Analysis, approximations and admission control of a multi-service multiplexing system with priorities

We consider an ATM system with an architecture which is designed to accommodate users with very different quality of service requirements. Sources which belong to a high priority class share a FCFS buffer, which has priority access to the trunk. A low priority class of sources have a separate FCFS buffer, which receives the residual bandwidth, if any. By administering admission control the service guarantees for both classes may be satisfied. The sources are bursty and stochastic fluid models are used to handle burst-scale congestion effects. We develop simple, fast and robust analytic approximations for the queue distributions in the two buffers. We calculate the admissible set by using our analytic approximations and find that it is reasonably accurate and a conservative approximation to the correct set. The key element in our analysis is a characterization of the output of the high priority buffer as another Markov-modulated fluid source. A refinement to the now well known effective bandwidth approximation is used to calculate buffer content distributions.