3Com VCX V7111, User Manual

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VCX V7111 VoIP Gateway User Guide
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ƒ Table MIB Objects: Contain multiple sections of management data. These objects are
distinguished from ‘Discrete’ items (above) by requiring a "." (dot) extension to their
names that uniquely distinguishes the particular value being referenced. The "." (dot)
extension is the "instance" number of an SNMP object. For "Discrete" objects, this
instance number is zero. For "Table" objects, this instance number is the index into the
SNMP table. SNMP tables are special types of SNMP objects which allow parallel arrays
of information to be supported. Tables are distinguished from scalar objects, so that
tables can grow without bounds. For example, SNMP defines the "ifDescr" object (as a
standard SNMP object) that indicates the text description of each interface supported by
a particular device. Since network devices can be configured with more than one
interface, this object can only be represented as an
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:
ƒ 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.
ƒ 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].
ƒ
The device has a mechanism to allow a manager to recover lost alarm raise and clear
notifications [maintains a log history].
ƒ 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.