How Precision Time Protocol is being deployed at Meta

This post details Meta's migration to Precision Time Protocol (PTP) for nanosecond-level system synchronization, a significant upgrade from the millisecond precision of NTP. It covers the architectural components of the PTP deployment, including the GNSS antenna, PTP rack with Time Appliances (featuring Time Cards and Network Cards with hardware timestamping), and the PTP client. Innovations include the use of GNSS-over-fiber technology for signal distribution, diversification of Time Card hardware through OCP collaboration, and the development of 'ptp4u' to scale PTP server capacity to 1 million clients per appliance. The post also highlights the importance of precise timing for distributed system guarantees like linearizability and showcases performance improvements over NTP.