Analysis of backpressure-type packet switches with input and output buffering

Abstract

The authors investigate the performance of packet loss and delay in a nonblocking backpressure-type packet switch with input and output queueing that is able to transfer up to L packets per slot to a given switch output. The switching fabric allows limited queueing at the output ports. Overflow at the output queues is prevented by using a backpressure mechanism and additional buffers at the input ports. The authors develop an analytical model of the switch architecture and analyse the impact of the backpressure effect on the switch performance for arbitrary output and input buffer sizes and different speed-up factors. The model is based on the output contention process and Geom/PH/1/K input queueing process. The output contention involved by packets at the head of input queues can be viewed as an independent phase type process. The result indicates that, when there are reasonable sizes of buffers at both input and output port and the backpressure mechanism is used, the switch with output buffers having a relatively small capacity and a speed-up factor of L = 2 approaches closely the ideal delay and packet loss performance of a pure output queueing switch at a reasonable input load condition.