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標題: ATM 交換器輸入端優先權控制策略之效益模型
Performance Modeling for Two Priority Control Policies for ATM Switches with Input Queueing
作者: 呂育健
Lu, Yu Chien
關鍵字: ATM;非同步傳輸模式;nonblocking packet switch;head-of-line;queueing;push out;partial buffer sharing;非阻隔封包交換器;頭位阻隔;排隊;排擠;部分緩衝器分享
出版社: 電機工程學系

Asynchronous Transfer Mode (ATM) has been adopted as the transport and switching mechanism for B-ISDN. Crossbar nonblocking packet switches are widely used as the fundamental architecture for ATM switch. This thesis studies an N N nonblocking packet switch with input queues and two priority classes of cells which can be used to support traffic with different QoS requirements. Two queueing policies (push out and partition buffer sharing) are studied here. Under both policies, packets of high priority and low priority classes are queued when waiting for service, and high priority packets prevail over low priority packets at the inputs as well as the outputs. In the push out policy, high priority packets and low priority packets can enter the input buffer when the input buffer is not full. When the input buffer is full, only high priority packets can enter the queue by forcing out low priority packets in the queue. In the partition buffer sharing policy, high priority packets can enter the input buffer when the input buffer is not full. Low priority packets can enter the input buffer when the current occupancy of input buffer has not reached a pre-specified threshold. An approximate two-dimensional Markov-chain model is developed for studying the performance under both policies, based on some independence assumptions and by using an equivalent queueing system to estimate the services capability seen by each input. From this model, we obtain the throughput, packet drop probability, and queue length distribution of high priority and low priority packets. The results are verified with simulation.
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