In every broadcasting application, all devices must exchange media data continuously while remaining tightly synchronized with each other at all times. That’s why, as broadcasting facilities worldwide make the transition from serial digital interface (SDI) to partial or complete reliance on IP technology, accurate and reliable time transfer over Ethernet has become key. In the July issue of the SMPTE Motion Imaging Journal, authors Nikolaus Kerö and Thomas Kernen present an in-depth discussion of the challenges in their paper, “A Multipronged Approach to Effectively Secure SMPTE ST 2059 Time Transfer.” https://ieeexplore.ieee.org/document/9470359
SMPTE has specified in its ST 2059 standards the use of Precision Time Protocol (PTP), as defined in the IEEE 1588 standards for media signal generation and synchronization. While proven to deliver an accuracy within 1 μs for all types of networks, PTP’s vulnerability to error is a major concern in maintaining an uninterrupted, bidirectional message flow. Therefore a series of enhancements has been developed to ensure robust, resilient and secure synchronization.
The paper’s authors consider four possible PTP Error Conditions that can occur in the network, and offer ways the broadcasting industry can efficiently use and benefit from the new enhancements of the ST 2059 standard:
To make things even more challenging, the four error conditions are not mutually exclusive, and each can occur either permanently and transiently. These failures can occur either inadvertently due to misconfigured or malfunctioning PTP devices somewhere in the network, or be caused deliberately as a result of a malicious attack against the integrity of the timing network. Here, the authors propose basic security countermeasures against malicious attacks:
In broadcasting applications, even transient faults which jeopardize the integrity of the time transfer mechanism must be avoided at all costs. As the authors of this article show, PTP is a highly effective and accurate means of synchronizing devices connected to each other via an Ethernet network, and their resilience can be further improved using state-of-the-art cryptographic methods, supported by the latest version of the IEEE 1588 standard.
Interested in digging deeper into synchronization using Precision Time Protocol? Read the complete article in July’s issue of the SMPTE Motion Imaging Journal.https://www.smpte.org/motion-imaging-journal