The Influence of Service-Time Variability in a Closed Network of Queues

This paper describes the effect of service-time variability on the standard performance measures of a closed network of single-server queues with the first-come first-served discipline and one job class. Several service-time variability principles are proposed to serve as rough practical guidelines. The most interesting one states that the mean queue length at a bottleneck queue typically decreases when the variability of the service time at that queue is increased. The principles are supported here by numerical examples and theorems in special cases. The principles are also applied to test approximation procedures.