INTERNATIONAL TELECOMMUNICATION UNION

ITU-T X.220
TELECOMMUNICATION (03/93)
STANDARDIZATION SECTOR
OF ITU
OPEN SYSTEMS INTERCONNECTION GENERAL
CONNECTION MODE PROTOCOL SPECIFICATIONS
USE OF X.200-SERIES PROTOCOLS
IN CCITT APPLICATIONS
ITU-T Recommendation X.220
(Previously CCITT Recommendation)
FOREWORD
The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom-
munication Union. The ITU-T 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 World Telecommunication Standardization Conference (WTSC), which meets every four years, established the
topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics.
ITU-T Recommendation X.220 was prepared by the ITU-T Study Group VII (1988-1993) and was approved by the
WTSC (Helsinki, March 1-12, 1993).
___________________
NOTES
1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT
ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was
created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the
Radiocommunication Sector.
In order not to delay publication of this Recommendation, no change has been made in the text to references containing
the acronyms CCITT, CCIR, or IFRB or their associated entities such as Plenary Assembly, Secretariat, etc. Future
editions of this Recommendation will contain the proper terminology related to the new ITU structure.
2 In this Recommendation, the expression Administration is used for conciseness to indicate both a
telecommunication administration and a recognized operating agency.
ITU 1993
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 X.220 (03/93) 1
Recommendation X.220
Recommendation X.220 (03/93)
USE OF X.200-SERIES PROTOCOLS IN CCITT APPLICATIONS
(Melbourne, 1988; revised Helsinki, 1993)
The CCITT,
considering
(a) that Administrations in many countries are implementing a variety of telecommunications services;
(b) that these services may be carried on a variety of networks;
(c) that users of these services desire a unifying architecture for the applicable protocols;
(d) that such an architecture is provided by Recommendation X.200 which defines the Reference Model of Open
Systems Interconnection for CCITT applications;
(e) that a number of protocols conforming to this architecture are defined in the X.200-Series of
Recommendations and in other Recommendations,
unanimously declares
that for CCITT applications the functional suites of protocols, which involve the use of protocols in the X.200-Series of
Recommendations, are summarized in this Recommendation. Details, as well as any conformance requirements, are
contained in the relevant Recommendations.
A growing number of data terminal equipments are being designed to support more than one CCITT service and/or are
being designed to be capable of being connected to more than one type of network. In order to facilitate the design of
such equipments, the various OSI protocol suites involving use of the X.200-Series of Recommendations are
documented herein.
These protocol suites are depicted in Figure 1, which portrays the protocols according to the seven layers defined in
Recommendation X.200. The CCITT applications covered are Message Handling Systems (MHS), Directory,
Transaction Processing (TP), Systems Management, Teletex and Document Architecture Transfer and Manipulation.
The networks covered are PSPDN, CSPDN, PSTN and ISDN. The intent is to give a general view of the set of protocol
suites in a single figure, while relying on the other Recommendations referenced to provide the necessary additional
details.
2 Recommendation X.220 (03/93)
T0713850-92/d01
APPLICATION
LAYER USER
APPLICATION
LAYER
PRESENTATION
LAYER
SESSION
LAYER
TRANSPORT
LAYER
NETWORK
LAYER
DATA LINK
LAYER
PHISICAL
LAYER
MHS
(see X.400)
Note 17
Document architecture,
transfer and
manipulation
(see T.400)
Systems
management
(see X.700 and X.701)
Directory
(see X.500)
transaction
processing
(see X.860)
Teletext
(see T.61)
(Note 18)
Document transfer and manipulation
T.433
(DTAM)
(Note 15)
Directory
X.519
TP
X.862
MHS 84
P2 X.420
MHS
Pedi
X.435
MHS
Pvm
X.440
MHS
P2
X.420
MHS
84
P1
X.411
MHS
84
P3
X.411
MHS
P1
X.419
MHS
P7 X.419
P3 X.419
(Note 20)
(Note 19)
(Note 14)
SMF
X.730-
X.736,
X.740
(X.721)
CCR
X.852
(Note 16)
Teletex access
to MHS
T.330
(Note 12)
Teletex and
group 4 facsimile
control procedures
T.62BIS
ROS
84
X.410
ROSE
X.229
(Note 13)
RTS 84
X.410
RTSE
X.228
ACSE X.227
Presentation protocol X.226
Session protocol X.225
Transport protocol X.224 (Note 11)
X.25 call
procedures
X.25 data
transfer
X.21 call
procedures
(Note 7)
X.25 PLP or
T.70 (Notes 8, 9)
Telephone call
procedures
(Note 7)
X.25 PLP
(Notes 8, 9)
Q.931
(Note 7)
X.25 PLP
(Notes 8, 9)
X.25 data
transfer
Q.931 (Note 10)
+ X.25 call
procedures
X.25 LAPB
X.21 or
X.21BIS
Two syn. chars.
(see X.21)
LAPB
(Notes 3, 4)
PSPDN CSPDN
X.21 or X.21BIS
or X.22
PSTN
LAPB
(Notes 3, 4, 5)
e.g. V.24
(Notes 1, 2)
Q.921
LAPB
(Notes 3, 4)
I.430 or
I.431
ISDN
(circuit
switched)
Q.921 and
X.25 LAPB
(Note 6)
I.430 or
I.431
ISDN
(packet
switched)
CMIP
X.711
Call
control
phase
Call
control
phase
Data
transfer
phase
Data
transfer
phase
Recommendation X.220 (03/93) 3
NOTES
1 The modem may also be integrated within the terminal and in such cases V.24 need not apply. For Telematic terminals see
3.2.1/T.70.
2 For automatic calling and/or answering, V.25 or V.25 bis may be applicable.
3 For terminals connected to a PSTN, CSPDN or ISDN (circuit switched) and accessing a PSPDN in accordance with X.32
or X.31, the X.25 LAPB procedures are used as set forth in X.32 or X.31.
4 For DTE-to-DTE connections, Telematic terminals employ the X.75 LAPB procedures for single link operation (see
3.2.2/T.70, 3.3.2/T.70 and 2.1.2.2/T.90). For other terminals, the ISO 7776 LAPB procedures may apply for DTE-to-DTE
connections.
5 For half duplex operation over the PSTN, the LAPD procedures are extended to include a half duplex transmission module
(HDTM) as defined in 5.6/X.32 and in T.71.
6 Terminals obtaining packet access on the D-channel use the LAPD procedures of Q.921 to support both the Q.931 access
connection control procedure (if needed) and the X.25 packet layer procedures. Terminals obtaining packet access on the B-channel
use the LAPD procedures of Q.921 to support the Q.931 access connection control procedure (if needed) and the X.25 LAPB
procedures to support the X.25 packet layer procedures.
7 For terminals connected to a PSTN, CSPDN or ISDN (circuit switched) and accessing a PSPDN in accordance with X.32
or X.31, the network connection is established by two stage selection: the first stage uses the call control procedures of the attached
network (as shown in this figure) and the second stage uses the X.25 call control procedures.
8 For terminals connected to a PSTN, CSPDN or ISDN (circuit switched) and accessing a PSPDN in accordance with X.32
or X.31, the X.25 packet layer procedures apply during the data transfer phase of the PSTN, CSPDN or ISDN. However, for
Telematic terminals connected to a CSPDN and accessing a PSPDN, a minimum network layer functionality is required during the
data transfer phase of the CSPDN (see 3.3.3/T.70).
9 For DTE-to-DTE connections, Telematic terminals connected to a CSPDN use the minimum network layer functionality
(see 3.3.3/T.70) during the data transfer phase of the CSPDN and Telematic terminals connected to a PSTN use the X.25 packet layer
procedures (see 3.2.3/T.70): Telematic terminals connected to an ISDN (circuit switched) use the X.25 packet layer procedures as
specified in ISO/IEC 8208 (see 2.2.5/T.90). For other terminals, the ISO/IEC 8208 X.25 packet layer procedures may apply for DTE-
to-DTE connections.
10 The Q.931 access connection control procedures are used if needed.
11 For Telematic terminals, the transport protocol is in accordance with 5/T.70 plus Annexes A/T.70 and B/T.70: the use of
X.224 class 0 plus application rules is optional but needs further consideration to ensure that there are no discrepancies with T.70. For
terminals communicating with network based services such as MHS, CMIP, TP and Directories, the X.224 procedures apply including
the mandatory support of class 0.
12 T.62 bis, together with the relevant service and protocol elements of X.215 and X.225, are intended to be equal to T.62.
13 To obtain backward compatibility with X.410 (1984), RTSE uses the X.410-1984 mode services of ACSE and the
presentation layer. The normal mode is used in all other cases.
14 Directory and CMIP use ROSE but not RTSE.
15 The use of ROSE in the T.400-Series is for further study.
4 Recommendation X.220 (03/93)
16 T.330 describes Group 4 Facsimile and Teletex access to the MHS Interpersonal Messaging System (IPMS) in the T.62
bis/X.225 environment.
17 The use of MHS to transfer documents conforming to the T.410-Series is described in T.411.
18 Character repertoire definition of T.61 only.
19 Systems management functions, including protocol specifications (by reference to X.721), are prescribed in X.730-X.736
and X.740. Further study is underway to specify additional systems management functions.
20 X.852, the Commitment, Concurrency and Recovery (CCR) protocol, is currently at the stage of draft Recommendation.
FIGURE 1/X.220
Protocol suites