An efficient single-iteration single-bit request scheduling algorithm for input-queued switches

Abstract

Aiming at minimizing communication overhead of iterative scheduling algorithms for input-queued packet switches, an efficient single-iteration single-bit request scheduling algorithm called Highest Rank First with Request Compression 1 (HRF/RC1) is proposed. In HRF/RC1, scheduling priority is given to the preferred input–output pair first, where each input has a distinct preferred output in each time slot. If an input does not have backlogged packets for its preferred output, each of its non-empty VOQs sends a single-bit request to the corresponding output. This single bit distinguishes one longest VOQ from other non-empty VOQs among an input port. If an output receives a request from its preferred input, it grants this input. Otherwise, it gives the higher priority to the longest VOQ than other non-empty VOQs. Similarly, an input accepts the grant following the same propriety sequence. In case of a tie, the winner is selected randomly. Compared with other single-iteration algorithms with comparable communication overhead, we show by simulations that HRF/RC1 always gives the best delay-throughput performance.