Workload optimality in switches without arrivals

Gagan Raj Gupta, Sujay Sanghavi, Ness B. Shroff

Abstract: We analyze a switch with cross-bar constraints. Beginning with an initial loading and no further arrivals, we provide necessary conditions for a scheduling policy to minimize the workload at all times. We show that these conditions are sufficient for a switch of size N x 3 or smaller. We then consider a weaker notion of optimality: cumulative average workload optimality. Using a counter example for a 7 x 7 switch, we show that it is not possible to approximate the cumulative average workload within (1+4/475) of the optimal at all times. We conjecture that the workload under the MVM policy is within twice of the optimal at all times.