QOS MANAGEMENT USING PRIORITY CONTROL IN ATM NETWORKS

Abstract

The Asynchronous Transfer Mode(ATM) will provide a wide range of services with diversified characteristic(e.g bit rate and burstiness) and Quality Of Service(QOS) requirements. In an ATM network, various types of traffics are statistically multiplexed to efficiently utilize the network resources. Howevei, the excessive use of the bandwidth may cause traffic dependent deteriorations, such as cell delay and loss at the buffer.., Therefore, bandwidth management and traffic controls are required to meet the QOS requirements. In a QOS control method, there are two ways to satisfy the cell delay: (a) To guarantee the maximum delay time of each class by determining the upper limit of queue length_ corresponding to the minimum bandwidth allocated to each class;So that any cell that eventually might exceed its delay bound i,s discarded immediately due to buffer overflow. (b) To use larger queues; "clipped cells", which exceed the. delay bound are also counted in lost cells. Cell loss rate' is satisfied by controlling the traffic load by way of call admission control under the condition that maximum delay time is already guaranteed by either scheme (a) or scheme (b). Here scheme (b) is studied and control performance is evaluated by determining the admissible offered load region. Results illustrate that method (b) enlarges the admissible offered load region in comparison to that of scheme (b) (studied in [6J).and dynamic control of priority ratio is not needed as suggested for scheme (a) in [6).