A Parallel-Polled Virtual Output Queued Switch with a Buffered Crossbar

* This material is based upon work supported by the National Science Foundation under Grant No. 9875177. Abstract Input buffered switches with Virtual Output Queues (VOQ) are scalable to very high speeds, but require switch matrix scheduling algorithms to achieve high throughput. Existing scheduling algorithms based on parallel requestgrant-accept cycles cannot natively support variable length Ethernet packets. In this paper, a Parallel-Polled VOQ (PPVOQ) architecture is proposed that natively supports variable length packets. Small amounts of FIFO buffering within a crossbar are used. Using simulation, the PP-VOQ with buffered crossbar switch is shown to have lower switch delay at high offered loads than an iSLIP switch for both cell and variable-length packet traffic. The PP-VOQ switch does not require internal speed-up or complex reassembly mechanisms. Priority mechanism implemented in both the iSLIP and PPVOQ switches are demonstrated to provide guaranteed rate and bounded delay for schedulable traffic.