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A Timeout Based Message Ordering Protocol for a Lightweight Software Implementation of TMR Systems

Lookup NU author(s): Dr Paul EzhilchelvanORCiD, Dr Neil Speirs



Replicated processing with majority voting is a well known method for achieving reliability and availability - two key attributes of dependability. Triple Modular Redundant (TMR) processing is the most commonly used version of that method. Replicated processing requires that the replicas reach agreement on the order in which input requests are to be processed. Almost all synchronous and deterministic ordering protocols published in the literature are time based in the sense that they require replicasÆ clocks to be kept synchronised within some known bound. We present a protocol for TMR systems that is based on timeouts and therefore does not require clocks to be kept in bounded synchronism. The design of the protocol exploits features that are so characteristic of a TMR system; consequently, the protocol keeps the input ordering delays as small as possible. We prove that the upper bound on ordering delays of our protocol is the smallest that can be achieved by a timeout based protocol. We also identify application contexts where the timeout based protocol may be preferable to the time based approach.

Publication metadata

Author(s): Ezhilchelvan PD, Brasileiro FV, Speirs NA

Publication type: Report

Publication status: Published

Series Title: Department of Computing Science Technical Report Series

Year: 1997

Pages: 36

Print publication date: 01/01/1997

Source Publication Date: 1997

Report Number: 582

Institution: Department of Computing Science, University of Newcastle upon Tyne

Place Published: Newcastle upon Tyne