Modeling and Control of bittide Synchronization
Sanjay Lall, Călin Caşcaval, Martin Izzard, Tammo Spalink · 2022 American Control Conference (ACC) · 2022
Distributed system applications rely on a fine-grain common sense of time. Existing systems maintain this by keeping each independent machine as close as possible to wall-clock time through a combination of software protocols and precision hardware references. This approach is expensive, requiring protocols to deal with asynchrony and its performance consequences. Moreover, at datacenter scale it is impractical to distribute a physical clock as is done on a chip or printed circuit board. In this paper we introduce a distributed system design that removes the need for physical clock distribution or mechanisms for maintaining close alignment to wall-clock time, and instead provides applications with a perfectly synchronized logical clock. We discuss the abstract frame model (AFM), a mathematical model that underpins the system synchronization. The model is based on the rate of communication between nodes in a topology without requiring a global clock. We show that there are families of controllers that satisfy the properties required for existence and uniqueness of solutions to the AFM, and give examples.