On fairness in polling systems

Which service discipline is more fair, exhaustive or gated? gated or globally-gated? How can we compare their fairness level? These questions are usually answered by handwaving as no fundamental research in this topic was yet conducted. Polling systems are widely used in many computer networks where several users compete for access to a common resource. Fairness is a fundamental aspect of polling systems; perhaps it serves as the motivation behind various polling schemes. Despite this fundamental role, fairness to customers in polling systems has not been extensively studied to date. This work is an attempt to model fairness in polling systems and study the relative fairness of various polling schemes. We focus, in the context of this work, on evaluating the system’s obedience to the FCFS policy as a measure of the fairness experienced by the individual customers. Using this metric we study the cyclic polling system under five different service disciplines: exhaustive, gated, binomial-gated, two-stage gated and globally-gated. For these systems we derive their “fairness” level both in a discrete system model and in a continuous model. We use the analysis as well as numerical examples to provide basic observations on fairness of polling systems.