PTP

PTP, or Precision Time Protocol, is a family of time synchronization protocols defined by IEEE 1588. It is designed to synchronize clocks in distributed systems across a computer network with high precision, commonly achieving sub-microsecond accuracy in well-configured local networks. PTP is widely used in environments requiring coordinated actions or accurate time-stamping, such as telecom networks, data centers, industrial automation, and financial trading systems. The standard has evolved through revisions, with IEEE 1588-2008 and IEEE 1588-2019, and is extended by profiles like 802.1AS for Ethernet-based time synchronization in Time-Sensitive Networking (TSN).

PTP operates through a master-slave clock hierarchy. The Best Master Clock Algorithm (BMCA) selects the grandmaster clock based on factors such as clock quality and priority settings. Network elements can function as boundary clocks or transparent clocks to manage delays and propagate timing information without introducing large errors. In a two-step clock, the grandmaster sends a Sync message with a precise transmit timestamp, followed by a Follow_Up message containing the exact timing information. A slave may issue a Delay_Request and receive a Delay_Response to measure path delay. Through these exchanges, slaves discipline their local clocks to align with the grandmaster.

Implementation and usage require hardware support. Accurate timestamping is critical, and hardware timestamping in network interface cards and switches minimizes jitter and switch-induced delays. PTP profiles tailor the protocol to specific domains, such as telecom, power utilities, or automotive industries. While more precise than the Network Time Protocol (NTP) for LANs, PTP relies on compatible devices and properly configured networks; virtualization and wireless links can degrade accuracy.

See also: time synchronization, Network Time Protocol, TSN.