ZyXEL Communications Prestige 2302RL Support Notes page 68

There are two versions of SNMP: Version 1 and Version 2. ZyXEL supports SNMPv1. Most of the changes
introduced in Version 2 enhance SNMP's security capabilities. SNMP encompasses three main areas:
1. A small set of management operations.
2. Definitions of management variables.
3. Data representation.
Operations allowed are: Get, GetNext, Set, and Trap. These functions operate based on variables stored on
network nodes. Examples of variables include statistic counters and node port status. All SNMP management
functions are carried out through these simple operations. No action operations are available, but these can be
simulated by the setting the variable flags. For example, to reset a node, a counter variable called 'time to reset'
can be set to a value which causes 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 set of variables that each node supports is called the
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 types (including TCP, IP, UDP, SNMP, etc.) 'system' and 'interface.'
The Internet Management Model is as shown in figure 1. Interactions between the NMS and the managed
devices can be any of the four command types:
6. Reads
Read is used to monitor the managed devices. NMSs read variables are maintained by the devices.
7. Writes
Write is used to control the managed devices. NMSs write variables are stored in the managed devices.
8. Traversal operations
All contents copyright (c) 2007 ZyXEL Communications Corporation.
Prestige 2302RL Support Notes
Management Information Base
(MIB). MIB is made
68