Logical Synchrony and the bittide Mechanism

TL;DR

This paper introduces logical synchrony, a framework enabling tightly coordinated distributed computing without a global clock, using logical latency and multiclock networks, exemplified by the bittide mechanism.

Contribution

It presents a novel logical synchrony framework, models multiclock networks, and introduces the bittide mechanism for clock control in distributed systems.

Findings

Logical synchrony allows coordination without a global clock.

Multiclock networks refine logical synchrony models.

Bittide mechanism ensures buffer stability and synchronization.

Abstract

We introduce logical synchrony, a framework that allows distributed computing to be coordinated as tightly as in synchronous systems without the distribution of a global clock or any reference to universal time. We develop a model of events called a logical synchrony network, in which nodes correspond to processors and every node has an associated local clock which generates the events. We construct a measure of logical latency and develop its properties. A further model, called a multiclock network, is then analyzed and shown to be a refinement of the logical synchrony network. We present the bittide mechanism as an instantiation of multiclock networks, and discuss the clock control mechanism that ensures that buffers do not overflow or underflow. Finally we give conditions under which a logical synchrony network has an equivalent synchronous realization.