The time for TSN is coming

30 May 2023

Suzanne Gill reports on the benefits that Time Sensitive Networking can offer in industrial applications, once the barriers to its adoption are overcome.

Time Sensitive Networking (TSN) is the IEEE 802.1Q defined standard technology to provide deterministic messaging on Ethernet. Before TSN, standard Ethernet had no pure Layer 2 deterministic capability so the technology is important for the industrial sector because it enables real-time communication via Ethernet, between machines and devices that have traditionally used a variety of different communication protocols. 

Jordon Woods, Director of Analog Devices Deterministic Ethernet Technology Group and an Avnu Alliance member, explains further: “Industrial control applications require consistent data delivery from sensors to controllers and actuators and it is critical that this data is deterministic. Some level of determinism is needed, for example, to ensure a control loop is closed in a specified interval of time. TSN is one way to ensure that this control data traffic is prioritised and delivered on time by securing bandwidth in the network infrastructure while simultaneously allowing noncritical forms of data traffic to coexist on the same network. TSN offers several benefits for Industrial Internet of Things (IIoT) networks, such as security enhancements and futureproofing, by aligning with IT standards, efficient management and control, and convergence of traffic with mixed criticality.” 

Because TSN is part of standard Ethernet, control networks can take advantage of best practices for security that have been developed and used into Ethernet for decades. TSN also adds flexible traffic ‘policing’ functions, which provide additional protections against traffic storms and other forms of attack. 

TSN also scales naturally with Ethernet, which means that the technology will not be limited regarding bandwidth and other performance criteria. In addition, new nodes can be easily added and discovered via standard networking protocols. 

IIoT adoption is seeing industry moving beyond single-function networks to realise the benefits of a converged network foundation with the coexistence of different traffic types and devices on the same physical network. TSN provides the tools to enable this convergence and the exchange of real-time control, telemetry, and general IT information, all managed securely by IT and OT, reducing infrastructure costs and the resources needed to manage and maintain the network.

“TSN has enabled the convergence of networks and systems that were previously kept separate for operational integrity, real-time performance, safety or security reasons. Breaking down communication barriers between critical and noncritical systems is a foundational concept of IIoT,” said Jordan.
Mitigating performance issues
Discussing the benefits of TSN, Dr Al Beydoun, President and Executive Director at ODVA, said: “TSN allows network performance issues to be mitigated, for example, by increasing the total bandwidth or by identifying the root cause of the traffic bottlenecks and working to remove them via network segmentation or the addition of managed network switches to filter unnecessary traffic.

“Properly configured, 60802 TSN networks should be able to simply prioritise the most important safety and I/O traffic while allowing other diagnostic and non-time critical packets to wait until the pipeline is freed up.” 60802 TSN is able to significantly reduce the amount of jitter, latency, and lost packets due to messages exceeding the available bandwidth via traffic management. 

Al offered some TSN use case examples. “Artificial Intelligence (AI) neural networks and Machine Learning (ML) algorithms that rely on camera images and training models to identify quality defects compared to the desired output, present potential use cases for TSN. 

“Over time, higher resolution images, additional camera angles, or an increased number of images could be transported over the network to help the algorithm improve quality with additional input. TSN ensures that the critical information on the network would be able to continue to arrive when needed, despite any increases in the amount of data relative to total bandwidth. 

“Another possible use case is the transport of different communication protocols through the network to a consolidated edge device for upload to the cloud. While this data would not be used for control, it is important to ensure that it doesn’t interrupt other critical control traffic on the network. The ability to include many different types of devices, such as machine vision, surveillance cameras, safety light curtains, and more, on the same network will simplify planning and make it easier for data to flow from the plant floor to the controller, edge, and the cloud.”

According to Al, challenges related to large scale adoption of 60802 TSN include development of the prioritisation mechanisms that will need to be configured within switches across the broader network to ensure appropriate quality of service is applied to each packet during transportation. He said: “Without software configuration tools that allow for centralised commissioning diagnostics, and configuring network changes for all different types of traffic –regardless of protocol, device type, or vendor – the value of TSN is significantly reduced and other solutions become more practical.” Additionally, because the IEC/IEEE 60802 TSN specification hasn’t been finalised yet, there are risks associated with installing TSN devices too early in case of interoperability issues with devices that don’t adhere to the final specification. “So, the release of scalable and interoperable TSN configuration tools, along with 60802 TSN compliant devices, will be critical to the long-term success of TSN,” said Al. 

Exciting times
Also commenting on the current barriers to the adoption of TSN technology, Greg Schlechter, President at Avnu Alliance, said: “Like any new open ecosystem things can seem a bit chaotic, but it is also an exciting time to see where and how it is being used in early pilots and implementations.  We are still in the adoption phase where the different parts of the ecosystem are now being filled by actual products.”

With many of the large industrial protocols such as Profinet, Ethernet/IP, CC Link and OPC Foundation announcing support for TSN, the ecosystem is moving forward. “Avnu has joined with many of these protocol organisations, including CC-Link Partner Association, ODVA, OPC Foundation, and PROFIBUS & PROFINET International, to develop a single test plan to test for conformance the IEEE/IEC 60802 profile for TSN for Industrial Automation,” continued Greg.  “This initiative is called the TSN Industrial Association Conformance Collaboration (TIACC). The announcement of the TIACC cooperation on TSN interoperability is key to having common approaches to the use of TSN in industrial settings and converged networks. 
“In addition, the leading silicon vendors are working together with Avnu Alliance to develop a foundation of silicon and IP products’ for endpoint and switches with TSN capabilities at the component and supporting software level. This effort will support cross-industry collaboration and help the industry more quickly and easily build these products.” 

So, like any new technology adoption, things are transitioning slowly but surely. There will be no overnight change.  The good news is that with such strong industry cooperation and market interest growing at the same time, there appears to be a favourable environment for the TSN ecosystem to grow quickly. 

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