A Dynamic Timeout Scheme for Wormhole Routing Networks

Po-Chi Hu Lucent Technologies Inc. 200 Schulz Drive Red Bank, NJ 07701 Leonard Kleinrocky Department of Computer Science University of California, Los Angeles Los Angeles, CA 90095-1596 Abstract In a previous paper [1], we proposed and analyzed a timeout scheme to alleviate network congestion and thus improve the throughput for a wormhole routing network in local area network (LAN) environments. This timeout scheme was proved to be e ective, but the optimal timeout value varies with packet size, propagation delay, and other network parameters. To tune the timeout value automatically, two dynamic timeout methods are presented in this paper. The rst method, called \Immediate Timeout Or Wait" (ITOW), compares the costs for timeout and waiting. Thus, it decides to reject a worm immediately or to allow the worm to wait until the timeout occurs. The second method, called \Cost Equilibrium Point" (CEP), sets the timeout value to the point where the timeout and waiting costs are the same, thereby determining the timeout value automatically. From simulation, the results show that the rst method simpli es the choice of the timeout value and the second method performs well if a cost factor for timeout is given properly. Both methods improve the network throughput signi cantly.