A Probabilistic Priority Scheduling Discipline for High Speed Networks

In high speed networks, the Strict Priority (SP) scheduling discipline is perhaps the most common and simplest method to schedule packets from different classes of applications, each with diverse performance requirements. With this discipline, however, packets at higher priority levels can starve packets at lower priority levels. To resolve this starvation problem, we propose to assign a parameter to each priority queue in the SP discipline. The assigned parameter determines the probability with which its corresponding queue is served when the queue is polled by the server. We thus form a new packet scheduling discipline, referred to as the Probabilistic Priority (PP) discipline. By properly setting the assigned parameters, service differentiation as well as fairness among traffic classes can be achieved in PP. In addition, the PP discipline can be easily reduced to the ordinary SP discipline or to the reverse SP discipline.