The IEEE 1588 Precision Time Protocol ultimately became the de facto method for precision Ethernet synchronization. Currently, the PTP is evolving from a method for providing synchronized time over Ethernet to a fundamental building block of TSN. The IEEE 802.1AS and 802.1AS-2020 PTP profiles are helping to enable enhanced network features such as IEEE 802.1Qbv time window-based scheduling.
To support these efforts, Calnex has participated in Plugfests at ISW in Stuttgart for several years, providing systems to measure device performance and compliance with 802.1AS and 802.1AS-2020. Plugfest participants can test their synchronized bridges and switched endpoints quickly and easily. If there is sufficient confidence in the device itself, it is then possible to test their devices in a multi-vendor environment and gain even more insight.

The experience of many deployments of the tool at events shows that all this leads to rapid improvements. To compare synchronization performance against the limits defined in 802.1AS Annex B and identify protocol interoperability issues, it is pleasing to see that device performance has steadily improved in terms of both protocol compliance and timing accuracy.

Adam Paterson is Product Manager at Calnex Solutions.

© Calnex Solutions

In the early days, devices sometimes only worked in terms of timing but were not protocol compliant, or vice versa, or perhaps only supported one network speed. The fact that products were intended to serve different industries made non-compliance and interoperability issues more likely. Today, increasing technology interest and demand for reliable TSN implementations is leading to more and more fully standards-compliant devices, ensuring both the interoperability and underlying time synchronization that is essential for successful TSN implementation.

With the upcoming release of 802.1AS-2020, a new wave of product testing is expected. Based on the progress we have seen in recent years, we are confident that we will once again see an industry ready to take advantage of this technology.

On the subject

Part 3 of the TSN series

© WEKA Trade Media

Here you can find the technical report "Prototyping and Testing of TSN", which is part of this article and which deals with the questions of what contribution cross-manufacturer testbeds make and how the implementations of TSN standards and interoperability can be tested.