A New Method for Deadlock Elimination in Computer Networks with Irregular Topologies

* This work has been supported by NSF grant MIP-9630096 Abstract In this paper we consider the problem of deadlock-free wormhole unicast routing in networks with irregular topologies. To prevent deadlocks, for each router some input/output pairs (turns) have to be prohibited. We analyze the problem of minimizing the number of prohibited turns for providing deadlock-free routing. A new algorithm is proposed, which guarantees that this number does not exceed 1/3 of the total number of turns and that it is still possible to send messages between any two initially connected nodes. To the best of our knowledge this is the first meaningful upper bound on the fraction of turns to be prohibited to prevent deadlocks for networks with an irregular toplogy. Also, the problem of routing in the presence of prohibited turns is considered and appropriate methods developed.