Device testing & time-sensitive networking in the IIoT

Dec. 19, 2018
There is a need for the assurance of interoperability at this larger scale.

By Rene Hummen is a senior architect with Hirschmann Automation and Control  & Georg Kroiss oversees business development (industrial) with TTTech, both members of Avnu Alliance.

Central to the growth of the IIoT are the networks that relay data from an increasing number (and variety) of devices. Consequently, there is a need for greater scalability through the convergence of different types of traffic onto a single network infrastructure and the assurance of interoperability at this larger scale.

Likewise, there is a need for greater reliability and interoperability across the network to ensure the timely transfer of information to systems with increasingly complex needs, including time synchronization that needs to be managed within tenths of a nanosecond in some specific environments.

Hirschmann Automation and Control's Rene Hummen

Leading industrial and transportation companies will demand the same high levels of reliability, security and safety for their control systems within the IoT as is provided today by a multitude of specialized (but often proprietary and segregated) communication technologies. Of course, these requirements with regard to reliability and security must be addressed in connected and open infrastructures, which leads to challenges in deployment and diagnosis not seen before in these types of systems. 

With more operations seeking streamlined processes that save money and time, network-infrastructure improvements are a key step in the development of IIoT solutions. This means that there will be an increasing need for interoperability, efficiency and determinism on the network as new automation capabilities arise.

Enter: deterministic ethernet-based networking with TSN.

Deterministic ethernet-based networking with IEEE Time Sensitive Networking (TSN) fills an important gap in standard networking—it offers guaranteed latency and delivery for critical traffic while 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 of defining an industrial-automation profile based on the IEEE TSN standards.

Of course, this is only one step in the process.

To ensure device interoperability after implementation of a profile, device testing and collaboration with industry groups, certification and other considerations are important to creating devices that will work adequately in devices now and in the future.

Testbeds: Testing use of TSN in real-world applications

Testing a network’s capabilities before implementation is key to developing a successful network design—testbeds offer systems designers the chance to see how their devices and networks perform in real-world settings before they’re installed and devices are rolled out to customers. The Industrial Internet Consortium (IIC) is one group working with leading vendors and manufacturers in industrial automation to help ensure that a network of TSN devices appropriately work together.

TTTech's Georg Kroiss

As the world’s first testbed for TSN, the IIC’s TSN for Flexible Manufacturing testbed was developed with two major goals: to show TSN’s readiness to accelerate the marketplace and to highlight the business value of adopting open, interoperable standards in automation networks. It stands as a showcase of the value that TSN standards and the ecosystem of manufacturing applications bring to the market, including the ability for IIoT to incorporate high-performance and latency-sensitive applications.

The benefit of the testbed is that it demonstrates real-world industrial use cases leveraging TSN. One such envisioned use case is a setup of two separate large-scale robot and automation control suppliers who are seeking to implement TSN technology to increase interoperable communication between their devices and systems. They will coordinate and manage controllers and the monitoring of the sensor data between robots and the controllers.

This coordination requires a combination of receiving highly time-sensitive, synchronized information from sensors and then passing control commands back into the environment to other types of devices on the network. Without TSN, these companies would have to perform this communication with separate proprietary, non-standardized networking technologies that may not talk to each other on an IoT network.

Plugfests are another opportunity to bring together representatives from various manufacturers creating TSN-based products who want to test their devices for interoperability in a real-time setting. Groups including IIC and Avnu Alliance regularly host plugfests to bring together member organizations to offer manufacturers a way to test in real-time and gain insight from the various best practices and lessons learned.

Universal test plans & conformance-testing tools

While testbeds and plugfests help test for a certain degree of interoperability and enable 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.

Test plans give organizations a roadmap that guides them to develop TSN and IoT-ready products. Based on industry-accepted requirements for TSN network interoperability, test plans for conformance from organizations like Avnu Alliance help 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 in 2017 and continues 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.

Organizations like Avnu leverage the above mentioned IIC testbed by evaluating the developed test plans and procedures early on with testbed participants and leading IIoT manufacturers. 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 its test plans with more TSN testbeds as a concerted effort toward “One TSN” network.

Some organizations are even moving toward development of conformance test tools to help device manufacturers better prepare for TSN compliance. At the recent SPS-IPC Drives show in November, the University of Stuttgart ISW lab, in partnership with Avnu, demonstrated 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 could interface with a variety of test equipment (from low-cost to high-performance) and provide a consistent user interface and results report that could then be utilized by end vendors as well as testbeds, test houses and protocol groups to conduct in-house conformance testing of TSN devices. This 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 aim to ensure interoperability at the foundational network layer 2 with TSN.  Many organizations, such as OPC Foundation and the various fieldbus organizations, 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 and Avnu Alliance intends to make its TSN test plans available to application-layer protocol organizations that 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 organizations and industry leaders will create a faster process toward an open, interoperable ecosystem of devices that take advantage of Time Sensitive Networking’s full benefits. Organizations like Avnu Alliance build upon the work of these standardization bodies and ensure that all ecosystem players implement TSN in an interoperable manner by providing conformance test plans and test procedures.

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