Compensation of asymmetrical latency for ethernet clock synchronization

Clock synchronization has become an indispensable service in most distributed systems as it allows to sort events on a common time scale and coordinate collaborative actions.With the demand for even higher synchronization accuracy, new challenges and barriers have to be tackled to fulfill these requirements. One of them, the inevitable signal propagation time between the devices, is compensated in many state-of-the-art synchronization protocols by round-trip measurements, neglecting any form of delay asymmetry of the communication link. In this paper, we analyze the impact of asymmetry in networks based on the physical layer of copper-based Ethernet and compare different approaches on how to mitigate the impact of asymmetry. We propose a non-invasive system performing asymmetry measurements on a link basis and show that such a system can integrate into existing synchronization solutions.