Design & Implementation of PTP Boundary Clocks on P4-Programmable Systems

Precision Time Protocol (PTP) is an important pillar of IEEE 802.1Q Time-Sensitive Networking (TSN) standard to realize deterministic networking. TSN requires tight time synchronization using PTP and thus requires nanosecond resolution timing control of switch resources. Current solutions lack the performance and flexibility to provide an integrated solution. This paper presents P4PTP, a modular design for PTP Boundary Clocks on P4-programmable targets. It is validated on the P4 reference software switch (Bmv2) and a Netronome Agilio SmartNIC. Two implementation approaches have been explored - a complete data plane solution and a hybrid solution combining data plane packet processing and control-plane computation by developing a P4Runtime controller, and their performance are evaluated. The achieved synchronization precision supports requirements of various TSN use-cases. Comparisons are made to a standard PTP-supported COTS switch and to an Intel NIC. Portability and scalability are addressed by running the solution on 1000 Bmv2 targets and using a centralized controller to control the switches.