3Com Switch 4200G Configuration Guide

286 CHAPTER 34: RMON CONFIGURATION
You can specify a network device to act in one of the following ways in response to
an event:
■ Logging the event
■ Sending trap messages to the NMS
■ Logging the event and sending trap messages to the NMS
Alarm group
RMON alarm management enables monitors on specific alarm variables (such as the
statistics of a port). When the value of a monitored variable exceeds the threshold, an
alarm event is generated, which triggers the network device to act in the set way.
Events are defined in event groups.
With an alarm entry defined in an alarm group, a network device performs the
following operations accordingly:
■ Sampling the defined alarm variables (alarm-variable) once in each specified period
(sampling-time)
■ Comparing the sampled value with the set thresholds and triggering the
corresponding events if the former exceeds the latter
Extended alarm group
With extended alarm entry, you can perform operations on the samples of an alarm
variable and then compare the operation result with the set threshold, thus
implement more flexible alarm functions.
With an extended alarm entry defined in an extended alarm group, the network
devices perform the following operations accordingly:
■ Sampling the alarm variables referenced in the defined extended alarm expressions
once in each specified period
■ Performing operations on sampled values according to the defined operation
formulas
■ Comparing the operation result with the set thresholds and triggering
corresponding events if the former exceeds the latter.
History group
History group contains the records of statistical network values collected periodically
and is stored temporarily for later retrieval. A history group can provide the history
data of the statistics on network segment traffic, error packets, broadcast packets,
utilization and collision times.
With the history data management function, you can configure network devices such
as collecting history data, collecting periodically the data of a specific port and saving
them.
Statistics group
Statistics group contains the statistics of each monitored port on a network device.
An entry in a statistics group is an accumulated value counting from the time when
the corresponding event is defined.
The statistics include the number of the following items: collisions, packets with cyclic
redundancy check (CRC) errors, undersize (or oversize) packets, broadcast packets,
multicast packets, and received bytes and packets.