Adaptive wormhole routing in tori with faults

The authors present a method to enhance wormhole routing algorithms for deadlock-free fault-tolerant routing in tori. They consider arbitrarily-located faulty blocks and assume only local knowledge of faults. Messages are routed via shortest paths when there are no faults, and this constraint is only slightly relaxed to facilitate routing in the presence of faults. The key concept used is that, for each fault region, a fault ring consisting of fault free nodes and physical channels can be formed around it. These fault rings can be used to route messages around fault regions. We prove that, at most, four additional virtual channels are sufficient to make any fully-adaptive algorithm tolerant to multiple faulty blocks in torus networks. Simulation results are presented for fully-adaptive algorithm showing that good performance can be obtained with as many as 10% links faulty