CRMA: An access scheme for high-speed LANs and MANs

Abstract

Cyclic-reservation multiple access (CRMA) is presented as an access scheme for high-speed local and metropolitan area networks (LANs and MANs) based on slotted unidirectional bus structure, both folded and dual-bus configurations. CRMA consists of two novel mechanisms: cyclic-reservation access and reservation-cancellation backpressure. The cyclic-reservation access provides both throughput efficiency and flexibility in capacity allocation. This flexibility can be used to achieve any set of fairness conditions. The reservation-cancellation backpressure minimizes the worst-case access delay. CRMA provides the capability of reserving consecutive slots for transmitting a packet, thus facilitating reassembly. The flexibility in bandwidth allocation, together with the capability of efficiently utilizing the network with a few users, makes CRMA well suited to supercomputer-networking applications, such as visualization, high-resolution graphics, and image-retrieval systems. The recovery from transmission errors is simple owing to the centralized-global-queue approach. These properties make CRMA suitable for both LANs and MANs in the gigabit-per-second, as well as the 100-Mb/s speed range.