3Com 4007, Руководство по внедрению, Страница: 639 / 684

Remote Monitoring (RMON) 639
Figure 81 shows a counter with thresholds set manually.
Figure 81 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 either:
■
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 first risen above the high threshold.)
For example, in Figure 81, 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