FDQ: the fair distributed queue MAN

A new protocol, fair distributed queue (FDQ), suitable for very high speed metropolitan area networks (MANs), is presented. FDQ is a slotted system implemented on a unidirectional fiber bus. It has similarities to the distributed queue dual bus (DQDB) protocol. FDQ achieves full throughput efficiency independent of the bus length, the transmission speed, and the number of nodes. FDQ allocates equal bandwidth under heavy load to all active users in a time period less than or equal to the round-trip propagation delay without wasting bandwidth. Its delay characteristics were studied via simulation and compared to DQDB. FDQ has lower average delays under a Poisson load than the DQDB protocol with or without the bandwidth balancing mechanism. The implementation of priority levels and detailed timing structure of the protocol are also described. It was shown that FDQ´s delay and throughput characteristics were only slightly affected by increasing distances or the number of nodes