Bidirectional shufflenet: a multihop topology for backpressure flow control

The traditional shufflenet multihop virtual topology for optical networks does not provide easy support for backpressure flow control on a hop-by-hop basis. In the context of an optical backbone network interconnecting high speed electronic LANs that use wormhole routing, as in the Supercomputer SuperNet (SSN) project, hop-by-hop flow control is required in the optical network to eliminate losses due to buffer overflows. We modify the shufflenet topology by using bidirectional links to obtain a new topology called bidirectional shufflenet. This topology provides a natural support for the hop-by-hop backpressure flow control mechanism. We demonstrate the need for flow control in the wormhole routing context. We compare the average hops with the shufflenet and bilayered shufflenet. Then, we compare shufflenet with bidirectional shufflenet via simulation to show the performance improvements yielded by the latter. The throughput of the bidirectional shufflenet is better for large worms while the delay is comparable. The length of the worm has a clear effect on the throughput and delay values obtained