Tree-Based Multicast in Wormhole-Routed Torus Networks

A tree-based multicast algorithm for wormhole-routed torus networks which makes use of multiple edge-disjoint spanning trees is presented. Techniques for constructing two edge-disjoint spanning trees in 2-dimensional tori are rst described and analyzed. The disjoint spanning-tree multi-cast (DSTM) algorithm which uses the two disjoint spanning trees together with an up-down routing strategy to provide deadlock-free unicast and multi-cast routing is then speciied. In contrast with single spanning tree algorithms which use non-tree links only as shortcuts, DSTM uses all but two links as (primary) tree links and, therefore, better balances network traac and resource utilization. In regard to worst-case unicast performance in a traac-free situation , we prove that the combined diameter of our dual-tree network is no greater than twice that of the torus. Furthermore, simulation results demonstrate that DSTM outperforms the best single tree approach in 2-dimensional torus networks by up to a factor of two, both for pure multicast and for combined unicast/multicast traac.