PPSi - A free software PTP implementation

This paper describes a new open source implementation of the Precision Time Protocol (PTP) [1] called PTP Ported To Silicon (PPSi) [2]. It was developed to fill in a niche in the free software world for a PTP daemon that is easily portable to a wide range of architectures and highly modular to enable protocol extensions - two key requirements of its driving force, the White Rabbit (WR) Project [3] [4]. PPSi´s core protocol code is common for all the supported architectures ranging from a Linux PC to a soft-core processor running in a Field Programmable Gate Array (FPGA) - a feature minimizing code duplication, easing debugging, and facilitating new developments. This paper gives an overview of PPSi´s internals describing design choices as well as the means of achieving portability and extensibility. A detailed example of a simulator architecture proves the design advantages. With an increasing number of supported architectures and a wide use in WR networks, PPSi is becoming an appealing PTP implementation also outside of the White Rabbit Community.