A pipelined packet scheduler for high speed optical switches

摘要

A pipelined scheduler which allows easy implementation and control and further fair scheduling among input lines of a crossbar high speed switch fabric is discussed. By means of a round-robin communication scheme, a systematically ordered sequence of visits to time slots can be obtained regardless of whether the number of scheduler modules is even or odd by framing the time axis and using a priority matrix to reserve future time slots. Further, a Carry Over Round-robin Pipelined Scheduler (CORPS) achieves scalability to a large number of ports. Moreover, CORPS achieves one scheduling decision per line per slot, by scheduling packets in future slots. It is well suited to the support of Quality of Service traffic, since the choice of the queues to be scheduled is arbitrary. CORPS limits itself to resolve, in a fair way, the contention for output ports.