Backlog Aware Low Complexity Schedulers for Input Queued Packet Switches

Abstract

We study the problem of packet scheduling in input queued packet switches, with an emphasis on low complexity and ease of implementation. Toward this end, we propose a class of subset based schedulers, wherein an N x N switch is operated using only a small set of N configurations in every time-slot. We show that the performance of subset based scheduling is comparable to that of the benchmark maximum weight matching (MWM) scheduler, albeit at much lower complexity. Next, we relate subset based scheduling to the well known wrapped wavefront arbiter (WWFA) [14] and propose BA-WWFA, a backlog aware version of WWFA. The BA-WWFA scheduler significantly enhances the performance of WWFA, while retaining its ease of hardware implementation. The performance gains are especially noteworthy under non-uniform loading of the switch. Given their ease of implementation and MWM like performance, the schedulers proposed in this paper represent an attractive option for high performance packet switching.