Using a multipath network for reducing the effects of hot spots

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 performance of these networks is satisfactory for uniform network traffic. More recently, several studies have indicated that the performance of MIN´s 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 saturation caused by hot spots. Simulation is used to evaluate the performance of the proposed approaches. The objective of this evaluation is to show that, under certain conditions, the performance of the network with the usual routing scheme is severely degraded by the presence of hot spots. With the proposed approaches, 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