Device Management; Snmp Management; Snmp Overview; Snmp Messages - AudioCodes Mediant 2000 User Manual

Mediant 2000/SIP User's Manual
6

Device Management

6.1

SNMP Management

6.1.1

SNMP Overview

SNMP (Simple Network Management Protocol) is a standard network-based client/Server-based
control protocol to manage devices in the Network. The client program (called the Network
Manager) makes connections to a Server program, called the SNMP Agent. The SNMP Agent,
embedded on a remote network device, serves information to the Network Manager regarding the
device's status. The database used by the Agent to retrieve information, is referred to as the
SNMP Management Information Base (MIB), and is a standard set of statistical and control
values. Apart from the standard MIBs documented in IETF's RFCs, SNMP additionally allows the
usage of private MIBs, containing non-standard information set.
Directives, issued by the network manager client 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 the identifier, or set the identifier to a new value.
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 network management
client programs so that they can become aware of MIB variables and their usage.
The Mediant 2000/SIP contains an embedded SNMP Agent supporting both general network
MIBs (such as the IP MIB), VoP-specific MIBs (such as RTP, MGCP, Trunk, etc.) and a
proprietary MIB (known also as AudioCodes MIB) enabling a deeper probe into the "inner
working" of the Gateway. All the supported MIBs files are supplied as part of the release.
6.1.2

SNMP Messages

Four types of SNMP messages are defined:
"
"Get"
"
"Get-Next"
"
"Set"
"
"Trap"
Each of the following 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 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
the 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 until an error
is encountered (indicating that all MIB object names have been "walked").
"
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.
"
Trap Message: The SNMP standard furnishes a mechanism by which devices can "reach
out" to a network manager on their own (via the "trap" message) to notify the manager of a
problem with the device. This typically requires each device on the network to be configured
to issue SNMP traps to one or more network devices that are awaiting these traps. The Trap
Version 4.2 Beta
Request that returns the value of a named object.
Request that returns the next name (and value) of the "next" object
supported by a network device given a valid SNMP name.
Request that sets a named object to a specific value.
Message generated asynchronously by network devices. It notifies the
network manager of a problem apart from polling of the device.
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6. Device Management
June 2003