PRIORITY ASSIGNMENT CONTROL OF ATM LINE BUFFERS WITH MULTIPLE QOS CLASSES

Asynchronous transfer mode (ATM) networks will provide multimedia services with diversified traffic flow characteristics and quality requirements. In such a multimedia environment, the bandwidth efficiency can be improved by defining multiple quality of service (QOS) classes and using a traffic control which manages required QOS of each class individually (QOS control). Priority assignment control is presented as a QOS control method in an ATM switching node. In order to quantitatively evaluate the control performance, the region determined by the offered load of each class where the QOS requirements of all the classes are satisfied (admissible offered load region) is analytically obtained and various combinations of two classes and related control effects are discussed. The results illustrate that when required values of cell loss rate and delay time are both different between the classes, the control effect is large; however, when only either of them is different, the effect is relatively small. This control method is more effective when the interclass quality difference is bigger and the burstiness of the traffic is stronger. The control scheme to enlarge the actual admissible offered load region by adaptively changing the priority assignment ratio is presented and its feasibility is confirmed by the simulation.