Threshold and Bounded-Delay Voting in Critical Control Systems


Paul Caspi and Rym Salem

FTRTFT2000, Poona, September 2000.


This paper investigates the possibility of implementing fault tolerance in control systems without using clock synchronization. We first show that threshold voting applies to stable continuous systems and that bounded delay voting applies to combinational systems. We also show that 2/2 bounded delay voting is insensitive to Byzantine faults and applies to stable sequential systems. It thus allows the implementation of hybrid fault tolerance strategies.


Postscript