Layered Shortest Path (LASH) Routing in Irregular System Area Networks
IPDPS '02 Proceedings of the 16th International Parallel and Distributed Processing Symposium
Fast Dynamic Reconfiguration in Irregular Networks
ICPP '00 Proceedings of the Proceedings of the 2000 International Conference on Parallel Processing
The Journal of Supercomputing
Layered Routing in Irregular Networks
IEEE Transactions on Parallel and Distributed Systems
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Networks of workstations are becoming a cost-effective alternative for small-scale parallel computing. Although they may not provide the closely coupled environment of multicomputers and multiprocessors, they meet the needs of a great variety of parallel computing problems at a lower cost. However, in order to achieve a high efficiency, the interconnects used to build the network of workstations must provide a very high bandwidth and low latencies, making their design a critical issue.Recently, a very efficient flow control protocol for networks of workstations has been proposed by the authors. This protocol multiplexes physical channels between several virtual channels and minimizes the use of control flits by transmitting several data flits each time a virtual channel gets the link. In this protocol, a virtual channel sends data flits until the message blocks or is completely transmitted. However, it can reduce network throughput, by increasing short message latency, due to long messages monopolizing channels and hindering the progress of short messages.In this paper, we analyze the impact of limiting the number of flits (block size) that a virtual channel can send once it gets the link. We propose a new version of the previous flow control protocol that is easily implementable on hardware. Simulation results show that limiting the maximum block size is not a good design decision, because the overall network performance decreases. Only when short message latency is crucial, it is acceptable to limit the block size.