- PTPd is a complete, BSD licensed, open source code implementation of the IEEE 1588-2008 PTP specification. Currently only Unix-like computers can run the software, but this essentially meaning that, FreeBSD, Linux, Mac OSX, Minix3 and QNX computers can participate in PTP networks. PTPd can act as a master on a system with an external time source, such as a GPS card, or NTP running as a client.
- 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.
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.
A test in 2010 on an Intel Gigabit Network card noted offset converging to varying between around 1–100 microseconds in a pure software implementation, and to around a microsecond when using hardware assisted PTP.