the network.
B.2.77 Temporary trunk blocking after release (national use)
(This section is not applicable to the international interface.)
Recommendation Q.767 137
B.2.78 Transit network selection (national use)
(This section is not applicable to the international interface.)
B.2.79 Transmission medium requirement
Information sent in the forward direction indicating the type of transmission medium required for the
connection (e.g. 64 kbit/s unrestricted, speech).
B.2.80 User service information
Information sent in the forward direction indicating the bearer capability requested by the calling party.
B.2.81 User-to-user indicators
Information sent in association with a request (or response to a request) for user-to-user signalling
supplementary service(s).
Only the default value is allowed to be sent on the international interface.
B.2.82 User-to-user information
Information generated by a user and transferred transparently through the interexchange network between the
originating and terminating local exchanges.
B.2.AA Connected line identity request indicator
Information sent in the forward direction indicating a request for the connected party number to be returned.
B.2.BB Network discard indicator
This indicator indicates that user to user information included in the call control message has been discarded
by the network.
Recommendation Q.767
138 Recommendation Q.767
ANNEX C
(to Recommendation Q.767)
Formats and codes
C.1 General
ISDN user part messages are carried on the signalling link by means of signal units the format of which is
described in Recommendation Q.703, 2.2.
The format of and the codes used in the service information octet are described in Recommendation Q.704,
14.2. The service indicator for the ISDN user part is coded 0101.
The signalling information field of each message signal unit containing an ISDN User Part message consists
of an integral number of octets and encompasses the following parts (see Figure C-1/Q.767):
a) routing label;
b) circuit identification code;
c) message type code;
d) the mandatory fixed part;
e) the mandatory variable part;
f) the optional part, which may contain fixed length and variable length parameter fields.
Note The service information octet, the routing label and circuit identification code are not included in the
SCCP user data parameter transferred between the ISDN user part and signalling connection control part.
A description of the various message parts is given in the following sections.
Recommendation Q.767 139
FIGURE C-1/Q.767
ISDN user part message parts
C.1.1 Routing label
The format and codes used for the routing label are described in Recommendation Q.704, 2.2. For each
individual circuit connection, the same routing label must be used for each message that is transmitted for that
connection.
C.1.2 Circuit identification code
The format of the circuit identification code (CIC) is shown in Figure C-2/Q.767.
Routing label
Circuit identification code
Message type code
Mandatory fixed part
Mandatory variable part
Optional part
140 Recommendation Q.767
FIGURE C-2/Q.767
Circuit identification field
The allocation of circuit identification codes to individual circuits is determined by bilateral agreement and/or
in accordance with applicable predetermined rules.
For international applications, the four spare bits of the circuit identification field are reserved for CIC
extension, provided that bilateral agreement is obtained before any increase in size is performed. For national
applications, the four spare bits can be used as required.
Allocations for certain applications are defined below :
a) 2048 kbit/s digital path
For circuits which are derived from a 2048 kbit/s digital path (Recommendations G.732 and G.734)
the circuit identification code contains in the 5 least significant bits a binary representation of the
actual number of the time slot which is assigned to the communication path.
The remaining bits in the circuit identification code are used, where necessary, to identify these
circuits uniquely among all other circuits of other systems interconnecting an originating and
destination point.
8 7 6 5 4 3 2 1
Circuit identification code
(least significant bits)
Spare
CIC
(most significant
bits)
Recommendation Q.767 141
b) 8448 kbit/s digital path
For circuits which are derived from a 8448 kbit/s digital path (Recommendations G.744 and G.747)
the circuit identification code contains in the 7 least significant bits an identfication of the circuit
which is assigned to the communication path. The codes in Table C1/Q.767 are used.
The remaining bits in the circuit identification code are used, where necessary, to identify these
circuits uniquely among all other circuits of other systems interconnecting an originating and
destination point.
TABLE C-1/Q.767
c) Frequency division multiplex (FDM) systems in networks using the 2048 kbit/s pulse code modulation
standard
For frequency division multiplex systems existing in networks that also use the 2048 kbit/s pulse
code modulation standard, the circuit identification code contains in the 6 least significant bits the
identification of a circuit within a group of 60 circuits carried by 5 basic frequency division
multiplex groups which may or may not be part of the same supergroup. The codes in Table C-
2/Q.767 are used.
The remaining bits in the circuit identification code are used, where necessary, to identify these
circuits uniquely among all other circuits of other systems interconnecting an originating and
destination point.
0 0 0 0 0 0 0 Circuit 1
0 0 0 0 0 0 1 Circuit 2
0 0 1 1 1 1 1 Circuit 32
0 1 0 0 0 0 0 Circuit 33
1 1 1 1 1 1 0 Circuit 127
1 1 1 1 1 1 1 Circuit 128
142 Recommendation Q.767
TABLE C-2/Q.767
The message type code consists of a one octet field and is mandatory for all messages. The message type code
uniquely defines the function and format of each ISDN user part message. The allocation with reference to the
appropriate descriptive section of this Recommendation is summarized in Table C-3/Q.767.
C.1.4 Formatting principles
Each message consists of a number of PARAMETERS listed and described in C.2. Each parameter has a
NAME which is coded as a single octet (see Table C-4/Q.767). The length of a parameter may be fixed or variable, and
a LENGTH INDICATOR of one octet for each parameter may be included as described below.
0 0 0 0 0 0 Unallocated
0 0 0 0 0 1 Circuit 1
1st basic (FDM) group
0 0 1 1 0 0 Circuit 12
0 0 1 1 0 1
0 0 1 1 1 0
0 0 1 1 1 1
0 1 0 0 0 0
0 1 0 0 0 1
Circuit 1
Circuit 2
Circuit 3
Unallocated
Circuit 4
2nd basic (FDM) group
0 1 1 0 0 1 Circuit 12
0 1 1 0 1 0 Circuit 1
0 1 1 1 1 1
1 0 0 0 0 0
1 0 0 0 0 1
Circuit 6
Unallocated
Circuit 7
3rd basic (FDM) group
1 0 0 1 1 0 Circuit 12
1 0 0 1 1 1 Circuit 1
1 0 1 1 1 1
1 1 0 0 0 0
1 1 0 0 0 1
1 1 0 0 1 0
1 1 0 0 1 1
Circuit 9
Unallocated
Circuit 10
Circuit 11
Circuit 12
4th basic (FDM) group
1 1 0 1 0 0 Circuit 1
1 1 1 1 1 1 Circuit 12 5th basic (FDM) group
C.1.3 Message type code
Recommendation Q.767 143
The detailed format is uniquely defined for each message type as described in C.3.
Between parameters there should be no unused (i.e. dummy) octets.
A general format diagram is shown in Figure C-3/Q.767.
1 2 3 4 5 6 7 8
T1148210-92/d14
Order of bit transmission
Order of octet
transmission
Routine label
Circuit identification code
Message type code
Mandatory parameter A
Mandatory parameter F
Pointer to parameter P
Pointer to start of optional part
Length indicator of parameter M
Pointer to parameter M
Parameter M
Length indicator of parameter P
Parameter P
Parameter name = X
Length indicator of parameter X
Parameter X
Parameter name = Z
Length indicator of parameter Z
Parameter Z
End of optional parameter field
Mandatory
fixed part
Mandatory
variable part
Optional part
FIGURE C-3/Q.767
144 Recommendation Q.767
C.1.5 Mandatory fixed part
Those parameters that are mandatory and of fixed length for a particular message type will be contained in the
mandatory fixed part. The position, length and order of the parameters is uniquely defined by the message type, thus the
names of the parameters and the length indicators are not included in the message.
C.1.6 Mandatory variable part
Mandatory parameters of variable length will be included in the mandatory variable part. Pointers are used to
indicate the beginning of each parameter. Each pointer is encoded as a single octet. The name of each parameter and the
order in which the pointers are sent is implicit in the message type. Parameter names are, therefore, not included in the
message. The details of how pointers are encoded is found in C.2.3. The number of parameters, and thus the number of
pointers is uniquely defined by the message type.
A pointer is also included to indicate the beginning of the optional part. If the message type indicates that no
optional part is allowed, then this pointer will not be present. If the message type indicates that an optional part is
possible (reflected by the presence of an end of optional parameter octet in Tables C-5 through C-28 / Q.767), but
there is no optional part included in this particular message than a pointer field containing all zeros will be used. It is
recommended that all future message types with a mandatory variable part indicate that an optional part is allowed.
All the pointers are sent consecutively at the beginning of the mandatory variable part. Each parameter
contains the parameter length indicator followed by the contents of the parameters.
If there are no mandatory variable parameters, but optional parameters are possible, the start of optional
parameters pointer (coded all 0s if no optional parameter is present and coded 0000001 if any optional parameter is
present) will be included.
C.1.7 Optional part
The optional part consists of parameters that may or may not occur in any particular message type. Both fixed
length and variable length parameters may be included. Optional parameters may be transmitted in any order. Each
optional parameter will include the parameter name (one octet) and the length indicator (one octet) followed by the
parameter contents.
C.1.8 End of optional parameters octet
If optional parameters are present and after all optional parameters have been sent, an end of optional
parameters octet containing all zeros will be transmitted.
If no optional parameter is present an end of optional parameter octet is not transmitted.
Recommendation Q.767 145
C.1.9 Order of transmission
Since all the fields consist of an integral number of octets, the formats represented as a stack of octets. The
first octet transmitted is the one shown at the top of the stack and the last is the one at the bottom (see
Figure C-3/Q.767).
Unless otherwise indicated, within each octet and subfield the bits are transmitted with the least significant bit
first.
C.1.10 Coding of spare bits
Spare bits are coded 0 unless indicated otherwise.
C.1.11 National message types and parameters
(This section is not applicable to the international interface.)
C.2. Parameter formats and codes
C.2.1 Message type codes
The encoding of the message type is shown in Table C-3/Q.767.
C.2.2 Coding of the length indicator
The length indicator field is binary coded to indicate the number of octets in the parameter content field. The
length indicated does not include the parameter name octet or the length indicator octet.
C.2.3 Coding of the pointers
The pointer value (in binary) gives the number of octets between the pointer itself (included) and the first octet
(not included) of the parameter associated with that pointer.
The pointer value all zeros is used to indicate that, in the case of optional parameters, no optional parameter is
present.
C.3 ISDN user part parameters
C.3.1 Parameter names
The parameter name codes are given in Table C-4/Q.767 together with references to the subsections in which
they are described.
146 Recommendation Q.767
TABLE C-3/Q.767
Note the format of this message is a national matter.
Message type
Reference
(table)
Code
Address complete C-5/Q.767 00000110
Answer C-6/Q.767 00001001
Blocking C-23/Q.767 00010011
Blocking acknowledgement C-23/Q.767 00010101
Call modification completed C-24/Q.767 00011101
Call modification request C-24/Q.767 00011100
Call modification rejeet C-24/Q.767 00011110
Call progress C-7/Q.767 00101100
Circuit group blocking C-25/Q.767 00011000
Circuit group blocking ack. C-25/Q.767 00011010
Circuit group query C-26/Q.767 00101010
Circuit group query response C-8/Q.767 00101011
Circuit group reset C-26/Q.767 00010111
Circuit group reset ack. C-9/Q.767 00101001
Circuit group unblocking C-25/Q.767 00011001
Circuit group unblocking ack. C-25/Q.767 00011011
Charge information see/Q.767 00110001
Confusion C-10/Q.767 00101111
Connect C-11/Q.767 00000111
Continuity C-12/Q.767 00000101
Continuity check request C-23/Q.767 00010001
Delayed release C-21/Q.767 00100111
Facility accepted C-27/Q.767 00100000
Facility reject C-13/Q.767 00100001
Facility request C.27/Q.767 00011111
Forward transfer C-21/Q.767 00001000
Information C-14/Q.767 00000100
Information request C-15/Q.767 00000011
Initial address C-16/Q.767 00000001
Loop back acknowledgement C-23/Q.767 00100100
Overload C-23/Q.767 00110000
Pass along C-28/Q.767 00101000
Release C-17/Q.767 00001100
Release complete C-18/Q.767 00010000
Reset circuit C-23/Q.767 00010010
Resume C-22/Q.767 00001110
Subsequent address C-19/Q.767 00000010
Suspend C-22/Q.767 00001101
Unblocking C-23/Q.767 00010100
Unblocking acknowledgement C-23/Q.767 00010110
Unequipped CIC C-23/Q.767 00101110
User -to user information C-20/Q.767 00101101
Reserved (used in 1984 version) 00001010
00001011
00001111
00100010
00100011
00100101
00100110
Recommendation Q.767 147
TABLE C-4/Q.767
Parameter name
Reference

Code
Access transport C.3.2 00000011
Automatic congestion level C.3.3 00100111
Backward call indicators C.3.4 00010001
Call modification indicators C.3.5 00010111
Call reference C.3.6 00000001
Called party number C.3.7 00000100
Calling party number C.3.8 00001010
Calling partys category C.3.9 00001001
Cause indicators C.3.10 00010010
Circuit group supervision message type indicator C.3.11 00010101
Circuit state indicator C.3.12 00100110
Closed user interlock code C.3.13 00011010
Connected number C.3.14 00100001
Connection request C.3.15 00001101
Continuity indicators C.3.16 00010000
End of optional parameters C.3.17 00000000
Event information C.3.18 00100100
Facility indicators C.3.19 00011000
Forward call indicators C.3.20 00000111
Information indicators C.3.21 00001111
Information request indicatos C.3.22 00001110
Nature of connection indicators C.3.23 00000110
Optional backward call indicators C.3.24 00101001
Optional forward call indicators C.3.25 00001000
Original called number C.3.26 00101000
Range and status C.3.27 00010110
Redirecting number C.3.28 00001011
Redirection information C.3.29 00010011
Redirection number C.3.30 00001100
Signalling point code C.3.31 00011110
Subsequent number C.3.32 00000101
Suspend/resume indicators C.3.33 00100010
Transmit network selection C.3.34 00100011
Transmission medium requirement C.3.35 00000010
User service information C.3.36 00011101
User-to-user indicators C.3.37 00101010
User-to-user information C.3.38 00100000
Reserved (used in 1984 version Red book)
Reserved for multi slot identifier
00010100
00011001
00011011
00011100
00011111
00100101
148 Recommendation Q.767
C.3.2 Access transport
The format of the access transport parameter field is shown in Figure C-4/Q.767.
FIGURE C-4/Q.767
Access transport parameter field
The information element is coded as described in Recommendation Q.931, 4.5. Multiple Q.931
information elements can be included within the access transport parameter. The information elements applicable
to a particular usage of the access transport parameter are dependent on, and will be determined by, the relevant
procedures.
The maximum length should only be limited by the message length as the content of the ATP will probably
evolve in the future.
C.3.3 Automatic congestion level
The format of the automatic congestion level parameter field is shown in Figure C-5/Q.763.
FIGURE C-5/Q.767
Automatic congestion level parameter field
8 7 6 5 4 3 2 1
1
:
Information element(s)
n
8 7 6 5 4 3 2 1
Automatic congestion level
Recommendation Q.767 149
The following codes are used in the automatic congestion level parameter field :
00000000 spare
00000001 congestion level 1 exceeded
00000010 congestion level 2 exceeded
} 00000011 ,to,11111111 spare
C.3.4 Backward call indicators
The format of the backward call indicators parameter field is shown in Figure C-6/Q.767.
FIGURE C-6/Q.767
Backward call indicators parameter field
The following codes are used in the backward
call indicators parameter field :
bits B A: Charge indicator
0 0 no indication
0 1 no charge
1 0 charge
1 1 spare
The interpretation of these bits depends only on the originating exchange.
bits D C: Called partys status indicator
0 0 no indication
0 1 subscriber free
1 0 connect when free, not used
1 1 spare
bits F E: Called partys category indicator
0 0 no indication
0 1 ordinary subscriber
1 0 payphone
1 1 spare
8 7 6 5 4 3 2 1
1 H G F E D C B A
2 P O N M L K J I
150 Recommendation Q.767
bits H G: End-to-end method indicator (Note)
0 0 no end-to-end method available (only link-by-link method available)
0 1 pass along method available, not used
1 0 SCCP method available, not used
1 1 pass along and SCCP methods available, not used
bit I: Interworking indicator (Note)
0 no interworking encountered
1 interworking encountered
bit J: End-to-end information indicator (Note)
0 no end-to-end information available
1 end-to-end information available, not used
bit K: ISDN User Part indicator (Note)
0 ISDN User Part not used all the way
1 ISDN User Part used all the way
bit L: Holding indicator (national use)
0 holding not requested
1 holding requested, not used
bit M: ISDN access indicator
0 terminating access non-ISDN
1 terminating access ISDN
bit N: Echo control device indicator
0 incoming half echo control device not included
1 incoming half echo control device included
bits P O: SCCP method indicator
0 0 no indication
0 1 connectionless method available, not used
1 0 connection oriented method available, not used
1 1 connectionless and connection oriented methods available, not used
Note Bits G K and O P constitute the protocol control indicator.
C.3.5 Call modification indicators
(This section is not applicable to the international interface.)
C.3.6 Call reference
(This section is not applicable to the international interface.)
Recommendation Q.767 151
C.3.7 Called party number
The format of the called party number parameter field is shown in Figure C-9/Q.767.
FIGURE C-9/Q.767
Called party number parameter field
The following codes are used in the subfields of the called party number parameter field:
a) Odd/even indicator
0 even number of address signals
1 odd number of address signals
b) Nature of address indicator
0000000 spare
0000001 subscriber number, not used
0000010 spare, reserved for national use, not used
0000011 national (significant) number
0000100 international number

0000101
to
1101111
spare

1110000
to
1111110
reserved for national use, not used
1111111 spare
8 7 6 5 4 3 2 1
1
Odd/
even
Nature of address indicator
2
INN
ind.
Numbering
plan
Spare
3
2nd address
signal
1st address
signal
:
n
Filler
(if necessary)
n-th address
signal
152 Recommendation Q.767
c) Internal network number indicator (INN ind.)
0 routing to internal network number allowed
1 routing to internal network number not allowed
d) Numbering plan indicator
000 spare
001 ISDN (Telephony) numbering plan (Recommendation E.164, E.163)
010 spare
011 Data numbering plan (Recommendation X.121), not used
100 Telex numbering plan (Recommendation F.69), not used
101 reserved for national use, not used
110 reserved for national use, not used
111 spare
e) Address signal
0000 digit 0
0001 digit 1
0010 digit 2
0011 digit 3
0100 digit 4
0101 digit 5
0110 digit 6
0111 digit 7
1000 digit 8
1001 digit 9
1010 spare
1011 code 11
1100 code 12
1101 spare
1110 spare
1111 ST
The most significant address signal is sent first. Subsequent address signals are sent in successive 4-
bit fields.
f) Filler
In case of an odd number of address signals, the filler code 0000 is inserted after the last address
signal.
C.3.8 Calling party number
The format of the calling party number parameter field is shown in Figure C-10/Q.767:
Recommendation Q.767 153
Note When the address presentation restricted indicator
indicates address not available, octets 3 to n are omitted.
FIGURE C-10/Q.767
Calling party number parameter field
The following codes are used in the calling party number parameter field:
a) Odd/even indicator:
See C.3.7 a).
b) Nature of address indicator
0000000 spare
0000001 subscriber number, not used
0000010 spare, reserved for national use, not used
0000011 national (significant) number, not used
0000100 international number

0000101
to
1101111
spare

1110000
to
1111110
reserved for national use, not used
1111111 spare
Note Other types of nature of address indications (e.g. transit exchange identity) are for further study.
8 7 6 5 4 3 2 1
1
Odd/
even
Nature of address indicator
2
NI
ind.
Numbering
plan
Presentat.
Restriction
Screening
indicator
3
2nd address
signal
1st address
signal
:
n
Filler
(if necessary)
n-th address
signal
154 Recommendation Q.767
c) Calling party number incomplete indicator (NI)
0 complete
1 incomplete, not used
d) Numbering plan indicator
See C.3.7 d).
e) Address presentation restricted (Pres. Restric.) indicator
00 presentation allowed
01 presentation restricted
10 address not available (Note), not used
11 spare
Note When the address is unavailable, the subfields in items a), b), c) and d) are coded with 0's.
f) Screening indicator
00 reserved (Note), not used
01 user provided, verified and passed
10 reserved (Note), not used
11 network provided
Note Code 00 and 10 are reserved for "user provided, not verified" and user provided, verified and failed
respectively.
g) Address signal
0000 digit 0
0001 digit 1
0010 digit 2
0011 digit 3
0100 digit 4
0101 digit 5
0110 digit 6
0111 digit 7
1000 digit 8
1001 digit 9
1010 spare
1111 code 11
1100 code 12

1101
to
1111
spare
h) Filler
See C.3.7 f).
Recommendation Q.767 155
C.3.9 Calling partys category
The format of the calling partys category parameter field is shown in Figure C-11/Q.767.
FIGURE C-11/Q.767
Calling partys category parameter field
The following codes are used in the calling partys category parameter field:
00000000 calling partys category unknown at this time not used
00000001 operator, language French
00000010 operator, language English
00000011 operator, language German
00000100 operator, language Russian
00000101 operator, language Spanish

00000110
00000111
00001000
available to Administrations for
selecting a particular language
by mutual agreement
00001001 reserved (see Recommendation Q.104) (Note), not used
00001010 ordinary calling subscriber
00001011 calling subscriber with priority
00001100 data call (voice band data)
00001101 test call
00001110 spare
00001111 payphone

00010000
to
11011111
spare

11100000
to
11111110
reserved for national use, not used
11111111 spare
Note In national networks code 00001001 may be used to indicate that the calling party is a national
operator.
8 7 6 5 4 3 2 1
Calling partys category
156 Recommendation Q.767
C.3.10 Cause indicators
The format of the cause indicators parameter field is shown in Figure C-12/Q.767.
FIGURE C-12/Q.767
Cause indicator parameter field
The following codes are used in the subfields of the cause indicators parameter field:
a) Extension indicator (ext)
0 octet continues through the next octet (e.g. octet 1 to 1a), not used
1 last octet
b) Coding standard
00 CCITT standard, as described below
01 reserved for other international standards (Note), not used
10 national standard (Note), not used
11 standard specific to identified location (Note), not used
Note These other coding standards should be used only when the desired cause cannot be
represented with the CCITT standard.
c) Location
0000 user
0001 private network serving the local user, not used
0010 public network serving the local user, not used
0011 transit network
0100 public network serving the remote user
0101 private network serving the remote user
0111 international network
1010 beyond an interworking point, all other values are reserved.
Note Depending on the location of the users, the public network serving the local user may be the same
network serving the remote user. Rules for coding the location field are defined in Recommendation Q.931
Annex J.
8 7 6 5 4 3 2 1
1 Ext |
Coding
standard
Spare Location
2 Ext | Cause value
Recommendation Q.767 157
d) Recommendation
(This section is not applicable to the international interface.)
e) Cause value
The cause value is divided into two fields, a class (bits 5 through 7) and a value within a class (bits 1
through 4). The decimal equivalent of the cause value is shown in brackets beside the cause value.
Class 000 and 001 normal event:
0000001 (1) unallocated (unassigned) number
0000010 (2) no route to specified transit network (national use), not used
0000011 (3) no route to destination
0000100 (4) send special information tone
0000101 (5) misdialled trunk prefix, not used
0010000 (16) normal call clearing
0010001 (17) user busy
0010010 (18) no user responding
0010011 (19) no answer from user (user alerted)
0010101 (21) call rejected
0010110 (22) number changed
0011011 (27) destination out of order
0011100 (28) address incomplete
0011101 (29) facility rejected
0011111 (31) normal unspecified
Class 010 resource unavailable:
0100010 (34) no circuit available
0100110 (38) network out of order
0101001 (41) temporary failure
0101010 (42) switching equipment congestion
0101100 (44) requested channel not available
0101111 (47) resource unavailable unspecified
Class 011 service or option not available:
0110010 (50) requested facility not subscribed, not used
0110111 (55) incoming calls barred within CUG
0111001 (57) bearer capability not authorized
0111010 (58) bearer capability not presently available
0111111 (63) service/option not available unspecified
Class 100 service or option not implemented:
1000001 (65) bearer capability not implemented
1000101 (69) requested facility not implemented, not used
1000110 (70) only restricted digital information bearer capability is available, not used
1001111 (79) service or option not implemented unspecified
158 Recommendation Q.767
Class 101 invalid mesage (e.g. parameter out of range):
1010111 (87) called user not member of CUG
1011000 (88) incompatible destination
1011011 (91) invalid transit network selection (national use), not used
1011111 (95) invalid message unspecified
Class 110 Protocol error (e.g. unknown message):
1100001 (97) message type non existent or not implemented, not used
1100011 (99) parameter nonexistent or not implemented - discarded, not used
1100110 (102) recovery on timer expiry
1100111 (103) parameter nonexistent or not implemented - passed on, not used
1101111 (111) protocol error unspecified
Class 111 interworking:
1111111 (127) interworking unspecified
f) Diagnostic
(This section is not applicable to the international interface.)
C.3.11 Circuit group supervision message type indicator
The format of the circuit group supervision message type indicator parameter field is shown in
Figure C-14/Q.767.
FIGURE C-14/Q.767
Circuit group supervision message type parameter field
The following codes are used in the circuit group supervision message type indicator parameter field:
bits B A: Type indicator
0 0 maintenance oriented
0 1 hardward failure oriented
1 0 reserved for national use (used in 1984 version), not used
1 1 spare
bits C H: Spare
8 7 6 5 4 3 2 1
H G F E D C B A
Recommendation Q.767 159
C.3.12 Circuit state indicator
(This section is not applicable to the international interface.)
C.3.13 Closed user group interlock code
The format of the closed user group interlock code parameter field is shown in Figure C-16/Q.767.
FIGURE C-16/Q.767
Closed user group interlock code
The following codes are used in the subfields of the closed user group interlock code parameter field:
a) Network identity (NI) (octets 1 and 2)
Each digit is coded in the binary coded decimal representation from 0 to 9.
If the first digit of this field is coded 0 or 9, the telephony country code (TCC) follows in the second
to fourth NI digits (the most significant TCC digit is in the 2nd NI digit). If the TCC is one or two
digits long, the excess digit(s) is inserted with the code for RPOA or network identification, if
necessary. If octet 2 is not required, it is coded all 0.
Coding of the first digit as 1 or 8 is excluded:
If the first digit is not 0, 9, 1 or 8 this field contains a data network identification code (DNIC) as
defined in Recommendation X.121.
b) Binary code (octets 3 and 4)
A code allocated to a closed user group administered by a particular ISDN or data network. Bit 8 of
octet 3 is the most significant and bit 1 of octet 4 is the least significant.
Only international interlock codes shall be used.
8 7 6 5 4 3 2 1
1 1st NI digit 2nd NI digit
2 3rd NI digit 4
th
NI digit
3
Binary code
4
160 Recommendation Q.767
C.3.14 Connected number
The format of the connected number parameter field corresponds to the format shown in Figure C-17/Q.767.
Note When the address presentation restricted indicator
indicates address not available, octets 3 to n are omitted.
FIGURE C-17/Q.767
Connected number parameter field
The following codes are used in the subfields of the connected number parameter field:
a) Odd/even indicator
0 even number of address signals
1 odd number of address signals
b) Nature of address indicator
0000000 spare
0000001 subscriber number, not used
0000010 spare, reserved for national use, not used
0000011 national (significant) number, not used
0000100 international number

0000101
to
1101111
spare

1110000
to
1111110
reserved for national use, not used
1111111 spare
8 7 6 5 4 3 2 1
1
Odd/
even
Nature of address indicator
2 Spare
Numbering
plan
Presentat.
restriction
Screening
indicator
3
2nd address
signal
1st address
signal
:
n
Filler
(if necessary)
n-th address
signal
Recommendation Q.767 161
c) Numbering plan indicator
000 spare
001 ISDN (Telephony) numbering plan (Recommandations E.164 and E.163)
010 spare
011 Data numbering plan (Recommendation X.121), not used
100 Telex numbering plan (Recommendation F.69), not used
101 reserved for national use, not used
110 reserved for national use, not used
111 spare
d) Address presentation restricted (Pres. Restric.) indicator
00 presentation allowed
01 presentation restricted
10 address not available (Note)
11 spare
Note When the address is unavailable, the subfields in items a), b) and c) are coded with 0's.
e) Screening indicator: see C.3.8 f)
f) Address signal: see C.3.8 g)
g) Filler: see C.3.7 h).
C.3.15 Connection request
(This section is not applicable to the international interface.)
C.3.16 Continuity indicators
The format of the continuity indicators parameter field is shown in Figure C-19/Q.767.
FIGURE C-19/Q.767
Continuity indicators parameter field
The following codes are used in the continuity indicators parameter field:
bit A: Continuity indicator
0 continuity check failed
1 continuity check successful
bits B-H: Spare
8 7 6 5 4 3 2 1
H G F E D C B A
162 Recommendation Q.767
C.3.17 End of optional parameters indicator
The last optional parameter field of a message is followed by the end of optional parameters indicator, which
occupies a one octet field containing all zeros.
C.3.18 Event information
The format of the event information parameter field is shown in Figure C-20/Q.767.
FIGURE C-20/Q.767
Event information parameter field
The following codes are used in the forward call indicators parameter field:
bits G F E D C B A: Event indicator
0 0 0 0 0 0 0 spare
0 0 0 0 0 0 1 ALERTING
0 0 0 0 0 1 0 PROGRESS
0 0 0 0 0 1 1 in-band information or an appropriate pattern is now available
0 0 0 0 1 0 0 call forwarded on busy, not used
0 0 0 0 1 0 1 call forwarded on no reply, not used
0 0 0 0 1 1 0 call forwarded unconditional, not used

0 0 0 0 1 1 1
to
1 1 1 1 1 1 1
spare
bit H: Event presentation restricted indicator
0 no indication
1 presentation restricted, not used
C.3.19 Facility indicator
(This section is not applicable to the international interface.)
8 7 6 5 4 3 2 1
H G F E D C B A
Recommendation Q.767 163
C.3.20 Forward call indicators
The format of the forward call indicators parameter field is shown in Figure C-22/Q.767.
FIGURE C-22/Q.767
Forward call indicators parameter field
The following codes are used in the forward call indicators parameter field:
bit A: National/international call indicator
0 call to be treated as a national call
1 call to be treated as an international call
This bit can be set to any value in the country of origin. In the international network this bit is not checked. In
the destination country, calls from the international network will have this bit set to 1.
bits C B: End-to-end method indicator (Note)
0 0 no end-to-end method available (only link-by-link method available)
0 1 pass along method available, not used
1 0 SCCP method available, not used
1 1 pass along and SCCP methods available, not used
bit D: Interworking indicator (Note)
0 no interworking encountered (No. 7 signalling all the way)
1 interworking encountered
bit E: End-to-end information indicator (Note)
0 no end-to-end information available
1 end-to-end information available, not used
bit F: ISDN user part indicator (Note)
0 ISDN user part not used all the way
1 ISDN user part used all the way
bits H G: ISDN user part preference indicator
0 0 ISDN user part preferred all the way
0 1 ISDN user part not required all the way
1 0 ISDN user part required all the way
1 1 spare
8 7 6 5 4 3 2 1
1 H G F E D C B A
2 P O N M L K J I
164 Recommendation Q.767
bit I: ISDN access indicator
0 originating access non-ISDN
1 originating access ISDN
bits K J : SCCP method indicator
0 0 no indication
0 1 connection method available, not used
1 0 connection oriented method available, not used
1 1 connectionless and connection oriented methods available, not used
bit L: Spare
bits M-P: Reserved for national use
Note Bits B-F and J-K constitute the protocol control indicator.
C.3.21 Information indicators
(This section is not applicable to the international interface.)
C.3.22 Information request indicators
(This section is not applicable to the international interface.)
C.3.23 Nature of connection indicators
The format of the nature of connection indicators parameter field is shown in Figure C-25/Q.767.
FIGURE C-25/Q.767
Nature of connection indicators parameter field
The following codes are used in the nature of connection indicators parameter field:
bits B A: Satellite indicator
0 0 no satellite circuit in the connection
0 1 one satellite circuit in the connection
1 0 two satellite circuits in the connection
1 1 spare
bits D C: Continuity check indicator
0 0 continuity check not required
0 1 continuity check required on this circuit
1 0 continuity check performed on a previous circuit
1 1 spare
8 7 6 5 4 3 2 1
H G F E D C B A
Recommendation Q.767 165
bit E: Echo control device indicator
0 outgoing half echo control device not included
1 outgoing half echo control device included
bits F-H: Spare
C.3.24 Optional backward call indicators
The format of the optional backward call indicators parameter field is shown in Figure C-26/Q.767.
FIGURE C-26/Q.767
Optional backward call indicators parameter field
The following codes are used in the optional backward call indicators parameter field:
bit A: In-band information indicator
0 no indication
1 in-band information or an appropriate pattern is now available
bit B: Call forwarding may occur indicator
0 no indication
1 call forwarding may occur, not used
bits C-D: Spare
bits E-H:Reserved for national use, not used
C.3.25 Optional forward call indicators
The format of the optional forward call indicators parameter field is shown in Figure C-27/Q.767.
FIGURE C-27/Q.767
Optional forward call indicators parameter field
8 7 6 5 4 3 2 1
H G F E D C B A
8 7 6 5 4 3 2 1
H G F E D C B A
166 Recommendation Q.767
The following codes are used in the optional forward call indicators parameter field:
bits B A: Closed user group call indicator
0 0 non-CUG call
0 1 spare
1 0 closed user group call, outgoing access allowed
1 1 closed user group call, outgoing access not allowed
bit C-G: Spare
bit H: Connected line identity request indicator
0 not requested
1 requested
C.3.26 Original called number
(This section is not applicable to the international interface.)
C.3.27 Range and status
The format of the range and status parameter field is shown in Figure C-29/Q.767.
FIGURE C-29/Q.767
Range and status parameter field
8 7 6 5 4 3 2 1
1 Range
2
Status
n
Recommendation Q.767 167
The following codes are used in the subfields of the range and status parameter field:
a) Range
A number in pure binary representation ranging from 1 to 255. Range code 0 indicates absence of
the status field. The number represented by the range code +1 indicates the range of circuits affected
by the message.
b) Status
THE STATUS SUBFIELD CONTAINS FROM 2 TO 256 STATUS BITS NUMBERED FROM 0 TO
255. Status bit 0 is located in bit position 1 of the first status subfield octet. Other status bits follow
in numerical order. The number of relevant status bits in a given status subfield is equal to range +1.
Each status bit is associated with a circuit identification code such that status bit n is associated with
circuit identification code m+n, where m is the circuit identification code contained in the message.
The status bits are coded as follows :
in circuit group blocking messages
0 no indication
1 blocking
in circuit group blocking acknowledgement messages
0 no indication
1 blocking acknowledgement
in circuit group unblocking messages
0 no indication
1 unblocking
in circuit group unblocking acknowledgement messages
0 no indication
1 unblocking acknowledgement
in circuit group reset acknowledgement messages
0 not blocked for maintenance reasons
1 blocked for maintenance reasons
The number of circuits affected by a group supervision message is limited to 32 or less. For the group reset
and query messages this requires that the range value be 31 or less. For the group blocking and unblocking messages the
range value may be up to 255, but the number of status bits set to 1 must be 32 or less.
For the group blocking, unblocking and reset messages, range code 0 is reserved.
168 Recommendation Q.767
C.3.28 Redirecting number
(This section is not applicable to the international interface.)
C.3.29 Redirection information
(This section is not applicable to the international interface.)
C.3.30 Redirection number
(This section is not applicable to the international interface.)
C.3.31 Signalling point code (national use)
(This section is not applicable to the international interface.)
C.3.32 Subsequent number
The format of the subsequent number parameter field is shown in Figure C-32/Q.767.
FIGURE C-32/Q.767
Subsequent number parameter field
The following codes are used in the subfields of the subsequent number parameter field:
a) Odd/even indicator: see C.3.7 a)
b) Address signal: see C.3.7 e)
c) Filler: see C.3.7 f).
8 7 6 5 4 3 2 1
1
Odd/
even
Spare
2
2nd address
signal
1st address
signal
n
Filler
(if necessary)
n-th address
signal
Recommendation Q.767 169
C.3.33 Suspend/resume indicators
The format of the suspend/resume indicators parameter field is shown in Figure C-33/Q.767.
FIGURE C-33/Q.767
Suspend/resume indicators parameter field
The following codes are used in the suspend/resume indicators parameter field:
bit A: Suspend/resume indicator
0 ISDN subscriber initiated
1 network initiated
bits B-H: Spare
C.3.34 Transit network selection (national use)
(This section is not applicable to the international interface.)
8 7 6 5 4 3 2 1
H G F E D C B A
170 Recommendation Q.767
C.3.35 Transmission medium requirement
The format of the transmission medium requirement parameter field is shown in Figure C-35/Q.767.
FIGURE C-35/Q.767
Transmission medium requirement parameter field
The following codes are used in the transmission medium requirement parameter field.
00000000 speech
00000001 spare
00000010 64 kbit/s unrestricted
00000011 3.1 kHz audio
00000100 alternate speech (service 2)/64 kbit/s unrestricted (service 1) (Note 1), not used
00000101 alternate 64 kbit/s unrestricted (service 1)/speech (service 2) (Note 2), not used
00000110 spare
00000111 reserved for 2 64 kbit/s unrestricted, not used
00001000 reserved for 384 kbit/s unrestricted, not used
00001001 reserved for 1536 kbit/s unrestricted, not used
00001010 reserved for 1920 kbit/s unrestricted, not used

00001011
to
11111111
spare
Note 1 The initial mode is speech.
Note 2 The initial mode is 64 kbit/s unrestricted.
8 7 6 5 4 3 2 1
Transmission medium requirement
Recommendation Q.767 171
C.3.36 User service information
The format of the user service information parameter field is shown in Figure C-36/Q.767. This format is the
same as the bearer capability information element from Recommendation Q.931 and not all capabilities coded here are
supported at this time. More detailed information on the use of the User service Information is given in 4.3 of
Rec. Q.767.
Note 1 Octet 2a is omitted if default values apply to all fields of octets 2a
and 2b.
Note 2 Octet 2b is omitted if default values apply to all fields of octet 2b.
Note 3 Octets 3, 4, 5 or any combination of these octets may be omitted.
Octet 3 may be extended as described in C.3.36 k).
FIGURE C-36/Q.767
User service information parameter field
The following codes are used in the subfields of the user service information parameter field:
a) Extension indicator (ext)
0 octet continues through the next octet (e.g. octet 2 to 2a, 2a to 2b, 3 to 3a)
1 last octet
8 7 6 5 4 3 2 1
1
Ext.
Coding
standard
Information transfer
capability
2
Ext.
Transfer
mode
Information transfer
rate
2
a
Ext. Structure Configuration Establishment
2b
Ext. Symmetry
Information transfer rate
(destination to origination)
3
Ext. Layer ident.
User information
Layer 1 protocol
4
Ext. Layer ident.
User information
Layer 2 protocol
5
Ext. Layer ident.
User information
Layer 3 protocol
172 Recommendation Q.767
b) Coding standard
00 CCITT standardized coding as described below
01 reserved for other international standards (Note)
10 national standard (Note)
11 standard defined for the network (either public or private) present on the network side of the
interface (Note)
Note These other coding standards should only be used when the desired bearer capability cannot
be represented with the CCITT standardized coding.
c) Information transfer capability
00000 speech
01000 unrestricted digital information
01001 restricted digital information
10000 3.1 kHz audio
10001 7 kHz audio
11000 video
All other values are reserved.
d) Transfer mode
00 circuit mode
10 packet mode
All other values are reserved.
e) Information transfer rate (octets 2 and 2b) (Note 1)
00000 This code shall be used for packetmode calls
10000 64 kbit/s
10001 2 64 kbit/s (Note 2)
10011 384 kbit/s
10101 1536 kbit/s
10111 1920 kbit/s
All other values are reserved.
Note 1 When octet 2b is omitted, the bearer capability is bidirectional symmetric at the
information transfer rate specified in octet 2. When octet 2b is included, the information rate in octet
2 refers to the origination to destination direction.
Note 2 For this case, the coding of octets 1 and 2a refers to both 64 kbit/s circuits.
f) Structure
000 default (Note 1)
001 8 kHz integrity (Note 2)
100 service data unit integrity
111 unstructured
All other values are reserved.
Recommendation Q.767 173
Note 1 If octet 2a is omitted, or the structure field is coded 000, then the value of the structure
attribute is according to the following :
Note 2 When the information transfer rate 2 64 kbit/s is used, 8 kHz integrity with restricted
differential time delay (RDTD) is offered.
g) Configuration
00 point-to-point
All other values are reserved. If omitted, the configuration is assumed to be point-to-point.
h) Establishment
00 demand
All other values are reserved. If omitted, the establishment is assumed to be demand.
i) Symmetry
00 bidirectional symmetric
All other values are reserved. If omitted, the symmetry is assumed to be bidirectional symmetric.
j) Layer identification
00 reserved
01 user information layer 1 protocol
10 user information layer 2 protocol
11 user information layer 3 protocol
Note Bits 5-1 of the same octet represent the corresponding identification as per points k), l) and
m) below. If octet 3, 4 or 5 is omitted, the corresponding user information protocol is assumed to be
undefined.
Transfer mode Transfer capability Structure
circuit speech 8 kHz integrity
circuit unrestricted digital 8 kHz integrity
circuit restricted digital 8 kHz integrity
circuit audio 8 kHz integrity
circuit video 8 kHz integrity
packet unrestricted digital service data unit integrity
174 Recommendation Q.767
k) User information layer 1 protocol identification
00001 CCITT standardized rate adaption V.110/X.30. This implies the presence of octet 3a defined in
C.3.36 k) 1), and optionally octets 3b, 3c and 3d defined in C.3.36 k) 2) below.
00010 Recommendation G.711 law
00011 Recommendation G.711 A law
00100 Recommendation G.721 32 kbit/s ADPCM and Recommendation I.460
00101 Recommendations G.722 and G.724 for 7 kHz audio
00110 Recommendation G.735 for 384 kbit/s video
00111 non-CCITT standardized rate adaption. This implies the presence of octet 3a, and optionally 3b,
3c and 3d. The use of this codepoint indicates that the user rate specified in octet 3a is defined
in accordance with the non-CCITT standardized rate adaption scheme. Additionally, octets 3b,
3c and 3d, if present, are defined consistent with the specified rate adaption.
01000 CCITT standardized rate adaption V.120. This implies the presence of octet 3a defined in
C.3.36 k) 1), octet 3b defined in C.3.36 k) 3), and optionally octets 3c and 3d defined in
C.3.36 k) 2) below.
01001 CCITT standardized rate adaption X.31 HDLC flag stuffing.
All other values are reserved.
Note Octet 3 shall be omitted if the transfer mode is "circuit mode", the information transfer
capability is "unrestricted digital information" or "restricted digital information" and the user
information layer 1 protocol is not to be identified to the network; octet 3 may be omitted if the
transfer mode is "packetmode"; otherwise octet 3 shall be present.
1) Octet 3a for layer 1 rate adaption (see Figure C-37/Q.767)
FIGURE C-37/Q.767
Basic layer 1 rate adaption fields
8 7 6 5 4 3 2 1
3a Ext.
Synch/
asynch
Negot. User rate
Recommendation Q.767 175
The synchronous/asynchronous indicator is coded:
0 synchronous
1 asynchronous
Octets 3b to 3d may be omitted in case of synchronous user rates.
The negotiation indicator is coded:
0 in-band negotiation not possible
1 in-band negotiation possible
Note See Recommendations V.110 and X.30
The user rate is coded:
00000 rate indicated by E-bits Rec. I.460
00001 0.6 kbit/s Recs. V.6 and X.1
00010 1.2 kbit/s Rec. V.6
00011 2.4 kbit/s Recs. V.6 and X.1
00100 3.6 kbit/s Rec. V.6
00101 4.8 kbit/s Recs. V.6 and X.1
00110 7.2 kbit/s Rec. V.6
00111 8.0 kbit/s Rec. I.460
01000 9.6 kbit/s Recs. V.6 and X.1
01001 14.4 kbit/s Rec. V.6
01010 16.0 kbit/s Rec. I.460
01011 19.2 kbit/s Rec. V.6
01100 32.0 kbit/s Rec. I.460
01110 48.0 kbit/s Recs. V.6 and X.1
01111 56.0 kbit/s Rec. V.6
10101 0.1345 kbit/s Rec. X.1
10110 0.100 kbit/s Rec. X.1
10111 0.075/1.2 kbit/s Recs. V.6 and X.1 (Note)
11000 1.2/0.075 kbit/s Recs. V.6 and X.1 (Note)
11001 0.050 kbit/s Recs. V.6 and X.1
11010 0.075 kbit/s Recs. V.6 and X.1
11011 0.110 kbit/s Recs. V.6 and X.1
11100 0.150 kbit/s Recs. V.6 and X.1
11101 0.200 kbit/s Recs. V.6 and X.1
11110 0.300 kbit/s Recs. V.6 and X.1
11111 12 kbit/s Recs. V.6 and X.1
All other values are reserved.
Note The first rate is the transmit rate in the forward direction of the call. The second rate is the
transmit rate in the backward direction of the call.
176 Recommendation Q.767
2) Octets 3b, 3c and 3d for Recommendations V.110/X.30 rate adaption (see Figure C-38/Q.767)
Note Octets 3c and 3d may be omitted.
FIGURE C-38/Q.767
Recommendation V.110/X.30 rate adaption extension fields
Intermediate rate indicator is coded:
00 not used
01 8 kbit/s
10 16 kbit/s
11 32 kbit/s
Network independent clock (NIC) on transmission (TX) indicator is coded:
0 not required to send data with NIC
1 required to send data with NIC
Note Refers to transmission in the forward direction of the call, see Recommendations V.110 and
X.30.
Network independent clock (NIC) on reception (Rx) indicator is coded :
0 cannot accept data with NIC (i.e. sender does not support this optional procedure)
1 can accept data with NIC (i.e. sender does support this optional procedure)
Note Refers to transmission in the backward direction of the call, see Recommendations V.110
and X.30.
8 7 6 5 4 3 2 1
3b Ext.
Intermediate
rate
NIC
on Tx
NIC
on Rx
Flow
cont.
on Tx
Flow
cont.
on Rx
Spare
3c Ext.
Number of
stop bits
Number of
data bits
Parity
3d Ext.
Duplex
mode
Modem type
Recommendation Q.767 177
Flow control on transmission (Tx) indicator is coded:
0 not required to send data with flow control mechanism
1 required to send data with flow control mechanism
Note Refers to transmission in the forward direction of the call, see Recommendations V.110
and X.30.
Flow control on reception (Rx) indicator is coded:
0 cannot accept data with flow control mechanism (i.e. sender does not support this optional
procedure)
1 can accept data with flow control mechanism (i.e. sender does support this optional
procedure)
Note See Recommendations V.110 and X.30.
Number of stop bits indicator is coded:
00 not used
01 1 bit
10 1.5 bits
11 2 bits
Number of data bits indicator, including parity bit if present, is coded :
00 not used
01 5 bits
10 7 bits
11 8 bits
Parity indicator is coded:
000 odd
010 even
011 none
100 forced to 0
101 forced to 1
All other values are reserved.
Duplex mode indicator is coded:
0 half duplex
1 full duplex
modem type indicator is coded according to network specific rules.
178 Recommendation Q.767
3) Octet 3b for Recommendation V.120 rate adaption (see Figure C-39/Q.767)
Note Octets 3c and 3d in Figure C-38/Q.767 may also be present.
FIGURE C-39/Q.767
Recommendation V.120 rate adaption extension fields
Rate adaption header/no header indicator is coded:
0 rate adaption header not included
1 rate adaption header included
Multiple frame establishment support in data link indicator is coded :
0 multiple frame establishment not supported, only UI frames allowed
1 multiple frame establishment supported
Mode of operation indicator is coded:
0 bit transparent mode of operation
1 protocol sensitive mode of operation
Logical link identifier (LLI) negotiation indicator is coded:
0 default, LLI = 256 only
1 full protocol negotiation (Note)
Note A connection over which protocol negotiation will be executed is indicated in bit 2 of
octet 3b.
Assignor/assignee indicator is coded:
0 message originator is "default"assignee"
1 message originator is assignor only
In-band/out-of-band negotiation indicator is coded:
0 negotiation is done with USER INFORMATION messages on a temporary signalling
connection
1 negotiation is done inband using logical link zero
8 7 6 5 4 3 2 1
3b Ext.
Hdr/
Hdr
no hdr
Multi.
frame
supp.
Mode
LLI.
Neg.
Assigner/
Assignee
Inband/
Outband
Spare
Recommendation Q.767 179
l) User information layer 2 protocol identification
00010 Recommendation Q.921 (I.441)
00110 Recommendation X.25, link level
All other values are reserved. If the transfer mode is packet mode, this octet shall be present. In other
cases, the octet is present only if the protocol is to be identified to the network.
m) User information layer 3 protocol identification
00010 Recommendation Q.931 (I.451)
00110 Recommendation X.25, packet level
All other values are reserved. The octet is present only if the protocol is to be identified to the
network.
C.3.37 User-to-user indicators
The format of the user-to-user indicators parameter field is shown in Figure C-40/Q.767.
FIGURE C-40/Q.767
User-to-user indicators parameter field
The following codes are used in the user-to-user indicators parameter field:
bit A Type
0 request, not used
1 response
If bit A equals 0 (request):
bits C B: Service 1
0 0 no information
0 1 spare
1 0 request, not essential
1 1 request, essential
8 7 6 5 4 3 2 1
H G F E D C B A
180 Recommendation Q.767
bits E D: Service 2
0 0 no information
0 1 spare
1 0 request, not essential
1 1 request, essential
bits G F: Service 3
0 0 no information
0 1 spare
1 0 request, not essential
1 1 request, essential
bit H Spare
If bit A equals 1 (response):
bits C B: Service 1
0 0 no information
0 1 not provided, not used
1 0 provided, not used
1 1 spare, not used
bits E D: Service 2
0 0 no information
0 1 not provided, not used
1 0 provided, not used
1 1 spare, not used
bits G F: Service 3
0 0 no information
0 1 not provided, not used
1 0 provided, not used
1 1 spare, not used
bit H Network discard indicator
0 no information, not used
1 UUI discarded by the network
Recommendation Q.767 181
C.3.38 User-to-user information
The format of the user-to-user information parameter is shown in Figure C-41/Q.767.
FIGURE C-41/Q.767
User-to-user information parameter field
The format of the user-to-user information parameter field is coded identically to the protocol discriminator
plus user information field described in Recommendation Q.931, 4.5.29.
C.4 ISDN User Part messages and codes
In the following tables the format and coding of ISDN User Part messages is specified. For each message, a
list of the relevant parameters is given and for each parameter :
a reference to the section where the formatting and coding of the parameter content is specified;
the type of the parameter. The following types are used in the tables :
F = Mandatory Fixed Length parameter;
V = Mandatory Variable Length parameter;
O = Optional parameter of fixed or variable length;
the length of the parameter. The value in the table includes:
for type F parameters the length, in octets, of the parameter content;
for type V parameters the length, in octets, of the length indicator and of the parameter content.
The minimum and the maximum length are indicated;
for type O parameters the length, in octets, of the parameter name, length indicator and parameter
content. For variable length parameters the minimum and maximum length is indicated.
8 7 6 5 4 3 2 1
1
: User-to-user information
n
182 Recommendation Q.767
For each message type, type F parameters and the pointers for the type V parameters must be sent in the order
specified in the tables.
The routing label and circuit identification code fields, which are transmitted ahead of the message type field if
required are not shown. Parameter names, pointers to mandatory variable fields and the optional part, and length
indicators appear in the message in accordance with Figure C-3/Q.767 and are not shown explicitly in Tables C-5/Q.767
to C-28/Q.767.
TABLE C-5/Q.767
Message type: Address complete
a)
Some networks may only support up to 35 octets.
Parameter Reference Type
Length
(octets)
Message type
Backward call indicators
Optional backward call indicators
Cause indicators
Connected number
Call reference
User-to-user indicators
User-to-user information
Access transport
End of optional parameters
2.1
3.4
3.24
3.10
3.14
3.6
3.37
3.38
3.2
3.17
F
F
O
O
O
O
O
O
O
O
1
2
3
4
4-12
7
3
3-131
a)
3-?
1
Recommendation Q.767 183
TABLE C-6/Q.767
Message type: Answer
a)
Some networks may only support up to 35 octets
.
TABLE C-7/Q.767
Message type: Call progress
a)
Some networks may only support up to 35 octets.
Parameter Reference Type
Length
(octets)
Message type
Backward call indicators
Optional bacward call indicators
Call reference
User-to-user indicators
User-to-user information
Connected number
Access transport
End of optional parameters
2.1
3.4
3.24
3.6
3.37
3.38
3.14
3.2
3.17
F
O
O
O
O
O
O
O
O
1
4
3
7
3
3-131
a)
4-12
3-?
1
Parameter Reference Type
Length
(octets)
Message type
Event information
Cause indicators
Call reference
Backward call indicators
Optional backward call indicators
Access transport
User-to-user indicators
User-to-user information
Redirection number
End of optional parameters
2.1
3.18
3.10
3.6
3.4
3.24
3.2
3.37
3.38
3.30
3.17
F
F
O
O
O
O
O
O
O
O
O
1
1
4
7
4
3
3-?
3
3-131
a)
5-12
1
184 Recommendation Q.767
TABLE C-8/Q.767
Message type: Circuit group querry reponse, not used
TABLE C-9/Q.767
Message type: Circuit group reset acknowledgement
TABLE C-10/Q.767
Message type: Confusion, not used
TABLE C-11/Q.767
Message type: Connect
a)
Some networks may only support up to 35 octets.
Parameter Reference Type
Length
(octets)
Message type
Range and sttus
2.1
3.27
F
V
1
3-34
Parameter Reference Type
Length
(octets)
Message type
Backward call indicators
Optional backward call indicators
Connected number
Call reference
User-to-user indicators
User-to-user information
Access transport
End of optional parameters
2.1
3.4
3.24
3.14
3.6
3.37
3.38
3.2
3.17
F
F
O
O
O
O
O
O
O
1
2
3
4-12
7
3
3-131
a)
3-?
1
Recommendation Q.767 185
TABLE C-12/Q.767
Message type: Continuity
TABLE C-13/Q.767
Message type: Facility reject, not used
TABLE C-14/Q.767
Message type: Information, not used
TABLE C-15/Q.767
Message type: Information request, not used
Parameter Reference Type
Length
(octets)
Message type
Continuity indicators
2.1
3.16
F
F
1
1
186 Recommendation Q.767
TABLE C-16/Q.767
Message type: Initial address
a)
For national use only
b)
Some networks may only support up to 35 octets.
c)
This parameter can be repeated in case of an alternate bearer service, in which ease the initial parameter represents the
initial establishment mode.
Parameter Reference Type
Length
(octets)
Message type
Nature of connection indicators
Forward call indicators
Calling partys category
Transmission medium requirement
Called party number
Transit network selection
a)
Call reference
Calling party number
Optional forward call indicators
Redirecting number
Redirection information
Closed user group interlock code
Connection request
Original called number
User-to-user information
b)
Access transport
User service information
c)
User to user indicators
End of optional parameters
2.1
3.23
3.20
3.9
3.35
3.7
3.34
3.6
3.8
3.25
3.28
3.29
3.13
3.15
3.26
3.38
3.2
3.36
3.37
3.17
F
F
F
F
F
V
O
O
O
O
O
O
O
O
O
O
O
O
O
O
1
1
2
1
1
4-11
4-?
7
4-12
3
4-12
3-4
6
7-9
4-12
3-131
3-?
4-13
3
1
Recommendation Q.767 187
TABLE C-17/Q.767
Message type: Release
a)
For national use only
b
Some networks may only support up to 35 octets.
TABLE C-18/Q.767
Message type: Release complete
Parameter Reference Type
Length
(octets)
Message type
Cause indicators
Redirection information
Redirection number
Signalling point code a)
Acces transport
User-to-user information b)
Automatic congestion level
End of optional parameters
2.1
3.10
3.29
3.30
3.31
3.2
3.38
3.3
3.17
F
V
O
O
O
O
O
O
O
1
3
3-4
5-12
4
3-?
3-131
3
1
Parameter Reference Type
Length
(octets)
Message type
Cause indicators
End of optional parameters
2.1
3.10
3.17
F
O
O
1
4
1
188 Recommendation Q.767
TABLE C-19/Q.767
Message type: Subsequent address
TABLE C-20/Q.767
Message type: User-to-user information, not used
TABLE C-21/Q.767
Message type: Delayed release (national use)
Message type: Forward transfer
Parameter Reference Type
Length
(octets)
Message type
Subsequent number
End of optional parameters
2.1
3.32
3.17
F
V
O
1
3-10
1
Parameter Reference Type
Length
(octets)
Message type
Call reference
End of optional parameters
2.1
3.6
3.17
F
O
O
1
7
1
Recommendation Q.767 189
TABLE C-22/Q.767
Message type: Suspend
Message type: Resume
TABLE C-23/Q.767
Message type: Blocking
Message type: Blocking acknowledgement
Message type: Continuity check request
Message type: Loop back acknowledgment (national use), not used
Message type: Overload, not used
Message type: Reset circuit
Message type: Unblocking
Message type: Unblocking acknowledgement
Message type: Unequipped circuit identification code (national use), not used
TABLE C-24/Q.767
Message type: Call modification completd, not used
Message type: Call modification request, not used
Message type: Call modification reject, not used
Parameter Reference Type
Length
(octets)
Message type
Suspend/Resume indicators
Call reference
End of optional parameters
2.1
3.33
3.6
3.17
F
F
O
O
1
1
7
1
Parameter Reference Type
Length
(octets)
Message type 2.1 F 1
190 Recommendation Q.767
TABLE C-25/Q.767
Message type: Circuit group blocking
Message type: Circuit group blocking acknowledgement
Message type: Circuit group unblocking
Message type: Circuit group unblocking acknowledgement
TABLE C-26/Q.767
Message type: Circuit group reset
Message type: Circuit group query, not used
a)
The status subfield is not present.
TABLE C-27/Q.767
Message type: Facility accepted, not used
Message type: Facility request, not used
Parameter Reference Type
Length
(octets)
Message type
Circuit group supervision message type indications
Range and status
2.1
3.11
3.27
F
F
V
1
1
3-34
Parameter Reference Type
Length
(octets)
Message type
Range and status a)
2.1
3.27
F
V
1
2
Recommendation Q.767 191
TABLE C-28/Q.767
Message type: Pass along, not used
ANNEX C.A
(to Annex C of Recommendation Q.767)
Interpretation of spare codes
See 4.1.1.
ANNEX D
(to Recommendation Q.767)
Signalling procedures
D.1 General
D.1.1 Relationship with other Recommendations
This Recommendation describes the signalling procedures for the set-up and cleardown of national and
international ISDN connections. THE MESSAGES AND SIGNALS ARE DEFINED IN 3.3 AND ANNEX B AND THEIR FORMAT AND
CONTENT ARE GIVEN IN 3.4 AND ANNEX C, 3.6 AND ANNEX E CONTAINS THE PROCEDURES FOR SUPPLEMENTARY SERVICES.
D.1.2 Numbering (see Recommendations E.163, E.164)
The procedures described assume that the ISDN uses the international numbering plan defined for the ISDN
and thus provides a basic circuit switched service between ISDN terminals or between ISDN terminals and terminals
being connected to the existing international telephony network.
D.1.3 Address signalling
In general, the call set-up procedure described is standard for both speech and non-speech connections using
en-bloc address signalling for calls between ISDN terminals. Overlap address signalling is also specified.
Note The use of en-bloc or overlap signalling is based on bilateral agreements.
192 Recommendation Q.767
D.1.4 Basic procedures
The basic call control procedure is divided into three phases: call set-up, the data/conversation phase and call
cleardown. Messages on the signalling link are used to establish and terminate the different phases of a call. Standard
inband supervisory tones and/or recorded announcements are returned to the caller on speech and 3.1 kHz connections to
provide information on call progress. Calls originating from ISDN terminals may be supplied with more detailed call
progress information by means of additional messages in the access protocol supported by a range of messages in the
network.
D.1.5 Signalling methods
ONE SIGNALLING METHOD IS USED IN THIS RECOMMENDATION:
link-by-link;
end-to-end.
This method is primarily used for messages that need to be examined at each exchange (see D.2). The end-
to-end methods are used for messages of end point significance (see Annex E). and may be used for messages of end
point significance. (However, the messages may be affected by processing delays.)
D.1.6 Layout of Annex D
THE PROCEDURES SPECIFIED IN D.2 OF THIS RECOMMENDATION RELATE TO BASIC CALLS (I.E. CALLS NOT
INVOLVING SUPPLEMENTARY SERVICES). Section D.3 of this Recommendation specifies the procedures relating to end-to-
end signalling connections. THE ADDITIONAL REQUIREMENTS TO BE MET IN THE CASE OF CALLS INVOLVING SUPPLEMENTARY
SERVICES AND NETWORK UTILITIES ARE SPECIFIED IN ANNEX E. THE TIMERS USED IN THIS RECOMMENDATION ARE SUMMARIZED
IN ANNEX D.A. The SDLs for the ISDN-UP are presented in Annex D.B.
D.1.7 Interworking with other signalling systems or user parts
Only some examples are included in this Recommendation and these should not be used as a definitive
interworking guide.
D.2 Basic call control and signalling procedures
FIGURES D-1/Q.767 TO D-10/Q.767 AT THE END OF THIS SECTION SHOW THE ISDN CALL SET-UP SEQUENCES WHICH
ARE DESCRIBED BELOW.
D.2.1 Successful call set-up
D.2.1.1 Forward address signalling en bloc operation
D.2.1.1.1 Actions required at originating exchange
a) Circuit selection
When the originating exchange has received the complete selection information from the calling
party, and has determined that the call is to be routed to another exchange, selection of a suitable,
free, inter-exchange circuit takes place and an initial address message is sent to the succeeding
exchange.
Recommendation Q.767 193
Appropriate routing information is either stored at the originating exchange or at a remote database
to which a request may be made.
The selection of the route will depend on the called party number, connection type required and the
network signalling capability required. This selection process may be performed at the exchange or
with the assistance of the remote database.
In addition, in the case of a subscriber with digital access, the set-up message contains bearer
capability information which is analyzed by the originating exchange to determine the correct
connection type and network signalling capability. The bearer capability information will be mapped
into the user service information parameter of the initial address message. The information received
from the access interface is used to set the value of the transmission medium requirement parameter.
The first value of bearer information received will be used to set the initial mode of the connection.
The connection types allowed are:
speech;
3.1 kHz audio;
64 kbit/s unrestricted;
alternate speech/64 kbit/s unrestricted;
alternate 64 kbit/s unrestricted/speech.
The network signalling capabilities allowed are:
ISDN-UP preferred;
ISDN-UP required;
ISDN-UP not required (any signalling system).
The information used to determine the routing of the call by the originating exchange will be
included in the initial address message (as transmission medium requirement and forward call
indicators), to enable correct routing at intermediate exchanges. The initial address message conveys
implicitly the meaning that the indicated circuit has been seized.
In the case where N 64 kbit/s (N > 2) connections are required, the procedures for a single
64 kbit/s connection may be used if the N 64 kbit/s are contiguous 64 kbit/s channels and are pre-
assigned for N 64 kbit/s use.
If subaddress information is received from the calling access, this information is passed unchanged
to the destination exchange in the access transport parameter of the initial address message.
b) Address information sending sequence
The sending sequence of address information on international calls will be the country code (not sent
to an incoming international exchange) followed by the national (significant) number. On national
connections, the address information may be the local number or the national (significant) number as
required by the Administration concerned. For calls to international operator positions (Code 11 and
Code 12), refer to Recommendation Q.107.
The end-of-pulsing (ST) signal will be used whenever the originating exchange or the outgoing
exchange is in a position to know by digit analysis that the final digit has been sent.
194 Recommendation Q.767
c) Initial address message
The initial address message (IAM) in principle contains all the information that is required to route
the call to the destination exchange and connect the call to the called party.
All initial address messages will include a protocol control indicator (in the forward call indicator
parameter) and a transmission medium requirement parameter.
The originating exchange will set the parameters in the protocol control indicator and in the ISDN-
UP preference indicator to indicate:
i) the only type of end-to-end method that can be accommodated ( D.3);
ii) the availability of Signalling System No. 7 signalling;
iii) the use of the ISDN-UP;
iv) whether further information is available (to be requested before the called party is alerted);
v) network signalling capability required, e.g. ISDN-UP required all the way.
The ISDN-UP preference indicator is set according to the bearer service, teleservice and
supplementary service(s) requested. The exact setting depends on the service demand conditions and
may be different depending on individual cases. In principle, if the service demand requires ISDN-
UP to be essential, then the indicator is set to "required"; if the service required is optional but
preferred, it is set to "preferred", otherwise it is set to "not required". The indicator is set to either
"required" or "preferred", or "not required", according to the most stringent condition required by
one or more of the parameters in the initial address message. In addition, if end-to-end signalling
method is essential to provide the requested service, the indicator should always be set to "required"
(see Recommendation E.172).
The transmission medium requirement parameter contains the connection type required information,
e.g. 3.1 kHz audio.
The originating exchange may also include in the initial address message:
i) a call reference (including the point code of the originating exchange) to enable the destination
exchange to establish an end-to-end connection ( 3);
ii) the calling party number if this is to be passed forward without being requested. The calling
party number could contain Code 11 or 12 if the call is from an international operator;
iii) an SCCP connection request parameter; and
iv) other information related to supplementary services and network utilities.
The initial address message can contain an access transport parameter.
d) Transfer of information not included in the initial address message
This section is not applicable to the international interface.
e) Completion of transmission path
Through-connection of the transmission path will be completed in the backward direction (the
transmission path is completed in the forward direction on receipt of a connect or answer message) at
the originating exchange immediately after the sending of the initial address message, except in those
cases where conditions on the outgoing circuit prevent it (see D.2.1.9).
It is also acceptable that on speech or 3.1 kHz audio calls, through-connection of the transmission
path will be completed in both directions immediately after the initial address message has been sent,
except in those cases where conditions on the outgoing circuit prevent it (see D.2.1.9).
Recommendation Q.767 195
f) Network protection timer
When the originating exchange or the controlling exchange has sent the initial address message the
awaiting address complete timer (T7) is started. If timer (T7) expires, the connection is released and
an indication is returned to the calling subscriber.
D.2.1.1.2 Actions required at an intermediate exchange
a) Circuit selection
An intermediate exchange, on receipt of an initial address message, will analyze the called party
number and the other routing information [(see D.2.1.1.1 a)] to determine the routing of the call. If
the intermediate exchange can route the call using the connection type specified in the transmission
medium requirement parameter, a free inter-exchange circuit is seized and an initial address message
is sent to the succeeding exchange. Within a network, if the intermediate exchange does not route the
call using just the connection type specified in the transmission medium requirement parameter, the
exchange may also examine the user service information containing the bearer capability information
(if available) to determine if a suitable route can be selected. In this case, if a new connection type is
provided, the transmission medium requirement parameter is modified to the new connection type.
For calls between networks, the gateway exchange (e.g. outgoing ISC) must ensure that the
transmission medium requirement parameter is set according to the service requested by the
customer (see Recommendation E.172). More specifically, this parameter is carried unchanged
within the international network.
When no echo suppressor or nature-of-circuit indication is received from a preceding exchange using
a signalling system with fewer facilities, the indicators will be considered as received "no" unless
positive knowledge is available.
b) Parameters in the initial address message
An intermediate exchange may modify signalling information received from the preceding exchange
according to the capabilities used on the outgoing route. Signalling information that may be changed
is nature of connection indicator, end-to-end method indicator; the most significant digits in the
called party number may be amended or omitted [see D.2.1.1.1 b)]. A change of the end-to-end
method used may also alter parameters (see D.3). Other signalling information is passed on
transparently, e.g. the access transport parameter, user service information, etc.
c) Completion of transmission path
Through-connection of the transmission path in both directions will be completed at an intermediate
exchange immediately after the initial address message has been sent, except in those cases where
conditions on the outgoing circuit prevent it (see D.2.1.9).
D.2.1.1.3 Actions required at the destination exchange
a) Selection of called party
Upon receipt of an initial address message, the destination exchange will analyze the called party
number to determine to which party the call should be connected. It will also check the called party's
line condition and perform various checks to verify whether or not the connection is allowed. These
checks will include correspondence of compatibility checks, e.g. checks associated with
supplementary services.
196 Recommendation Q.767
At this point, certain call set-up information may need to be obtained from an originating or
controlling exchange (see D.2.1.6). Examination of the protocol control indicator will show
whether end-to-end information is necessary to be obtained before further processing of the call, in
this case the SCCP, pass along or information request and information messages can be used.
In this case where the connection is allowed, the destination exchange will set up a connection to the
called party. If a continuity check has to be performed on one or more of the circuits involved in a
connection, setting up of the connection to the called party must be prevented until the continuity of
such circuits has been verified.
D.2.1.2 Forward address signalling Overlap operation
D.2.1.2.1 Actions required at originating exchange
a) Circuit selection
When the originating exchange has received sufficient information [see D.2.1.2.1 c)] from the
calling party to determine that the call is to be routed to another exchange, selection of a suitable,
free, inter-exchange circuit takes place and an initial address message is sent to the succeeding
exchange.
Appropriate routing information is either stored at the originating exchange or at a remote database
to which a request may be made.
The selection of the route will depend on the called party number, connection type required and the
network signalling capability required. This selection process may be performed at the exchange or
with the assistance of a remote database.
In addition, in the case of a subscriber with digital access, the set-up message contains bearer
capability information which is analyzed by the originating exchange to determine the correct
connection type and network signalling capability. The bearer capability information will be mapped
into the user service information parameter of the initial address message. The information received
from the access interface is used to set the value of the transmission medium requirement parameter.
The first value of bearer information received will be used to set the initial mode of the connection.
The connection types allowed are:
speech;
3.1 kHz audio;
64 kbit/s unrestricted;
alternate speech/64 kbit/s unrestricted;
alternate 64 kbit/s unrestricted/speech.
The network signalling capabilities allowed are:
ISDN-UP preferred;
ISDN-UP required;
ISDN-UP not required (any signalling system).
Recommendation Q.767 197
The information used to determine the routing of the call by the originating exchange will be
included in the IAM (as transmission medium requirement and forward call indicators), to enable
correct routing at intermediate exchanges. The IAM conveys implicitly the meaning that the
indicated circuit has been seized.
In the case where N 64 kbit/s (N 2) connections are required, the procedures for a single
64 kbit/s connection may be used if the N 64 kbit/s are contiguous 64 kbit/s channels and are pre-
assigned for N 64 kbit/s use.
If subaddress information is received from the calling access, this information is passed unchanged
to the destination exchange in the access transport parameter of the initial address message only.
b) Address information sending sequence
The sending sequence of address information on international calls will be the country code (not sent
to an incoming international exchange) followed by the national (significant) number. On national
connections, the address information may be the local number or the national (significant) number as
required by the Administration concerned. For calls to international operator positions (Code 11 and
Code 12), refer to Recommendation Q.107.
The end-of-pulsing (ST) signal will be used whenever the originating exchange or the outgoing
exchange is in a position to know by digit analysis that the final digit has been sent.
c) Content of initial and subsequent address messages
The initial and subsequent address messages in principle contain all of the information that is
required to route the call to the destination exchange and connect the call to the called party. The
contents of the initial address message is the same as described in D.2.1.1.1 c). The only purpose
of the subsequent address message is to carry further digits.
All digits required for routing the call through the international network will be sent in the IAM. On
calls with a country code in the number (except in the case of calls to special operators), the IAM
will contain a minimum of 4 digits and should contain as many digits as are available. Within
national networks the address information contained within the IAM may vary depending on the
routing requirement within the network.
The remaining digits of the number may be sent in subsequent address messages containing one or
several digits as they are received. Efficiency can be gained by grouping together as many digits as
possible. However, to prevent an increase in postsending delay in those cases where overlap
operation with subscribers' dialling is used, it may be desirable to send the last few digits
individually.
The end-of-pulsing (ST) signal is always sent in the following situations:
i) semi-automatic calls;
ii) test calls; and
iii) when the end-of-pulsing (ST) signal is received.
In automatic working, the end-of-pulsing (ST) signal will be sent whenever the originating or
outgoing exchange is in a position to know, by digit analysis, that the final digit has been sent. Digit
analysis may consist of an examination of the country code and counting the maximum (or fixed)
number of digits of the national number. In other cases, the end-of-pulsing signal is not sent and the
end-of-address information is determined by the receipt of the address complete message or connect
message from the incoming exchange.
198 Recommendation Q.767
d) Transfer of information not included in the initial address message
This section is not applicable to the international interface.
e) Completion of transmission path
Through-connection of the transmission path in the backward direction (the transmission path is
completed in the forward direction on receipt of connect or answer message) at the originating
exchange will be completed except in the cases where conditions on the outgoing circuit prevent it
(see D.2.1.9):
i) immediately after the sending of the initial address message; or
ii) when digit analysis or timer (T10), or receipt of the address complete message indicates that all
digits have been received.
It is also acceptable that on speech or 3.1 kHz audio calls, through-connection of the transmission
path will be completed in both directions immediately after the initial address message has been sent,
except in the cases where conditions on the outgoing circuit prevent it (see D.2.1.9).
f) Network protection timer
Each time when the originating exchange has sent an address message, the awaiting address
complete timer (T7) is started. If timer (T7) expires, the connection is released and an indication is
sent to the calling subscriber.
D.2.1.2.2 Actions required at an intermediate exchange
a) Circuit selection
An intermediate exchange, on receipt of an IAM, will analyze the digits available and the other
routing information [see D.2.1.2.1 a)] to determine the routing of the call. If the intermediate
exchange can route the call using the connection type specified in the transmission medium
requirement parameter, a suitable free inter-exchange circuit is seized and an IAM is sent to the
succeeding exchange. If the number of digits in the called party number are not sufficient to route the
call, the routing will be carried out when the intermediate exchange has received additional digits in
subsequent address message(s). Any address digits received in subsequent address messages during
the circuit selection process may be included in this IAM. Any subsequent address messages
received after the IAM has been sent are forwarded to the succeeding exchange as subsequent
address message(s).
Within the network, if the intermediate exchange does not route the call just using the connection
type specified in the transmission medium requirement parameter, the exchange may also examine
the user service information containing the bearer capability information (if available) to determine if
a suitable route can be selected. In this case the transmission medium requirement parameter is
modified to the new connection type.
For calls between networks, the gateway exchange (e.g. outgoing ISC) must ensure that the
transmission medium requirement parameter is set according to the service requested by the
customer (see Recommendation E.172). More specifically, this parameter is carried unchanged
within the international network.
When no echo suppressor or nature-of-circuit indication is received from a preceding exchange using
a signalling system with fewer facilities, the indicators will be considered as received "no" unless
positive knowledge is available.
Selection of the outgoing national circuit normally can start at an incoming international exchange
on receipt of the IAM and signalling can proceed on the first national link.
Recommendation Q.767 199
b) Parameters in the initial address message
An intermediate exchange may modify signalling information received from the preceding exchange
according to the capabilities used on the outgoing route. Signalling information that may be changed
is nature of connection indicator, end-to-end method indicator; the most significant digits in the
called party number may be amended or omitted [see D.2.1.1.1 b)]. A change of the end-to-end
method used may also alter parameters (see D.3). Other signalling information is passed on
transparently, e.g. the access transport parameter, user service information, etc.
c) Completion of transmission path
Through-connection of the transmission path in both directions will be completed at an intermediate
exchange immediately after the initial address message has been sent, except in those cases where
conditions on the outgoing circuit prevent it (see D.2.1.9).
D.2.1.2.3 Actions required at the destination exchange
a) Selection of called party
Upon the receipt of the sufficient called party number information, the destination exchange will
analyze the called party number to determine to which party the call should be connected. It will also
check the called party's line condition and perform various checks, to verify whether or not the
connection is allowed. These checks will include correspondence of compatibility checks, e.g.
checks associated with supplementary services.
At this point, certain call set-up information may need to be obtained from an originating or
controlling exchange (see D.2.1.6). Examination of the protocol control indicator will show
whether end-to-end information is necessary to be obtained before further processing of the call, in
this case the SCCP, pass along or information request and information messages can be used.
In the case where the connection is allowed, the destination exchange will set up a connection to the
called party. If a continuity check has to be performed on one or more of the circuits involved in a
connection, setting up of the connection to the called party must be prevented until the continuity of
such circuits has been verified.
D.2.1.3 Calling party number
THE CALLING PARTY NUMBER CAN ONLY BE INCLUDED IN THE INITIAL ADDRESS MESSAGE [SEE D.2.1.1.1 c) AND
D.2.1.2.1 C)].
D.2.1.4 Address complete message, connect message and call progress message
D.2.1.4.1 Return of address complete message from destination exchange
An address complete message will be sent from the destination exchange as soon as it has been determined
that the complete called party number has been received, or an indication received from the called party that an inband
tone is being connected (for this case see D.2.1.5 and D.2.2.4). However, there is no direct mapping from alerting,
received from the access signalling system, to address complete in the network. In the case that the continuity check is
performed, the destination exchange will withhold sending the address complete message until a successful continuity
indication has been received (see D.2.1.9).
200 Recommendation Q.767
Address complete is sent from the destination exchange in the following conditions:
1) In the case where the terminating access is non ISDN, the following action takes place at the destination
exchange:
a) In all cases an address complete message is sent as soon as it has been determined that the complete
called party number has been received, and the destination exchange established that the subscriber
is free. Indicators in the address complete message will be set to indicate:
call line status: "Subscriber free";
ISDN access indicator: "Non ISDN".
b) In the case of a PBX, an address complete message is sent as soon as it has been determined that the
called party number has been received. Indicators in the address complete message will be set to
indicate:
called line status: "No indication";
ISDN access indicator: "Non ISDN".
2) In the case where the terminating access is ISDN, the following conditions can apply:
a) If an indication that the address is complete or no status indication has been received from the ISDN
access prior to the destination exchange determining that the complete called party number has been
received, the indicators in the address complete message will be set as follows:
called line status: "No indication";
ISDN access indicator: "ISDN".
Note In case a) the indication that the destination user is being alerted is transferred in a call
progress message (see D.2.1.5).
b) The destination exchange concludes from the receipt of an indication from the ISDN access that the
complete called party number has been received. In this case the indicators in the address complete
message will be set as follows:
called line status: "Subscriber free";
ISDN access indicator: "ISDN".
D.2.1.4.2 Return of connect message from the destination exchange
If a connect indication is received from the ISDN access under the following conditions:
no alerting indication received from the ISDN access; and
an address complete message has not yet been sent by the destination exchange,
a connect message is sent by the destination exchange. This connect message signifies both address complete and
answer conditions.
Indicators in the connect message will indicate:
called line status: "Subscriber free";
ISDN access indicator: "ISDN".
The destination exchange will through-connect before the connect message is sent.
Recommendation Q.767 201
D.2.1.4.3 Receipt of address complete message or connect message at an intermediate exchange
Upon receipt of an address complete message, an intermediate exchange will send the corresponding address
complete message to the preceding exchange. If a connect message is received at an intermediate exchange instead of an
address complete message, a connect message will be sent to the preceding exchange.
D.2.1.4.4 Receipt of address complete message or the connect message at the originating exchange
a) When the originating exchange receives an address complete message, the appropriate exchange
functions take place.
b) On receipt of an address complete message with the called line status indicator set to "subscriber free", an
alerting indication is passed to the calling party if possible.
c) On receipt of the address complete message, the awaiting address complete timer (T7) is stopped and the
awaiting answer timer (T9) is started. If timer (T9) expires, the connection is released and an indication is
sent to the calling subscriber.
d) If the connect message is received, then the appropriate exchange functions take place. The awaiting
address complete timer (T7) is stopped (see D.2.1.7.2).
D.2.1.4.5 Through-connection and awaiting answer indication at the destination exchange
The sending of the awaiting answer indication (e.g. ring tone) at the destination exchange depends on the type
of call. On speech and 3.1 kHz calls and call to an analogue called party, the awaiting answer indication is applied to the
transmission path to the calling party from the destination exchange on receipt of an alerting indication from the called
party or from information contained within the destination exchange that the called party will not or is prohibited from
providing inband tone.
Regardless of whether tones are to be provided or not, the destination exchange will through-connect after the
reception of the connection indication from the called party and before sending the answer/connect message to the
preceding exchange.
If the destination exchange does not send the awaiting answer indication because the destination user provides
for the sending of tones, then the destination exchange will through-connect the transmission path in the backward
direction on receipt of the progress indication.
The complete through-connection of the transmission path at answer is covered in D.2.1.7.
D.2.1.4.6 Address complete message with charging information
The address complete message carries a charge indicator.
D.2.1.4.7 Address complete message with other information
Additional information can be included in the address complete messages (e.g. related to supplementary
services, see Annex E).
D.2.1.4.8 Return of address complete message in interworking situations
An address complete message will not be sent until the cross-office check is made, if applicable (see
D.2.1.10).
202 Recommendation Q.767
If the succeeding network does not provide electrical called-partys-line-condition indications, the last
Signalling System No. 7 exchange shall originate and send an address complete message when the end of address
signalling has been determined:
a) by receipt of an end-of-pulsing (ST) signal; or
b) by receipt of the maximum number of digits used in the national numbering plan; or
c) by analysis of the national (significant) number to indicate that a sufficient number of digits has been
received to route the call to the called party; or
d) by receipt of an end-of-selection signal from the succeeding network (e.g. number received signal in
Signalling System No. 5); or
e) exceptionally, in the succeeding network uses overlap signalling and number analysis is not possible, by
observing that timer (T10) has elapsed since the last digit was received, and that no fresh information has
been received; in such circumstances, transmission to the national network of the last digit received must
be prevented until the end of the waiting period which causes an address complete message to be sent
backward. In this way, it is ensured that no national answer signal can arrive before an address complete
message has been sent.
If in normal operation, a delay in the receipt of an address complete signal from the succeeding network is
expected, the last common channel signalling exchange will originate and send an address complete message 15 to
20 seconds [(timer (T11)] after receiving the latest address message. The time-out condition is an upper limit
considering the clauses of D.2.9.10.3 (20 to 30 seconds waiting for address complete message timer (T7) for outgoing
international exchanges in abnormal release conditions).
D.2.1.4.9 Return of sub-address information in address complete message, connect message or call progress
message
IF SUB-ADDRESS INFORMATION IS RECEIVED FROM THE CALLED ACCESS, THIS INFORMATION IS PASSED UNCHANGED
TO THE ORIGINATING EXCHANGE IN THE ACCESS TRANSPORT PARAMETER OF THE ANSWER MESSAGE, OR CONNECT MESSAGE.
D.2.1.5 Call progress
The call progress message is sent (ONLY AFTER THE ADDRESS COMPLETE MESSAGE) from an exchange in the
backward direction indicating that an event has occurred during call set-up which should be relayed to the calling party.
D.2.1.5.1 Return of call progress message from the destination exchange
The call progress message is sent from the destination exchange if the address complete message has been sent
and subsequently:
an indication is received that the called party is being alerted,
the call progress message contains an event indicator that is set to "alerting";
a progress indication is received from the called party,
the call progress message contains an event indicator that is set to "progress".
Recommendation Q.767 203
If the indication received from the called party contains a "progress indication", this is carried by the call
progress message in the access transport parameter (transported unchanged across the public network).
The destination exchange may, on receipt of the indication from the called party that contains an appropriate
progress indicator, through-connect the speech path (see D.2.1.4.5).
In the case of call failure and the connection of a tone or announcement being returned before the address
complete message has been returned, see ( D.2.2.4).
D.2.1.5.2 Action at an intermediate exchange
On receipt of a call progress message an intermediate exchange will send the corresponding call progress
message to the preceding exchange.
D.2.1.5.3 Actions at the originating exchange
On receipt of a call progress message at the originating exchange, no state change occurs (i.e. the awaiting
address complete or the awaiting answer timer IS not stopped), and the appropriate indication is sent to the calling user.
If the call progress message contained information carried in the access transport parameter, it is transferred unaltered
into the indication returned to the calling user.
D.2.1.6 Information messages
This section is not applicable to the international interface.
D.2.1.7 Answer message
The called party may also provide its own subaddress to complement the connected line identification as
provided in the COL service. This subaddress is transported from the destination to the originating exchange, in the
ANM or CON. Connected line subaddress information is conveyed in the ATP parameter in the ANM or CON.
D.2.1.7.1 Return of answer message from destination exchange
When the called party answers, the destination exchange connects through the transmission path and the
ringing tone is removed if applicable. An answer message to the preceding exchange is sent. If the destination exchange
is the exchange controlling charging, then charging may begin.
D.2.1.7.2 Receipt of answer message at intermediate exchange
Upon receipt of an answer message, an intermediate exchange sends the corresponding answer message to the
preceding exchange and, if this is the exchange controlling charging, charging may begin, and timer (T9) is stopped.
D.2.1.7.3 Receipt of answer message at originating exchange
When the originating exchange receives an answer message indicating the required connection has been
completed, the transmission path is connected-through in the forward direction, if not already connected. The awaiting
answer timer (T9) is stopped. If the originating exchange is the exchange controlling charging, charging may begin if
applicable. The calling party is informed.
204 Recommendation Q.767
D.2.1.7.4 Return of answer from automatic terminals
When connections are set up to terminals having an automatic answer feature, the alerting indication may not
be received from the called party. If a destination exchange receives an answer indication, an answer message is sent
provided that an address complete message has been sent, otherwise the connect message is sent.
D.2.1.7.5 Answer with charging information
The answer message received from the destination exchange or from a succeeding network carries a charge
indicator.
D.2.1.8 Continuity-check
Because the signalling in Signalling System No. 7 does not pass over the circuit, facilities should be provided
for making a continuity-check of the circuit in the circumstances described below.
The application of the continuity-check depends on the type of the transmission system used for the circuit.
For transmission systems having some inherent fault indication features giving an indication to the switching
system in case of fault, a continuity-check is not required. However, a per call continuity-check may be needed on fully
digital circuits when circuits or bundles of circuits in primary multiplex groups are dropped and inserted en route
between switches, and alarm indications carried on bits of the primary multiplex frame structure are lost in passing
through an intermediate transmission facility that does not relay them transparently. Typical, per call continuity-checks
may be needed when the transmission link between switches contains a TDMA satellite system, a digital circuit
multiplication system or a digital access and cross-connection system, where fault indications are lost (see
Recommendation Q.33).
When an initial address message is received with a request for a continuity-check (either on this circuit or on a
previous circuit), timer T8 is started. On receipt of a continuity message, timer T8 is stopped.
If timer T8 expires, the connection is cleared.
If an indication of continuity check failure is received in a continuity message, timer T27 is started awaiting a
continuity re-check request. Also the connection to the succeeding exchange, if any, is cleared. Timer T27 is stopped
when the continuity re-check message is received and timer T36 is started awaiting a continuity or a release message.
If either timer T27 or timer T36 expires, a reset circuit message is sent to the preceeding exchange. On
reception of the release complete message, the circuit is set to idle.
Recommendation Q.767 205
When an initial address message is received with a request for a continuity-check relating to a digital circuit
having inherent fault indication, one of the following actions is taken, either:
a) the continuity-check request is disregarded; or
b) a continuity-check loop is connected and the maintenance system is alerted. In this case the call may fail
since no continuity signal may be received from the distant end.
Note The reception of such a request could only be caused by an abnormal condition such as administrative
errors or the occurrence of signalling errors.
WHEN THE CIRCUIT TYPE IS UNKNOWN TO AN SS NO. 7 EXCHANGE, OR IN AN APPLICATION WHERE BOTH ANALOGUE
AND DIGITAL CIRCUITS MAY BE SERVED OR WHEN NO FAULT INDICATION ACCORDING TO RECOMMENDATION Q.33 IS AVAILABLE,
A CONTINUITY-CHECK LOOP SHOULD ALWAYS BE CONNECTED IN THE FOLLOWING CASE:
i) WHEN INITIAL ADDRESS MESSAGES WITH A CONTINUITY-CHECK REQUEST INDICATION ARE RECEIVED;
ii) when continuity-check request messages are received.
Means should be provided in S.S. No. 7 to detect circuit identification code misunderstandings between
S.S. No. 7 exchanges.
For exchanges having both analogue and digital circuits served by S.S. No. 7, the continuity-check initiated by
a continuity-check request message could be used to test for proper alignment of circuit code identities. On those
exchanges, reception of a continuity-check request message should always cause a loop to be attached to the circuit.
Alternative methods for detection of circuit identity misunderstandings in exchanges with all digital circuits
may be employed.
The continuity-check is not intended to eliminate the need for routine testing of the transmission path.
The continuity check of the circuit will be done, link-by-link, on a per call basis or by a statistical method prior
to the commencement of conversation. Procedures and requirements are specified in Recommenda-tion Q.724, 7.
The actions to be taken when pilot supervision used are describe in Recommendation Q.724, 9.
D.2.1.9 Special procedures at an interworking point
D.2.1.9.1 Completion of transmission path at an interworking exchange
In general, completion of the transmission path at an interworking point should occur as soon as possible
during the call set-up phase. The actual point of switch-through will vary depending on the interworking signalling
system, e.g. whether inband or outband signalling is used or whether a continuity-check procedure is applied.
206 Recommendation Q.767
When interworking with other internationally specified signalling systems, the following rules on switch-
through should be applied:
When a continuity-check is made on the outgoing circuit, and early connection is made, there is a possibility
that the calling party has its go and return paths temporarily looped (from the instant of through-connection to the instant
of loop removal of the incoming end of the circuit). This problem can be prevented by using the optional single report
continuity-check procedure given in Recommendation Q.724, 7.3.
D.2.1.9.2 Alerting of called party
If in an interworking situation a continuity-check has to be performed on one or more of the circuits involved
in the connection preceding the interworking point, appropriate measures must be taken to prevent alerting of the called
party until the continuity of such circuits has been verified. Interworking situations which could be discriminated are:
a) S.S. No. 7 any non No. 7 signalling system;
b) International S.S. No. 7 national S.S. No. 7 not performing continuity-check.
For a), the last digit(s) of the national number have to be withheld in any (interworking) transit exchange or
terminating exchange in case of DDI (direct dialling in) or the alerting of the called party is postponed in the terminating
exchange in case of non DDI.
For b), either the last digit(s) of the national number are withheld in the incoming international transit
exchange, a transit exchange in the national network or the terminating exchange in case of DDI (direct dialling in) or
the setting up of the connection to the called party is postponed in the terminating exchange in case of non DDI.
S.S. No. 7 S.S. No. 7 When no continuity-check is to be made on the outgoing circuit, through-connection should occur
after sending the initial address message. When continuity-check is to be made on the outgoing
circuit, through-connection should occur after residual check tone has propagated through the
return path of the circuit (see Recommendation Q.724, 7.3).
S.S. No. 6 S.S. No. 7
S.S. No. 5 S.S. No. 7
R1 S.S. No. 7
S.S. No. 7 S.S. No. 6
When no continuity-check is to be made on the outgoing circuit, through-connection can occur
after sending the initial address message. When continuity-check is to be made on the outgoing
circuit, through-connection can occur after residual check tone has propagated through the return
path of the circuit (see Recommendation Q.724, 7.3).
R2 S.S. No. 7 Through-connection should occur after receipt of address complete.
S.S. No. 7 S.S. No. 5
S.S. No. 7 R1
Through-connection can occur after sending ST (end-of-pulsing) signal and removal of possible
check loop.
S.S. No. 7 R2 Through-connection should occur after sending of address complete.
Recommendation Q.767 207
D.2.1.10 Cross-office check
For digital exchanges, the requirements mentioned in Recommendation Q.543 shall be met. For other
exchanges, Administrations shall ensure the reliability of a connection through a switching machine (cross-office check)
either on a per call basis or by a statistical method. With either method, the probability of the connection being
established with an unacceptable transmission quality should not exceed 0.00001 as the long-term average.
D.2.1.11 Charging procedures
D.2.1.11.1 Basic call charging
Charging will normally begin when the exchange(s) controlling charging receives the answer or connect
message from the network. Optionally, an Administration may wish to begin charging prior to the receipt of the answer
or connect message for national and/or international calls.
D.2.1.11.2 Network charging messages (national option)
This section is not applicable to the international interface.
D.2.1.12 Forward transfer message
The forward transfer message may be sent in telephony semi-automatic working in either of the following two
cases:
a) Following a call switched automatically to a subscriber, or following a call established via a special
operator, the controlling operator wishes to call in an assistance operator. On receipt of the forward
transfer message at the incoming international exchange, an assistance operator is called in.
b) Following a call via codes 11 and 12, the controlling operator wishes to recall the incoming international
exchange. Receipt of the forward transfer message at the incoming international exchange recalls the
incoming operator on calls completed via the operator positions at the exchange.
Note Procedures are not supported by all network operators.
D.2.1.13 Transit network selection (national option)
This section is not applicable to the international interface.
D.2.2 Unsuccessful call set-up
If at any time in the call set-up the connection cannot be completed, a release message is returned. This
message contains the reason.
D.2.2.1 Actions at exchange initiating a release message
The initiating exchange immediately starts the release of the switched path (if established). THE EXCHANGE
SENDS A RELEASE MESSAGE TO THE PRECEDING EXCHANGE AND TIMERS T1 AND T5 ARE STARTED TO ENSURE THAT A RELEASE
COMPLETE MESSAGE IS RECEIVED FROM THE PRECEDING EXCHANGE WITHIN TIME T1 (EXPIRATION OF TIMERS T1 AND T5 IS
COVERED IN D.2.10.6).
208 Recommendation Q.767
D.2.2.2 Actions at intermediate exchange
On receipt of a release message from the succeeding exchange, an intermediate exchange:
i) immediately starts the release of the switched path; when the circuit is reselectable, a release complete
message is returned to the succeeding exchange;
ii) at the same time as the start of the release of the switched path, a release message is sent to the preceding
exchange.
TIMERS T1 AND T5 ARE STARTED TO ENSURE THAT A RELEASE COMPLETE MESSAGE IS RECEIVED FROM THE
PRECEDING EXCHANGE (EXPIRATION OF TIMERS T1 AND T5 IS COVERED IN D.2.10.6).
D.2.2.3 Actions at the controlling exchange (i.e. the exchange controlling the call)
On receipt of a release message from the succeeding exchange, the controlling exchange starts the release of
the switched path.
In addition, the controlling exchange will (if applicable):
a) return an indication (in-band or out-band) to the calling party (see D.2.2.4); or
b) attempt to re-route the call set-up; or
c) initiate release procedures to the preceding exchange (as described in D.2.2.4).
In case a) above an indication is carried in the call progress message or address complete message indicating
in-band information is available (see D.2.2.4).
When the controlling exchange is ready for circuit re-selection, a release complete message is sent to the
succeeding exchange.
D.2.2.4 Tones and announcements
If a call set-up fails and an in-band tone or announcement has to be returned to the calling party from an
exchange or called party, the exchange or user concerned connects the in-band tone to the transmission path.
If an address complete message has been returned to the preceding exchange, a call progress message
indicating that in-band tone information is available is returned to the preceding exchange (see D.2.1.5).
If an address complete message has not been returned to the preceding exchange already, an address complete
message, with the appropriate cause parameter and the "in-band information" indicator set in the optional backward call
indicator, will be returned to the originating exchange.
D.2.2.5 Address Incomplete
The determination that proper number of digits has not been received can be made at once if the end-of-
pulsing signal is received.
When overlap working is used and the end of pulsing has not been received, the release message with cause 28
(address incomplete ) will be sent 15-20 seconds (T35) after receipt of the last digit and before receipt of the minimum
or fixed number of digits for forward routing of the call.
Recommendation Q.767 209
D.2.3 Normal call release
The release procedures are based on a two-message (release, release complete) approach whereby the release
message initiates release of the circuit switched connection.
The same procedures are used in the network irrespective of whether they are initiated by the calling party, the
called party or the network. The normal release procedure can be prevented by the network if this is required on a
particular call (see D.2.6).
To satisfy the need for rapid transfer of release across the network, it is required that the circuit is selectable
from the subsequent exchange within the mean cross-office transfer time, T
cu
, for simple messages as specified in
Recommendation Q.766.
D.2.3.1 Release initiated by a calling party
a) Actions at the originating exchange
On receipt of a request to release the call from the calling party, the originating exchange
immediately starts the release of the switched path. A RELEASE MESSAGE TO THE SUCCEEDING
EXCHANGE AND TIMERS T1 AND T5 ARE STARTED TO ENSURE THAT A RELEASE COMPLETE MESSAGE IS
RECEIVED FROM THE SUCCEEDING EXCHANGE WITHIN TIME T1 (EXPIRATION OF TIMERS T1 AND T5 IS
COVERED IN D.2.10.6).
b) Actions at an intermediate exchange
On receipt of a release message from the preceding exchange, an intermediate exchange:
i) immediately starts the release of the switched path; when the circuit is reselectable, a release
complete message is returned to the preceding exchange;
ii) at the same time as the start of the release of the switched path, sends a release message to the
succeeding exchange. TIMERS T1 AND T5 ARE STARTED TO ENSURE THAT A RELEASE COMPLETE MESSAGE
IS RECEIVED FROM THE SUCCEEDING EXCHANGE (EXPIRATION OF TIMERS T1 AND T5 IS COVERED IN
D.2.10.6.)
c) Actions at the destination exchange
On receipt of a release message from the preceding exchange, the destination exchange will start the
release of the switched path.
When the circuit is ready for reselection, a release complete message is returned to the preceding
exchange.
d) Charging
This section is not applicable to the international interface.
e) Collision of release messages
In the case when two points in the connection both initiate the release of a call, a release message
may be received at an exchange from a succeeding or preceding exchange after the release of the
switched path is initiated. In this case, the exchange will return a release complete message to the
exchange from which the concerned release message was received. The release complete message
will be sent when the circuit is ready for re-selection.
210 Recommendation Q.767
D.2.3.2 Release initiated by a called party
The procedures in D.2.3.1 apply, except that the functions at the originating and destination exchanges are
transposed.
D.2.3.3 Release initiated by the network
The procedures in D.2.3.1 apply, except that they can be initiated at any exchange (originating, destination or
intermediate).
D.2.3.4 Storage and release of IAM information
Each exchange of the connection shall store during the call set-up the information contained in the initial
address message sent (the originating exchange) or received (intermediate or destination exchange). The information to
be stored includes all parameters in the IAM. The contents of the IAM information shall be updated, if the value of
parameters change during the call set-up.
The IAM information can be released from memory:
a) in the originating exchange when the address complete message or connect message has been received
and the calling party does not subscribe to a supplementary service which would cause a new call set-up
(e.g. call transfer). The release of the information when the calling party does subscribe to a
supplementary service is covered in Annex E;
b) in the intermediate exchange when the address complete message or the connect message has been
received;
c) in the destination exchange when the address complete message or connect message has been sent and the
called party does not subscribe to a supplementary service which would cause a new call set-up (e.g. call
transfer). The release of the information when the called party does subscribe to a supplementary service
is covered in Annex E, and when the call is released earlier and no automatic repeat attempt is to be
attempted.
D.2.4 Transfer of user-to-user information
D.2.4.1 Requirements for transfer of user-to-user data
See Annex E.
D.2.5 Suspend, resume
D.2.5.1 Suspend
The suspend message indicates a temporary cessation of communication without releasing the call. It can only
be accepted during the conversation/data phase. A suspend message can be either generated in response to a suspend
request from the calling/called party or generated by the network in response to a clearback indication from an
interworking node or an on-hook condition from an analogue called (telephone) party.
D.2.5.1.1 Suspend initiated by a calling party
A suspend message is generated in response to a suspend request or notification from a calling party. The
suspend request controlling exchange is within the network of the suspend initiating user.
Recommendation Q.767 211
a) Actions at originating exchange
On receipt of a suspend request or notification from the calling party, the originating exchange sends
a suspend message to the succeeding exchange.
b) Actions at an intermediate exchange
On receipt of the suspend message from the preceding exchange, the intermediate exchange sends a
suspend message to the succeeding exchange.
c) Actions at destination exchange
On receipt of the suspend message from the preceding exchange, the destination exchange informs
the called party that a suspend has been requested.
d) Actions at the suspend request controlling exchange
On receipt of the suspend request from a user or the suspend message, the controlling exchange
starts a timer (T2) to ensure that a resume request or resume message is received within timer (T2). If
the timer (T2) expires, the procedures in D.2.5.3 apply.
D.2.5.1.2 Suspend initiated by a called party
The procedures in D.2.5.1.1 apply, except that the functions at the originating and destination exchanges are
transposed.
The suspend request controlling exchange is within the network of the suspend initiating user.
D.2.5.1.3 Suspend initiated by the network
A suspend message can be generated by the network in response to a clearback indication from an
interworking node or an on-hook condition from an analogue called party.
a) Action at the terminating exchange (destination) or an interworking exchange
On receipt of an on-hook condition in the terminating exchange or a clearback signal at the
interworking exchange, the exchange may send a suspend (network) message to the preceding
exchange.
b) Action at the intermediate exchange
On receipt of a suspend message, the exchange will send a suspend message to the preceding
exchange.
c) Action at the controlling exchange
On receipt of the on-hook condition or clearback indication or suspend message, the controlling
exchange starts a timer (T6) to ensure that an off-hook condition, a re-answer indication, a resume
(network) message or a release message is received. The value of this timer (T6) is covered in
Recommendation Q.118. If the timer (T6) expires, the procedures in D.2.5.3 apply.
D.2.5.2 Resume
A resume message indicates a request to recommence communication. A request to release the call received
from the calling or called party will override the suspend/resume sequence and the procedures given in D.2.3 will be
followed.
212 Recommendation Q.767
D.2.5.2.1 Resume initiated by a calling party
Having initiated a suspend condition, a calling party may request a reconnection within timer T2. The
procedures in D.2.5.1.1 items a), b) and c) apply, except that the resume message replaces the suspend message. On
receipt of the resume message, the controlling exchange cancels the timer (T2).
D.2.5.2.2 Resume initiated by a called party
The procedures in D.2.5.2.1 apply, except that the functions at the originating and destination exchange are
transposed.
D.2.5.2.3 Resume initiated by the network
A resume message is initiated by the network, if a suspend message had previously been sent, in response to a
re-answer indication from an interworking node or an off-hook condition from an analogue called party.
a) Action at the terminating exchange or interworking exchange
On receipt of a re-answer indication at the interworking exchange or an off-hook condition in the
terminating exchange, the exchange may send a resume (network) message to the preceding
exchange if a suspend (network) message had previously been sent.
b) Actions of the intermediate exchange
On receipt of a resume message, the exchange will send a resume message to the preceding
exchange.
c) Action of the controlling exchange (i.e. exchange controlling the call)
On receipt of the off-hook condition, re-answer signal, release message or resume message the
controlling exchange stops the timer (T6) [started in D.2.5.1.3 c)].
D.2.5.3 Expiration of timer (T2) or timer (T6)
If a request for reconnection or a resume message is not received within timer (T2) or timer (T6) covered in
Recommendation Q.118, then the controlling exchange will initiate the release procedure outlined in D.2.3.3. Cause
value #102 is used in the release message.
D.2.6 Delayed release (national option)
This section is not applicable to the international interface.
D.2.7 In-call modification
This section is not applicable to the international interface.
D.2.8 Echo control procedure
D.2.8.1 General
The echo control procedure is used on a per call basis to convey information between exchange nodes about
the demand and ability to insert echo control devices.
The procedure is invoked when a call is to be routed on a connection for which echo control is necessary. It
could be initiated at the originating exchange or at an intermediate exchange.
Recommendation Q.767 213
D.2.8.2 Forward direction
D.2.8.2.1 Actions at the originating exchange
If an originating exchange has sufficient information to determine that echo control is necessary for the
outgoing circuit, then:
an outgoing half echo control device is enabled; and
the echo control device indicator of the nature of connection indicators parameter field in the IAM is set.
D.2.8.2.2 Actions at an intermediate exchange
If an intermediate exchange has sufficient information to determine that echo control is required for the
outgoing circuit, then one of the following actions can occur:
a) When the nature of connection indicators parameter field in the IAM indicates that an echo control device
is already included:
no change to the nature of connection indicators parameter field in the IAM is made;
an incoming half echo control device is reserved; and
any outgoing half echo control device is disabled.
b) When the nature of connection indicators parameters in the IAM does not indicate that an echo control
device is already included:
an outgoing half echo control device is enabled; and
the echo control device indicator in the nature of connection indicators parameter field is set.
If the intermediate exchange has sufficient information to determine that echo control is not required for the
outgoing circuit, then one of the following actions can occur:
a) When the nature of connection indicators parameter field in the IAM indicates that an echo control device
is already included:
no change to the nature of connection indicators parameter field in the IAM is made; and
an incoming half echo control device is reserved.
b) When the nature of connection indicator parameter field in the IAM does not indicate that an echo control
device is already included:
no additional action is required.
D.2.8.2.3 Actions at the destination exchange
See D.2.8.3.1 below.
214 Recommendation Q.767
D.2.8.3 Backward direction
D.2.8.3.1 Actions at the destination exchange
Upon the receipt of an IAM with the indication "outgoing half echo control device included" in the nature of
connection indicators parameter field, the following action is taken:
an incoming half echo control device is enabled; and
the echo control device indicator of the backward call indicators parameter field in the first backward
message (i.e. ACM or connect or call progress) is set.
If the destination exchange is unable to include an incoming half echo control device, the information is
conveyed to the preceding exchange by an echo control device indicator in THE BACKWARD CALL INDICATORS PARAMETER
FIELD in the first backward message.
D.2.8.3.2 Actions at an intermediate exchange
Upon receipt of the first backward message (i.e. ACM or connect or call progress) in response to an IAM with
echo control indication, then one of the following actions can occur:
a) When the backward call indicators parameter field indicates that an incoming half echo control device is
not already included:
the reserved incoming half echo control device is included; and
the echo control device indicator in the backward call indicators parameter field is set.
b) When the backward call indicators parameter field indicates that an incoming half echo control device is
already included:
the reserved incoming half echo control is released; and
no change to the backward call indicators parameter field in the backward message is made.
D.2.8.3.3 Actions at the originating exchange
No additional action is required.
D.2.9 Network features
D.2.9.1 Automatic repeat attempt
Automatic repeat attempt, as defined in Recommendation Q.12, is provided in Signalling System No. 7. An
automatic repeat attempt will be made (up to the point when the initial address message information is released, see
D.2.3.4):
i) on detection of dual seizure (at the non-control exchange) (see D.2.10.1.4);
ii) on receipt of the blocking message after sending an address message and before any backward message
has been received (see D.2.9.2);
iii) on receipt of a reset circuit message after sending an address message and before a backward message has
been received [see D.2.10.3.1 e)];
iv) on failure of continuity-check, when a continuity check is performed;
v) on receipt of an unreasonable message during call set up (see D.2.10.5).
Recommendation Q.767 215
D.2.9.2 Blocking and unblocking of circuits and circuit groups
The blocking (unblocking) message and the circuit group blocking (unblocking) message are provided to
permit the switching equipment or maintenance system to remove from (and return to) traffic the distant terminal(s) of a
circuit or group of circuits because of a fault or to permit testing.
Since the circuits served by the ISDN user part have both-way capability, the blocking message or circuit
group blocking message can be originated by either exchange. The receipt of a blocking message or a circuit group
blocking message will have the effect of prohibiting non test calls on the relevant circuit(s) outgoing from the exchange
until an unblocking message or an appropriate circuit group unblocking message is received, but will not prohibit test
calls incoming to that exchange. An acknowledgement sequence is always required for the blocking and unblocking
message as well as for the circuit group blocking message and circuit group unblocking messages using the blocking
acknowledgement message, the unblocking acknowledgement message, the appropriate circuit group blocking
acknowledgement messages and the appropriate circuit group unblocking acknowledgement message respectively. The
acknowledgement is not sent until the appropriate action either blocking or unblocking has been taken. The release
message should not override a blocking message and return circuits to service which might be faulty. The blocked
circuit(s) will be returned to service on transmission of the unblocking acknowledgement message or the appropriate
circuit group unblocking acknowledgement message at one exchange and on receipt of the unblocking
acknowledgement message or the appropriate circuit group unblocking acknowledgement message at the other
exchange.
D.2.9.2.1 Other actions on receipt of a blocking message
In the event of a blocking message being received, after an initial address message has been sent in the
opposite direction on that circuit, and before a backward message relating to that call has been received, an automatic
repeat attempt will be made on another circuit. The exchange receiving the blocking message releases the original call
attempt in the normal manner after sending the blocking acknowledgement message and will not seize that circuit for
subsequent calls.
If the blocking message is received:
after an initial address message has been sent for that circuit in the opposite direction and after at least one
backward message relating to that call has been received; or
after an initial address message has been received for that circuit beforehand, the exchange will not seize
that circuit for subsequent calls.
The fact that the circuit is engaged on a call will not delay transmission of the blocking (unblocking)
acknowledgement message.
If a blocking message is sent and subsequently an initial address message is received in the opposite direction,
the following action is taken:
for test calls, the call should be accepted, if possible. In the case where the test call cannot be accepted,
the blocking message must be returned;
for calls other than test calls, the blocking message must be returned and the initial address message
discarded.
When a circuit is blocked by use of the blocking message, the maintenance system should be informed at both
ends of the circuit.
216 Recommendation Q.767
D.2.9.2.2 Circuit group blocking and unblocking messages
The following circuit group blocking (unblocking) messages and their corresponding acknowledgement
messages are provided:
maintenance oriented circuit group blocking (unblocking) message;
hardware failure oriented circuit group blocking (unblocking) message.
The circuits to be blocked (unblocked) are indicated in the status field.
The maximum number of circuits to be blocked (unblocked) with one circuit group blocking (unblocking)
message is limited to 32.
A received circuit group blocking (unblocking) acknowledgement message has to match in the parameter
value of the circuit identification code, the circuit group supervision message type indicator, and the range field (see
Annex C) with the previously sent group blocking (unblocking) message in order to be considered a valid
acknowledgement.
A circuit is controlled by the ISDN user part if it can be used by the ISDN user part as a circuit switched
bearer. Hence, time slots in a digital path that are used for synchronisation (e.g. time slot 0 in a 2048 kbit/s digital path)
or as signalling channels are not circuits whose control is allocated to the ISDN user part.
Some of the circuit identification code values covered by the range field of a circuit group blocking
(unblocking acknowledgement) message may not be allocated to any circuit. Then the corresponding status bits in the
status field are set to 0. This is not allowed for the circuit identification code values related to status bits being set to 1.
Those circuit identification code values must always be allocated to circuits whose control is allocated to the ISDN user
part. In particular, the circuit identification code value indicated in the label of a message must be allocated to a circuit.
The maintenance oriented circuit group blocking (unblocking) procedures set (remove) the same blocking
states as the blocking (unblocking) procedures. This means that a blocking state set by a maintenance oriented circuit
group blocking message or indicated as blocked for maintenance purposes in the status field of a circuit group reset
acknowledgement message can be removed by an unblocking message. Similarly, a blocking state set by a blocking
message can be removed by a maintenance oriented circuit group unblocking message.
The maintenance blocked state set by maintenance oriented circuit group blocking message, by a status
indicator in a circuit group reset acknowledgement message or a blocking message cannot be removed by a hardware
oriented circuit group unblocking message.
The range of circuits to be blocked (unblocked) is indicated in the range field. Those circuits within the range
that have to be blocked (unblocked) are indicated in the status field. The same rule applies to the acknowledgements.
For the circuits blocked for maintenance reasons, the same conditions apply and the same actions have to be
taken as described in D.2.9.2.1.
Recommendation Q.767 217
For the circuits seized by ongoing calls or call attempts and blocked for reasons of harware failure, the
following actions will be taken:
all interconnected circuits have to be released by the appropriate messages;
the affected circuits are set to the condition "idle hardware blocked" without any exchange of release
messages.
The fact that a circuit is engaged on a call will not delay the transmission of the corresponding circuit group
blocking (unblocking) acknowledgement message.
The hardware blocked state can only be removed by a hardware failure oriented circuit group unblocking
message.
For all instances of circuit group blocking, the maintenance system should be notified at both ends of the
circuit(s).
D.2.9.2.3 Abnormal blocking and circuit group blocking procedures
The following procedures are designed to cover abnormal cases which may occur in the circuit group
blocking/unblocking procedures.
i) If a circuit group blocking message is received relating to remotely blocked circuits, then blocking
acknowledgement indications for those circuits are given in the status field of the corresponding circuit
group blocking acknowledgement message which will be sent in response.
ii) If a circuit group unblocking message is received relating to circuits which are not in the state remotely
blocked, then unblocking acknowledgement indications for those circuits are given in the status field of
the corresponding circuit group unblocking acknowledgement message which will be sent in response.
iii) When an exchange upon receipt of a circuit group blocking (unblocking) message is not able to give an
appropriate blocking (unblocking) acknowledgement indication for each circuit identification code (e.g.
because that/those circuit identification code(s) is(are) not allocated to any circuit at the receiving
exchange) for which also a blocking (unblocking) indication is given in the status field of the received
group blocking (unblocking) message, then no blocking (unblocking) acknowledgement indication
relating to that/those circuit identification code(s) will be given in the status field of the corresponding
circuit group blocking (unblocking) acknowledgement message which will be sent in response.
iv) If a circuit group blocking acknowledgement message in response to a circuit group blocking message is
received containing in the status field no blocking acknowledgement indications for the circuits which are
to be blocked due to the previously sent circuit group blocking message, tHEN THE MAINTENANCE SYSTEM
SHOULD BE NOTIFIED FOR THE CIRCUITS CONCERNED. The same rule applies to the unblocking procedures.
v) If a circuit group blocking acknowledgement message in response to a circuit group blocking message is
received containing in the status field blocking acknowledgement indications for the circuits which are
not to be blocked due to the previously sent circuit group blocking message and are not marked locally
blocked, THEN THE MAINTENANCE SYSTEM SHOULD BE NOTIFIED for the circuits concerned.
218 Recommendation Q.767
vi) If a circuit group unblocking acknowledgement message in response to a group unblocking message is
received containing in the status field unblocking acknowledgement indications for circuits which are not
to be unblocked due to the previously sent circuit group unblocking message and have to remain marked
locally blocked, then THE MAINTENANCE SYSTEM SHOULD BE NOTIFIED for the circuits concerned.
vii) If a circuit group blocking acknowledgment message which is not expected as an acknowledgement for
any circuit group blocking message is received:
relating to circuits which all are in the status locally blocked the received circuit group blocking
acknowledgement will be discarded,
relating to circuits PART OR ALL OF WHICH ARE NOT IN THE STATUS LOCALLY BLOCKED, THEN THE
MAINTENANCE SYSTEM SHOULD BE NOTIFIED.
viii) If a circuit group unblocking acknowledgement message which is not expected as an acknowledgement
for any circuit group unblocking message is received:
relating to circuits none of which is in the status locally blocked, then the circuit group unblocking
acknowledgement message will be discarded,
relating to circuits part or all of which are locally blocked, then THE MAINTENANCE SYSTEM SHOULD BE
NOTIFIED FOR THE CIRCUITS CONCERNED.
ix) If a circuit group blocking (unblocking) message or a circuit group blocking (unblocking)
acknowledgement message refers to status changes for more than 32 circuits, the receiving exchange
SHALL discard that message.
x) If a blocking message is received for a blocked circuit, a blocking acknowledgement message will be
sent.
xi) If an unblocking message is received for an unblocked circuit, an unblocking acknowledgement message
will be sent.
xii) If a blocking acknowledgement message, which is not expected as an acknowledgement for a blocking
message, is received:
relating to a circuit which is locally blocked, the blocking acknowledgement message is
discarded,
relating to a circuit which is not locally blocked, then THE MAINTENANCE SYSTEM SHOULD BE
NOTIFIED.
xiii) If an unblocking acknowledgement message, which is not an expected response to an unblocking
message, is received:
relating to a circuit which is not locally blocked, the received unblocking acknowledgement message
is discarded,
relating to a circuit which is locally blocked, then THE MAINTENANCE SYSTEM SHOULD BE
NOTIFIED.
xiv) If a non test initial address message is received on a remotely blocked circuit, the remotely blocked state
of the circuit is removed and the initial address message is processed normally unless the circuit is also
locally blocked in which case the initial address message is discarded. This applies to the blocking state
whether maintenance, hardware or both. However, it should not be the preferred method of unblocking a
circuit.
Recommendation Q.767 219
D.2.9.3 Circuit group query
This section is not applicable to the international interface.
D.2.10 Abnormal conditions
D.2.10.1 Dual seizure
Because Signalling System No. 7 circuits have the capability of bothway operation, it is possible that the two
exchanges will attempt to seize the same circuit at approximately the same time.
D.2.10.1.1 Unguarded interval
The exchange must detect dual seizure and take action as defined in D.2.10.1.4.
D.2.10.1.2 Detection of dual seizure
A dual seizure is detected by an exchange from the fact that it receives an initial address message for a circuit
for which it has sent an initial address message, but before it receives a valid backwards message.
D.2.10.1.3 Preventive action
Different methods for circuit selection can be envisaged to minimise the occurrence of dual seizure. In the
following, two methods are described. Further study is required to determine the field of application of each method and
to ensure that the two methods do inter-work satisfactorily.
Other methods for circuit selection may also be used provided that they give the same degree of protection
against dual seizure also when one of the methods specified is used at the other end.
Method 1
An opposite order of selection is used at each exchange of a bothway circuit group.
Method 2
Each exchange of a bothway circuit group has priority access to the group of circuits which it is controlling
(see D.2.10.1.4). Of this group the circuit which has been released the longest is selected (first-in, first-out). In addition
each exchange of a bothway circuit group has non-priority access to the group of circuits which it is non-controlling. Of
this group the latest released circuit is selected (last-in, first-out) if all circuits in the group are busy.
For call control purposes a bothway circuit group can be subdivided into subgroups in an exchange.
It is necessary to take preventive action in cases where Signalling System No. 7 uses a signalling data link with
long propagation time.
D.2.10.1.4 Action to be taken on detection of dual seizures
Each exchange will control one half of the circuits in a bothway circuit group. On detection of a dual seizure,
the call being processed by the control exchange for that circuit will be completed and the received initial address
message will be disregarded.
220 Recommendation Q.767
Under these conditions, the call being processed by the control exchange will be allowed to mature. The call
being processed by the non-control exchange will be backed off and the switch-path released. A release message will not
be sent. The non-control exchange will make an automatic repeat attempt on the same or on an alternative route.
For the purpose of resolution of dual seizure on bothway circuits, the exchange with the higher signalling point
code will control all even-numbered circuits (circuit identification code) and the other exchange the odd-numbered
circuits. The designation of control may also be used for maintenance system purposes.
D.2.10.2 Transmission alarm handling for digital inter-exchange circuits
When fully digital circuits are provided between two exchanges, which have some inherent fault indication
feature giving an indication to the switching system when faults on transmission systems are detected, the switching
system should inhibit selection of the circuits concerned for the period the fault conditions persist.
D.2.10.3 Reset of circuits and circuit groups
In systems which maintain circuit status in memory, there may be occasions when the memory becomes
mutilated. In such a case the circuits must be reset to the idle condition at both exchanges to make them available for
new traffic. Since the exchange with the mutilated memory does not know whether the circuits are idle, busy outgoing,
busy incoming, blocked, etc., reset circuit messages or a circuit group reset message should be sent as appropriate for the
affected circuits.
D.2.10.3.1 Reset circuit message
If only a few circuits are concerned, a reset circuit message should be sent for each affected circuit.
On receipt of a reset circuit message, the receiving (unaffected) exchange will:
a) If it is the incoming or outgoing exchange on a connection in any state of call set-up or during a call,
accept the message as a release message and respond by sending a release complete message, after the
circuit has been made idle.
b) If the circuit is in the idle condition, accept the message as a release message and respond by sending a
release complete message.
c) If it has previously sent a blocking message, or if it is unable to release the circuit as described above,
respond by the blocking message. If an incoming or outgoing call is in progress, this call should be
released and the circuit returned to the "idle, blocked" state. A release complete message is sent following
the blocking message. The blocking message should be acknowledged by the affected exchange. If the
acknowledgement is not received, the repetition procedure specified in D.2.10.4 should be followed.
d) If it has previously received a blocking message, respond by releasing a possible outgoing call or call
attempt on the circuit, remove the blocked condition, restore the circuit to the idle state, and respond with
a release complete message.
e) If the message is received after the sending of an initial address message but before receipt of a backward
message relating to that call, clear the circuit and make an automatic repeat attempt on another circuit if
appropriate.
f) If the message is received after having sent a reset circuit message, respond by a release complete
message. THE CIRCUIT SHALL BE MADE AVAILABLE FOR SERVICE AFTER RECEIPT OF THE APPROPRIATE
ACKNOWLEDGEMENT MESSAGE.
g) Clear any interconnected circuits by the appropriate method (e.g. release).
Recommendation Q.767 221
The affected exchange will then reconstruct its memory according to the received response(s) to the reset
circuit and respond to the message(s) in the normal way, i.e. blocking acknowledgement message in response to a
blocking message.
If no release complete message is received in acknowledgement to the reset circuit message before
4-15 seconds (T16), the reset circuit message should be repeated. If an acknowledgement for the message is not received
within 1 minute (T17), after the initial reset circuit message, the maintenance system should be notified. However, the
sending of the reset circuit message should continue at 1 minute (T17) intervals until maintenance intervention occurs.
D.2.10.3.2 Circuit group reset message
If a considerable number of circuits or all circuits are affected by a memory mutilation, (a) circuit group reset
message(s) should be used to make them available for new traffic.
The maximum number of circuits to be reset with a circuit group reset message is limited to 32.
On receipt of a circuit group reset message, the receiving (unaffected) exchange will:
a) restore the circuits to the idle state;
b) send the appropriate circuit group blocking message(s) if it had previously sent a hardware failure
oriented circuit group blocking message;
c) respond by a circuit group reset acknowledgement message in which the status indicator bits of the
circuits available for service or blocked for reasons of hardware failure are coded 0 and the status
indicator bits of all circuits blocked for maintenance reasons are set to 1;
d) if it had previously received (a) blocking message(s) or (a) circuit group blocking message(s) for one or
more of the circuit(s) involved, the blocked condition will be removed and the circuits will be made
available for service;
e) if a circuit group reset message is received concerning circuits for which a circuit group reset message or
reset circuit message(s) have been sent, the circuits concerned are made available for service after receipt
of the appropriate acknowledgement message;
f) appropriate messages should be sent on interconnected circuits to release them.
The affected exchange will then reconstruct its memory according to the possibly received circuit group
blocking messages and the received circuit group reset acknowledgement message. It will respond to the possibly
received circuit group blocking messages in the normal way.
If no acknowledgement to a circuit group reset message is received before 4-15 seconds (T22), the circuit
group reset message should be repeated. If an acknowledgement for the circuit group reset message is not received
within 1 minute (T23) after sending the initial circuit group reset message, the maintenance system should be notified.
However, the sending of the circuit group reset message should continue at 1 minute (T23) intervals until maintenance
intervention occurs.
A correct acknowledgement should match the original circuit group reset message in range and circuit
identification code indicated in the routing label.
222 Recommendation Q.767
The circuit identification code in the routing label of both circuit group reset messages and circuit group reset
acknowledgement messages should belong to a circuit whose control is allocated to the ISDN-UP.
All circuit identification codes in the range of a circuit group reset and circuit group reset acknowledgement
message must belong to circuits whose control is allocated to the ISDN-UP.
D.2.10.3.3 Abnormal circuit group reset message procedures
i) If a circuit group reset message is received indicating reset of more circuits than allowed by the receiving
exchange, it is discarded.
ii) If a circuit group reset acknowledgement message is received which is not a correct response to a sent
circuit group reset message, it is discarded.
iii) If a circuit group reset message is received requesting reset of circuits that are not controlled by the ISDN
user part, or a circuit group reset acknowledgement message that contains circuit identification codes that
are not controlled by the ISDN-UP, the message is discarded.
D.2.10.4 Failure in the blocking/unblocking sequence
An exchange will repeat the blocking (unblocking) message or the circuit group blocking (unblocking)
message on failure to receive the appropriate acknowledgement in response to one of these messages before
4-15 seconds (T12 for Blocking message, T14 for Unblocking message, T18 for Circuit group blocking message, T20
for Circuit group unblocking message). (see D.2.9.2).
If the appropriate acknowledgement is not received within a period of one minute (T13 for Blocking message,
T15 for Unblocking message, T19 for Circuit group blocking message, T21 for Circuit group unblocking message) after
sending the initial blocking (unblocking) message or group blocking (unblocking) message, the maintenance system
should be alerted, the repetition of the blocking (unblocking) message or circuit group blocking (unblocking) message
should be continued at one-minute intervals until maintenance intervention occurs and the circuit(s) taken out of
(returned to) service as appropriate.
D.2.10.5 Receipt of unreasonable and unrecognized signalling information messages
The message transfer part of the signalling system will avoid missequencing, or double delivery, of messages
with a high reliability (Recommendation Q.706, 2). However, undetected errors at the signalling link level and
exchange malfunctions may produce signalling information messages that are either ambiguous or inappropriate.
The procedures listed below do not include the procedures for the blocking, circuit group blocking and the
circuit group reset; these are covered in D.2.9.2.3 and D.2.10.3.3 respectively.
Recommendation Q.767 223
D.2.10.5.1 Handling of unexpected messages
An unexpected message is one which is recognized and valid but has been received in the wrong phase of the
call.
In order to resolve possible ambiguities in the state of a circuit when unexpected messages are received, the
following will apply:
a) if a release message is received relating to an idle circuit, it will be acknowledged with a release complete
message;
b) if a release complete message is received relating to an idle circuit, it will be discarded;
c) if a release complete message is received relating to a busy circuit for which a release message has not
been sent, the circuit will be released and a release message will be sent (the possibility of maintaining the
connection is for further study);
d) if other unreasonable signalling information is received, the following actions will be undertaken:
if the circuit is idle, the reset circuit message is sent;
if the circuit has been seized by a call, after receipt of a backward message required for the call set-
up, the unreasonable signalling information is discarded;
if the circuit has been seized by a call, before receipt of a backward message required for the call set-
up, the reset circuit message is sent. If the circuit is seized by an incoming call, the call will be
released. If the circuit is seized by an outgoing call, an automatic repeat attempt is provided on
another circuit;
e) if unreasonable signalling information caused by conflicting code point values in the protocol control
indicator as specified in Annex C is received in a backwards call set-up message, and if the conflicting
conditions can be reconciled by assuming lower network capability in the affected parameter, the call
should be allowed to continue if the service requirements for the call can be satisfied.
Except in certain cases (see D.2.10.1), any other unexpected messages received will be discarded. If the
discarding of the signalling information prevents a call from being completed, that call will eventually be released by the
expiry of a time out.
D.2.10.5.2 General requirements on receipt of unrecognized signalling information messages and parameters
SEE RECOMMENDATION Q.767 4.1.1.
D.2.10.5.3 Procedures for the handling of the unrecognized messages or parameters
SEE RECOMMENDATION Q.767 4.1.1.
224 Recommendation Q.767
D.2.10.6 Failure to receive a "release complete" message time T1 and T5
If a release complete message is not received in response to a release message before time (T1), the exchange
will retransmit the release message.
On TRANSMITTING the initial release message, a one-minute timer (T5) is started. If no release complete
message is received on the expiry of this timer (T5), the exchange shall:
i) send a reset circuit message;
ii) alert the maintenance system;
iii) remove the circuit from service;
iv) continue the sending of the reset circuit message at 1-minute intervals until maintenance action occurs.
D.2.10.7 Failure to receive a response to an information request message
This section is not applicable to the international interface.
D.2.10.8 Other failure conditions
D.2.10.8.1 Inability to release in response to a release message
If an exchange is unable to return the circuit to the idle condition in response to a release message, it should
immediately remove the circuit from service, alert the maintenance system and send the blocking message.
Upon receipt of the blocking acknowledgement message, the release complete message is sent in
acknowledgement of the release message.
D.2.10.8.2 Call-failure
The call-failure indication (cause #31) is sent in a release message (see D.2.2) whenever a call attempt fails
and other specific signals do not apply. Reception of the release message at any Signlalling System No. 7 exchange will
cause the release message to be sent to preceding exchanges. If the signalling does not permit the release message to be
sent, the appropriate signal, tone or announcement is sent to preceding exchanges.
D.2.10.8.3 Abnormal release conditions
If the conditions for normal release as covered in D.2.3 are not fulfilled, release will take place under the
following conditions:
a) Outgoing international or national controlling exchange
The exchange shall:
release all equipment and the connection on failure to meet the conditions for normal release of
address and routing information before 20-30 seconds after sending the latest address message;
release all equipment and release the connection on failure to receive an answer message within time
(T9) specified in Recommendation Q.118 after the receipt of the address complete message.
Recommendation Q.767 225
b) Incoming international exchange
An incoming international exchange shall release all equipment and the connection into the national
network and send back a release message in the following cases:
on failure to receive a continuity message if applicable before 10-15 seconds (T8) after receipt of the
initial address message; or
on failure to receive a backward signal from a national network (where expected) before
20-30 seconds (T7) after receipt of the latest address message; or
on receipt of a release message after an address complete message has been generated;
on failure to receive an address message before 15-20 seconds (T35) after receipt of the latest
address message and before the minimum or fixed number of digits have been received.
The procedures for the release message are detailed in D.2.2.2.
c) Transit exchange
The exchange shall release all equipment and the connection and send back the release message in the
following cases:
on failure to receive a continuity message if applicable before 10-15 seconds after receipt of the
initial address message; or
on failure to meet the conditions for normal release as covered in D.2.3 before 20-30 seconds after
sending the latest address message;
on failure to receive an address message before 15-20 seconds (T35) after receipt of the latest
address message and before the minimum or fixed number of digits have been received.
The procedures for the release message are detailed in D.2.2.2.
D.2.10.8.4 If messages are lost during an end-to-end transfer, appropriate actions will be taken according to the type
of end-to-end technique being used.
D.2.10.8.5 For calls involving the SCCP, expiration of the call supervision timer (concerned with call set-up) will
result in the SCCP being notified of an error condition.
D.2.10.9 Temporary trunk blocking (TTB) (national use)
This section is not applicable to the international interface.
D.2.10.10 Temporary trunk blocking before release of call (use of a discrete overload message)
This section is not applicable to the international interface.
226 Recommendation Q.767
D.2.11 ISDN user part signalling congestion control
D.2.11.1 General
On receipt of congestion indication primitives (see also Recommendation Q.704 11.2.3), the ISDN user part
should reduce traffic load (e.g. call attempts) into the affected direction in several steps.
D.2.11.2 Procedures
When the first congestion indication primitive is received by the ISDN user part, the traffic load into the
affected direction is reduced by one step. At the same time two timers T29 and T30 are started. During T29 all received
congestion indication primitives for the same direction are ignored in order not to reduce traffic too rapidly. Reception of
a congestion indication primitive after the expiry of T29, but still during T30, will decrease the traffic load by one more
step and restart T29 and T30. This stepwise reduction of the ISDN user part signalling traffic is continued until
maximum reduction is obtained by arriving at the last step. If T30 expires (i.e. no congestion indication primitives
having been received during the T30 period), traffic will be increased by one step and T30 will be restarted unless full
traffic load has been resumed.
Timers T29 and T30 have the following values:
T29 = 300-600 ms,
T30 = 5-10 s.
The number of steps of traffic reduction and the type and/or amount of increase/decrease of traffic load at the
various steps are considered to be an implementation matter.
D.2.12 Automatic congestion control
Automatic congestion control (ACC) is used when an exchange is in an overload condition (see also
Recommendation Q.542). Two levels of congestion are distinguished: a less severe congestion threshold (congestion
level 1) and a more severe congestion threshold (congestion level 2).
If either of the two congestion thresholds are reached, an automatic congestion level parameter is added to all
release messages generated by the exchange. This parameter indicates the level of congestion (congestion level 1 or 2) to
the adjacent exchanges. The adjacent exchanges, when receiving a release message containing an automatic congestion
level parameter, should reduce their traffic to the overload affected exchange.
If the overloaded exchange returns to a normal traffic load, it will cease including automatic congestion level
parameters in release messages.
The adjacent exchanges then, after a predetermined time, automatically return to their normal status.
D.2.12.1 Receipt of a release message containing an automatic congestion level parameter
When an exchange receives a release message containing an automatic congestion level parameter, the ISDN
user part should pass the appropriate information to the signalling system independent network management/overload
control function within the exchange. This information consists of the received congestion level information and the
circuit identification to which the release message applies.
Recommendation Q.767 227
If the ACC procedure is not implemented, the ACC parameter is not acted upon and discarded as normal.
ACC actions are applicable only at exchanges adjacent to the congested exchange. Therefore, an exchange that
receives a release message containing an automatic congestion level parameter should discard that parameter after
notifying the network management/overload control function.
D.2.12.2 Actions taken during overload
Whenever an exchange is in an overload state (congestion level 1 or 2), the signalling system independent
network management/overload control function will direct the ISDN user part to include an automatic congestion level
parameter in every release message transmitted by the exchange.
The network management/overload control function will indicate which congestion level (1 or 2) to code in the
automatic congestion level parameter.
When the overload condition has ended, the network management/overload control function will direct the
ISDN user part to cease including automatic congestion level parameters in the transmitted release messages.
D.2.13 Unequipped circuit identification code message (national option)
This section is not applicable to the international interface.
T1148220-92/d15
Calling
party
Originating
local exch.
Transit
exch.
Transit
exch.
Terminating
local exch.
Called
party
Set-up
(complete)
IAM (Note 3) IAM (Note 3)
Set-up
Address complete
(no indication)
Address complete
(no indication)
Address complete
(no indication)
Accepted
Answered
Alerting
Connect Answer Answer Answer
Progress
(alerting)
Progress
(alerting)
Progress
(alerting) (Note 2)
Alerting
(Note 1)
Connect
(Note 8)
Switchpath completed in backward direction
Switchpath completed in forward direction
Switchpath completed in both directions
Charging begins (optionally charging may begin prior to answer)
Note 1 The alerting message may not be given by a called terminal having automatic answer. Under these circumstances the Connect
Message will not be sent as soon as the Connect Message is received and through connection of the speech path has been completed.
Note 2 For telephone calls within the ISDN, ringing tone will be applied by the terminating exchange as soon as it knows that the
subscriber is free. In the case of a PABX connected to the access interface there is the option of an early through connection of the
switchpath so that the in-band call arrival indication generated in the PABX is returned to the calling user. For data calls, ringing tone is
not applied.
Note 3 The continuity check may be applicable on an intermediate circuit if analogue circuits are used.
Note 8 Access protocol example is for point-to-point operation only.
FIGURE D-1/Q.767
Successfull ordinary call (en bloc operation)
Notes referring to Figures D-1/Q.767 and D-2/Q.767
IAM (Note 3)
Connect
228 Recommendation Q.767
T1148230-92/d16
Calling
party
Originating
local exch.
Transit
exch.
Transit
exch.
Terminating
local exch.
Called
party
Set-up (incomplete)
IAM (Note 3) IAM (Note 3)
Assume number
length known
Set-up
Accepted
Answered
Alerting
Connect Answer Answer Answer
Address complete
(subscriber free)
Alerting
(Note 1)
Connect
Switchpath completed in backward direction
Switchpath completed in forward direction
Switchpath completed in both directions
Charging begins (optionally charging may begin prior to answer)
FIGURE D-2/Q.767
Successfull ordinary call (overlap operation)
Address complete
(subscriber free)
Address complete
(subscriber free)
(Note 2)
SAM
SAM
SAM
SAM
SS 7 signalling
available
IAM (Note 3)
Final set-up
(This figure is not applicable to the international interface)
FIGURE D-3/Q.767
Recommendation Q.767 229
T1148240-92/d17
Calling
party
Originating
local exch.
Transit
exch.
Transit
exch.
Terminating
local exch.
Called
party
Call set-up for a normal call to point
of call rejection
FIGURE D-4/Q.767
Unsuccessful call set-up (no rerouting)
Transit
exch.
Call cannot be
accepted
Node releases
Release (reason)
Indication to
terminal
Release (reason) Release (reason) Release (reason)
Release switchpath
RLC RLC RLC RLC
Call set-up
230 Recommendation Q.767
T1148250-92/d18
Calling
party
Originating
local exch.
Transit
exch.
Transit
exch.
Terminating
local exch.
Called
party
FIGURE D-5/Q.767
Suspend request and resume
Transit
exch.
Suspend
Resume
Suspend
Resume
Suspend
Resume
Suspend
Resume
Suspend
Resume
Notify
Notify
Start
time out
Stop
time out
Recommendation Q.767 231
T1148260-92/d19
Calling
party
Originating
local exch.
Transit
exch.
Transit
exch.
Terminating
local exch.
Called
party
FIGURE D-6/Q.767
Suspend request with no connection
Transit
exch.
Suspend
No resume
request
Suspend Suspend Suspend Suspend Notify
Start
time out
Time out
matures
Disconnect Disconnect
REL
Remove
switchpath
REL REL REL
RLC RLC RLC RLC
Remove
switchpath
Remove
switchpath
Remove
switchpath
Remove
switchpath
232 Recommendation Q.767
T1148270-92/d20
Calling
party
Originating
local exch.
Transit
exch.
Transit
exch.
Terminating
local exch.
Called
party
FIGURE D-7/Q.767
Normal call release
Transit
exch.
Disconnect
Disconnect REL
Remove
switchpath
REL REL REL
RLC RLC RLC RLC
Disconnect REL
RLC
REL
RLC
REL
RLC
REL
RLC
Release Disconnect
Release
Remove
switchpath
Remove
switchpath
Remove
switchpath
Remove
switchpath
Remove
switchpath
Remove
switchpath
Remove
switchpath
Remove
switchpath
Remove
switchpath
Calling party clears
Called party clears
Call disconnected
(normally)
Recommendation Q.767 233
TABLE D-1/Q.767 (sheet 1 of 6)
Timers used in Annex D
Symbol Time-out value Significance Cause for initiation Normal termination At expiry Section
T1 4-15 seconds Local When release message is sent At the receipt of release complete
message
Re-transmit release message and
start timer T1
2.2 2.3.1
2.10.6
T2 3 min Dual When suspend request controlling
exchange receives suspend (user)
message
At the receipt of resume (user)
message at controlling exchange
Initiate release procedure 2.5.1.1
2.5.2.1
2.5.3
T3 Not used on the international
interface
2.6
T4 Not used on the international
interface
2.7.1
2.7.2
T5 1 min Local When initial release message is sent At receipt of release complete
message
Send reset circuit message, alert
maintenance personnel and remove
the circuit from service, stop T1
start T17. Procedure continues until
maintenance intervention occurs
2.2
2.3.1
2.10.6
T6 Covered in
Rec. Q.118
Dual When controlling exchange
receives suspend (network)
At the receipt of resume (network)
message
Initiate release procedure 2.5.1.3
2.5.2.3 2.5.3
234 Recommendation Q.767
TABLE D-1/Q.767 (sheet 2 of 6)
Timers used in Annex D
Symbol Time-out value Significance Cause for initiation Normal termination At expiry Section
T7 20-30 s Dual When the latest address message is
sent
When the condition for normal
release of address and routing
information is met (receipt of
ACM, CON messages)
Release all equipment and
connection (send release message)
2.1.1.1
2.1.4.4
2.1.4.8
2.1.2.1 f)
2.10.8.3
T8 10-15 s Local When transit or incoming
international exchange receives
initial address message requiring
continuity check on this circuit, or
indicates that continuity check has
been performed on a previous
circuit
At receipt of continuity message Release all equipment and
connection into national network
(send release message)
2.1.8
2.10.8.3
T9 Interval
specified in
Rec. Q.118
Dual When national controlling or
outgoing international exchange
receives ACM
At the receipt of answer Release connection and send back
release message
2.1.4.4
2.1.7.2
2.1.7.3
2.10.8.3
T10 4-6 s Dual When last digit is received in
interworking situations
At the receipt of fresh information Send address complete message 2.1.2.1 e)
2.1.4.8
T11 15-20 s Dual When latest address message is
received in interworking situations
When ACM is sent Send address complete message 2.1.4.8
Recommendation Q.767 235
TABLE D-1/Q.767 (sheet 3 of 6)
Timers used in Annex D
Symbol Time-out value Significance Cause for initiation Normal termination At expiry Section
T12 4-15 s Local When blocking message in sent At receipt of blocking
acknowledgement
Re-transmit blocking message and
start T12
2.10.4
T13 1 min Local When initial blocking message is
sent
At receipt of blocking
acknowledgement
Transmit blocking message, alert
maintenance personnel and start T13;
stop T12. Procedure continues until
maintenance intervention occurs
2.10.4
T14 4-15 s Local When unblocking message is sent At receipt of unblocking
acknowledgement
Re-transmit unblocking message
and start T14
2.10.4
T15 1 min Local When initial unblocking message is
sent
At receipt of unblocking
acknowledgement
Re-transmit unblocking message
and alert maintenance personnel,
start T15, and stop T14. Procedure
continues until maintenance
intervention occurs
2.10.4
T16 4-15 s Local When reset circuit message is sent
not due to the expiry of Timer T5
At the receipt of the
acknowledgement (RLC message)
Re-transmit reset circuit message
start T16
2.10.3.1
T17 1 min Local When initial reset circuit message is
sent
At the receipt of the
acknowledgement
Alert maintenance personnel,
retransmit reset circuit message,
start T17 and stop T16. Procedure
continues until maintenance
intervention occurs
2.10.3.1
236 Recommendation Q.767
TABLE D-1/Q.767 (sheet 4 of 6)
Timers used in Annex D
Symbol Time-out value Significance Cause for initiation Normal termination At expiry Section
T18 4-15 s Local When group blocking message is
sent
At receipt of group blocking
acknowledgement
Re-transmit group blocking
message and start T18
2.10.4
T19 1 min Local When initial group blocking
message is sent
At receipt of group blocking
acknowledgement
Re-transmit group blocking
message, alert maintenance
personnel, start T19 and stop T18.
Procedure continues until
maintenance intervention occurs
2.10.4
T20 4-15 s Local When group unblocking message is
sent
At receipt of group unblocking
acknowledgement
Re-transmit group unblocking
message and start T20
2.10.4
T21 1 min Local When initial group unblocking
message is sent
At the receipt of group unblocking
acknowledgement
Re-transmit group unblocking
message, alert maintenance
personnel, start T21 and stop T20.
Procedure continues until
maintenance intervention occurs
2.10.4
T22 4-15 s Local When circuit group reset message is
sent
At the receipt of the
acknowledgement
Re-transmit circuit group reset
message, start T22
2.10.3.2
Recommendation Q.767 237
TABLE D-1/Q.767 (sheet 5 of 6)
Timers used in Annex D
Symbol Time-out value Significance Cause for initiation Normal termination At expiry Section
T23 1 min Local When initial circuit group reset
message is sent
At receipt of the acknowledgement Alert maintenance personnel and
start T23, re-transmit circuit group
reset message, stop T22. Procedure
continues until maintenance
intervention occurs
2.10.3.2
T24 < 2 s Local When check tone is sent At the receipt of backward check
tone
Send continuity message with
failure indication and:
a) start T25 if continuity check was
asked in an IAM and make
automatic repeat attempt, or
b) start T26 if continuity check was
asked in a CCR
Rec. Q.724, 7.4.1
T25 1-10 s Local When initial continuity check
failure is detected
Send CCR message and repeat
continuity check
Rec. Q.724, 7.3
T26 1-3 min Local When second or subsequent
continuity check failure is detected
Send CCR message and repeat
continuity check
Rec. Q.724, 7.3
T27 4 min Local When continuity check failure
indication is received
At receipt of continuity check
request message
Send reset circuit message; start
T16 and T17
2.1.8
T28 Not used ont the international
interface
2.9.3.2
238 Recommendation Q.767
TABLE D-1/Q.767 (sheet 6 of 6)
Timers used in Annex D
Symbol Time-out value Significance Cause for initiation Normal termination At expiry Section
T29 300-600 ms Local Congestion indication received when
T29 not running
New congestion indication will be
taken into account
2.11.2
T30 5-10 s Local Congestion indication received when
T29 not running
Restore traffic by one step if not yet
at full load and start T30
2.11.2
T31 Not used on the international
interface
3.7.2
3.7.3
3.7.4
T32 Not used on the international
interface
3.7.5
T33 Not used on the international
interface
2.1.6.2
2.10.7
T34 Not used on the international
interface
2.9.3.2
T35 15-20 s Dual At receipt of the latest digit
(< > ST) and before the minimum
or fixed number of digits have been
received
At receipt of ST or when the
minimum or fixed number of digits
have been received
Send release message (cause 28) 2.2.5
2.10.8.3
T36 10-15 s Local When transit or incoming
international exchange receives
continuity check request message
At receipt of continuity or release
message
Release all equipment, sent reset
circuit message, start T16 and T17
2.1.8
Recommendation Q.767 239
D.3 End-to-end signalling
This section is not applicable to the international interface.
ANNEX E
(to Recommendation Q.767)
ISDN supplementary services
E.1 General
E.1.1 THIS RECOMMENDATION DESCRIBES THE SIGNALLING PROCEDURES FOR SUPPLEMENTARY SERVICES TO BE USED IN
CONJUNCTION WITH THE ISDN USER PART DEFINED IN RECOMMENDATIONS Q.761 TO Q.764 AND Q.766 AND ANNEXES A, B,
C AND D TO THIS RECOMMENDATION and the Transaction Capabilities Applications Part (TCAP) defined in
Recommendations Q.771-774.
Each Supplementary service has been defined in separate sections, each containing the complete procedures
for encompassing both the ISDN User Part and the procedures to be used on the top of TCAP where appropriate.
Each section contains a general paragraph giving details of the specific service with references to the Stage I
and II descriptions defined in the relevant Recommendations of the I.200 and Q.80-Series. The call set-up procedures
and the actions taken at originating exchanges, etc. are defined. Arrow diagrams showing the message flows for both
successful and unsuccessful establishment of the service are generally included. The formats and codings aspects are not
defined in this Recommendation but references are made to the appropriate ISDN User Part, TC or SCCP
Recommendations.
E.1.2 Information request/response
This section is not applicable to the international interface.
E.1.3 Exceeding the maximum message length (e.g. ISDN User Part 272 octets)
If for any reason the combination of basic plus supplementary service information causes the overall
maximum length of the message (e.g. initial address message) to be exceeded, then the user-to-user supplementary
service 1, if included, should be rejected (see E.2 covering interactions).
The combination of other services which may cause the message length to be exceeded will depend on the call
state and the requested service.
E.1.4 Layout of Annex E
E.1 General
E.2 User-to-user signalling (Note)
E.3 Closed user group
E.4 Calling line identification (presentation and restriction)
E.5 Direct dialling in
E.6 Call forwarding (Note)
E.7 Time-out table for supplementary services (requires further study)
E.8 Description of the connected Line Identification Presentation and Restriction service
240 Recommendation Q.767
Direct Dialling In and multiple subscriber number are supported, but are without significance to the
international interface.
Sub-addressing and terminal portability are implicitly supported as part of the basic Q.767 procedures.
Note The text for the explicit invocation of the user-to-user signalling has been included as Annex A.
E.2 User-to-User Signalling service
E.2.1 General description of User-to-User service
The User-to-User Signalling Supplementary service(s) provide(s) a means of communication between two
users by using the ISDN User Part or SCCP PROTOCOL defined in Recommendations Q.761 to Q.764 and Q.766 and
Annexes A, B, C and D to this Recommendation. In order for the services to be usable, they also have to be provided in
the access protocol.
User-to-user signalling is used to exchange I.257 information between two users to provide the user-to-user
services described in Recommendation I.257. This section is specific to Signalling System No. 7. The general
description for services 1-3 may be found in the last mentioned Recommendation and the functional description in
Recommendation Q.87.
E.2.1.1 User-to-user services
ONLY IMPLICIT USER SERVICE 1 IS SUPPORTED.
Service 1: user-to-user signalling exchanged during the set-up and clearing phases of a call, within ISDN User
Part call set-up and release messages as defined in ANNEX C;
Service 2: user-to-user signalling exchanged during call set-up between the address complete or call progress
messages and the answer or connect messages, within user-to-user information messages; and
Service 3: user-to-user signalling exchanged while a call is in the active state, within user-to-user information
messages.
UP TO 128 OCTETS OF USER INFORMATION MAY BE TRANSFERRED IN A MESSAGE. THE 128 OCTETS DO NOT INCLUDE
THE PARAMETER NAME, THE LENGTH AND THE PROTOCOL DISCRIMINATOR.
E.2.1.2 Service request
Service 1 IS requested implicitly by the presence of the user-to-user information parameter in the initial address
message. An implicit request is "non-essential" by default.
Explicit requests of Service 1 and 2 must be in the Initial Address Message. Service 3 may be explicitly
requested in the Initial Address Message during call set-up. When there is an explicit request, a single user-to-user
indicators parameter will be used with one of the following indications for each of the three services:
no information;
requested, non-essential;
requested, essential.
Recommendation Q.767 241
E.2.1.3 Response (Confirmation)
THE DISCARD OF USER-TO-USER INFORMATION BY THE NETWORK, EXCEPT IN THE CASE OF PSTN INTERWORKING OR
TERMINATING ACCESS NON-ISDN, IS EXPLICITLY NOTIFIED BY THE USER-TO-USER INDICATOR PARAMETER IN THE APPROPRIATE
BACKWARD MESSAGE. BIT H IS CODED "UUI DISCARDED BY THE NETWORK" AND BITS CB ARE CODED "NO INFORMATION". NO
INFORMATION IS GIVEN IF THE CALLED USER DOES NOT UNDERSTAND THE SERVICE OR CANNOT SUPPORT THE SERVICE.
E.2.1.4 Flow control
This section is not applicable to the international interface.
E.2.2 Procedures for user-to-user signalling associated with circuit-switched call
The following sections only specify the signalling procedure used to implicitly invoke the service 1. Signalling
procedures defined to support the other services are specified in Annex A.
E.2.2.1 User-to-User Signalling, service 1
E.2.2.1.1 General characteristics
Service 1 allows users to communicate with User-to-User Signalling by transferring user-to-user information
within ISDN User Part messages during the call set-up and clearing phases. The user-to-user signalling service provided
is not a guaranteed service. If for any reason the combination of the basic plus supplementary service information causes
the overall maximum length of the messages to be exceeded OR IF 128 OCTETS OF USER-TO-USER INFORMATION CANNOT BE
SUPPORTED IN THE IAM, THEN THE USER-TO-USER INFORMATION PARAMETER IS DISCARDED AND A USER-TO-USER INDICATOR
PARAMETER IS SENT IN THE FIRST APPROPRIATE BACKWARD MESSAGE (E.G ACM OR CON). NO TRUNCATION OF USER-TO-USER
INFORMATION IS PERFORMED.
E.2.2.1.2 User-to-User Signalling in the call set-up phase implicit service request
Procedures for call set-up are as described in D.2, with the following changes:
Service 1 may be invoked by sending the user-to-user information parameter of variable length that is
specified in C.3.34 in an initial address message that is requested in a call set-up request from call control. This
information parameter is transported across the network and delivered unchanged to the terminating call control for the
called user. The user-to-user indicators parameter will not be sent.
242 Recommendation Q.767
The reception of a user-to-user information parameter in a call set-up or release request from the terminating
call control is an implicit indication of the acceptance of service 1.
The user or network may not be able to interpret incoming user-to-user information. In such situations, the
user should discard this information without disrupting normal call handling. No specific signalling is provided by the
network to accommodate this situation.
If no UUS information is sent in the IAM, the incoming (outgoing) national network should prevent the
transmission of UUS in the backward (forward) direction.
E.2.2.1.3 Interworking
In the case of interworking with a non-ISDN network, the "interworking" protocol control information will be
returned to the originating exchange in the first appropriate message, e.g. an address complete message. Two ISDN
networks that interwork may have to retain knowledge of the service request until it is clear whether both can support
the service.
E.2.2.1.4 Rejection of implicit service requests
NETWORKS THAT CANNOT PROVIDE THE REQUESTED SERVICE WILL RETURN A REJECT INDICATION IN THE USER-TO-
USER INDICATOR PARAMETER IN THE FIRST APPROPRIATE BACKWARD MESSAGE. BIT H IS CODED "UUI DISCARDED BY THE
NETWORK" AND BITS CB ARE CODED "NO INFORMATION".
E.2.2.1.5 User-to-user signalling in the call clearing phase
A user-to-user information parameter may be included in the release message. The user-to-user information
parameter received at the distant exchange in the release message is passed to the call control for the remote user. In the
case of simultaneous clearing of the call, the release message may not reach the distant local exchange and the user-to-
user information will be lost.
E.2.2.1.6 Message flow diagrams
The message flow diagrams are shown in Figure E-1/Q.767 as well as the use of user-to-user signalling
service 1 when implicitly requested in a point-to-point configuration.
The messages shown with dashed lines are not part of the ISDN User Part protocol and are for information
only. For detailed information on the access protocol user-to-user procedures, the ISDN access protocol
Recommendation should be examined.
Recommendation Q.767 243
T1148280-92/d21
Originating
local exchange
Transit
exchange
Terminating
user
FIGURE E-1/Q.767
UUS service 1 (implicit request, called user is point-to-point)
Terminating
local exchange
Originating
user
UUI
ACM
ANM
IAM
REL
RLC
User-to-user signalling
Address complete message
Answer message
Initial address message
Release
Release complete
Note 1 In the case where an ALERTING indication is carried by a call progress message, the user-to-user
information parameter may also be transported in the call progress message.
Note 2 In the case where the called user is an automatic answering terminal, the user-to-user information
parameter may be transported in a CONnect message.
ANM
(UUI)
244 Recommendation Q.767
E.2.2.2 Interaction with other supplementary services
E.2.2.2.1 Call forwarding services
This section is not applicable to the international interface.
E.2.2.2.2 Call Waiting service
This section is not applicable to the international interface.
E.2.2.2.3 Other services
There are no known interactions with services other than those listed.
E.2.2.2.4 State transition diagrams
The state transition diagrams may be found in stage 2 descriptions of the user-to-user service.
E.3 Closed User Group (CUG)
E.3.1 General
The Closed User Group (CUG) supplementary service enables a group of users to intercommunicate only
among themselves or, as required, one or more users may be provided with incoming/outgoing access to users outside
the group.
The stage 1 definition of the CUG service is given in Recommendation I.255, and its stage 2 service definition
including network functions are given in Recommendation Q.85.
The realization of the CUG facilities is done by the provision of interlock codes and is based on various
validation checks as defined in Q.85 at call set-up, determining whether or not a requested call to or from a user having a
CUG facility is allowed. In particular, a validation check is performed by verifying that both the calling and called
parties belong to the CUG indicated by the interlock code.
The data for each CUG that a user belongs to can either be stored at the local exchange to which the user is
connected (decentralized administration of CUG data), or at dedicated point(s) in the network (centralized administration
of CUG data).
Recommendation Q.767 245
IN E.3.2, the call set-up procedure based on decentralized administration of CUG data is specified, making
use of the ISDN User Part as defined in Recommendations Q.761 to Q.764 and Q.766 and Annexes A, B, C and D to
this Recommendation.
In E.3.3, the call set-up procedure based on centralized administration of CUG data is specified, making use
of the ISDN User Part as defined in Recommendations Q.761-764 and Q.766 and the Transaction Capabilities
Application Part (TCAP) as defined in Recommendations Q.771-775.
Section E.3.4 specifies the application service element (ASE), situated above the Transaction Capabilities
Application Part (TCAP), and used for CUG validation check with centralized administration of CUG data.
The administration of CUG data is considered as a national matter.
E.3.2 Call set-up procedure with decentralized or centralized administration of CUG data
E.3.2.1 Originating exchange
The actions at the originating exchange at call set-up from a user belonging to a CUG depend on the result of
the validation checks performed there, based on whether the user belongs to one or more CUGs and on the combination
of CUG facilities that applies.
a) CUG call without outgoing access
If the result of the validation check indicates that the call should be dealt with as a CUG call, the
interlock code of the selected CUG is obtained. The initial address message forwarded to the next
exchange then includes the interlock code together with an indication that the call is a CUG call
without outgoing access. The ISUP preference indicator of the forward call indicators parameter in
the IAM is set to "ISUP required all the way".
b) CUG call with outgoing access
If the result of the validation check indicates that the call should be dealt with as a CUG call with
outgoing access, the interlock code of the selected CUG together with an outgoing access indication
is obtained. The initial address message forwarded to the next exchange then includes the interlock
code together with an indication that the call is a CUG call for which outgoing access is allowed. The
ISUP preference indicator of the forward call indicators parameter in the IAM is set to "ISUP
preferred all the way", unless another service requires a more stringent setting.
246 Recommendation Q.767
c) Non-CUG call
If the result of the validation check indicates that the call should be dealt with as a non-CUG call, the
initial address message forwarded to the next exchange then does not include an interlock code nor a
CUG call indication.
d) Call rejected
If the result of the validation check indicates that the call is to be rejected, the call set-up is not
initiated.
E.3.2.2 Transit exchange
With the possible exception of some gateway exchanges, Each transit exchange sets up a CUG call as an
ordinary call. The information related to the CUG facilities received from the preceding exchange, i.e. an interlock code,
a CUG call indication possibly with an indication that outgoing access is allowed is forwarded to the succeeding
exchange.
In the case of an international CUG call, no special functions are required at the gateway exchange provided
that the international interlock code assigned to the international CUG concerned is used in the national network.
However, in the case where a national interlock code other than the applicable international interlock code is used within
a national network, interlock code conversion is required at the gateway (or corresponding) exchange.
In case of interworking with a network which does not support the CUG facility, the incoming gateway
exchange may release the call, depending on the contents of the CUG call indicator in the received IAM. The action at
the gateway exchange, in this case, is indicated in Table E-1/Q.767. IN CASES WHERE A CALL IS REJECTED AS THE RESULT OF
THE INTERWORKING, A RELEASE MESSAGE INCLUDING THE CAUSE PARAMETER INDICATING # 87 IS SENT TOWARDS THE
ORIGINATING EXCHANGE.
TABLE E-1/Q.767
Action at the incoming gateway with a network without CUG capability
CUG call indicator in IAM Action at the gateway exchange
CUG without outgoing access Release the call with cause # 87
CUG with outgoing access
a)
Treat the call as an ordinary call
a)
Non-CUG Treat the call as an ordinary call
a)
Discard the interlock code parameter and change the CUG call indicator of the
optional forward call indicator to indicate non-CUG call or discard the whole
parameter if appropriate.
Recommendation Q.767 247
E.3.2.3 Destination exchange
At the destination exchange, a validation check of the acceptability of a call is made according to the rule
specified in Recommendation Q.85, where either the calling party (as indicated by a CUG call indication in the initial
address message received) or the called party belongs to a CUG. The call set-up is continued only in cases where the
information received checks with the information stored at the destination exchange. Table E-2/Q.767 indicates the
action to be taken by the destination exchange as the result of the validation check.
TABLE E-2/Q.767
Handling of a CUG call at the destination exchange
In cases where a call is rejected as the result of the validation check because of incompatible CUG
information, a release message including the cause parameter indicating one of the following values is sent towards the
originating exchange:
# 55 Incoming calls barred within CUG
# 87 Called user not member of CUG
# 88 Incompatible destination
Class of called user
CUG call
indicator
in IAM
CUG match
check CUG CUG + IA
No CUG
No ICB ICB No ICB ICB
CUG with OA
Match CUG call Release
cause # 55
CUG call Release
cause # 55
Release the call
not allowed
No match Release the call with
cause # 87
Release the call with
cause # 87
with cause # 87
CUG with OA
Match
CUG call Release
cause # 55
CUG + OA
call
Non-CUG
call
Non-CUG call
allowed
No match Release the call with
cause # 87
Non-CUG call
Non-CUG
Release the call with
cause # 87
Non-CUG call Non-CUG call
IA Incoming access
OA Outgoing access
ICB Incoming calls barred
Match The interlock code in the received IAM matches one of the CUGs to which the called user belongs.
No match The interlock code does not match any of the CUGs to which called user belongs.
Note As OA attribute of the called user is of no concern at the destination exchange, the CUG + OA class is
equivalent to CUG, and CUG/IA class is equivalent to CUG + IA in this table. Subscription of preferential CUG by the
called user is also of no concern in this table.
248 Recommendation Q.767
Figure E-2/Q.767 illustrates example message flows for CUG calls with decentralized administration of
CUG data.
T1148290-92/D23
Originating
exchange
Transit
exchange
Terminating
user
Originating
exchange
Originating
user
Setup
Call proceeding
(Note 1)
a)
IAM
b)
(Note 2)
IAM
b)
(Note 3)
Setup
ACM
ACM
Alerting
Connect
Alerting
Connect acknowledge
Connect information
ANM
CPG (alerting)
ANM
CPG (alerting)
a) Successful establishment of a CUG call
b) Unsuccessful establishment of a CUG call
Setup
Call proceeding
(Note 1)
IAM
b)
(Note 2)
IAM
b)
(Note 3)
REL
c)
RLC
REL
c)
RLC
Release
Disconnect
Release complete
OE
TE
DE
Originating exchange
Transit exchange
Destination exchange
IAM
CPG
ANM
ACM
Initial address message
Call progress
Answer message
Address complete message
a) ( ) indicates exchange functions. These are described below in Figure E-3/Q.767.
b) IAM contains the interlock code and CUG call indication, possible with outgoing access.
c) REL contains the cause parameter to indicate why the call is being released.
Note 1 Validation check on whether the request call is allowed to the calling user, based on the data stored
at the originating exchange.
Note 2 In the case of an international gateway exchange, interlock code conversion if the national network
is not using international interlock codes.
Note 3 Validation check on whether the requested call is allowed to the called user, based on the data stored
at the destination exchange.
FIGURE E-2/Q.767
Example message flow for a CUG call with decentralized administration
Recommendation Q.767 249
E.3.3 Call set-up procedure with centralized administration of CUG data
This section is not applicable to the international interface.
E.3.4 ASE for CUG service with centralized administration of CUG data
This section is not applicable to the international interface.
E.3.5 Interactives with other supplementary services
There are no known interactions with supplementary services applicable at the international interface.
E.4 General description of the Calling Line Identity Presentation and Restriction service
Calling Line Identification Presentation (CLIP) is a supplementary service offered to the called party which
provides the calling partys ISDN number, possibly with additional address information (E.G. CALLING PARTY SUB-
ADDRESS), if any, to the called party.
Calling Line Identification Restriction (CLIR) is a supplementary service offered to the calling party to restrict
presentation of the calling partys ISDN number, possibly with additional address information (E.G. CALLING PARTY SUB-
ADDRESS), if any, to the called party.
THE STAGE 1 DEFINITIONS FOR THE CLIP AND CLIR SERVICES ARE GIVEN IN RECOMMENDATION I.251 AND THE
STAGE 2 SERVICE DEFINITIONS INCLUDING NETWORK FUNCTIONS, ARE GIVEN IN RECOMMENDATION Q.84. THIS STAGE 3
DESCRIPTION OF CLIP AND CLIR USE THE ISDN USER PART PROTOCOL AS DEFINED IN RECOMMENDATIONS Q.761 TO Q.764
AND Q.766 AND ANNEXES A, B, C AND D TO THIS RECOMMENDATION.
E.4.1 Description of the Calling Line Identity Presentation) (CLIP) service
Calling Line Identity Presentation (CLIP) is a user facility that enables a user to be informed on incoming
calls, of the address of the calling party. When provided, the facility applies to all incoming calls except for when the
calling party has the Calling Line Identity Restriction (CLIR) facility active (see E.4.2 below) or the complete number
of the calling party is not available at the destination exchange.
THE CALLING LINE IDENTITY (CLI) IS THE ISDN NUMBER OF THE CALLING PARTY (WITH ADDITIONAL ADDRESS
INFORMATION, E.G. CALLING PARTY SUB-ADDRESS, IF ANY) WHICH MAY BE PROVIDED BY THE NETWORK OR PARTLY BY THE
CALLING PARTY.
In the case where a national network does not always provide the CLIP facility, the included CLI may be the
known part of the ISDN number at the interworking point (e.g. Trunk Code).
IN THE CASE WHERE A CALLING PARTY IS AN ISPBX, THE NETWORK SENDS THE ISDN NUMBER INCLUDING THE DDI
DIGITS OF THE EXTENSION AS THE CLI IF THE LATTER IS PROVIDED BY THE CALLING PARTY, OR THE NETWORK PROVIDED
DEFAULT NUMBER IF THE EXTENSION NUMBER IS NOT PROVIDED.
When the CLI is provided by the user or ISPBX, it is verified or screened for validity by the network, i.e. the
CLI provided by the user is within the known number range for that user.
i) If the user provided CLI is valid, the Calling Party Number parameter field contains the CLI in the
address signals with the screening indicator set to "user provided verified and passed".
250 Recommendation Q.767
ii) If the user provided CLI is not valid or screened, the originating exchange defaults to the network
provided CLI for the address signals of the Calling Party Number parameter field with the screening
indicator set to "network provided".
When the CLI is provided by the network, the originating exchange includes the stored CLI set against the
calling party and sets the screening indicator to "network provided".
The CLI sent to the called user should contain all the necessary digits to enable a call to be established in the
reverse direction.
Note This may not always be possible if, for example, the DDI extension of an ISPBX is not provided by
the calling party.
Information indicating that a subscriber has the user access to the CLIP facility is available in the exchange to
which the subscriber is connected.
E.4.1.1 Call set-up procedure
SYSTEMATIC INCLUSION IN THE IAM IS THE ONLY METHOD USED WHEN THE CLI IS AVAILABLE.
E.4.1.1.1 The Calling Line Identity is include in the initial address message
When the CLI is available for insertion in the IAM, the systematic inclusion of this parameter, in the IAM, is
recommended. However, it is realized that under certain interworking conditions, the CLI may only be available
subsequent to the transmission of the IAM.
The release of restricted CLIs across international boundaries is decided by bilateral agreement. If any
agreements requires restricted CLIs not to be passed, then the originating gateway shall ensure that no such CLIs are
sent. [Note This bilateral agreement may depend on the application of override categories in the destination network
(see E.4.2.2.1 and E.4.2.2.2).]
In this situation, to avoid unnecessary unsuccessful requests for the CLI, the following procedures are
recommended:
a) If the CLI cannot be included in the IAM (for any reason) but is available and may be requested with a
good chance of receiving it, then the optional field "calling party number parameter" should not be
included in the IAM.
b) If the CLI cannot be transferred (because it is not allowed to be passed or because the national network
cannot provide the number), then the optional field "calling party number parameter" should be included
in the IAM with the indication "presentation restricted" or "address not available" set as appropriate in the
Address Presentation Restricted indicator.
The CLI is sent to the called party in accordance with the user-network interface protocol.
IF NO ADDRESS SIGNALS ARE TO BE SENT, THEN THE CALLING PARTY NUMBER PARAMETER SHALL NOT BE SENT. WHEN
INTERWORKING WITH SIGNALLING SYSTEMS WHICH DO NOT SUPPORT CALLING LINE IDENTITY (E.G. N5) OR FROM WHICH
CALLING LINE IDENTITY IS NOT IMMEDIATELY AVAILABLE (E.G. TUP), THE CALLING PARTY NUMBER PARAMETER IS NOT SENT.
ONLY COMPLETE CALLING PARTY NUMBERS ARE SENT.
Recommendation Q.767 251
E.4.1.1.2 The Calling Line Identity is not included in the initial address message
IF NO CALLING PARTY NUMBER PARAMETER IS RECEIVED IN THE INITIAL ADDRESS MESSAGE, THEN IT IS A FUNCTION
OF THE USER-NETWORK INTERFACE NOT TO PRESENT THE CALLING PARTY SUB-ADDRESS, IF RECEIVED, TO THE USER.
E.4.1.1.3 Message sequence diagrams for CLIP
Figures E-6/Q.767 and E-7/Q.767 describe the message flows for CLIP.
T1148300-92/d23
Set-up IAM IAM Set-up
Calling
user
Originating
exchange
Transit
exchange
Terminating
exchange
Called
user
Calling Party Number
(user provided/verified)
Set-up IAM IAM Set-up
Calling Party Number
not provided
"Calling Party Number
parameter" omitted
(CLI)
PR = 00
SI = 01
a) CLI
provided
in the
IAM
b) CLI not
provided
in the
IAM
PR
SI
Presentation restricted
Screening indicator
FIGURE E-6/Q.767
Calling Line Identification Presentation
Presentation allowed CLI provided by the calling user
(CLI)
PR = 00
SI = 01
T1148310-92/d24
Set-up IAM IAM Set-up
Calling
user
Originating
exchange
Transit
exchange
Terminating
exchange
Called
user
Calling Party Number
(network provided)
Set-up IAM IAM Set-up
Calling Party Number
not provided
"Calling Party Number
parameter" omitted
a) CLI
provided
in the
IAM
b) CLI not
provided
in the
IAM
PR
SI
Presentation restricted
Screening indicator
FIGURE E-7/Q.767
Calling Line Identification Presentation
Presentation allowed CLI provided by the originating node
PR = 00
SI = 11
PR = 00
SI = 11
252 Recommendation Q.767
E.4.2 Description of the Calling Line Identity Restriction (CLIR) service
Calling Line Identification Restriction (CLIR) is a user facility offered to restrict the presentation of the
Calling Line Identity to the Called Party.
THE CALLING LINE IDENTITY (CLI) IS THE ISDN NUMBER OF THE CALLING PARTY WITH ADDITIONAL ADDRESS
INFORMATION (E.G. CALLING PARTY SUB-ADDRESS) IF PRESENT.
Information that a subscriber has the Calling Line Identity Restriction facility is available at the exchange to
which the subscriber is connected.
E.4.2.1 Normal case
When CLIR is applicable, the originating exchange will provide the destination node with a notification that
the Calling Line Identity is not allowed to be presented at the called party. In this case, the Calling Line Identity will be
marked as presentation restricted, in the Address Presentation Restricted Indicator, when it is passed across the network,
in either an initial address message or Information Message. In the case of CLIR, the Calling Line Identity will not be
included in the call offering to the called partys installation.
E.4.2.2 Abnormal case
E.4.2.2.1 Override category within an ISDN
As a national option, the terminating exchange can override the presentation restriction indication and the CLI
presented at the called subscriber for specific called partys categories (e.g. Police).
E.4.2.2.2 Override category between ISDNs
When a call originates in one ISDN network and terminates in another ISDN network and CLIR is applicable,
the rules and regulations of the destination (host) network should apply.
For example, if an override category is not available in the originating network but is available in the
destination network. The destination network can still override the presentation restriction whenever CLI is available at
this network.
As a national option the originating network can restrict the CLI to the destination network if the CLIR is
applicable.
E.4.2.2.3 Interworking with non-ISDN or via non-ISDN
On calls to or via non-ISDN networks, it cannot be guaranteed that the CLIR indication will be carried to the
destination network.
IF CLIR IS APPLICABLE AND THE RESTRICTION INDICATOR CANNOT BE CONVEYED ON THE NEXT SIGNALLING SECTION,
THE INTERWORKING EXCHANGE WILL NOT SEND THE CLI AND ANY ADDITIONAL ADDRESS INFORMATION PROVIDED BY THE
CALLING PARTY (E.G. CALLING PARTY SUB-ADDRESS).
If the destination network receives a Calling Line Identity without any indication of presentation allowed or
restricted, the destination network will act according to its rules and regulations.
Recommendation Q.767 253
E.4.2.2.4 Restriction of additional address information
Any additional address information provided by the calling party, E.G. CALLING PARTY SUB-ADDRESS, will also
be subject to the CLIR supplementary service as indicated in the presentation restriction indicator in the Calling Party
Number parameter field.
E.4.2.2.5 Message Sequence diagrams for CLIR
Figure E-8/Q.767 describes the message flow for CLIR.
T1148320-92/d25
Set-up IAM IAM Set-up
Calling
user
Originating
exchange
Transit
exchange
Terminating
exchange
Called
user
Calling Party Number
not provided
Set-up IAM IAM Set-up
Calling Party Number
not provided
"Calling Party Number
parameter" omitted
PR = 01
SI = 01
PR = 01
SI = 01
a) CLI
provided
in the
IAM
b) CLI not
provided
in the
IAM
PR
SI
Presentation restricted
Screening indicator
FIGURE E-8/Q.767
Calling Line Identification Restriction
Presentation not allowed CLI provided by the calling user
(CLI)
(presentation
restricted)
(CLI)
(presentation
restricted)
E.4.3 Nodal signalling function SDLs for CLIP and CLIR
Nodal signalling function procedures for CLIP and CLIR are described in Figures E-10/Q.767
and E-11/Q.767.
254 Recommendation Q.767
T1148330-92/d26
Idle
Set-up
IAM
CL
identity
present
Note 1
Yes
No
No
Number
Complete
Omit "Calling
Party Number
parameter field"
from IAM
Presentation
allowed
Yes
No
Yes
Yes
Special
agreement
on PR
International
number
Yes
No No
Delete trunk prefix
(if any)
Add originating
country code
Set nature of
address indicator
to "international
number"
Omit Calling
Party Number
parameter
from IAM
Keep PR and SI
as provided by the
incoming network
Note 2
IAM
Idle
CL
PR
SI
NI
Calling line
Presentation restriction
Screening indicator
Number incomplete indicator
Note 1 This flow assumes that there is no restriction on passing non-restricted CLIs across the International
boundary. If no such agreement exists then any CLI in the incoming IAM will be removed.
Note 2 Allowed values for the international section are:
PR = 00 or 01
SI = 01 or 11
NI = 0
FIGURE E-10/Q.767
Nodal signalling functions for CLIP and CLIR
Outgoing International Gateway
Recommendation Q.767 255
T1148340-92/d27
Idle
Set-up
IAM
CL
identity
present
Add international
prefix (optional)
Keep PR and SI
as provided
IAM
Idle
CL
PR
SI
Calling line
Presentation restriction
Screening indicator
FIGURE E-11/Q.767
Nodal signalling function for CLIP and CLIR
destination international gateway exchange
Yes
No
E.4.4 Interaction of CLIP with other supplementary services
E.4.4.1 Calling Line Identification Restriction
The calling line identification will not be present if the calling user has an arrangement to inhibit the
presentation of his number to the called party.
256 Recommendation Q.767
E.4.4.2 Call Forwarding
This section is not applicable to the international interface.
E.4.4.3 Call Waiting
This section is not applicable to the international interface.
E.4.4.4 Closed User Group
No interaction.
E.4.4.5 Direct Dialling In
This section is not applicable to the international interface.
E.4.4.6 User-to-User Information
No interaction.
E.4.4.7 Other services
There are no known interactions with supplementary services applicable at the international interface other
than those listed.
E.4.5 Interaction of CLIR with other supplementary services
E.4.5.1 Calling Line Identification Presentation
Calling Line Identification Restriction will take precedence over Calling Line Identification Presentation.
The only occasion when a user subscribing to Calling Line Identification Presentation can take precedence
over Calling Line Identification Restriction is when the user has override category. This is a national option.
E.4.5.2 Call Forwarding
This section is not applicable to the international interface.
E.4.5.3 Call Waiting
This section is not applicable to the international interface.
Recommendation Q.767 257
E.4.5.4 Closed User Group
NO INTERACTION
E.4.5.5 Direct Dialling In
This section is not applicable to the international interface.
E.4.5.6 User-to-User Information
No interaction.
E.4.5.7 Other services
There are no known interactions with supplementary services applicable at the international interface other
than those listed.
E.5 Direct Dialling In (DDI)
This section is not applicable to the international interface.
E.6 Call Forwarding services
This section is not applicable to the international interface.
E.7 Time-out table
This section is not applicable to the international interface.
ANNEX E-A: Signalling procedures for the explicit invocation of User-to-User Signalling services 1, 2 and 3
This section is not applicable to the international interface.
E.8 Description of the connected Line Identification Presentation and Restriction service
Connected Line Identification Presentation (COLP) is a supplementary service offered to the calling party
which provides the connected partys ISDN number, with additional address information (e.g. connected party sub-
address) if any, to the calling party at the call establishment phase.
Connected Line Identification Restriction (COLR) is a supplementary service offered to the connected party to
restrict presentation of the connected partys ISDN-number, with additional address information (e.g. connected party
sub-address) if any, to the calling party.
The Stage 1 CCITT definitions for the COLP and COLR services are given in Recommendations I.251.5 and
I.251.6 respectively. The stage 2 CCITT descriptions are contained in Recommendations Q.81, 5 and Q.81, 6
respectively. This stage 3 description of COLP and COLR uses the ISDN User Part protocol as defined in the CCITT
Recommendations Q.761 to Q.764 and Q.766 and Annexes A, B, C and D to this Recommendation.
258 Recommendation Q.767
E.8.1 Description of the Connected Line Identification Presentation (COLP) service
Connected Line Identity Presentation (COLP) is a user facility that enables a user to be informed, on outgoing
calls, of the address of the connected party. When provided, the facility applies to all outgoing calls except for when the
connected party has the Connected Line Identity Restriction (COLR) facility active (see E.8.2 below).
The Connected Line Identity (COL) is the ISDN number of the connected party (with additional address
information, e.g. connected party sub-address, if any) which may be provided by the network or by the connected party
or partially by the network with the rest provided by the connected party.
Only full international number, including the country code, should be passed across the international
boundary.
Moreover, the information on the COL may include address information generated by the connected user and
transparently transported by the network. The sub-address is subject to a maximum of 20 octets. (The length of the sub-
address is not checked at international gateways.) The network is not responsible for the content of this additional
address information.
The destination exchange shall deliver the COL only if it was requested at call set-up. However, if it is
received in the answer of connect message when it has not been requested, it should not be considered as a protocol error
and the call should be allowed to continue.
In the case where a connected party is a DDI ISPBX extension, the network sends the ISDN number and the
DDI number of the extension as the COL if the extension digits are provided by the connected party. If the extension
digits are not provided, the network sends the ISDN default number. The default number is stored within the network
but the value is agreed between the Administration and the customer concerned.
When the COL is provided by the user or ISPBX, it is verified or screened for validity by the network, i.e. the
COL provided by the user is within the known number range for that user.
i) If the user provided COL is valid, the Connected Number parameter field contains the COL in the address
signals with the screening indicator set to "user provided verified and passed".
ii) If the user provided COL is not valid or screened, the destination exchange inserts the default number for
the Address Signals with the screening indicator set to "network provided".
Recommendation Q.767 259
When the COL is provided by the network, the terminating exchange includes the stored COL set against the
Connected party and sets the screening indicator to "network provided".
Information indicating that a subscriber has the user access to the COLP facility is available in the exchange to
which the subscriber is connected.
The destination gateway can remove the COL digits and indicate that connected line identity is not available.
E.8.1.1 Call set-up procedure
The call control procedure and the information included in call control messages vary, depending on whether
the calling party has indicated, in the optional forward call indicator in the IAM, a request to use the COLP facility for
this call.
E.8.1.1.1 The Request of COLP facility is included in the initial address message
When the calling party user has subscribed to the COLP facility, the originating exchange, if the Connected
Line Identification is supported by the network, must include in the IAM an indication to request the COLP facility.
The Connected Line Identification is determined by the destination exchange. If the connected party number is
received from the connected user, the information is verified and passed to the originating exchange. If no information is
received from the connected user, the destination exchange shall generate the connected party number.
The information is conveyed by the network in the Connected Number parameter field of the answer (ANM)
or connect (CON) message. The service has no impact on the signalling procedures.
Optionally, a connected party sub-address may be included, if received from the called party user, in the
connected sub-address information element which is added to the ATP (Access Transport parameter) of these messages.
260 Recommendation Q.767
Both parameters, ATP and Connected Number are sent to the originating exchange.
If the COL cannot be transferred (because its presentation is restricted or because the national network cannot
provide the number), then the Connected Number parameter should be included in the ANM or CON messages with the
indication "Presentation restricted" or "Address not available" set as appropriate in the Address Presentation Restriction
Indicator.
In the case of Connected Number Presentation Restriction, the COL with the presentation restriction indication
will be forwarded to the originating exchange but not presented to the calling party (unless the national option of the
override category is invoked).
In the case of interworking between ISDNs, the destination network can restrict the presentation of the COL. If
this option is invoked, the COL shall be marked as not available.
No particular actions are required at intermediate exchanges.
At the international boundary, the destination gateway can remove the Connected Number digits if it cannot be
released to the originating network and a COL not available indication will be passed to the originating network (address
presentation restricted indicator set to address not available).
At the originating exchange, when a Connected Party Number is received in the Answer or Connect message,
the originating exchange determines if the information may be presented to the user.
Note If no Connected Party Number Parameter or a restricted connected number is received in the Answer
or Connect Message, then it is a function of the user-network interface not to present the connected party sub-address, if
received, to the user.
E.8.1.1.2 COLP Facility not requested by the Calling Party User
When the calling party user has not subscribed to the COLP facility, no particular actions are required. When a
request for the COL is not included in the IAM, the Connected Number parameter should not be included in either the
answer or connect message. However, if it is included under these circumstances, it should not be considered as a
protocol error and the call should continue.
E.8.1.1.3 Message sequence diagrams for COLP
Figure E-14/Q.767 describes the message flows for COLP.
Recommendation Q.767 261
T1148350-92/d28
Set-up IAM IAM Set-up
Calling
user
Originating
exchange
Transit
exchange
Terminating
exchange
Called
user
Alerting ACM ACM Alerting
a) COL
provided by
the called
user
b)
FIGURE E-14/Q.767
Connected Line Identification Presentation
Connected NUM
+ Subaddress
(optional)
COLP-request
Connect ANM/CON Connect ANM/CON
Connected NUM
+ Subaddress
(if provided
PR = 00
SI = 01)
Connected NUM
+ Subaddress
(optional)
(Note 1)
COL not
provided by
the called
user or
provided
but no valid
or screened
Set-up IAM IAM Set-up
Alerting ACM ACM Alerting
COLP-request
Connect ANM/CON Connect ANM/CON
Connected NUM
PR = 00
SI = 11
COLP-request
Note 1 The connect message is appropriate only if the answer condition is detected prior to the return of the address complete message.
Note 2 This service is subscribed by the calling user and the request is included by the originating exchange.
COLP-request
Connected NUM
PR = 00
SI = 11
Connected NUM
Connected NUM
+ Subaddress
(if provided
PR = 00
SI = 01)
262 Recommendation Q.767
E.8.2 Description of the Connected Line Identity Restriction (COLR Service)
Connected Line Identification Restriction (COLR) is a user facility offered to restrict the presentation of the
COL to the calling party. The information that the called subscriber has the COLR facility is available at the call
terminating exchange.
When COLR is applicable and activated, the destination exchange provides the originating node with a
notification that the connected users ISDN number and any Sub-address information is not allowed to be presented to
the calling user. In this case no connected party number is included in the call connected information sent to the calling
user.
The presentation restriction function does not influence the forwarding of the connected number within the
network as part of the basic service procedure.
The passing of restricted Connected Number parameters across international boundaries is decided by bilateral
agreements. If any agreement requires restricted Connected Number parameters not to be passed, then the terminating
gateway shall ensure that no such Connected Number parameters are sent.
Note This bilateral agreement may depend on the application of override categories in the originating
network (see 8.2.2).
The restriction service is applied universally for all services for a particular customer.
E.8.2.1 Call set-up procedure
When the calling party user has subscribed to the COLP facility, the originating exchange includes in the IAM
an indication to request the COL. If the called party user has subscribed to the COLR facility, the destination exchange
will send the Connected Line Identity to the originating exchange, with an indication that the presentation is restricted
(Address presentation restricted indicator set to presentation restricted).
This information is conveyed by the network in the Connected Number parameter field of the ANM or CON
messages. The service has no impact on the signalling procedures.
No particular actions are required at intermediate exchanges.
At the international boundary, the destination gateway can remove the COL if it cannot be released to the
originating network and change the Address presentation restricted indicator, set to presentation restricted, into address
not available.
At the originating exchange, when a Connected party Number is received in the ANM or CON message with
the indication that the presentation is restricted, the originating exchange must not present the COL to the user.
Recommendation Q.767 263
E.8.2.2 Override category
E.8.2.2.1 Override category within an ISDN
As a national option, the originating exchange can override the Presentation Restriction Indication and the
COL is then presented to the calling subscriber for specific calling partys categories (e.g. Police).
When a call originates in one ISDN network and terminates in another ISDN network and COLR is applicable,
the rules and regulations of the originating (host) network should apply.
E.8.2.2.2 Override category between ISDNs
For example, if an override category is not available in the destination network but is available in the
originating network, the originating network can still override the presentation restriction whenever COL is available at
this network.
As a national option, the destination network can restrict the COL to the originating network if COLR is
applicable.
E.8.2.3 Interworking with non-ISDN or via non-ISDN
On calls from or via non-ISDN networks, it cannot be guaranteed that the COLR indication will be carried to
the originating network.
If COLR is applicable and the restriction indicator cannot be conveyed on the preceding signalling section, the
interworking exchange will not send the COL.
If the originating network receives a Connected Line Identity without any indication of presentation allowed or
restricted, the originating network will act according to its rules and regulations.
E.8.2.4 Restriction of additional address information
Any additional address information provided by the Connected party, e.g. connected party sub-address, will
also be subject to the COLR supplementary service as indicated in the address presentation restriction indicator in the
Connected Number parameter.
E.8.2.5 Message sequence diagrams for COLR
Figure E-15/Q.767 describes the message flow for COLR.
264 Recommendation Q.767
T1148360-92/d29
Set-up IAM IAM Set-up
Calling
user
Originating
exchange
Transit
exchange
Terminating
exchange
Called
user
Alerting ACM ACM Alerting
a) COL
provided by
the called
user
b)
FIGURE E-15/Q.767
Connected Line Identification Restriction
COLP-request
(Note 1)
COLP-request
Connect ANM/CON Connect ANM/CON
Connected NUM
+ Subaddress
(optional)
(Note 3)
COL not
provided by
the called
user or
provided
but not valid
or screened
Set-up IAM IAM Set-up
Alerting ACM ACM Alerting
COLP-request
Connect ANM/CON Connect ANM/CON
Connected NUM
PR = 01
SI = 11
COLP-request
Connected NUM
PR = 01
SI = 11
Note 1 This service is subscribed by the calling user and the request is included by the originating exchange.
Note 2 This service is subscribed by the called user and stored at the destination exchange.
Note 3 The connect message is appropriate only if the answer condition is detected prior to the return of the address complete message.
(Note 2)
Connected NUM
+ Subaddress
(if provided
PR = 01
SI = 01)
Connected NUM
+ Subaddress
(if provided
PR = 01
SI = 01)
E.8.3 Nodal Signalling Function SDLs for COLP and COLR
Nodal signalling function procedures for COLP and COLR are described in Figures E-16/Q.767
to E-19/Q.767.
Recommendation Q.767 265
2
3
1
T1148370-92/d30
2
3
1
Idle
CON or ANM
Was
COL requested
on this call
Is COL
to be provided
anyway
No
COL
available
Yes
Yes
No
Yes
Yes
Yes
No
No
No
Set PR = 10
SI = 11
COL
supplied by
connected
user
Verification
of COL
Add missing
part of COL
COL = default
number
(Note)
Set SI = 11 Set SI = 01
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
Note The default number is a network supplied default number.
FIGURE E-16/Q.767 (sheet 1 of 2)
Nodal signalling functions for COLP and COLR terminating local exchange
(This figure is not applicable for the international interface and provided for information only)
266 Recommendation Q.767
1
2 3
1
2
3
T1148380-92/d31
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
FIGURE E-16/Q.767 (sheet 2 of 2)
Idle
CON or ANM
Set nature of address
and incomplete
number indication
Omit Connected Party
Number parameter
field from
CON or ANM
Set PR = 01 Set PR = 00
Any
presentation
restriction
No
Yes
Nodal signalling functions for COLP and COLR terminating local exchange
(This figure is not applicable for the international interface and provided for information only)
Recommendation Q.767 267
2
3
4 1
1
4
3
2

T1148390-92/d32
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
FIGURE E-17/Q.767 (sheet 1 of 2)
Idle
CON or ANM
Has
COL been
requested
No
Is COL
to be provided
anyway
COL
present
Presentation
allowed
Special
agreement on
PR
No
No
No
Note
Yes
Yes
Note This flow assumes that there is no restriction on passing non-restricted COLs across the international boundary
if no such agreement exists then any COL in the incoming CON or ANM will be removed and the PR indicator set
to 10."COL not available".
Nodal signalling function for COLP and COLR incoming international gateway
Yes
Yes
Yes
No

268 Recommendation Q.767
T1148400-92/d33
1
3 4 2 3, 4, 2
1
FIGURE E-17/Q.767 (sheet 2 of 2)
Nodal signalling function for COLP and COLR incoming international gateway
International
number
Delete trunk
prefix (if any)
Add terminating
country code
Set nature of
address indicator to
"International number"
Set PR = 10
Set SI = 11
Keep PR and SI
as provided by
the I/C network
Omit COL
Set PR = 01
Set SI = 11
Omit Connected
Party Number
parameter field
from CON or ANM
CON or ANM
Idle
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
Yes
No
Recommendation Q.767 269
T1148410-92/d34
FIGURE E-18/Q.767
Nodal signalling function for COLP and COLR originating international gateway exchange
Omit Connected
Party Number
parameter field
from CON or ANM
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
Idle
CON or ANM
Has COL been
requested
CL
identity
present
Maintain
PR = 10
SI = 11
Add international
prefix (optional)
Keep PR and SI
as provided
CON or ANM
Idle
No
Yes
No
Yes
270 Recommendation Q.767
T1148420-92/d35
Idle
CON or ANM
COLP
subscription
or provided by
default
COL
identity
available
Any
presentation
restrictions
No information
about the connected
party is sent to
the calling party
No
Yes
No
Yes
Yes
No
Address information
will not be presented
to the calling party
Set PR = 00
Keep SI as
provided
Note 1
Note 3
Set PR = 10
Set SI = 11
Note 2
CON or ANM
Idle
FIGURE E-19/Q.767
Nodal signalling functions for COLP and COLR originating local exchange
(This figure is not applicable for the international interface and provided for information only)
COL
PR
SI
Connected line identity
Presentation restriction
Screening indicator
Note 1 Presentation may be restricted due to national requirements or presentation restriction. Presentation restriction
may be overridden due to calling partys category (e.g. Police).
Note 2 In the case where the address information is indicated as not available due to interworking, etc. Only the indicators
are presented to the user.
Note 3 The "Connected Party Number parameter" is not included in the incoming CON or ANM.
Recommendation Q.767 271
E.8.4 Interaction of COLP with other supplementary services
E.8.4.1 Calling Line Identification Presentation
No interaction.
E.8.4.2 Calling Line Identification Restriction
If a user has Calling Line Identification Restriction (CLIR) activated, then COLR will also be activated.
Therefore, the number of the user will not be available for presentation on both incoming and outgoing calls.
E.8.4.3 Connected Line Identification Restriction
The Connected Line Identification will not be presented if the connected user has an arrangement to inhibit the
presentation of his number to the calling party.
E.8.4.4 Closed User Group
No interaction.
E.8.4.5 User-to-User Information
No interaction.
E.8.5 Interaction of COLR with other supplementary services
E.8.5.1 Calling Line Identification Presentation
If a user has COLR activated, then CLIR will also be activated. Therefore, the number of the user will not be
available for presentation on both incoming and outgoing calls.
E.8.5.2 Calling Line Identification Restriction
No interaction.
E.8.5.3 Connected Line Identification Presentation
COLR will take precedence over COLP.
The only occasion when a user subscribing to Connected Line Identification Presentation can take precedence
over Connected Line Identification Restriction is when the user has override category. This is a national option.
E.8.5.4 Closed User Group
No interaction.
E.8.5.5 User-to-User Information
No interaction.