Counters - 3Com LINKBUILDER 3C18500 User Manual

Counters

Counters are the MIB objects which hold and update the number of
occurrences of a particular event through a port, module, repeater or
on the network. The management facility reads the counters it needs
for the output, processes the information and displays the result. The
counter may be associated with a port, or a module, or a repeater, or
even a chassis. It can be counting any recurring event: typical examples
are traffic, collisions, and FCS errors.
When a port is disabled, some of the statistics counters associated with
it may no longer be updated.
When using the counters, it is better to employ differences between
values rather than spot values. By using values at fixed time intervals
the rates of change of the counters can be derived. The time intervals
can be as short or as long as you find convenient. These rates will be
more meaningful than spot values and may be compared to provide
more useful data.
There is a sound reason for using differences. The counters cannot be
infinite. They will roll-over (return to zero) when they reach their limit.
Thus a low value may or may not be truly representing the situation. A
negative difference indicates that roll-over has occurred. You can be
more sure of what has occurred by changing (either shortening or
lengthening) the time interval and comparing the results.
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