Hierarchical dynamic control of multiple traffic classes in ATM networks

A hierarchical control structure is proposed to ensure performance requirements and to maintain load balancing among different traffic classes at an ATM node. A two-level control hierarchy is defined, where one level performs fixed class-selective call admission control strategies that are periodically dynamically coordinated by a higher level bandwidth allocation controller. The call admission control rules are designed to maintain a certain grade of service, in terms of cell loss probability, given the buffer space and bandwidth (percentage of cells) assigned to each class. The assignment of buffers is performed off-line, whereas bandwidth shares are periodically recomputed on-line by the allocation controller, that attempts to minimize a cost function, accounting for overall cell loss and refused traffic. The bandwidth assignments obtained are passed to the call admission controllers, where they are used as parameters affecting the admission rules until the next intervention. The control structure, the strategies and the optimization algorithm used are described in detail, as well as the assumptions underlying the choices that have been made. Simulation results are reported and discussed.