A Knowledge-Theoretic Analysis of Uniform Distributed Coordination and Failure Detectors

TL;DR

This paper establishes a precise equivalence between achieving Uniform Distributed Coordination in unreliable systems and the existence of certain failure detectors, emphasizing the role of process knowledge about faults.

Contribution

It provides a knowledge-theoretic characterization of the conditions under which UDC can be achieved with or without bounds on faulty processes, linking failure detectors to process knowledge.

Findings

Perfect failure detectors are necessary and sufficient for UDC with no fault bound.

A generalized failure detector is required for UDC with a bounded number of faulty processes.

Knowledge about which processes are faulty is crucial for achieving UDC.

Abstract

It is shown that, in a precise sense, if there is no bound on the number of faulty processes in a system with unreliable but fair communication, Uniform Distributed Coordination (UDC) can be attained if and only if a system has perfect failure detectors. This result is generalized to the case where there is a bound t on the number of faulty processes. It is shown that a certain type of generalized failure detector is necessary and sufficient for achieving UDC in a context with at most t faulty processes. Reasoning about processes' knowledge as to which other processes are faulty plays a key role in the analysis.