A parallel-polled virtual output queued switch with a buffered crossbar

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 request grant-accept cycles cannot natively support variable length Ethernet packets. A parallel-polled VOQ (PP-VOQ) 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. The priority mechanism implemented in both the iSLIP and PP-VOQ switches are demonstrated to provide guaranteed rate and bounded delay for schedulable traffic.