Performance comparison of nonpreemptive and preemptive priority queueing strategies in ATM packet switch with input buffers

In this paper, we study the performances of nonpreemptive and preemptive priority queueing strategies in an asynchronous transfer mode (ATM) packet switch with input queues. We first investigate the priority effects on the ATM packet switch, and consider some variations of the priority queueing strategy. Next, we analyze the performances of delay and throughput for the priority queueing disciplines and obtain closed-form solutions. We then compare the performances of the nonpreemptive and preemptive schemes. From the results, we find that, in the switching system with the preemptive priority queueing strategy, the head-of-line (HOL) service time of a low-priority packet may be overlapped with the HOL service time of a high-priority packet when the HOL preemption occurs. Therefore, unlike a general queueing system, the preemptive priority queueing strategy can improve the performance of low- and high-priority packets. In addition, with the closed-form solutions obtained, we can reduce the computational complexity or eliminate heuristic adjustments to analyze the performance of the switching system with the priority queueing strategy.