Performance of high-speed token-passing networks.

摘要

In recent years, we have witnessed the widespread proliferation of local area networks (LANs). Among the most prominent new LAN protocols are variations of token-passing networks, including the Fiber Distributed Data Interface (FDDI). Recent trends in the design of new LAN protocols include the ability to carry high-bandwidth integrated traffic and the increasing use of network interconnection. In this thesis, we study performance issues related to these trends, as they appear in token-passing networks.; We present a simulation study of the mean packet waiting time for network access in networks using the timed-token protocol, such as FDDI. The timed-token protocol is a recent variation of token-passing protocols that is designed for high efficiency and dynamic bandwidth assignment in high-speed LANs. The simulation results are compared to previous closed-form analytical solutions for cyclic-service {dollar}M/G/1{dollar} polling models using the exhaustive service discipline. We find that the timed-token protocol can be accurately represented by polling models using exhaustive service if the utilization is less than 80% of the maximum.; An analytical approximation is proposed for finding the mean packet waiting times in the timed-token protocol when loads are high. This technique relies on use of a vacation model, in which attention is focused on operation of the protocol at a single station. The model is solved using an imbedded Markov chain, through which we obtain a large number of linear equations that allow for computation of the mean packet waiting times. Through simulation, we assess the accuracy of our approximation for a wide range of network parameters.; With application toward modeling network interconnection and client/server computing environments, we present a characterization of the traffic on high-speed token-ring networks such as FDDI. The traffic passing by an arbitrary point on the token-ring network is modeled through a Markov packet train characterization. The exact transition probabilities for the size of successive packet trains is found through use of the continuous polling model. A simulation study of a bridge for LAN/WAN interconnection is presented in order to investigate the accuracy of our traffic characterization.