Time-sensitive networking: device interoperability through common test procedures
Author : Rene Hummen, Senior Architect, Hirschmann & Georg Kroiss, Business Development Industrial, TTTech
26 November 2018
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Central to the IIoT’s growth are the networks that relay increasingly involved data from growing numbers of devices: what is needed, consequently, is greater scalability through the convergence of different types of traffic onto a single network infrastructure – and the assurance of interoperability at this larger scale.
After all, the IIoT itself is among one of the biggest business opportunities of the 21st century, and recent market reports and projections see the industrial automation equipment market as a central focus for that growth.
A 2017 report from IHS forecasts the industrial sector as being one-third of the total connected IoT devices by 2020 (Source: IoT Trend Watch), and as Grand View Research expects: the “global industrial IoT market will be worth $93B USD by 2025”.
Enter deterministic Ethernet-based networking with IEEE time-sensitive networking (TSN), which fills an important gap in standard networking: in particular, it offers guaranteed latency and delivery for critical traffic whilst allowing other traffic types on the same wire. It allows for IIoT to incorporate high-performance and latency-sensitive applications in a converged, robust network infrastructure.
In the industrial context, the IEEE/IEC 60802 joint working group has taken on the important task to define an industrial automation profile based on the IEEE TSN standards. Avnu Alliance builds upon the work of these standardisation bodies and ensures that all the ecosystem players implement TSN in an interoperable manner – by providing conformance test plans and test procedures.
Testbeds: testing use of TSN in real-world applications
Upfront testing of a new technology’s capabilities is key to understanding the path towards a successful network deployment. Testbeds offer systems designers the chance to see how their devices and networks perform in real-world settings, before they are being rolled out as products.
The Industrial Internet Consortium (IIC) is one group who are working with leading vendors and manufacturers in industrial automation to help ensure that a network of TSN devices work together appropriately.
As the world’s first testbed for TSN, the IIC’s TSN for Flexible Manufacturing testbed was developed with two major goals in mind: to show TSN’s readiness to accelerate the marketplace; and to highlight the business value of adopting open, interoperable standards in automation networks.
Universal test plans & conformance testing tools
While testbeds and plugfests help test for a certain degree of interoperability and allow companies to create real-world systems as an early check for potential problems, conformance testing systematically ensures both alignment with the standards and interoperability of devices in real-life settings.
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Based on industry-accepted requirements for TSN network interoperability, Avnu Alliance develops test plans for conformance to ensure interoperability at the network layer. Starting with Time Synchronization, or 802.1AS as the foundation for all TSN devices, Avnu released the first set of test plans at SPS IPC Drives in 2017, and they continue to work on extending these plans to other TSN standards.
The goal is to develop baseline test plans for the industrial market, which ensure that end devices, infrastructure components and silicon conform to the relevant IEEE and IEC standards.
Avnu leverages the abovementioned IIC Testbed by evaluating the developed test plans and procedures early on with testbed participants, such as Analog Devices, Belden/Hirschmann, Bosch Rexroth, Cisco, General Electric, National Instruments, Schneider Electric, and TTTech – many of whom are also Avnu Alliance members.
As the wide adoption of TSN has led to the emergence of other testbeds for TSN devices – including Labs Network Industrie 4.0 (LNI) and Edge Computing Consortium (ECC, in liaison with Avnu) – Avnu aims to share their test plans with more TSN testbeds as a concerted effort towards ‘One TSN’ network.
At the 2018 SPS-IPC Drives last month, Avnu participated alongside ISW University Stuttgart and IIC in a joint-booth, showcasing Avnu’s role in the TSN ecosystem – including a demonstration of a new proof-of-concept conformance testing tool, an automated Linux-Based Test Tool for Compliance Testing of 802.1AS to streamline conformance testing, and certification of TSN devices.
The test framework will interface with a variety of test equipment, from low-cost to high-performance, and it will provide a consistent user interface and results report that can be utilised by end vendors as well as testbeds, test houses and protocol groups to conduct in-house conformance testing of TSN devices.
IIoT laboratory | Credit: Avnu Alliance
Such a test framework reduces total testing process time and enables easier testing for vendors – both in-house and at testbeds – to provide test result details and allow for device debugging and problem-solving before products go to market.
Application layer testing
All of the above information provides for interoperability on the foundational network layer 2 with TSN. Many organisations, such as OPC Foundation and the various fieldbus organisations, have developed application layer protocols, which are well suited to work on top of TSN. OPC UA over TSN, supported by the OPC Foundation, is a prominent example.
Avnu Alliance intends to make their TSN test plans available to application layer protocol organisations who wish to test their protocols on top of TSN. The goal is to offer device manufacturers a one-stop-shop for certification of the entire stack and to impose no restrictions on the choice of test houses.
Together, this work across the industry and among various standards groups, protocol organisations and industry leaders will create a faster process towards an open, interoperable ecosystem of devices: namely those that take advantage of time-sensitive networking’s full benefits.
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