Nortel Networks TP-1610 SIP user manual About Snmp, Snmp Message Standard

Mediant 2000 SIP User’s Manual 11. SNMP-Based Management

11 SNMP-Based Management

Simple Network Management Protocol (SNMP) is a standard-based network control protocol used to manage elements in a network. The SNMP Manager (usually implemented by a Network Manager (NM) or an Element Manager (EM)) connects to an SNMP Agent (embedded on a remote Network Element (NE)) to perform network element Operation, Administration and Maintenance (OAM).

Both the SNMP Manager and the NE refer to the same database to retrieve information or configure parameters. This database is referred to as the Management Information Base (MIB), and is a set of statistical and control values. Apart from the standard MIBs documented in IETF RFCs, SNMP additionally enables the use of private MIBs, containing a non-standard information set (specific functionality provided by the NE).

Directives, issued by the SNMP Manager to an SNMP Agent, consist of the identifiers of SNMP variables (referred to as MIB object identifiers or MIB variables) along with instructions to either get the value for that identifier, or set the identifier to a new value (configuration). The SNMP Agent can also send unsolicited events towards the EM, called SNMP traps.

The definitions of MIB variables supported by a particular agent are incorporated in descriptor files, written in Abstract Syntax Notation (ASN.1) format, made available to EM client programs so that they can become aware of MIB variables and their use.

The device contains an embedded SNMP Agent supporting both general network MIBs (such as the IP MIB), VoP-specific MIBs (such as RTP) and our proprietary MIBs (acBoard, acGateway, acAlarm and other MIBs), enabling a deeper probe into the inter-working of the device. All supported MIB files are supplied to customers as part of the release.

11.1 About SNMP

11.1.1 SNMP Message Standard

Four types of SNMP messages are defined:

•Get - A request that returns the value of a named object.

•Get-Next - A request that returns the next name (and value) of the ‘next’ object supported by a network device given a valid SNMP name.

•Set - A request that sets a named object to a specific value.

•Trap - A message generated asynchronously by network devices. It is an unsolicited message from an agent to the manager.

Each of these message types fulfills a particular requirement of Network Managers:

•Get Request - Specific values can be fetched via the ‘get’ request to determine the performance and state of the device. Typically, many different values and parameters can be determined via SNMP without the overhead associated with logging into the device, or establishing a Transmission Control Protocol (TCP) connection with the device.

•Get Next Request - Enables the SNMP standard network managers to ‘walk’ through all SNMP values of a device (via the ‘get-next’ request) to determine all names and values that an operant device supports. This is accomplished by beginning with the first SNMP object to be fetched, fetching the next name with a ‘get-next’, and repeating this operation.

•Set Request - The SNMP standard provides a method of effecting an action associated with a device (via the ‘set’ request) to accomplish activities such as disabling interfaces, disconnecting users, clearing registers, etc. This provides a way of configuring and controlling network devices via SNMP.

Version 4.4 171 July 2005