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Network Management Using SNMP

1. SNMP Overview

The Simple Network Management Protocol (SNMP) is an applications-layer protocol used to exchange

the management information between network devices (e.g., routers). By using SNMP, network

administrators can more easily manage network performance, find and solve network problems. The

SNMP is a member of the TCP/IP protocol suite, it uses the UDP to exchange messages between a

management Client and an Agent, residing in a network node.

There are two versions of SNMP: Version 1 and Version 2. ZyXEL supports SNMPv2. Most of the

changes introduced in Version 2 increase SNMP's security capabilities. SNMP encompasses three main

areas:

1. A small set of management operations.

2. Definitions of management variables.

3. Data representation.

The operations allowed are: Get, GetNext, Set, and Trap. These functions operates on variables that

exist in network nodes. Examples of variables include statistic counters, node port status, and so on. All

of the SNMP management functions are carried out through these simple operations. No action

operations are available, but these can be simulated by the setting of flag variables. For example, to reset

a node, a counter variable named 'time to reset' could be set to a value, causing the node to reset after the

time had elapsed.

SNMP variables are defined using the OSI Abstract Syntax Notation One (ASN.1). ASN.1 specifies how

a variable is encoded in a transmitted data frame; it is very powerful because the encoded data is self-

defining. For example, the encoding of a text string includes an indication that the data unit is a string,

along with its length and value. ASN.1 is a flexible way of defining protocols, especially for network

management protocols where nodes may support different sets of manageable variables.

The net of variables that each node supports is called the Management Information Base (MIB). The

MIB is made up of several parts, including the Standard MIB, specified as part of SNMP, and Enterprise

Specific MIB, which are defined by different manufacturer for hardware specific management.

The current Internet-standard MIB, MIB-II, is defined in RFC 1213 and contains 171 objects. These

objects are grouped by protocol (including TCP, IP, UDP, SNMP, and other categories, including

'system' and 'interface.'

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ZyXEL Communications P-334WT Technical Information Seite 140