Simple performance analysis of a token ring metropolitan area network

Abstract

The performance of a MAN (metropolitan area network) based on a 100 Mbit s-1 optical backbone supporting several 10 Mbit s-1 metallic token passing LANs as well as a gateway to, say, an ISDN exchange is investigated analytically. Based on traffic intensity limitations, some simple performance bounds on the number of stations and LANs that can be supported in the network are first derived. The mean delay performance for intraLAN, interLAN and gateway traffic is then obtained and studied in a number of operating environments using the delay formulae for asymmetrical token passing networks. It is found that the various types of traffic have roughly the same, respectable, delay performance unless the number of stations or LANs is close to the simple bounds derived. Specifically, if the traffic intensity from each station is equal to that from a voice source, the total number of stations that can be supported on the entire network can range from slightly over 2000, when all the traffic is through the gateway, to several tens of thousands, when most of the traffic is intraLAN. The results presented can be used as a guideline for determining the ability of optically based MANs to support realtime voice and data traffic in various applications. Finally, some simulation results are presented to verify the analytical results obtained. © 1990.