What Is PTP?

Date First Published: 10th June 2022

Topic: Computer Networking

Subtopic: Internet Protocols

Article Type: Computer Terms & Definitions

Difficulty Level: 10/10

Learn more about what PTP is in this article.

Stands for Precision Time Protocol. PTP is an application-layer protocol used to synchronise clocks across computer networks. It has a similar role to the Network Time Protocol (NTP), but it is slightly different as PTP is a newer protocol that is more accurate than NTP in a LAN. As suggested in the word 'precision', PTP is accurate to sub-milliseconds rather than a few milliseconds. PTP can be used to synchronise financial transactions, mobile phone tower transmissions and other networks that require precise timing, but lack access to satellite navigation signals in a GPS network.

PTP uses a grandmaster clock to synchronise the communication and works on a master-slave architecture. The grandmaster clock is the main distributor of time in a multi-clock network, which has the role of transmitting time downstream to other master clocks. They receive UTC-based time information from an external time reference, usually a GNSS (Global navigation satellite system) satellite source. A single network connection is provided by the grandmaster, which sends synchronised information to the devices in the communication medium. However, if the master clock fails, the whole communication will stop.

History and Versions

The first version of PTP was defined in IEEE 1588-2002 in 2002. The second version of PTP was defined in IEEE 1588-2008 and is not backwards compatible with the original 2002 version. In November 2019, IEEE 1588-2019 was defined and is backwards compatible with the 2008 standard. It is unofficially known as PTPv2.1.

John Eidson led the IEEE 1588-2002 standardisation and according to him, “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 that require accuracies beyond those attainable using NTP. It is also designed for applications that cannot bear the cost of as GPS receiver at each node, or where GPS signals are inaccessible.”