A Simple Adaptive Routing Scheme for ShuffleNet Multihop Lightwave Networks.

Under uniform traffic conditions, the recently proposed ShuffleNet multihop lightwave network makes efficient use of the channels with a simple, fixed (i.e., single-path) routing algorithm. In this paper, we describe a simple, adaptive routing scheme for datagram (connectionless) and virtual circuit (connection oriented) transmission that relieves congestion resulting from nonuniform traffic patterns and network failures. It is a distributed algorithm that uses only local state information available at the users. When the network is "congestion free," the routing scheme delivers packets in the minimum number of hops. However, as a channel becomes overloaded, some of the traffic is distributed over less-busy channels by automatically "bumping" packets in "non-optimal" directions. The ShuffleNet connectivity makes it possible to quickly disperse packets away from congested portions of the network. Moreover, the adaptive algorithm decreases the chance for congestion to develop (and the need to bump packets) by routing each packet over less-busy channels whenever there exist multiple minimum-hop routing paths to the packet's destination. Simulations of the adaptive routing scheme for datagram transmission demonstrate its ability to support nonuniform traffic patterns, reduce the mean queue sizes and variances, and require small resequencing buffers.