REQUIREMENTS FOR DEADLOCK-FREE, ADAPTIVE PACKET ROUTING

This paper studies the problem of deadlock-free packet routing in para llel and distributed architectures. Three main results are presented. First, it is shown that the standard technique of ordering the buffers so that every packet always has the possibility of moving to a higher -ordered buffer is not necessary for deadlock freedom. Second, it is s hown that every deadlock-free. adaptive pocket routing algorithm can b e restricted, by limiting the adaptivity available, to obtain an obliv ious algorithm which is also deadlock-free. Third, it is shown that an y packet routing algorithm for a cycle or torus network which is free of deadlock and which uses only minimal length paths must require at l east three buffers in some node. This matches the known upper bound of three buffers per node for deadlock-free, minimal packet routing on c ycle and torus networks.