Tolerating transient and permanent failures

Abstract

We investigate the possibility of designing protocols that are both self-stabilizing and fault-tolerant, in the asynchronous model of distributed systems. We prove that no such protocols exist for a wide range of problems, including determining (even approximately) the size of the distributed system and leader election. All of these problems are solvable in asynchronous systems using (randomized) protocols that are only fault-tolerant (but not self-stabilizing); or only self-stabilizing (but not fault-tolerant). We then focus on the problem of computing distinct names for the processors in a ring. We give three (randomized) protocols that solve this problem in three settings satisfying increasingly weak assumptions: When processors know the exact size n of the ring; when they only know an upper bound on n; and when they have no information about n.