On Buffer Centering for Bittide Synchronization

Sanjay Lall, Calin Cascaval, Martin Izzard, Tammo Spalink

Abstract: We discuss distributed reframing control of bittide systems. In a bittide system, multiple processors synchronize by monitoring communication over the network. Processors remain in logical synchrony by controlling the timing of frame transmissions. The protocol for doing this relies upon an underlying dynamic control system where each node makes only local observations and performs no direct coordination with other nodes. In this paper we develop a control algorithm based on the idea of buffer centering, which allows all nodes to maintain small buffer offsets while also requiring very little state information. We demonstrate that with buffer centering we can achieve separate control of frequency and phase, allowing frequencies to be syntonized and also buffers to maintain desired offsets rather than combining their control via a proportional-integral controller. The minimalism of this approach offers the potential to simplify both boot processes and failure handling.