ZyXEL Communications P-660R-T1 Support Notes page 84

There are two versions of SNMP: Version 1 and Version 2. ZyXEL supports
SNMPv1. M ost 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 vari ables that exist in network nodes. Examples of variables includ
counters, node port status, and so on. All of the SNMP management functions are
carr ied out through these simple operations. No action operations are available, but
these ca n be simulated by the setting of flag variables. For example, to reset a nod
counter variable named 'time to reset' could be set to a value, causing the node to re
after th e 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
powerf ul because the encoded data is self-defining. For example, the encoding of a
text str ing includes an indication that the data unit is a string, along with
valu e. ASN.1 is a flexible way of defining protocols, esp
manage ment protocols where nodes may support different sets of m
variab les.
The net of variab les that each node supports is called the
Bas e (MIB). The MIB is made up of several parts
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 gr
other categories, including 'system' and 'interface.'
The Internet Management Model is as shown in figure 1. Interactions between the
NMS and managed devices can be any of four different types of commands:
Reads
Read is use d to monitor the managed devices, NMSs read variables that are
maintained by the devices.
Writes
Write is used to control the managed devices, NMSs write variables that are
stored in the managed devices.
All contents copyright © 2005 ZyXEL Communications Corporation.
ouped by protocol (including TCP, IP, UDP, SNMP, and
P-660 series Support Notes
e statistic
ecially for network
anageable
Management Information
, including the Standard MIB,
e, a
set
its length and
83