Universal wormhole routing

We examine the wormhole routing problem in terms of the "congestion" c and "dilation" d for a set of packet paths. We show, with mild restrictions, that there is a simple randomized algorithm for routing any set of P packets in O(cd/spl eta/ + cL/spl eta/log P) time, where L is the number of flits in a packet, and /spl eta/ = min {d,L]; only a constant number of flits are stored in each queue at any time. Using this result, we show that a fat-tree network of area /spl Theta/(A) can simulate wormhole routing on any network of comparable area with O(log/sup 3/ A) slowdown, when all worms have the same length. Variable-length worms are also considered. We run some simulations on the fat-tree which show that not only does wormhole routing tend to perform better than the more heavily studied store-and-forward routing, but that performance superior to our provable bound is attainable in practice.<
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