PTP Security Measures and their Impact on Synchronization Accuracy

The Precision Time Protocol (PTP) synchronizes clocks in a network with high precision. The protocol finds use in many areas, such as smart manufacturing, intra-vehicular networks, and critical infrastructure. It becomes clear that striving for security is an important goal. If an attacker succeeds in disturbing the network synchronization, the impact can result in a cascading set of failures. Unfortunately, neither the previous two IEEE standards for PTP, nor the popular implementation linuxptp, feature or implement sufficient security options.This work focuses on implementing the security extensions for PTP based on the latest PTP standard IEEE 1588-2019 to minimize the threat of attacks and their possible impact. We provide a detailed analysis on PTP synchronicity and security. Based on that, we design and implement software-only tooling to quantify the PTP performance using commercial off-the-shelf hardware and open-source solutions on a linear topology with four to nine hops.The measurements compare the End-to-End (E2E) and Peer-to-Peer (P2P) delay calculation modes and the usage of Transparent Clocks (TC) in parts of the network. Both E2E and P2P show visible degradation of clock synchronization with each hop and standard deviations of 118.6 to 571 ns. The TCs perform better, demonstrating a standard deviation between 90 to 140 ns on four to nine hops. We evaluate different logSyncInterval values corresponding to different PTP profiles and do not observe a major impact on the clock behavior caused by the extensions. The measurement precision of the system is within ±40 ns.Our evaluation of the newly implemented security extensions to linuxptp shows that the security extensions do not have a significant impact on the clock synchronization and our approach is a feasible addition to PTP. Besides, our contributions can aid network managers in assessing their PTP synchronicity systematically.