Rmon Groups - 3Com Baseline 2928 PWR Plus User Manual

RMON Groups

Among the RMON groups defined by RMON specifications (RFC 2819), the realized public MIB of the
device supports the statistics group, history group, alarm group, and event group.
Statistics group
The statistics group defines that the system collects statistics on various traffic information on an
interface (at present, only Ethernet interfaces are supported) and saves the statistics in the Ethernet
statistics table (ethernetStatsTable) for query convenience of the management device. It provides
statistics about network collisions, CRC alignment errors, undersize/oversize packets, broadcasts,
multicasts, bytes received, packets received, and so on.
After the creation of a statistics entry on an interface, the statistics group starts to collect traffic statistics
on the interface. The result of the statistics is a cumulative sum.
History group
The history group defines that the system periodically collects statistics on traffic information at an
interface and saves the statistics in the history record table (ethernetHistoryTable) for query
convenience of the management device. The statistics data includes bandwidth utilization, number of
error packets, and total number of packets.
A history group collects statistics on packets received on the interface during each period, which can be
configured through the command line interface (CLI).
Alarm group
The RMON alarm group monitors specified alarm variables, such as total number of received packets
(etherStatsPkts) on an interface. After you define an alarm entry the system gets the value of the
monitored alarm variable at the specified interval, when the value of the monitored variable is greater
than or equal to the upper threshold, an upper event is triggered; when the value of the monitored
variable is smaller than or equal to the lower threshold, a lower event is triggered. The event is then
handled as defined in the event group.
If the value of a sampled alarm variable overpasses the same threshold multiple times, only the first one
can cause an alarm event. That is, the rising alarm and falling alarm are alternate.
Event group
The event group defines event indexes and controls the generation and notifications of the events
triggered by the alarms defined in the alarm group and the private alarm group. The events can be
handled in one of the following ways:
Log: Logging event related information (the time of the event occurred, contents of the event, and
so on) in the event log table of the RMON MIB of the device, and thus the management device can
check the logs through the SNMP GET operation.
Trap: Sending a trap to notify the occurrence of this event to the network management station
(NMS).
1-2