On the effectiveness of topology update mechanisms for ATM networks

The topology update mechanism is a key element in a link-state routing algorithm, providing information on which all routing decisions are based. Topology update schemes are essential for coping with link/node failures and recoveries, increasing load levels, and the addition and deletion of links/nodes. The effectiveness of topology update mechanisms for ATM networks for connection oriented services is studied through simulation. We concentrate on link failures, and the rerouting that takes place after a failure. The proposed topology update scheme informs all network nodes of the status of the links/nodes and the flow levels on each link for each connection priority. We define a performance metric that measures the level of control message activity in the network. We compare the proposed scheme with one that does not provide flow level information, but only informs the routing entity at which link an establishing connection was blocked or preempted. The efficiency of the proposed scheme is shown to be much better than the alternative as measured by the defined performance metric