RMON Groups 15-7
Figure 15-1 shows a counter with thresholds set manually.
Figure 15-1 Manually Set Thresholds
You can associate an alarm with the high threshold, the low threshold, or
both. The actions that occur because of an alarm depend on the network
management application.
RMON Hysteresis Mechanism
The RMON hysteresis mechanism prevents small fluctuations in counter
values from causing alarms. Alarms occur only when one of these events
occurs:
■ The counter value exceeds the high threshold after previously falling
below the low threshold. (An alarm does not occur if the value has not
fallen below the low threshold before rising above the high threshold.)
■ The counter value falls below the low threshold after previously
exceeding the high threshold. (An alarm does not occur if the value
has not risen above the high threshold before falling below the low
threshold.)
For example, in Figure 15-1, an alarm occurs the first time that the
counter exceeds the high threshold, but not the second time. At the first
instance, the counter is rising from below the low threshold. In the
second instance, the counter is not rising from below the low threshold.
Time
Counter
User specified
high threshold
User specified
low threshold
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