Multimedia communication involving digital audio and/or digital video has rather strict delay requirements. A real-time channel is defined in this paper as a simplex connection between a source and a destination characterized by parameters representing the performance requirements of the client. A real-time service is capable of creating real-time channels on demand and guaranteeing their performance. These guarantees often take the form of lower bounds on the bandwidth allocated to a channel and upper hounds on the delays to he experienced by a packet on the channel. In this paper, we study the feasibility of providing real-time services on a packet-switched store-and-forward wide-area network with general topology. We describe a scheme for the establishment of channels with deterministic or statistical delay hounds, and present the results of the simulation experiments we ran to evaluate it. The results are encouraging: our approach satisfies the guarantees even in worst case situations, uses the network's resources to a fair extent, and efficiently handles channels with a variety of offered load and burstiness characteristics. Also, the packet transmission overhead is quite low, and the channel establishment overhead is small enough to be acceptable in most practical cases.

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 v ariations. For the most demanding applications, the network must o er a service which can provide deterministic guarantees for the maximum delay o f p a c k ets from all connections, referred to as bounded delay service. The admission control functions in a network with a bounded delay service must have available 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 tra c model, making the conditions applicable to a large class of tra c speci cations. A comparison of the new schedulability conditions with existing, less accurate, conditions show the e ciency gain obtained by using exact conditions. Examples are presented that show h o w the selection of a particular tra c speci cation and a schedulability condition impact the e ciency of a bounded delay service.

No abstract

No abstract