Time Transfer and Clock Synchronization Analysis over Spine-Leaf Networks

The integration of a time synchronization and time transfer system in data center networks is an increasingly common demand. Since moving the entire infrastructure of a data center network to switches with time-dedicated hardware is nowadays a considerable expense of resources, it is convenient to analyze and study it. In this paper we work on real hardware, presenting a characterization of the problem for a Spine-Leaf network by means of load variation tests proposed by the ITU, using the PTP protocol and common non-PTP aware switches. Through this study we manage to show, thanks to real measurements, the problem of dynamic asymmetry and how it affects the time distribution. Additionally, it is shown that if the network load is quadrupled, the PTP pk-pk offset through the network does not even double. Finally, thanks to long-term tests, we can conclude that time synchronization in a Spine-Leaf network shows considerable resilience to load changes.