Reducing the Effect of Hot Spots by Using a Multipath Network

One type of interconnection network for a medium to large-scale parallel processing system (i.e., a system with 26 to 216 processors) is a buffered packet-switched multistage interconnection network (MIN). It has been shown that the per formance of these networks is satisfactory for uniform network traffic. More recently, several studies have indicated that the performance of MINs is degraded significantly when there is hot spot traffic, that is, a large fraction of the messages are routed to one particular destination. A multipath MIN is a MIN with two or more paths between all source and destination pairs. This research investigates how the Extra Stage Cube multipath MIN can reduce the detrimental effects of tree satura tion caused by hot spots. Simulation is used to evaluate the per formance of the proposed approach. The objective of this evaluation is to show that, under certain conditions, the perfor mance of the network with the usual routing scheme is severely degraded by the presence of hot spots. With the proposed approach, although the delay time of hot spot traffic may be increased, the performance of the background traffic, which constitutes the majority of the network traffic, can be significantly improved.