Layered Shortest Path (LASH) Routing in Irregular System Area Networks

In recent years we have seen a growing interest in irregular network topologies for cluster interconnects. One problem related to such topologies is that the combination of shortest path and deadlock free routing is difficult. As a result of this the existing solutions for routing in irregular networks either guarantee shortest paths relative to some constraint (like up*/down*), or have to resort to deadlock recovery through non-minimal escape channels. In this paper we propose a method that guarantees shortest path routing and in-order delivery, and that uses virtual channels for deadlock avoidance. We present a theoretical upper bound on the number of virtual channels needed, and through extensive empirical testing we demonstrate that the actual number of virtual channels is very low even for large networks.