An analysis of finite capacity queues with priority scheduling and common or reserved waiting areas

Abstract

We present an efficient method for computing the steady state probabilities of a finite capacity queue with exponential service. Poisson arrivals, non-preemptive or preemptive-resume priority scheduling, and common or reserved waiting areas for high and low priority packets. Numerical results are presented for the complete sharing (CS), complete partition (CP), sharing with minimum allocation (SMA) and sharing with maximum queue length (SMXQ) buffer allocation schemes with two priority classes. Under complete sharing, the admitted arrival rates are independent of the priority ordering and the queue lengths and response (sojourn) times of the admitted packets need not be monotonic or even increasing in the offered loads. Under CP, SMA and SMXQ, low priority packets may be subject to starvation. Under all schemes considered, the response times of either priority classes may decrease as the total offered load is increased.