Snmp Extensibility Feature; Carrier Grade Alarm System; Active Alarm Table - 3Com VCX V7122 User Manual

a particular device. Since network devices can be configured with more than one
interface, this object can only be represented as an array.
By convention, SNMP objects are always grouped in an 'Entry' directory, within an object
with a 'Table' suffix. (The 'ifDescr' object described above resides in the 'ifEntry' directory
contained in the 'ifTable' directory).

SNMP Extensibility Feature

One of the principal components of an SNMP manager is a MIB Compiler which allows new
MIB objects to be added to the management system. When a MIB is compiled into an SNMP
manager, the manager is made 'aware' of new objects that are supported by agents on the
network. The concept is similar to adding a new schema to a database.
Typically, when a MIB is compiled into the system, the manager creates new folders or
directories that correspond to the objects. These folders or directories can typically be
viewed with a MIB Browser, which is a traditional SNMP management tool incorporated into
virtually all Network Management Systems.
The act of compiling the MIB allows the manager to know about the special objects
supported by the agent and access these objects as part of the standard object set.

Carrier Grade Alarm System

The basic alarm system has been extended to a carrier-grade alarm system. A carrier-grade
alarm system provides a reliable alarm reporting mechanism that takes into account EMS
outages, network outages, and transport mechanism such as SNMP over UDP.
A carrier-grade alarm system is characterized by the following:
The device has a mechanism that allows a manager to determine which alarms are
currently active in the device. That is, the device maintains an active alarm table.
The device has a mechanism to allow a manager to detect lost alarm raise and clear
notifications [sequence number in trap, current sequence number MIB object].
The device has a mechanism to allow a manager to recover lost alarm raise and clear
notifications [maintains a log history].
The device sends a cold start trap to indicate that it is starting. This allows the EMS to
synchronize its view of the device's active alarms.
The SNMP alarm traps are sent as in previous releases. This system provides the
mechanism for viewing of history and current active alarm information.

Active Alarm Table

The device maintains an active alarm table to allow a manager to determine which alarms
are currently active in the device. Two views of the active alarm table are supported by the
agent:
acActiveAlarmTable in the enterprise acAlarm
alarmActiveTable and alarmActiveVariableTable in the IETF standard ALARM-MIB
(rooted in the AC tree)
The acActiveAlarmTable is a simple, one-row per alarm table that is easy to view with a MIB
browser.
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