Title: A study of issues relating to real-time in distributed computer control systems
Abstract:This thesis studies a new technique for achieving co-ordination and consistency in distributed computer control systems making use of a global physical time reference (real-time) in the form of a set ...This thesis studies a new technique for achieving co-ordination and consistency in distributed computer control systems making use of a global physical time reference (real-time) in the form of a set of physical clocks synchronized to within a known tolerance of one another. The systems considered consist of a number of processing elements which communicate with one another by exchanging messages via a high-speed local area communication system. The system processors are assumed to be nearly autonomous and are not tightly synchronized. The main design goals reliability and maintainability.
An interprocess synchronization model requiring a commitment by each process sending a message not to alter its state until a specified future point in time forms the kernel of the proposed co-ordination technique. This is extended into a simple interaction mechanism and a contingent interaction mechanism providing for the programming of a wide class of application protocols. The maximum lifetime of a message should be equated to the commit-time specified by the sender of the message.
In distributed computer control systems, a fundamental problem related to interprocess synchronization is that of establishing a valid and consistent real-time representation of the state of the plant. This problem is analysed in detail within the framework of the interprocess synchronization model and a definition of consistency in this context is proposed. A distributed real-time algorithm for providing global consistency and a second algorithm for providing local consistency are developed. They have the advantage of automatically handling the case where redundant sources of messages carrying state values are present in the system.
An initial discussion of a distributed computer system architecture and the relevant design principles provides the framework for the theoretical development in the thesis. The underlying assumption of a set of synchronized physical clocks is examined and implementation of such a time reference is shown to be technically feasible.
The role of real-time in distributed computer control systems emerges as fundamental and pervasive. Real-time is an active element in the solution of problems in such systems and not merely as a performance constraint.Read More
Publication Year: 1984
Publication Date: 1984-01-01
Language: en
Type: article
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Cited By Count: 10
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