Performance of a packet switch with input and output queueing under unbalanced traffic

High performance in advanced packet switches can be achieved by providing queuing both at the input and the output ports. The author studies the performance of this class of switches under nonuniform traffic. Two different output queuing arrangements are considered, namely, the case where dedicated queues are provided at each output port, and the case where the output queuing space is shared among all the output ports. An analytical approach is presented for the performance study of these two schemes in the case of operation with fixed-size packets and under various degrees of traffic imbalance at the inputs or the outputs. The measures investigated include the average delay, the maximum throughput of the switch in the case of output traffic imbalance, and the saturation load in the case of input traffic imbalance. Analytical results for these measures are derived for the case of a switch with a large number of input and output ports. Numerical results for the maximum throughput and the saturation load are presented. It is demonstrated that the scheme of output sharing performs better than the scheme of dedicated output queuing