A Performance Criterion And Traffic Analysis For Polling Systems

AbstractPolting systems of various types are used in many computer communication systems today. Methods of traffic analysis developed recently for distributed-control loops, which are also a type of polling system, are shown to be applicable to most polling systems. The fixed, minimum time per polling sequence, D, is an excellent performance and design criterion for comparing the polling frequencies and response-times of different systems, designed to serve the same terminals, at all traffic intensities, r. If the sum of the lengths of the forward and return messages is T, then reducing D produces a proportionate increase in polling frequency and a proportionate decrease in response time until D » rT. Beyond this point little is to be gained by reducing D and all systems for which D << rT exhibit similar performance. The three parameters D, r, and T are sufficient to form a good estimate of the response-time of the system. Distributed-control loops can usually achieve tower values of D, and therefore bett...