Performance analysis of space-priority mechanisms in an input and output queueing ATM switch

In future high-speed integrated networks asynchronous transfer mode (ATM) switches should be able to accommodate diverse types of applications with different quality of services (QOS) and traffic requirements. Thus some types of priority control schemes are needed in ATM switches to increase the utilisation of switches and satisfy the QOS of each traffic type. The authors consider a nonblocking input and output queueing ATM switch with capacity m in which two classes of traffic are admitted. Each input queue adopts one of two space-priority mechanisms, partial push-out and partial buffer sharing, which assign priorities for buffer access to each traffic type according to its loss probability constraints. The distribution of input queue length and loss probabilities of each traffic class are obtained using the matrix-geometric solution method and their performance compared. Numerical analysis and simulation indicate that the switch utilisation with space-priority mechanisms satisfying the QOS of each traffic class is much higher than that of the switch without control and the required buffer size is reduced while satisfying the same QOS. The partial push-out scheme has a somewhat higher throughput than the partial buffer sharing scheme but the latter is preferred to the former owing to its lower implementation complexity