A New Scheduling Algorithm for Input-Queued Switches with Mixed Unicast and Multicast Traffic

We consider an NxN input-queued switch with N dedicated unicast virtual output queues (VOQs) and one shared multicast queue (MQ) at each input port. An efficient two-bit single-iteration (2BSI) scheduling algorithm is proposed to concurrently schedule both unicast and multicast traffic. In the request phase, a two-bit request message is used to indicate not only the type of the request (unicast/multicast) but also its importance (strong/weak). In the grant phase, multicast request is granted first, then strong unicast request, and finally weak unicast request. To minimize inconsistencies in the distributed arbitration process, the notion of preferred unicast/multicast relationship is adopted to desynchronize/synchronize the arbitration decisions made by different inputs/outputs. As compared to the existing schedulers, our 2BSI is one of the simplest algorithms to implement, and yet extensive simulation results show that it provides one of the best delay-throughput performances.