Evaluation of Transport Protocols for Real-Time Communication
W. Timothy Strayer, Alfred C. Weaver · 1988
this report is three-fold: (1) to identify communication functions which are considered useful within a communication system; (2) to document the extent to which these functions are incorporated in extant protocols; and (3) to identify those communication functions which are potentially useful for a real-time communication system. To accomplish these goals, section two makes some observations about the environment in which the real-time communication system is to serve --- namely, real-time distributed systems. Section three identifies the principles of real-time communication as reported in the archival literature. To provide a framework for the eventual comparison of protocols, section four briefly discusses the ISO OSI Reference Model and its suitability as a paradigm for realtime communications. Section five identifies those functions which are commonly found in transport protocols. In section six we discuss eight specific network protocols and characterize each by identifying the presense or absence of our identified transport functionalities. Section seven evaluates the protocols and comments on how well each would support real-time communication. Our conclusions are in section eight. 2. Real-Time Distributed Systems A real-time distributed system consists of some number of application programs (processes) which are physically distributed over a multiplicity of processing elements (processors), interconnected by a communications server (e.g., a local area network and its protocols). What makes the system real-time is that processes must complete their computations within a known and bounded time. The processes may be periodic or aperiodic (interrupt-driven), and the resources they require may be either local (on the same processor) or remote (on another processor)...