Granular Synchrony

TL;DR

This paper introduces granular synchrony, a new network timing model that combines different communication modes, providing a more realistic framework for distributed consensus and unifying existing models.

Contribution

The paper proposes granular synchrony as a novel, more accurate timing model and establishes conditions for fault-tolerant consensus within this framework.

Findings

Consensus achievable with fewer assumptions than full synchrony.

Unified framework encompassing existing timing models.

Conditions for crash and Byzantine fault tolerance derived.

Abstract

Today's mainstream network timing models for distributed computing are synchrony, partial synchrony, and asynchrony. These models are coarse-grained and often make either too strong or too weak assumptions about the network. This paper introduces a new timing model called granular synchrony that models the network as a mixture of synchronous, partially synchronous, and asynchronous communication links. The new model is not only theoretically interesting but also more representative of real-world networks. It also serves as a unifying framework where current mainstream models are its special cases. We present necessary and sufficient conditions for solving crash and Byzantine fault-tolerant consensus in granular synchrony. Interestingly, consensus among $n$ parties can be achieved against $f \geq n/2$ crash faults or $f \geq n/3$ Byzantine faults without resorting to full synchrony.