Exact Admission Control for Networks with a Bounded Delay Service


Jorg Liebeherr
Dallas E. Wrege
Department of Computer Science
University of Virginia
Charlottesville, VA 22903

Domenico Ferrari
University of California at Berkeley
and International Computer Science Institute
1947 Center St., Suite 600
Berkeley, CA 94704-1105


Abstract
To support the requirements for the transmission of continuous media, such as audio and video, multiservice packet switching networks must provide service guarantees to connections, including guarantees on throughput, network delays, and network delay variations. For the most demanding applications, the network must offer a service which can provide deterministic guarantees for the maximum delay of packets from all connections, referred to as bounded delay service. The admission control functions in a network with a bounded delay service must have available {\em schedulability conditions} that detect violations of delay guarantees in a network switch. In this study, exact schedulability conditions are presented for packet switches which transmit packets based on an Earliest-Deadline-First (EDF) or a Static-Priority (SP) algorithm. The schedulability conditions are given in terms of a general traffic model, making the conditions applicable to a large class of traffic specifications. A comparison of the new schedulability conditions with existing, less accurate, conditions show the efficiency gain obtained by using exact conditions. Examples are presented that show how the selection of a particular traffic specification and a schedulability condition impact the efficiency of a bounded delay service.