An arbitrarily precise time synchronization algorithm based on Ethernet Switch serialization

Abstract

It turns out that trying to play a worst-case traversal time (WCTT) scenario on a real experimentation platform is a Real-Time problem with extremely tight constraints. When two packets (with the same destination) arrive to two different input ports of a network switch within a time frame of only a few nanoseconds, the order of these packets in the output port queue will reflect this small nanoseconds arrival difference. Moreover, failing to emit packets within this tiny time frame will exhibit a different scenario than expected, potentially so radically different in farther places of the network that the behavior of the whole system seems affected by a butterfly effect. As we were trying to achieve the most precise clock synchronization we could with standard hardware, we have had the idea to turn this butterfly effect to our benefit and develop an arbitrarily precise time synchronization algorithm that only requires a standard Ethernet switch connecting the two hosts to synchronize and a third host on the network that will serve as a synchronization helper.