76Figure 28 Rising and falling alarm eventsPrivate alarm groupThe private alarm group calculates the values of alarm variables and compares the result with the definedthreshold, thereby realizing a more comprehensive alarm function.The system handles the prialarm alarm table entry (as defined by the user) in the following ways:• Periodically samples the prialarm alarm variables defined in the prialarm formula.• Calculates the sampled values based on the prialarm formula.• Compares the result with the defined threshold.• Generates an appropriate event if the threshold value is reached.NOTE:If an alarm entry crosses a threshold multiple times in succession, the RMON agent generates an alarmevent only for the first crossing. For example, if the value of a sampled alarm variable crosses the risingthreshold multiple times before it crosses the falling threshold, only the first crossing triggers a rising alarmevent. If the count result of the private alarm group overpasses the same threshold multiple times, only thefirst one can cause an alarm event. In other words, the rising alarm and falling alarm are alternate.Configuring the RMON statistics functionThe RMON statistics function can be implemented by either the Ethernet statistics group or the historygroup, but the objects of the statistics are different. You can configure a statistics group or a history groupaccordingly.• A statistics object of the Ethernet statistics group is a variable defined in the Ethernet statistics table,and the recorded content is a cumulative sum of the variable from the time the statistics entry iscreated to the current time. For more information, see “Configuring the RMON Ethernet statisticsfunction.”• A statistics object of the history group is the variable defined in the history record table, and therecorded content is a cumulative sum of the variable in each period. For more information, see“Configuring the RMON history statistics function.”
