On Real-Time Systems Using Local Area Networks.
MARYLAND UNIV COLLEGE PARK INST FOR ADVANCED COMPUTER STUDIES
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The design and the implementation of a real-time communication network has to meet goals of fault-free and timely delivery of messages, as defined by the applications served by this network. The time constraints of the applications are projected as stringent constraints on the local knowledge of time. However, the local knowledge of time in a distributed system requires the use of the communication network. The accuracy and coherence of this knowledge depend on the way clocks are synchronized. Therefore, the performance of clock synchronization algorithms due to the communication network, is a good criterion for analyzing the adequacy of a particular network architecture to real-time application. This paper examines the adequacy of LAN architecture for real-time applications through a delay model of a typical LAN. The model is applied to various clock synchronization algorithms, and error estimates for these algorithms are derived. An efficient environment, in which the uncertainties in message communication elapsed time is significantly reduced, is then described for layered protocol architecture. In addition, it is shown that predictable communication elapsed time can be compensated for in synchronization algorithms, significantly reducing the errors of these algorithms.
- Computer Systems