Bandwidth scheduling and its application in ATM networks

Abstract

The design goals for bandwidth schedulers in ATM switches are presented; one crucial goal is the ability to guarantee service bandwidth to individual queues. A performance criterion which can measure how well schedules can guarantee bandwidth, called the minimum-bandwidth property, is given and it is derived for a number of well-known schedulers. The minimum-bandwidth property is compared with another service measure called the service curve. Of the two measures, it is shown that the minimum-bandwidth property gives a superior method to determine how a scheduler guarantees bandwidth. The minimum-bandwidth property is useful in the context of a virtual channel within an ATM network because it makes possible end-to-end delay bounds and buffer sizing results, provided that the source is (o,p)-constrained. These results are applied in the case of prerecorded video transmission. Scheduler design goals other than service guarantees include the ability to control the idle bandwidth distribution and implementability at high speeds. The use of Hierarchical Round-Robin scheduling is argued on the grounds that it fulfills all the design goals. Finally, a method of providing bandwidth guarantees using an input-buffered switch, as opposed to an output-buffered switch, is discussed.