A CONTINUOUS MEDIA DATA TRANSPORT SERVICE AND PROTOCOL FOR REAL-TIME COMMUNICATION IN HIGH-SPEED NETWORKS

An important class of applications with real-time data transport requirements is defined by applications requiring transmission of data units at regular intervals. These applications, which we call continuous media (CM) clients, include video conferencing, voice communication, and high-quality digital sound. The design of a data transport service for CM clients and its underlying protocol (within the XUNET II project) is presented in this paper. The service makes use, in particular, of an a priori characterization of future data transmission requests by CM clients. First, we will give a few examples of CM clients and their specific data transmission needs. From these clients, we then extract a generalized list of data transport requirements for CM and describe the basic features of a service designed to meet these requirements. This service provides unreliable, in-sequence transfer (simplex, periodic) of so-called stream data units (STDUs) between a sending and a receiving client, with performance guarantees on loss, delay, and throughput. An important feature of the solution is the use of shared buffers to eliminate most direct client/service interactions and to smooth traffic pattern, which may be bursty due to fluctuations in the arrival process of data and variability of network delays. The paper concludes with some aspects of implementation.