DQMA and CRMA: New access schemes for Gbit/s LANs and MANs

Abstract

Distributed-queue multiple-access (DQMA) and cyclic-reservation multiple-access (CRMA) access schemes for gigabit-per-second local and metropolitan area networks are described. These schemes are based on a slotted unidirectional bus structure, with both folded and dual-bus configurations. Like the distributed-queue dual-bus (DQDB) scheme, both the DQMA and the CRMA access schemes achieve full throughput independent of network speed and distance. They have two significant advantages over DQDB. They provide throughput fairness even at high speeds and large distances, where DQDB exhibits dramatic unfairness, and, by allowing reservation of multiple consecutive slots, they make segment labeling unnecessary and facilitate packet reassembly significantly.