Rmon Groups - HP V1910 Switch Series User Manual

RMON groups

Among the RMON groups defined by RMON specifications (RFC 2819), the device uses the statistics
group, history group, event group, and alarm group supported by the public MIB. Besides, HP also
defines and implements a private alarm group, which enhances the functions of the alarm group. This
section describes the five kinds of groups.
Ethernet 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 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 rising threshold, a rising event is triggered; when the value of the monitored variable
is smaller than or equal to the falling threshold, a falling 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. In other words, the rising alarm and falling alarm are alternate. As shown in
Figure 76, the value of an alarm variable (the black curve in the figure) overpasses the threshold value
(the blue line in the figure) for multiple times, and multiple crossing points are generated, but only
crossing points marked with the red crosses can trigger alarm events.
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