A basic problem faced by designers of high-bandwidth switches and routers is to provide effective techniques for scheduling the routing of cells through crossbars. The problem is particularly important under heavy loads or when quality-of-service (QoS) is to be supported. Much previous work on scheduling has focused on maximum bipartite matching (MBM), maximum weight bipartite matching (MWBM), and heuristics to approximate MBM and MWBM solutions. In this paper, we introduce the shakeup technique: a randomized approach that can be used in conjunction with a number of existing heuristics to substantially improve solution quality. The shakeup approach is conceptually simple and is supported by both theoretical and experimental results. In addition, this paper provides for the first time a framework for experimental scheduler analysis. We give extensive head-to-head comparisons of stability ranges for a number of previously proposed schedulers, and work towards the development of benchmark traffic types.
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