PTPd is an open source

Open source

The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...

 implementation of the Precision Time Protocol

Precision Time Protocol

The Precision Time Protocol is a protocol used to synchronize clocks throughout a computer network. On a local area network it achieves clock accuracy in the sub-microsecond range, making it suitable for measurement and control systems....

 for Unix-like

Unix-like

A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....

computers.

Derivatives

• PTPd is an original complete BSD licensed open source code implementation of the IEEE 1588-2002 and later IEEE 1588-2008 PTP specification for an ordinary clock. Currently only Unix-like computers can run the compiled BSD source, but this essentially means that, Linux, Mac OSX, Minix3 and QNX OS computers can participate in PTP networks with limited difficulties. As the PTP protocol was designed with no interoperability with the NTP Service in mind, computers running NTP service should halt NTP service before running PTP service.
• ptpd2 is a complete open source implementation of the IEEE 1588-2008 (Version 2) PTP specification that is being actively developed (as of Feb 2011) and offers several additional features and enhancements past the original open source reference implementation.
• ptpv2d is GPL re-licensed open source code of IEEE 1588 version 1, version 2 and IEEE 802.1AS including hardware timestamping for Freescale MPC831x family of processors.

Accuracy

PTPd accuracy depends on how IEEE 1588 packets are timestamped on the participating machines. Currently, IEEE 1588 packets are timestamped in software in most implementations, i.e., interrupt latency, OS scheduling, and other software issues influence the accuracy of the acquired timestamps, and therefore, the accuracy of time synchronization. However, some hardware supports recording of timestamps in hardware, making it possible to acquire more precise send and receive timestamps. Software supporting this feature is starting to emerge providing increased and load independent accuracy. For example, a modified PTPd is available.