User`s manual

H.323 User's Manual 15. SNMP-Based Management
Version 5.0 347 December 2006
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.
15.2 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.
When the SNMP alarm traps are sent, the carrier-grade alarm system does not add or
delete alarm traps as part of the feature. This system provides the mechanism for viewing
of history and current active alarm information.
15.2.1 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.
The ALARM-MIB is currently a draft standard and therefore has no OID assigned to it. In
the current software release, the MIB is rooted in the experimental MIB subtree. In a future
release, after the MIB has been ratified and an OID assigned, it is to move to the official
OID.
15.2.2 Alarm History
The device maintains a history of alarms that have been raised and traps that have been
cleared to allow a manager to recover any lost, raised or cleared traps. Two views of the
alarm history table are supported by the agent:
 acAlarmHistoryTable in the enterprise acAlarm
 nlmLogTable and nlmLogVariableTable in the standard NOTIFICATION-LOG-MIB
As with the acActiveAlarmTable, the acAlarmHistoryTable is a simple, one-row-per-alarm
table that is easy to view with a MIB browser.