They will play an important role in Industry 4.0. Don’t say you don’t understand OPC UA and TSN.

To clarify the role of OPC UA, here is a quote from Stefan Hoppe, Vice President of the OPC Foundation: "OPC UA is not a protocol, but an information model." What he means is that OPC UA is first and foremost an information model. Of course, it is also a protocol for connecting clients and servers, but the strength of OPC UA is the address space, which is what makes OPC UA a universal application interface. OPC UA is very flexible and allows existing user interfaces (profiles of industrial Ethernet protocols) to be mapped to OPC UA. Therefore, almost every profile in the industrial Ethernet protocol now has a representation in the OPC UA address space or is being developed to achieve its representation. OPC UA has not yet specified these profiles (I/O, drives, safety, etc.), but this will most likely change. In the framework of Industry 4.0, OPC UA is seen as a very promising universal language for the future.

In contrast, TSN is an extension of IEEE-802.1 Ethernet with a whole host of new capabilities designed to make Ethernet more deterministic and real-time. Because many manufacturers are expected to produce TSN-enabled hardware in the future, it can also be seen as the democratization of real-time communications. Almost every protocol can gain real-time capabilities through TSN.

In this context, a pub/sub working group was established with the aim of specifying a real-time transport protocol for OPC UA with the help of TSN. This will make OPC UA real-time capable and thus an alternative to the Industrial Ethernet protocol. It will be welcomed above the traditional PLC level, as controllers from different manufacturers will be able to interact with OPC UA in real time. TSN will also provide OPC UA with guaranteed network bandwidth, so its robustness will be higher than what is currently possible.

However, pub/sub is not the only way to make OPC UA real-time capable. The industry is also working to develop an OPC UA model for DDS, a widely used and proven real-time protocol. This will enable the operation of distributed systems with DDS/TSN capabilities and use OPC UA as an application interface.

What the outcome will be remains to be seen.

Traditional Industrial Ethernet protocols are not going away. Some will still exist in different forms in the future (as profiles or profile families in OPC UA), and some will be based on TSN. Traditional fieldbuses will be replaced by Ethernet.

Once again, it is important to clarify that TSN does not automatically enable OPC UA. They are two completely separate technologies. OPC UA can play an important role in controller networks (controller to controller). Pub/sub with TSN is very strong here; whether it can also play a role at the field level remains to be proven, because OPC UA is not a small stack, at least not if you want to use all its advantages.

All user organizations are responding to the opportunities that TSN brings. TSN promises to provide more hardware choices, especially for infrastructure components, and to achieve higher speeds, i.e. 1 Gbps or more. Eventually, we will see Profinet® TSN, as well as EtherNet/IP® over TSN and OPC UA Pub/Sub.

At 100 Mbps, to get cycle times below 250μs, existing industrial Ethernet protocols would have to make significant modifications to standard Ethernet. The IEEE has not been very friendly to non-standard approaches such as EtherCAT® or even the lumped frame protocol on which Sercos is based. It is unlikely that these extensions will be included in the TSN standard.

For this problem, TSN will reach the limit defined by the IEEE, which is 250 μs at 100 Mbps - at least as long as true parallel operation of standard TCP/IP applications must be effective. If even shorter cycle times are required, the path to 1 Gbps is open.

Security generally uses the Black channel principle. Security is defined above the actual communication protocol. However, the reliability of the communication channel is one of the security considerations. TSN will not be less reliable than today's systems.

TSN adds determinism and real-time capabilities to standard Ethernet. In many cases, different protocols coexist in the same cable. TSN supports the robust coexistence of real-time and best-effort TCP/IP in one cable.

TSN is not a new Industrial Ethernet protocol. It is a unified extension of standard Ethernet with added real-time capabilities. We have already explained its advantages: hardware availability, unified infrastructure, and speed-independent definition.

Scalable, standardized hardware and infrastructure promises to reduce costs and unify technical know-how.

1 Gbps (and beyond) is a logical progression for today’s networks. Will it replace 100 Mbps? Not completely, but 1 Gbps enables new applications and can overcome performance bottlenecks for today’s data-intensive applications. TSN is not a new Industrial Ethernet protocol, but a unified extension to standard Ethernet that adds real-time capabilities.