Performance analysis and application of a two-priority packet queue

This paper analyzes the performance of a packet non-preemptive (PNP), two-priority queue that is modeled as a message M/G/1 system. We derive the average inqueue waiting time for a packet of given priority and the average message delays. To overcome mathematical complexity, this derivation employs the well-known but seldom used G/G/1 conservation law Because of the PNP discipline, the moments of low-priority traffic do not influence the average delay of the high-priority traffic. This model is compatible with the queueing discipline of the ISN trunk interface module (TIM). Among all the known practical queueing disciplines, the TIM discipline results in the shortest delay for short messages at reasonable expense to the long messages. Furthermore, the TIM discipline favors middle-sized time-sharing messages over long file-transfer messages, although not to the same extent as the round-robin algorithm.