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We have developed a new method to uniformly balance communication traffic over the interconnection network called Distributed Routing Balancing (DRB) that is based on limited and load-controlled path expansion in order to maintain a low message latency. DRB defines how to create alternative paths to expand single paths (expanded path definition) and when to use them depending on traffic load (expanded path selection carried out by DRB Routing). The alternative path definition offers a broad range of alternatives to choose from and the DRB Routing is designed with the goal of minimising monitoring and decision overhead. Evaluation in terms of latency and bandwidth is presented. Some conclusions from the experimentation and comparisons with existing methods are given. It is demonstrated that DRB is a method to effectively balance network traffic.

The increasing demand of parallel applications in ClusterComputing requires the use of Interconnection Networks to provide low and bounded communication delays. However, message congestion appears when communication load between nodes is not fairly distributed over the network. Congestion spreading increases latency and reduces network throughput causing important performance degradation. In this paper we present Dynamic Routing Balancing with Multipath Distribution (DRB-MD), a new method developed to control network congestion based on a uniform balancing of communication load. DRB-MD distributes the traffic load according to a gradual and load-controlled path expansion. It monitors message latency in network switches, makes decisions about how many alternative paths should be used, and finally decides which path (or paths) to use between each source-destination pair. Experiments with permutation patterns and hotspot traffic were conducted to evaluate DRB-MD performance under conditions commonly created by parallel scientific applications.

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