0 System - Level Modeling and Evaluation of Network Protocols

Since the first large-scale computer network was built in the early 1960s, the protocol design problem has become a more important issue to efficiently coordinate distributed system nodes. Recently, in response to the fast growing demand for connecting various devices with current network infrastructures, many intricate protocols have been designed to support communications across such heterogeneity. However, today very few tools that we can identify allow such a system-level simulation, including both protocols and models of system entities. Since simulation is the major stage in the development cycle of a complex hardware and software distributed system, a tool facilitates modeling and simulating protocols in a system context is substantially valuable. In this report, we propose a hybrid model of computation including CSP, FSM, and DE for specifying protocols as well as to enable mixing them with other subsystem models. Based on this proposal, a software tool, SiP (SPIN in Ptolemy), has been implemented by integrating a protocol simulation tool, SPIN, into a system-level design environment, Ptolemy. We demonstrate the expressive power of SiP by using it to specify several fundamental elements of network protocols ranging from the data link layer to the session layer in the OSI Reference Model. We also leverage the reusability feature of SiP to construct a model of a complete network system using those elements. From both the experience of protocol specification and the result of system-level simulation, SiP is proved to remarkably facilitate the design and performance evaluation of network protocols.