Window Mac Protocols for Real-Time Communication Services

In this paper, we consider a distributed real-time system based on a local area network with a bus topology, and propose a new suite of real-time medium access control protocols. The proposed suite is devoid of deficiencies (in supporting real-time communication) found in existing standards for bus-based systems. The suite consists of five medium access control protocols, viz., PRI, RTDG, RTVC, INTPVC, and INTPDG, all based on a uniform window splitting paradigm. The proto- col PRI implements priority-based on a uniform window splitting paradigm. The protocol RTDG implements real-time datagram arbitration, and the protocol RTVC may be used to implement the abstraction of real-time virtual circuits. The protocols INTPVC and INTPDG are integrated protocols that may be used to support both real-time datagram and real-time virtual circuit arbi- tration in an integrated manner on a common bus. We derive various properties exhibited by the protocols and also present the results of a performance evaluation through simulation. The results of the simulation study show that, in addition to providing the advantage of structural homogene- ity (enabling the use of a uniform medium access control logic and LAN controller hardware), the proposed suite of protocols also has excellent performance characteristics. Index Terms: broadcast bus topology, connectionless service, connection-oriented service, distributed real-time system, local area network, medium access control protocol, multiaccess com- munication, priority resolution, real-time communication, window protocol.