Designing Masking Fault-tolerance via Nonmasking Fault-tolerance 1

Masking fault-tolerance guarantees that programs continually satisfy their specii-cation in the presence of faults. By way of contrast, nonmasking fault-tolerance does not guarantee as much: it merely guarantees that when faults stop occurring, program executions converge to states from where programs continually (re)satisfy their speciication. In this paper, we show that an eeective method to design masking fault-tolerance is to rst design nonmasking fault-tolerance and to then transform the nonmasking fault-tolerant program minimally so as to achieve masking fault-tolerance. We demonstrate this method by designing novel fully distributed programs for leader election, mutual exclusion, and termination detection, that are masking tolerant of any nite number of process fail-stops and/or repairs.