This paper is a critique of major weaknesses of current techniques for analyzing the reliability of computer communication networks. Several of the most important factors influencing the reliability seen by users of such systems have been almost completely ignored or modeled in a rudimentary fashion. Ignoring such factors may be partially justified by the inherent complexity of the problems being studied, which often precludes exact computations being feasible for networks of any size, even with simplifying assumptions. Nevertheless, the results of models which ignore such factors are questionable even if they are computable. The focus of models of such networks should be on the effects of system malfunctions, degraded performance, excessive delays, etc., on system users. New approximate modeling techniques appear to be the most realistic approach to studying such problems.

This paper presents a new modular loop/ring architecture combining advantages of several earlier centralized and decentralized ring-structured loop networks while remaining simple. This is accomplished by introducing two major innovations: first, use of a separate control loop for control messages flowing between nodes and a loop controller; second, dynamically implementing partitionable segments between adjacent nodes and treating them as separate links for data transmission.

This paper presents a simplified approach to developing performance models for complex systems, such as distributed processing systems, and illustrates the approach by applying it to studying the performance of a new ring-structured microcomputer network. The approach utilizes both regression (curve-fitting) techniques and queueing theory analysis, and suggests that response times of the system studied can be closely approximated by a multiserver queueing model which is generalized to allow a noninteger number of servers. Both the approach and the approximate model developed appear to be applicable to a wide variety of systems.