Precision Time Protocol

The Precision Time Protocol (PTP) is a protocol for clock synchronization throughout a computer network with relatively high precision as compared to using the earlier developed Network Time Protocol (NTP) and therefore potentially higher accuracy depending on the configuration. In a local area network (LAN), accuracy can be sub-microsecond – making it suitable for measurement and control systems applications. PTP can be used to synchronize financial transactions, mobile phone tower transmissions, sub-sea acoustic arrays, and networks that require precise timing as an alternative to using the timestamp of satellite navigation signals or where sub-nanosecond accuracy as provided by the White Rabbit Project is unnecessary.

The first version of PTP, IEEE 1588-2002, was published in 2002. IEEE 1588-2008, also known as PTP Version 2, is not backward compatible with the 2002 version. IEEE 1588-2019 was published in November 2019 and includes backward-compatible improvements to the 2008 publication. IEEE 1588-2008 includes a profile concept defining PTP operating parameters and options. Several profiles have been defined for applications including telecommunications, electric power distribution and audiovisual uses. IEEE 802.1AS is an adaptation of PTP, called gPTP, for use with Audio Video Bridging (AVB) and Time-Sensitive Networking (TSN).

History

According to John Eidson, who led the IEEE 1588-2002 standardization effort, "IEEE 1588 is designed to fill a niche not well served by either of the two dominant protocols, NTP and GPS. IEEE 1588 is designed for local systems requiring accuracies beyond those attainable using NTP. It is also designed for applications that cannot bear the cost of a GPS receiver at each node, or for which GPS signals are inaccessible."

PTP was originally defined in the IEEE 1588-2002 standard, officially titled Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems, and published in 2002.