Initial testing has shown that OPC UA over TSN averages 18 times faster than existing industrial communication solutions, leading some in the industry to wonder whether such a dramatic leap is really necessary. To get to the bottom of this question, we spoke to one of the new technology's leading experts: Dietmar Bruckner.
Do you see a real need for a communication protocol with the performance of OPC UA over TSN?
Bruckner: It's true that we don't have applications today that require 18 times the performance of existing Industrial Ethernet protocols. Nevertheless, my answer to your question is a resounding yes.
OK, would you mind clarifying that for us?
Bruckner: You could probably get by for another two or three years just making incremental improvements to existing protocols. But that would be short sighted. With the success of OPC UA, industrial communication is currently experiencing the greatest upheaval since the advent of fieldbuses. If we look at the typical lifespans of fieldbus systems and Industrial Ethernet protocols, we can expect to be working with OPC UA over TSN for decades to come.
What are the implications of that in terms of performance?
Bruckner: To make it a future-proof investment that pays off long term, the protocol needs to be ready to meet 20 years of evolving performance requirements. Nobody wants to go to such lengths defining a new standard that will have to be fundamentally reworked only five years down the road. That's why it is so important that OPC UA over TSN is as powerful as possible right out of the gate.
About the interviewee
Dietmar Bruckner has published nearly 100 scientific papers and holds several patents in the field of real-time industrial communication. He is an active member of various standardization committees and working groups – including the IEEE and the OPC Foundation. At automation specialist B&R, Bruckner is responsible for R&D in the area of real-time communication.
When you talk about performance, what do you mean exactly?
Bruckner: It's a combination of things, but clearly one of the most important factors is the fastest cycle time that can be achieved. If your application has only a small number of network nodes, you can achieve very short cycle times even with a conventional 100-Mbit Industrial Ethernet protocol. At the rate things are currently progressing, however, we expect to see more and more plants and machinery with many hundreds or thousands of network nodes.
Why is that?
Bruckner: As they strive to respond to dynamic market demands, machine builders are making their machines more intelligent and more flexible. And to do that, they are using more sensors and actuators than ever. Many of these are directly integrated into the machine network as smart devices. Already, we've seen machines that synchronize more than 1,000 axes. That's precisely the type of situation where current technology starts to see cycle times go up over a millisecond. And there are plenty of processes where that is just too slow. That's why we need a powerful and high-performance machine network.
TSN and the role of the IEEE
The Institute of Electrical and Electronics Engineers (IEEE) is responsible for standardizing numerous global communication technologies, including Ethernet, WLAN and Bluetooth. IEEE standardization guarantees that any two devices will be able to communicate with each other, regardless of who manufactured them.
Time-sensitive networking (TSN) extends the Ethernet standard to include mechanisms for guaranteed real-time data transmission. The IEEE included the associated functions as sub-standards in the Ethernet standard IEEE 802.1. As a result, TSN devices from any manufacturer can communicate with each other in real time.
What role does bandwidth play?
Bruckner: For the user: an ever larger one. Machine vision, big data analytics, predictive maintenance – these new technologies generate enormous volumes of data that can quickly overwhelm today's 100-Mbit bus systems. And there's one other aspect that should not be underestimated: The more open the network, the more important it becomes to keep components in the field supplied with the latest security updates and operating system patches. You can only do that if you have the necessary bandwidth.
How does OPC UA over TSN handle this growing competition for bandwidth?
Bruckner: TSN has another advantage that comes into play here: it is independent of bandwidth. The user has access to the full bandwidth of the Ethernet hardware used, whether that's 1 Gbit/s, 2.5 Gbit/s, or eventually even more.
Wouldn't there be a way to do that using existing fieldbus systems?
Bruckner: No, because you can't simply compensate for their limitations by scaling them up to 1 or 10 Gbit/s. The rigid arbitration methods of a conventional bus system with a central master and fixed cycle distribution don't allow that. You have to remember: fieldbus technology dates back to the 1990s. When you plan and administer a TSN network, on the other hand, you're able to benefit from more modern IT infrastructure mechanisms. That's why OPC UA over TSN is even twice as fast as the fastest Gigabit fieldbus protocol.
One last question: Is OPC UA over TSN really ready for the big time? There are voices saying that standardization is still a long way off.
Bruckner: OPC UA over TSN is completely specified and ready for use. The IEEE completed work on 802.1AS-2020 in December of 2019. That was the last important piece of the puzzle for OPC UA over TSN. And the IEEE 802.1Qbv standard – the linchpin for all matters involving TSN performance – was adopted way back in 2016. In March of 2020, B&R became the first manufacturer to sell controllers fluent in OPC UA over TSN.