A very good place to start is with standards compliance testing. In our experience as a test equipment manufacturer, standards compliance testing in an early implementation phase is a very effective strategy, especially when the standards are not yet finalized and the implementations are still being adapted to the needs of different industries. The 802.1AS standard, which describes the use of the 'Best Master Clock Algorithm' (BMCA) for larger networks, as found in the industrial sector, serves as an example. This standard makes little sense in the automotive sector, as static and smaller networks are used here.
The Avnu Alliance is working on the definition of test plans for different industrial profiles for TSN technologies. These test plans are made available by Keysight in corresponding conformance test packages in test solutions. For example, the Avnu test plan 'Qbv for industrial applications' is very popular with manufacturers of TSN switches.

The test plan

Avik Bhattacharya is Product Manager L23 Network Infrastructure Testing at Keysight Technologies.

© Keysight Technologies

The validation strategy also depends on the interaction of the various TSN standards. For example, in a network in which 'Time aware
shaping' (802.1Qbv) and 'Frame Preemption' (802.1Qbu) are implemented. Here, a test plan must also take into account the special features resulting from the interaction of these two standards. Various components must interact in an industrial network: PLCs, robot elements, motors, sensors, HMIs and integrating switches for the cloud and the corporate IT network. As a result, the shared network transports different traffic flows, which in turn have different requirements in terms of latency, packet sizes and bandwidths. The biggest challenge in the test lab is to have a 'real-life' simulation available for validation.

The Industrial Internet Consortium (IIC) provides a white paper entitled 'Time Sensitive Networks for Flexible Manufacturing Testbed Characterization and Mapping of Converged Traffic Types', which describes a very good definition of traffic types in an industrial network. The IIC white paper focuses on the different types of traffic flows used by the Industrial Automation and Control System (IACS) that can affect the quality of service (QoS) of other traffic types. A 'real-life' simulation based on this IACS traffic profile is an excellent test for a TSN device to be used in an industrial network.

The value of interoperability test benches

Sebastian Sattler is a Senior System Engineer at Keysight Technologies.

© Keysight Technologies

TSN test benches allow manufacturers to bring in their implementations and compare their status with that of other manufacturers. Keysight recently participated in the TSN Plugfest organized by the IIC at the University of Stuttgart. Keysight conducted numerous functional, interoperability and conformance tests with industrial devices from the various participants. It was interesting to observe how the TSN implementations behaved when scaled accordingly, as well as the impact that one standard can have on the performance of other standards at system level.
A corresponding test report has already been published and shows the various test methods used at this plugfest: click here for the report.

On the topic

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.