In this paper, we consider a nonblocking ATM switch with capacity C which adopts a hybrid priority control scheme in input buffers. Each input queue has two separate buffer spaces with different sizes for two classes of traffic, and adopts a general state-dependent scheduling scheme which assigns priorities to each class dynamically. We obtain the distribution of input queue length, loss probabilities and mean waiting times of two traffic classes using a semi-Markov process concept and compare the performances of various scheduling schemes. Numerical analysis and simulation indicate that the utilization of the switch with the hybrid priority control scheme 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. Among the 5 scheduling schemes we have considered in this paper, the queue length threshold (QLT) scheme yields the highest utilization of the switch and has flexible performance which is adequate to satisfy, various values of QoS for two classes of traffics.
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