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Building TMR-Based Reliable Servers Despite Bounded Input Lifetimes

Lookup NU author(s): Dr Paul EzhilchelvanORCiD



This paper is on the construction of a server subsystem in a client/server system. The implementation of the server is based on the well-known triple modular redundancy (TMR) technique. The three server processes cooperate to process the client inputs in the same order to keep the server state consistent. While a client can fail by crashing and at least two server processes behave correctly, the third server process can behave in an arbitrary way (Byzantine behavior). Moreover, there is a bound on the communication delays between a client and a correct server process D and between every pair of correct server processes d. In order to satisfy local resource constraints, it is assumed that if a client input is deposited in the local memory of a server process at time t, then it is systematically discarded from this local memory at time t+ ? if it is still present. The problem addressed in the paper is new. It consists of the design of protocols that allow the correct server processes to order client inputs in the same way despite the combined effect of the bound ?, the behavior of the Byzantine server process, and the client crash failures. The paper presents two results. It first introduces an ordering protocol that works for all ? > D+3d. Then it shows an impossibility result that there is no ordering protocol when ? < D.

Publication metadata

Author(s): Ezhilchelvan PD, Hulary J-M, Raynal M

Publication type: Report

Publication status: Published

Series Title: Department of Computing Science Technical Report Series

Year: 2000

Pages: 18

Print publication date: 01/01/2000

Source Publication Date: 2000

Report Number: 701

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

Place Published: Newcastle upon Tyne