Network Support for Realtime Multi-Party Applications Amit Gupta, Wendy Heffner, Mark Moran, Clemens Szyperski The Tenet Group Computer Science Division, Department of EECS University of California at Berkeley and International Computer Science Insti- tute Berkeley, California 94704 ABSTRACT Many important applications of the future require predictable performance from the network service. For exam- ple, applications that support multimedia interactive com- munication between multiple remote participants (MIM appli- cations) have several such requirements: guaranteed throughput, bounded delay and delay-jitter. The Tenet group has implemented a suite of realtime protocols to provide a simplex unicast data service with performance guarantees [FBZ92]. In order to minimize the complexity of implementa- tion, the first scheme (Scheme1) was designed to provide minimal support for realtime communication. Therefore, Scheme1 is cumbersome and inefficient for multi-party com- munication. In this paper we describe extensions to this work to provide support for multi-party realtime communica- tion and a more flexible client-service interface. We refer to the resulting scheme as Scheme2. Support for multi-party communication falls in two areas: (i) networking abstractions for multi-party communi- cation (e.g., a of destination group id that allows sources to send data to a dynamically-changing group of interested parties); and (ii) optimizations that improve the efficient utilization of network resources for multi-party communica- tion (e.g. using true multicast). In order to improve the flexibility of the client- service interface, we allow several input parameters to be specified as ranges rather than point values. The client can then specify a desired value and a worst-acceptable value, thus eliminating the need for iterative negotiations. The next section will examine the requirements of MIM applications in more detail. Section 3 presents a descrip- tion of those aspects of the Scheme2 most relevant to sup- porting MIM applications, along with the rationale for some of the design choices. Section 4 illustrates the scheme with a simple example.