On The E ects of Message Scheduling for Packet Switching Interconnect Fabric

This report explores the impact of di erent message scheduling strategies on the performance of a packet-switched network under bursty tra c conditions and di erent routing strategies. Deterministic routing strategies are attractive because they are cheap and fast to implement. However, possible drawbacks include lower throughput, signi cantly increased message latency under heavy tra c, and high contention for resources. Adaptive routing strategies are more exible but inherently more complex which may result in slower routing. We investigate the trade-o s involved in using di erent routing strategies while intelligently scheduling the packets from various messages for injection into the interconnect. This paper presents the results of a simulation study designed to answer this question for realistic bursty tra c workloads. In particular we compare deterministic and two forms of adaptive strategies under three di erent message scheduling algorithms: FIFO, Round Robin and Alpha scheduling. Our results indicate that for some types of bursty tra c with high volume of short messages, adaptive routing does not improve the interconnect performance, either in latency or in throughput. These performance results can be achieved by using either Round Robin or Alpha scheduling, which both tend to smooth tra c burstiness. 1 Internal Accession Date Only