Distributed multicast contention resolution using content addressable FIFOs

Abstract

Space switches suffer from external blocking because of output port contention. We review contention resolution methods used to avoid external blocking, and choose a solution based on ring reservation, resulting in an elegant and efficient mechanism requiring only nearest-neighbor communications. In addition to external blocking, space switches suffer from head-of-line (HOL) blocking, and we propose a means of contention resolution that alleviates HOL blocking without arbitration time overhead. This method makes use of a novel Content Addressable FIFO, and its design and operation are described in detail. Multiple latency priorities are supported, and we introduce an efficient means of supporting multicasts, using call-splitting in our single-cycle windowing environment.