Nortel Passport 8600 Configuring page 45

When you create an alarm, you also select a sample type, 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. Therefore, an alarm could be created 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 per 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. Therefore, if you keep track of the current values of a given
delta-valued alarm and add them together, the result is twice the actual value.
(This result is not an error in the software.)
Note:
The example alarm described here will generate at least one alarm every five
minutes. The example is intended only to demonstrate how alarms fire; it is not a useful
alarm. Because of the high frequency, you may want to delete this alarm in a real world
scenario.
To create an alarm using default values and to receive statistics and history:
1
Make sure that RMON is globally enabled.
When you enable RMON globally, you also create a default rising and falling
event. The default for the events is log-and-trap, meaning you will receive
notification through a trap as well as through a log file.
2
From the Device Manager menu bar, choose RMON > Alarm Manager.
The Alarm Manager dialog box opens
Chapter 2 Configuring RMON
(Figure 9 on page 46).
Configuring Network Management
45