CORPS-a pipelined fair packet scheduler for high speed switches

Input queues have become an attractive switch architecture, since it was shown that a throughput of up to 100% is achievable when a virtual output queue (VOQ) is used. Although schedulers for VOQ switches have been proposed, pipelined schedulers, whose processing requirements increase at most linearly with line speeds, have not yet matured. We introduce CORPS, a pipelined scheduler which allows fair scheduling among input lines of a crossbar high speed switch fabric. By means of a round-robin communication scheme, CORPS achieves scalability to a large number of ports. Moreover, CORPS achieves one scheduling decision per line per slot, by scheduling packets into future slots. The tradeoffs involved are packet delay and utilization.