Input queuing of an internally nonblocking packet switch with two priority classes

An N×N nonblocking packet switch with two priority classes which can be used to support traffics with different requirements is analyzed. Real-time traffic such as voice is assigned high priority to satisfy its strict delay requirement, while data traffic uses a lower priority and utilizes the remaining system capacity. The switch operation is slotted, and at each time slot packets arrivals at the inputs have Bernoulli distributions with different probabilities for high-priority and low-priority classes. Packets of both priority classes can be queued when waiting for service; the service discipline is FCFS (first-come first-served) within each priority class. The authors provide explicit expressions for blocking probabilities and average delays. They also study system stability and show that the maximum throughput can in fact be higher than with no priority