Providing 100% throughput in a buffered crossbar switch

Buffered crossbar switches have received great attention recently because they have become technologically feasible, have simpler scheduling algorithms, and achieve better performance than a bufferless crossbar switch. Buffered crossbar switches have a buffer placed at each crosspoint. A cell is first delivered to a crosspoint buffer and then transferred to the output port. With a speedup of two, a buffered crossbar switch has previously been proved to provide 100% throughput. We propose what we believe is the first feasible scheduling scheme that can achieve 100% throughput without speedup and a finite crosspoint buffer. The proposed scheme is called SQUISH: a Stable Queue Input-output Scheduler with Hamiltonian walk. With SQUISH, each input/output first makes decisions based on the information from the virtual output queues and crosspoint buffers. Then it is compared with a Hamiltonian walk schedule to avoid possible "bad" states. We then prove that SQUISH can achieve 100% throughput with a speedup of one. Our simulation results also show good delay performance for SQUISH.