Avaya 3500 series Configuration Manual page 24

System Monitoring Fundamentals
falling alarm cannot fire because the baseline traffic is always greater than the value of the
falling threshold. By definition, the failure of the falling alarm to fire prevents the rising alarm
from firing a second time.
The following figure describes an alarm with a threshold less than 260.
Figure 2: RMON alarm thresholds
Creating alarms
Select a variable from the variable list and a port, or other switch component, to which it is
connected. Some variables require port IDs, card IDs, or other indices (for example, spanning
tree group IDs). Then select a rising and a falling threshold value. The rising and falling values
are compared against the actual value of the variable that you choose. If the variable falls
outside of the rising or falling value range, an alarm is triggered and an event is logged or
trapped.
After an alarm is created a sample type is also selected, which can be either absolute or delta.
Absolute alarms are defined on the cumulative value of the alarm variable. An example of an
alarm defined with absolute value is card operating status. Because this value is not
cumulative, but instead represents states, such as card up (value 1) and card down (value 2),
you set it for absolute value. You can create an alarm with a rising value of 2 and a falling value
of 1 to alert a user to whether the card is up or down.
Most alarm variables related to Ethernet traffic are set to delta value. Delta alarms are defined
based on the difference in the value of the alarm variable between the start of the polling period
and the end of the polling period. Delta alarms are sampled twice for each polling period. For
each sample, the last two values are added together and compared to the threshold values.
This process increases precision and allows for the detection of threshold crossings that span
the sampling boundary. If you track the current values of a delta-valued alarm and add them
together, therefore, the result is twice the actual value. (This result is not an error in the
software.)
24 Configuration — System Monitoring
Comments? infodev@avaya.com
March 2013