Time vs. space in fault-tolerant distributed systems

Algorithms for solving agreement problems can be classified in two categories: (1) those relying on failure detectors (FDs), which we call FD-based, and (2) those that rely on a group membership service (GMS), which we call GMS-based. This paper discusses the advantages and limitations of these two approaches and proposes an extension to the GMS approach that combines the advantages of both approaches, without their drawbacks. This extension leads us to distinguish between time-triggered suspicions of processes and space-triggered exclusions.