Load Balancing of Irregular System Area Networks through Multiple Roots

In recent years we have seen an increasing interest in irregular topologies in the interconnect communities. The predominant routing strategy for such networks is the up*/down* algorithm proposed in connection with Autonet. One problem with this algorithm is that it creates a configuration that is very prone to hot-spots near the root of the up*/down* tree. Previous methods for handling this problem are all based on minimal routing combined with escape paths in some form, but this solution requires functionality for adaptive routing to be implemented in the switches. Furthermore, technologies that require in-order delivery of packets, like the recent InfiniBand specification, cannot take advantage of such methods. In this paper we propose a simple method for load balancing that can be utilized for technologies with source routing or deterministic routing. Our simulation experiments show improvements in throughput of up to 85% in some cases.