Real-Time Multimedia Streams in a Differentiated Services Network

Multimedia applications are becoming increasingly popular on the Internet. These include semi real-time applications like video playback, but also interactive applications with hard real-time requirements like Internet telephony or videoconferencing. Common to the real-time applications is an inevitable requirement for transmission services with certain guaranteed qualities. The differentiated services architecture aims at providing these services. A prioritized transmission, which is necessary in the case of real-time data, can be achieved by applying the expedited forwarding, defined as a premium service. Nevertheless, especially if current hierarchical video encoding techniques are used, great benefits can be gained by extending the expedited forwarding by different levels of forwarding guarantees. Doing so allows finely tuned reactions to congestion in the network, based on the importance of the individual data packets, which is given by the hierarchy of the video encoding layers. In this paper we present a queue management and scheduling model, which is the basis for a new differentiated services per hop behavior group. The per hop behavior group extends the expedited forwarding by certain forwarding guarantees, as already applied by the assured forwarding per hop behavior group. We show simulation results, which prove the usefulness of this extension, especially for the transmission of hierarchically encoded video streams.