Performance modeling of a channel reservation service

Abstract

Certain applications, such as videoconferencing and information broadcast, require the ability to reserve network resources in advance. In a reservation system, users submit requests to a service center. Each request is characterized by a start time, a bandwidth requirement and a holding time. We consider a loss system where the service center rejects a request if it cannot accommodate the request at the preferred start time. Scheduling decisions may be made as soon as a request arrives or may be delayed until a later time. The latter allows the system to make more informed scheduling decisions, but the delay may be unacceptable to the users. In this paper, we investigate the benefits of delaying the scheduling decisions from the performance point of view. Our investigation is based on a reservation system that can accommodate a range of bandwidth requirements. Optimal scheduling decisions are first obtained for some static systems, that is, systems where all requests have arrived before the scheduling decisions are made. The results are then used to develop heuristic scheduling algorithms for systems with delayed decisions. Simulation results on the performance of these algorithms, as compared to a system where scheduling decisions are made immediately upon a request's arrival, are presented.