COMNET III CACI

For the FM functions, a distinction should be made between the continuity checking /
loopback OAM cells and the fault detection OAM cells. The former are modeled like the
PM OAM cells, using a session source and a user-defined inter-arrival time
between the endpoints of the OAM cell flow. For the fault detection OAM cells
however, you should make use of a message source. In this case, the frequency of
the OAM cells is determined by the failure characteristics of the nodes and links in the
model. COMNET III allows you to make use of triggers to model the interaction between
the arrival of an OAM cell and the failure of a topology component. You should set the
trigger parameters under the nodes and links in the network. Activating the Triggers
button on the node or link dialog boxes allows you to select the sources which should be
triggered. Under the Edit button of these triggers you can then set the triggering rule to
be upon node / link failure. You should then set the scheduling rule of the
respective message sources to be trigger only to link the generation process
of the OAM cell with the failure process. Note that this is the reason for using a
message source. If you chose a session source instead, COMNET III would
trigger an SVC upon node / link failure. This is clearly not the case in an ATM network
and would hence result in a wrong model.
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