A carrier sensed multiple access protocol high data rate ring networks

Abstract

This paper presents a significant extension of the CSMA network access protocol. The protocol is based on the facts that, at high data rates, networks can contain multiple messages simultaneously over their span, and that in a ring, nodes needs only to detect the presence of a message arriving from the immediate up stream neighbor. When an incoming signal is detected, the node truncates the message it is presently sending instead of aborting it. The system has been named Carrier Sensed Multiple Access Ring Network, CSMA/RN.Analytical studies using three performance factors, wait or access time, service time and response or end-to-end travel time are presented. The service time is basically a function of the network rate; it changes by a factor of 4 between no load and full load. Wait time, which is zero for no load, remains small for load factors up to 70% of full load. Response time, which adds travel time while on the network to wait and service time, is mainly a function of network length, especially for longer distance networks.Simulation results are shown for CSMA/RN where messages are removed at the destination. Destination removal on an average increases network load capacity by a factor of 2, i.e., a 1 Gbps network can handle a 2 Gbps load. A wide range of local and metropolitan area network parameters including variations in message size, network length and node count are studied. In all cases performance is excellent, and message fracture usually remains less than a factor of 4. Throughput, even at overload conditions, remains high for the protocol. The nominal network rate is 1 Gbps; however, performance remains good for data rates as low as 200 Mbps. Finally, a scaling factor based upon the ratio of message to network length demonstrates that the results of this paper, and hence, the CSMA/RN protocol, are applicable to wide area networks.