Design and evaluation of a parallel-polled virtual output queued switch

Input-buffered switches with virtual output queueing require crossbar switch matrix scheduling algorithms. Existing scheduling algorithms are non-deterministic and are based on parallel and iterative request-grant-accept arbitration schemes. This presents challenges to flow-level scheduling for guaranteed throughput and bounded delay services and also to scalability. In this paper, the parallel-polled virtual output queued (PP-VOQ) switch is presented. Using parallel token passing, the PP-VOQ switch has deterministic and bounded scheduling delay and is implementable for 16 or 32 ports of 10-Gigabit Ethernet. The PP-VOQ switch is shown, via simulation, to perform very similar to an iSLIP switch. The PP-VOQ switch is extended to a "cube switch" design that decouples input port VOQ selection from output port selection to reduce the scheduling delay and improve scalability. This decoupled parallel polling is very scalable and is shown to result in better performance than an iSLIP switch.