SNMP Reference Guide

Introduction 37
SNMP is a systems management standard originally designed for network
management. SNMP manages much more than networks. Information
Technology (IT) professionals use SNMP for monitoring and managing
computer systems and the various components and peripherals supported by
their systems.
SNMP standards are defined by the Internet Engineering Task Force (IETF).
SNMP version 1 was published in August 1988 and is the most commonly
supported version of SNMP. SNMP version 2 was first published in May 1993,
but has not gained widespread market acceptance. SNMP version 3 was
recently completed and has addressed security issues that exist in version 1.
All SNMP systems consist of one or more managed systems that provide data
through an SNMP agent to a management system. The management system
provides a user interface to view data from the managed systems. The
management system and managed systems communicate over a network
(typically through User Datagram Protocol/Internet Protocol [UDP/IP]).
The management system and a managed system communicate by means of a
common data schema. SNMP MIB files define the structure, type, and values
of the SNMP data. While MIBs can be standardized or enterprise specific,
most operating systems supply SNMP agents for the standard MIB-I and
MIB-II schemas. MIB-I defines a base set of standard management information
for systems implementing the Internet Protocol (IP) suite. MIB-II defines
characteristics of the system, characteristics of network interfaces, and
characteristics of components of the IP on the system. In addition to the
standard MIBs, many hardware vendors have defined MIBs that provide
management data specific to their systems and peripheral devices.
Monitored data can be retrieved through SNMP using the Get command.
Typically, this command requires the host name or IP address of the target
machine as well as the OID of the data to retrieve. Exact details are dependent
on the operating system and the development tools being used to create the
management application. The Get command has a variant known as GetNext.
SNMP MIB OIDs
Each data class within an MIB is defined by an OID. OIDs are unique across
all MIBs. An OID consists of a series of digits separated by periods. The OID
functions in a similar fashion to a phone number. The phone number
011-512-471-0000 uniquely identifies a single phone. The phone number can
be broken down into a number of components to uniquely identify a phone.