A simple incremental network topology for wormhole switch-based networks

Wormhole switching has become the most widely used switching technique for multicomputers. However the main drawback of wormhole switching is that blocked messages remain in the network, prohibiting other messages from using the occupied links and buffers. To address the deadlock problem without compromising communication latency and the incremental expansion capability that irregular networks can offer we propose a simple topology called Incremental Triangular Mesh (ITM) for switch-based networks. ITM is highly scalable, allows incremental expansion of systems, has guaranteed deadlock freedom, and can support contention-free multicast. First, we show that on an ITM, shortest path routing method will not deadlock, therefore it is ideal to be used as the escape paths in adaptive routing networks. Secondly, we show that it is possible to arrange the nodes of an ITM in a circular order so that two messages from independent parts of the circular order will not interfere with each other, and we can find a circular order for every ITM that has this contention-free property. This is extremely useful for implementing contention-free multicast and other collective communication operations. Our experimental results demonstrate that ITM provides better throughput than up-down routing