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Ethernet Statistics
RS400 125 ROS™ v3.5
2. Packet has invalid CRC.
Collisions
Synopsis: 0 to 4294967295
The number of received packets for which Collision Event has been detected.
Utilization
Synopsis: 0 to 4294967295
The best estimate of the mean physical layer network utilization on this interface during this
sampling interval (hundredths of percent)
4.4.3 RMON Alarms
RMON Alarms table configures the switch to examine the state of a specific statistic variable.
The record of this table contains an upper and a lower threshold for legal values of the statistic
in a given interval. This provides the ability to detect events occurring more quickly than a
specified maximum rate or less quickly than a specified minimum rate.
When a statistic value’s rate of change exceeds its limits an internal alarm of INFO level is
always generated. Internal alarms can be viewed using the Diagnostics menu, View Alarms
command.
Additionally, a statistic threshold crossing can result in further activity. The RMON Alarm record
can be configured to point to a particular RMON Event Record, which can generate an SNMP
trap, an entry in the switch’s event log or both. The RMON Event Record can “steer” alarms
towards different users defined in SNMP Users table.
The alarm record can point to a different event record for each of the thresholds, so
combinations such as “trap on rising threshold” or “trap on rising threshold, log and trap on
falling threshold” are possible.
If the very first statistic measurement (after switch reset or after the record is created)
immediately exceeds the configured thresholds decision, it is upon configuration whether or not
to generate an alarm.
The ability to configure upper and lower thresholds on the value of a measured statistic provide
for the ability to add hysteresis to the alarm generation process.
If the value of the measured statistic over time is compared to a single threshold, alarms will be
generated each time the statistic crosses the threshold. If the statistic’s value fluctuates around
the threshold, an alarm can generated every measurement period. Programming different upper
and lower thresholds eliminate spurious alarms. The statistic value must “travel” between the
thresholds before alarms can be generated.
The following figure illustrates the very different patterns of alarm generation resulting from a
statistic sample and the same sample with hysteresis applied.