TSN: Evolution, next steps for industrial systems

Technology Update: IEEE Time Sensitive Networking evolves standard Ethernet to enable deterministic networking that supports coexistence of critical and non-critical forms of traffic. Experts provide TSN updates and explanations.

By Control Engineering August 21, 2018

The latest set of IEEE 802.1 standards, Time Sensitive Networking (TSN), is an evolution of standard Ethernet to enable deterministic networking that supports critical and non-critical forms of traffic in coexistence. Industrial network system designers and engineers, as well as end-users, benefit from the use of TSN in their systems by accessing a network that promises reduced latency, shared synchronized time, and convergence of control traffic and standard Ethernet traffic. The technology continuously has been advancing alongside the Industrial Internet of Things (IIoT) with new capabilities, use cases, and tools that are contributing to industrial applications.

IIoT demand has been growing steadily and will continue to do so more rapidly due to advancement and adoption of networking technologies. According to a report by Zion Research, the IIoT market will grow due to the benefits of manufacturing cost reduction and sensor data contribution to real-time supply chain information. This growth is creating increased amounts of data that will be harvested through distributed networks and will require new standards for managing and transferring critical information. These factors create opportunities for IIoT, Industrie 4.0 and evolving technologies to support this necessary business shift.

Avnu Alliance, a consortium responsible for creating conformance tools for TSN device testing and fostering the manufacturer ecosystem of devices for industrial networked systems, is working to drive interoperability for IIoT devices. In 2017 Avnu Alliance’s industrial segment worked with top companies to advance tools for TSN via participation in TSN testbeds, plugfests, and interoperability workshops for industrial applications.

Updating a Control Engineering January 2017 article, "What does time-sensitive networking and real-time Ethernet data mean for the future of industrial systems?" Avnu Alliance explained the current status of TSN for industrial applications, the evolution of the technology and tools, and how they advance industrial systems.

Q: What updates can you tell us about TSN and Avnu Alliance since last year?

A: Todd Walter, National Instruments, Avnu Alliance industrial segment chair and board secretary: TSN tools and support continue growing each year; in 2017, there were training and best practice materials to speed applications in industrial automation. We also announced the first set of TSN conformance tests for industrial devices to test houses. Avnu has established common Audio Video Bridging [AVB] Work Group and TSN conformance and interoperability tests for various markets, and we are leveraging this experience to define a baseline certification program for the industrial market.

These conformance tests will ensure that the device or silicon conforms to the relevant IEEE standards, as well as additional requirements that Avnu has selected as necessary for proper system interoperability. With this defined procedure, manufacturers will be able to test devices for traffic shaping mechanisms, frame preemption, redundancy, ingress policing, strict priority, and security to ensure that their devices are conformant to TSN and will operate properly in real-world TSN systems.

We also strengthened and leveraged liaison relationships. Avnu is a member of the Industrial Internet Consortium (IIC) TSN Testbed. At Hannover Messe, we participated in the grand opening of the Edge Computing Consortium (ECC) TSN Testbed.

These groups and others are working together to create a unified standard and interoperable ecosystem for the industrial market. The market continues to require multiple upper layer protocols for networked industrial systems. Avnu bridges these various protocols with a common foundation and the accompanying conformance tests for that base communication level, including silicon and infrastructure. Avnu works with other protocol and standards organizations, such as OPC Foundation, which provides conformance testing for application layers to develop a certification program that will allow the industry to test for conformance at all layers and certify for interoperability based on those tests.

The ecosystem continues growing with more devices coming into the market. In March, Avnu members participated in the IIC TSN Testbed plugfest, with TSN devices from 25 companies. The more devices we see, the greater opportunity there is for fully realized industrial networks, but it also requires more collaboration across the ecosystem to deliver an interoperable foundation.

Q: What are the benefits of using TSN in industrial control systems?

A: Denzil Roberts, Ph.D., Intel Corp.: TSN can be beneficial for a wide range of industrial applications, including machine automation, manufacturing, healthcare, transportation, robotics, and more. These systems are highly software-defined and have high availability requirements; they’re built on a foundation of recent processing, communications, and software advancements, and include modifications by each industry for the reliability, longevity, and performance required.

Standard Ethernet had been used in these applications, but is insufficient, as without strict access and traffic control, it can’t guarantee network latency—an important component for closed-loop control. Process control applications devices require response time to be 20-100 microseconds across thousands of devices. For motion control applications, devices must respond within 0.5-2 microseconds, and there may be up to 300 drives.

TSN addresses these needs by ensuring bounded latency, reserved bandwidth, and distributed timing, which contribute to increased productivity and up-time. TSN also brings a holistic approach to network management, requiring new tools that enable offline modeling of the network traffic and simulation of loading prior to acquisition of hardware or commissioning in the field. Scheduling becomes more calculable from a mathematical perspective, allowing system designers to see in advance if the network will be successful. This dramatically changes the workflow for designing and planning networks and allows for prediction of the future capabilities possible to support business growth.

Q: How will the TSN conformance testing for industrial devices help adoption of this set of standards?

A: René Hummen, Hirschmann Automation and Control: Certification is an important step for any standards-based technology, including TSN. To start with, standards typically are written in a natural language, which—in contrast to constructed languages such as programming languages—commonly have ambiguities. These ambiguities may lead to different interpretations and implementations of a standard. This, in turn, hampers interoperability. Certification ensures that implementations are sufficiently lenient in their expectations and their behavior to support a common interpretation of a standard. In other words, certification guarantees that equipment from different vendors will work together. This means a customer can choose the equipment that fits requirements best without being restricted to one vendor.

Leading companies in the industrial communications sector have pledged commitment to ensuring the interoperability of deterministic industrial devices in cooperation with Avnu Alliance. These companies demonstrate interoperability among vendors with testbeds like the IIC TSN Testbed and LNI 4.0 TSN Testbed. Collaborative testbed efforts with other standards groups and manufacturers can help facilitate a cooperative certification program that becomes a "one-stop-shop" for the conformance and interoperability of TSN devices and higher-level protocols, enabling an ecosystem of devices that can reliably communicate with one another even as networks expand and mature.

Conformance testing and Avnu certification are key to the benefits of TSN as an interoperable standard for industrial automation, where increased IoT infrastructure and network capabilities require an interoperable ecosystem that allows for multiple manufacturers, protocols, and organizations to share the same TSN network. Avnu’s work will continue to advance conformance testing specifications and methods, which minimize conditions or special cases for device functionality, thus enabling greater adoption and a vibrant ecosystem.

Q: The industry seems keen on creating interoperability for industrial automation devices. Is participation in TSN testbeds enough?

A: Steve Zuponcic, Rockwell Automation, Avnu Alliance board member: Avnu has established several liaison relationships with other organizations that also are working in TSN-related areas. They include IIC, OPC Foundation, IEC, and IEEE. By leveraging these liaison partnerships, the lessons learned from testbeds and plugfests can be synthesized and efficiently communicated to accelerate the process of creating an open interoperable ecosystem.

Testbeds are only one in a sphere of elements that are required to achieve an interoperable ecosystem. Testbeds allow multiple vendors to test implementations against other vendors’ implementations; they test for a certain degree of interoperability—but it doesn’t necessarily mean that the products conform to the standards as they should. It’s possible that two vendors could interpret the standard incorrectly—but in the same way. These products might interoperate, but they wouldn’t conform to the standard. Conformance testing, on the other hand, is designed to run the product against a series of rigorous tests to ensure that the product meets the standards against which it was designed. These tests, once passed, result in certification of the product, which means that the product is marked to show that it has been tested for compliance against the standard and to operate with other certified products.

The focus of testbeds differs from conformance testing. And the roles of these tests are different, again, from that of the standards organizations writing the specs. They are complementary and create a stronger foundation for interoperability.

Lessons learned from ongoing TSN testbed activities and plugfests contribute to the conformance test development done within Avnu and will continue to feed into standards revisions as necessary. The conformance testing and certification provided through Avnu will be critical in providing the needed foundation for interoperable IIoT networks and give industrial vendors a more streamlined vehicle for participation in the TSN ecosystem, while helping end users with network convergence.

Q: How does Avnu Alliance work with other alliances and organizations such as Industrial Internet?

A: Paul Didier, Cisco, Avnu Alliance board member and IIC liaison: Avnu and IIC have a strong foothold in IIoT networking, but there are several organizations working together to create a unified standard and interoperable ecosystem. These include Avnu for conformance testing, IIC, Edge Computing Consortium and LNI 4.0 for the testbeds, as well as IEC, IEEE, and the OPC Foundation for establishing the standards. Avnu and the OPC Foundation are working together to create a one-stop-shop for OPC UA TSN conformance testing.

Eventually, industrial standards organizations like Profi, ODVA, PowerLink, and others, may take on testing functions to provide interoperability and compliance.

The liaison between Avnu Alliance and IIC has already yielded the TSN testbed, allowing manufacturers and Avnu members to attend plugfests. The number of plugfests has been growing, which helps more companies test TSN deployment in their devices in a real-world system scenario with other devices, and therefore, more quickly respond to market demands.

Our strengthened relationships with other alliances and protocol organizations signifies the progression of TSN for the industrial sector. Through joint efforts, we are working with as many organizations as we can to raise awareness and drive wider adoption of all open standards. Participation in joint activities—like the continued refinement and addition of use cases and products to the testbeds; identification, and sharing of IIoT best practices; realization of interoperability by harmonizing architecture and other elements; and collaboration on standardization—will ultimately create the ecosystem we all envision.

Q: What advancements in TSN are expected in the second half of 2018?

A: Tom Weingartner, ADI, Avnu Alliance board member: Avnu Alliance continuously supports TSN with new tools, events, education, and resources that contribute to a growing membership and ecosystem of interoperable TSN devices. We’ve recently been collaborating with the Edge Computing Consortium to announce their first OPC UA TSN Testbed at Hannover Messe in April 2018, and I was happy to represent Avnu at the press conference for this launch. The ECC OPC UA TSN testbed, covering six major industrial Internet scenarios, verifies the highly deterministic and low-latency characteristics of TSN, which was demonstrated at the show through several real-live manufacturing scenarios. The benefits of combining OPC UA and TSN include improved bandwidth, security, latency, synchronization and more, through vendor-independent communication. The testbed is an important proof of the interoperability of devices from a variety of manufacturers in one system.

Avnu will continue to increase support for industry testbeds and take the feedback and lessons learned from these platforms into our evolving conformance testing programs. From this Avnu-defined foundation, we intend to support additional capabilities, including support for multiple IEEE 1588 profiles, guidelines for scaling to very large network architectures, centralized and distributed network configuration, and aggregation/composition of multiple networks into one TSN-enabled network domain. Avnu is still focused on bringing the numerous other TSN features to the industry, including scheduled traffic, preemption, and strict priority queueing, to name a few. These are needed to support the different applications and traffic classes of industrial control systems. As the IEEE specifications and industrial market evolve, Avnu will continue to add certification and conformance tests for all appropriate TSN features.

Avnu remains committed to the goal of expediting an interoperable ecosystem of devices, and throughout 2018, we aim to solidify additional liaison relationships with other protocol organizations and standards groups. We will also continue driving Avnu certification for time synchronization, and develop additional best practices and use cases around system configuration and set-up of TSN-based industrial systems to foster deployment of TSN and facilitate system integration. These activities will take advantage of new updates to the test plans and test tools for TSN through support of the Avnu Alliance and its members.

– Edited by Mark T. Hoske, content manager, Control Engineering, CFE Media, mhoske@cfemedia.com.

KEYWORDS: TSN, Industrial Ethernet

  • Time Sensitivity Networking is an IEEE Ethernet standard.
  • Testbeds help development of IIoT technologies.
  • Avnu Alliance is advocating for certification for time synchronization.


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