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Background: Know: alarm , Prerequisites - hysteresis, Recognize:


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Engineering principle: hysteresisEdit

The object of using such engineering principle in network management is to allow the system to be proactive rather than reactive, instead of waiting for the problem to occur the manager could prevent it by preventive measures using hysteresis concept, it is applied in network managment as an alert system.

Alarm thresholds can be used to generate alarms when packet loss exceeds a defined value (threshold) and instead of generating a lot of alarms just one alarm is efficient. In order to avoid having multiple alarms when the value is near the threshold another threshold needs to be configured namely hysteresis threshold which is responsible of clearing the alarm if the value drops down the threshold and to allow new alarm to be triggered.

Frequent switching should be avoided when condition is near target. So two seperate thresholds are defined and switching occurrs only when one threshold is passed and smaller variations do not cause switching just like a heater turning on or off when temperature is near target.

Wiki3a

Threshold











The threshold value could be a binary value which can be used to trigger the alarm, and the alarm calls the event, then additional functions can be set such as sending a trap to the network manager.

Wiki3b

Alarm generation











References and further readings:


http://docstore.mik.ua/orelly/networking_2ndEd/snmp/ch09_01.htm
http://en.wikipedia.org/wiki/Hysteresis#Models_of_hysteresis

Clemm, A ,2007, Network Management Fundamentals, Cisco press, pp. 263-265