A TASK-ORIENTED PRIORITY QUEUE FOR TELEPHONE SWITCH DESIGN - WITH MODIFIED FCFS AND FORKING

When developing a telephone switch, it is useful to know how long it w ill take to process the various tasks associated with call processing. The model developed in this paper gives expected sojourn times far th ose tasks. It is a priority queueing model with a modified first-come first-served (FCFS) service discipline, which mimics the treatment of tasks in actual system software. The model is an M/G/1 queueing model with preemption (preemptive resume). It consists of multiple queues, o ne for each distinct priority, where each task has been preassigned a constant priority. Within each priority queue, the tasks are further g rouped by type. An arriving task will join the back of the group of ta sks of its type, regardless of where this group is positioned in the q ueue. Upon completion of a task, several tasks of different types can enter the priority queues. This is referred to as forking. Call proces sing involves many ordered sets of tasks (jobs or classes), some of wh ich will contain forks. The model produces results that compare favora bly with those obtained by simulation.