On Buffer Centering for Bittide Synchronization

Abstract: We discuss distributed reframing control of bittide systems. In a bittide system, multiple processors synchronize by monitoring communication over the network. The 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 reset control, which allows all nodes to maintain small buffer offsets while also requiring very little state information at each node. We demonstrate that with reframing, we can achieve separate control of frequency and phase, allowing both the frequencies to be syntonized and the buffers to be moved the desired points, rather than combining their control via a proportional-integral controller. This offers the potential for simplified boot processes and failure handling.