3Com 2500 manual Alarms, statistics counters associated with it, you misleading results

13-6 CHAPTER 13: REMOTE MONITORING (RMON) TECHNOLOGY

Alarms	The LANplex system supports the following syntax for alarms: counters,
	gauges, integers and timeticks. These mechanisms report information about
	the network to the network administrator. Counters, for example, hold and
	update the number of occurrences of a particular event through a port,
	module, or switch on the network. Alarms monitor the counters and report
	instances of when counters exceed their set threshold.
	Counters are useful when you compare their values at specific time intervals
	to determine rates of change. The time intervals can be short or long,
	depending on what you measure. Occasionally, reading counters can give
	you misleading results.
	Counters are not infinite, which makes rate comparisons an efficient way to
	use them. When counters reach a predetermined limit, they return to 0 (roll
	over). A single low counter value might accurately represent a condition on
	the network. It might simply indicate that a roll over has occurred.
	When you disable a port, the application might not update some of the
	statistics counters associated with it.
	An alarm calculates the difference in counter values over a set time interval
	and remembers the high and low values. When the value of a counter
	exceeds a preset threshold, the alarm reports this occurrence.
	You can assign alarms with Transcend Enterprise Manager or any other
	SNMP network management application to monitor any counter, gauge,
	time tick, or integer. Consult the documentation for your management
	application for details on setting up alarms.