Providing Delay Guarantee in Input Queued Switches: A Comparative Analysis of Scheduling Algorithms

Abstract

Real-time applications require switching components to deliver packets in bounded delay. Most of such switches are designed as output-queued switches, which suffer from bandwidth limitation. Input queued switches remedy this by introducing buffers at inputs, however due to input/output contention providing delay guarantee is difficult. Based on maximum weighted matching, we present several classes of schedulers, which provide best-effort delay guarantee for various delay classes. Each scheduler uses some combination of Round Robin and Earliest Deadline First policy at various service points. Comparative analysis is performed and some key parameters in the design of efficient schedulers with delay guarantee are provided. These parameters are: average match per time slot, average weight per match, and fairness. Finally, the effect of speedup is studied. Our schedulers can support variable length IP packets as well as multicast packets, the latter being supported by fanout splitting.