Chapter 9

Network Management
Computer
Networking: A
Top Down
Approach
Jim Kurose, Keith Ross
Addison-Wesley

All material copyright

J.F Kurose and K.W. Ross, All Rights Reserved

Network Management 9-1

Chapter 9: Network Management
Chapter goals:
 introduction to network management
 motivation
 major components
 Internet network management framework
 MIB: management information base
 SMI: data definition language
 SNMP: protocol for network management
 security and administration
 presentation services: ASN.1

Network Management 9-2

Chapter 9 outline
 What is network management?
 Internet-standard management framework

 Structure of Management Information: SMI

 Management Information Base: MIB
 SNMP Protocol Operations and Transport
Mappings
 Security and Administration
 ASN.1

Network Management 9-3

What is network management?
 autonomous systems (aka “network”): 1000s of interacting
hardware/software components
 other complex systems requiring monitoring, control:
 jet airplane
 nuclear power plant

"Network management includes the deployment, integration

and coordination of the hardware, software, and human
elements to monitor, test, poll, configure, analyze, evaluate,
and control the network and element resources to meet the
real-time, operational performance, and Quality of Service
requirements at a reasonable cost."
Network Management 9-4
 Infrastructure for network management
definitions:
managing entity agent data managed devices
managing contain
entity data managed device
managed objects
agent data whose
network
management
data is gathered into a
managed device
protocol agent data Management
managed device
Information
Base (MIB)
agent data
agent data
managed device
managed device

Network Management 9-5

Network management standards

OSI CMIP SNMP: Simple Network

 Common Management Management Protocol
Information Protocol  Internet roots
 designed 1980’s: the  started simple
unifying net  deployed, adopted rapidly
management standard  growth: size, complexity
 too slowly
 currently: SNMP V3
standardized
 de facto network
management standard

Network Management 9-6

Chapter 9 outline
 What is network management?
 Internet-standard management framework

 Structure of Management Information: SMI

 Management Information Base: MIB
 SNMP Protocol Operations and Transport
Mappings
 Security and Administration
 ASN.1

Network Management 9-7

SNMP overview: 4 key parts
 Management information base (MIB):
 distributed information store of network management data
 Structure of Management Information (SMI):
 data definition language for MIB objects
 SNMP protocol
 convey manager<->managed object info, commands
 security, administration capabilities
 major addition in SNMPv3

Network Management 9-8

SMI: data definition language
Purpose: syntax, semantics of Basic Data Types
management data well- INTEGER
defined, unambiguous Integer32
 base data types: Unsigned32
 straightforward OCTET STRING
 OBJECT-TYPE OBJECT IDENTIFIED
IPaddress
 data type, status, semantics
Counter32
of managed object
Counter64
 MODULE-IDENTITY
 groups related objects into
MIB module

Network Management 9-9

SNMP MIB
MIB module specified via SMI
MODULE-IDENTITY
(100 standardized MIBs, more vendor-specific)

MODULE OBJECT TYPE:

OBJECT TYPE:OBJECT TYPE:

objects specified via SMI

OBJECT-TYPE construct

Network Management 9-10

 SMI: object, module examples
OBJECT-TYPE: ipInDelivers MODULE-IDENTITY:
ipMIB
ipMIB MODULE-IDENTITY
ipInDelivers OBJECT TYPE LAST-UPDATED “941101000Z”
SYNTAX Counter32 ORGANZATION “IETF SNPv2
MAX-ACCESS read-only Working Group”
STATUS current CONTACT-INFO
“ Keith McCloghrie
DESCRIPTION
……”
“The total number of input DESCRIPTION
datagrams successfully “The MIB module for managing IP
delivered to IP user- and ICMP implementations, but
protocols (including ICMP)” excluding their management of
::= { ip 9} IP routes.”
REVISION “019331000Z”
………
::= {mib-2 48}
Network Management 9-11
 MIB example: UDP module
Object ID Name Type Comments
1.3.6.1.2.1.7.1 UDPInDatagrams Counter32 total # datagrams delivered
at this node
1.3.6.1.2.1.7.2 UDPNoPorts Counter32 # underliverable datagrams:
no application at port
1.3.6.1.2.1.7.3 UDInErrors Counter32 # undeliverable datagrams:
all other reasons
1.3.6.1.2.1.7.4 UDPOutDatagrams Counter32 # datagrams sent
1.3.6.1.2.1.7.5 udpTable SEQUENCE one entry for each port
in use by app, gives port #
and IP address

Network Management 9-12

 SNMP naming
question: how to name every possible standard object
(protocol, data, more..) in every possible network
standard??
answer: ISO Object Identifier tree:
 hierarchical naming of all objects
 each branchpoint has name, number

1.3.6.1.2.1.7.1
ISO udpInDatagrams
ISO-ident. Org. UDP
US DoD MIB2
Internet management
Network Management 9-13
OSI
Object
Identifier
Tree

Network Management 9-14

 SNMP protocol
Two ways to convey MIB info, commands:

managing managing
entity entity

request
trap msg
response

agent data agent data

managed device managed device

request/response mode trap mode

Network Management 9-15
SNMP protocol: message types
Message type Function
GetRequest
Mgr-to-agent: “get me data”
GetNextRequest
(instance,next in list, block)
GetBulkRequest

InformRequest Mgr-to-Mgr: here’s MIB value

SetRequest Mgr-to-agent: set MIB value

Response Agent-to-mgr: value, response to

Request
Trap Agent-to-mgr: inform manager
of exceptional event
Network Management 9-16
SNMP protocol: message formats
Get/set header Variables to get/set
PDU Error
Request Error
type Status Name Value Name Value ….
ID Index
(0-3) (0-5)

PDU Trap
type Enterprise Agent Type
Specific Time
Name Value ….
Addr code stamp
4 (0-7)
Trap header Trap info

SNMP PDU
(Protocol Data Unit)

Network Management 9-17

SNMP security and administration
 encryption: DES-encrypt SNMP message
 authentication: compute, send MIC(m,k):
compute hash (MIC) over message (m), secret
shared key (k)
 protection against playback: use nonce
 view-based access control:
 SNMP entity maintains database of access rights,
policies for various users
 database itself accessible as managed object!

Network Management 9-18

Chapter 9 outline
 What is network management?
 Internet-standard management framework

 Structure of Management Information: SMI

 Management Information Base: MIB
 SNMP Protocol Operations and Transport
Mappings
 Security and Administration
 The presentation problem: ASN.1

Network Management 9-19

The presentation problem
Q: does perfect memory-to-memory copy solve “the
communication problem”?
A: not always!

struct { test.code a test.code a

char code; test.x 00000001
int x; 00000011 test.x 00000011
} test; 00000001
test.x = 256;
test.code=‘a’ host 2 format
host 1 format

problem: different data format, storage conventions

Network Management 9-20
A real-life presentation problem:
? ?
? ? ? ?
? ?

Groovy!

grandma teenager

aging 70’s
hippie
Network Management 9-21
Presentation problem: potential solutions
1. Sender learns receiver’s format. Sender translates
into receiver’s format. Sender sends.
2. Sender sends. Receiver learns sender’s format.
Receiver translate into receiver-local format
3. Sender translates host-independent format. Sends.
Receiver translates to receiver-local format.

Network Management 9-22

 Solving the presentation problem
1. Translate local-host format to host-independent format
2. Transmit data in host-independent format
3. Translate host-independent format to remote-host format

“It is pleasing “It is pleasing

presentation to me!” presentation to me!” presentation
service service service

“Cat’s pajamas!” “Groovy!” “Awesome, dude!”

! ! ! !
! ! ! !

grandma aging 60’s teenager

hippie
Network Management 9-23
ASN.1: Abstract Syntax Notation 1
 ISO standard X.680
 used extensively in Internet
 defined data types, object constructors
 like SMI
 BER: Basic Encoding Rules
 specify how ASN.1-defined data objects to be transmitted
 each transmitted object has Type, Length, Value (TLV)
encoding

Network Management 9-24

TLV Encoding
Idea: transmitted data is self-identifying
 T: data type, one of ASN.1-defined types
 L: length of data in bytes
 V: value of data, encoded according to ASN.1 standard

Tag Value Type

1 Boolean
2 Integer
3 Bitstring
4 Octet string
5 Null
6 Object Identifier
9 Real
Network Management 9-25
 lastname ::= OCTET STRING {weight, 259}

TLV weight ::= INTEGER {lastname, “smith”}

encoding: module of data type

declarations written
instances of data type
specified in module
in ASN.1
example Basic Encoding Rules
(BER)

3
Value, 259
1
Length, 2 bytes 2
Type=2, integer 2
h transmitted
t byte
i stream
Value, 5 octets (chars)
m
s
Length, 5 bytes 5
Type=4, octet string 4
Network Management 9-26
SNMP Video

https://www.youtube.com/watch?v=3uhA8bdz8gI
https://www.youtube.com/watch?v=Lq7j-QipNrI
https://www.youtube.com/watch?v=tg47MZdtcAE

Network Management 9-27