TSN – turbo power for PROFINET and OPC UA

Time-Sensitive Networking – Straight talk: Our commitment to digitalization

Digitalization sets a high standard for industrial communication. Siemens is already relying on the rapidly growing open-communication standard Industrial Ethernet – with PROFINET at the field level and OPC UA at the control level. But Siemens is taking it one step further: with the Ethernet-based standard TSN (Time-Sensitive Networking) for reserved bandwidths, Quality of Service (QoS) mechanisms, low transmission latency, and parallel transmission of multiple protocols – including real-time-capable ones – in industrial networks.

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Matthias Gärtner
TSN FAQ 9 I Matthias Gärtner, product manager for the Digital Factory, Factory Automation, Siemens

"PROFINET over TSN" specification is complete


PROFINET specification 2.4 has been completed and can be downloaded by all PI members. This specification includes Time-Sensitive Networking (TSN) capabilities in the PROFINET standard for the first time. The publication was possible alongside the approval of PROFINET specification 2.4 by the PI. Naturally, specification 2.4 also includes all the details on PROFINET which are separate from TSN – as usual, PROFINET will remain fully compatible with all previous versions.

Experience gained from the use of PROFINET in the field as well as from the joint standardization activity from IEC/IEEE 60802 (converged TSN network) will be incorporated step by step. 
 

Find more information on the PI website.
 

(More FAQs about TSN will follow. The already published FAQs can be found in the "What is TSN" section further down the page.)

What is Time-Sensitive Networking (TSN)?

Straight talk on the path to the future: PROFINET and OPC UA over TSN.

Increasing digitalization of production processes requires more and more openness, robustness, determinism, and flexibility in industrial communication. Only production that communicates and responds extremely agilely can ensure the fast and reliable manufacturing of individual products while also meeting tight delivery schedules.

Straight talk for a giant step toward digitalization

While industrial control systems are dependent on real-time communication, IT systems rely primarily on open access to data. That’s why companies operate these networks separately. In the face of increasing digitalization, this separation must now be replaced by open, end-to-end networking that permits flexible, deterministic production. TSN (Time-Sensitive Networking) creates a standardized basic technology within the framework of IEEE 802.1 for guaranteed Quality of Service (QoS) and increased demands in the Ethernet. TSN comprises a series of individual standards that exclusively pertains to the OSI layer 2 of communication. This means that the user interface remains unchanged even with TSN.

 

From the automotive industry and machine-building to the food and beverage industry: TSN offers decisive advantages for industrial production, including reserved bandwidths, Quality of Service (QoS) mechanisms, low transmission latency, and parallel transmission of multiple protocols – including real-time ones. Siemens will be relying on TSN to help shape the digital transformation of industrial networks – from the field level and machine-to-machine (M2M) communication to the control and operator levels.

Driving development together

TSN has already gotten off to a promising start. As part of its ongoing development, it’s being tested at Labs Network Industrie 4.0 (LNI4.0). LNI4.0 is connecting testing environments and installations throughout Germany to further the advance of Industrie 4.0, and Siemens is one of the founding members. Along with a number of other industrial enterprises, the company is doing everything it can to test TSN interoperability with multiple vendors, and is conducting research in the test bed to assess the potential of TSN for M2M communication and machine networking all the way to the cloud. The knowledge obtained will be made available to standardization committees as needed for use in future development.

Frequently asked questions about Time-Sensitive Networking (TSN)

TSN stands for time-sensitive networking. It is a set of different standards for transmitting data in Ethernet networks. These standards are currently being defined by the standardization organization for Ethernet-based communication IEEE 802.1.
TSN also consists of a series of individual standards that mainly expand the data link layer (Layer 2 of the ISO-OSI model) of the communication system. TSN is thus not a complete communication protocol but rather a basic technology that can be used by higher-level applications. Higher protocols, such as PROFINET and OPC UA, are found on Layers 5 through 7 of the ISO-OSI model and remain unchanged.

Basically, Ethernet with TSN supplements the existing Ethernet mechanisms in the areas of Quality of Service (QoS), including bandwidth reservation, as well as synchronization, low latencies, and even seamless redundancy.

 

The applications signal their communication requirements on the network and are guaranteed the requested QoS from the network. The various connections run in streams that enjoy bandwidth protection thanks to resource allocation in the memories of Ethernet switches. Basically, each of these streams can be given a real-time capability. As a result of these encapsulated streams, TSN also makes it possible to run multiple real time-capable protocols simultaneously in a single network (network convergence). This is fundamentally different from today’s Ethernet-based real-time protocols, such as PROFINET, where the network only allows PROFINET as the only real-time capable protocol (besides TCP/IP based traffic).

No.
PROFINET runs on Layer 7 (application layer) in the ISO-OSI model and provides mechanisms for configuring and diagnosing components independently of the physical transport layer (Layer 2). PROFINET has been based on IEEE standards from the very beginning. Since TSN is also standardized within IEEE, this expands PROFINET’s capabilities within a TSN network on Layer 2.

 

PROFINET offers services that are necessary for automation, such as cyclical and acyclical data, alarms/diagnoses, parameterization, etc. IEEE mechanisms such as TSN alone cannot replace these services.
TSN is therefore not in competition with PROFINET but rather describes basic IEEE mechanisms that can use communication protocols such as PROFINET or OPC UA.

 

Of course, the RT and IRT mechanisms will remain part of the PROFINET specification and benefit from PROFINET innovations.

 

By the way, PROFINET over TSN addresses not only the IRT applications (clock-synchronous motion control applications) but also the range of applications addressed with RT.

In a "convergent network" data from various applications can be transferred simultaneously across a single line.

 

This way, real-time data can be transmitted in parallel using OPC UA over TSN, cloud data based on MQTT, video data and other industrial real-time capable protocols such as PROFINET over TSN.

A "TSN-capable" hardware block is needed for TSN; the currently installed Ethernet blocks generally cannot be expanded by software to include TSN functionality.

 

It is foreseeable, however, that the "standard Ethernet block" will be a TSN-capable Ethernet block in the future. That is the main motivating factor for Siemens to put PROFINET on TSN. All of the major block manufacturers have already begun to develop, or have at least announced that they will develop hardware blocks with TSN mechanisms. For device manufacturers, this results in many possibilities for the various hardware designs of their devices.

As a communication technology, TSN supports only the subordinate Layer 2 mechanisms. In addition to this, protocols such as PROFINET and OPC UA are also needed to reliably exchange user data. These protocols handle, for example, transport security.

OPC Unified Architecture (OPC UA)  is the data exchange standard for secure, reliable, manufacturer- and platform-independent industrial communication. It ensures the exchange of data between products of different manufacturers across operating systems.

OPC UA’s strength is based on a powerful, object-oriented information model that can be browsed remotely as well as on a service-oriented architecture (SoA) by providing a wide range of different services, such as data access, alarms and conditions, methods, Historian, etc. It is therefore far more than “just” a protocol and is highly suitable for exchanging data between applications of many different manufacturers in automation engineering. OPC was defined for vertical communication and not for IO communication.

OPC UA is THE industrial interoperability standard and offers many benefits for industry, such as:

  • Platform independence – from embedded microcontrollers to cloud-based infrastructure
  • Integrated security – encryption, authentication, and monitoring
  • Comprehensive information modeling – definition of complex information (like companion specs such as PackML)
  • Functional security – based on proven PROFIsafe mechanisms

Yes, because OPC UA has its strengths in vertical communication and networking of machines at control level, while PROFINET meets all requirements in the field. That's why the strategy at Siemens stays the same:

  • Control level and above = OPC UA, also possible with Safety
  • Field level = PROFINET

The original OPC was based on the Microsoft Windows mechanism OLE (Object Linking and Embedding) with DCOM.

 

OPC UA (Unified Architecture) was developed for use across platforms, independently of Windows. It is based on Standard Ethernet mechanisms.

OPC UA originated in vertical communication and is now becoming established in the market for M2M communication as well.  

 

The need for real-time communication on the controller level should essentially be limited to controller-to-controller communication. For technical reasons, only the OPC UA PubSub method can be combined with TSN. Client/server accesses naturally also run via the Ethernet-based network with TSN mechanisms (a so-called TSN network), but, since they are TCP/IP-based, cannot be mapped in real-time capable and bandwidth-protected streams.

PROFINET’s strengths are on the field level. Over the medium term, PROFINET will also be mapped to the TSN mechanisms, making it 100% IEEE-compliant, even in clock-synchronous applications.

The upcoming IEC/IEEE 60802 standard is a project of IEC SC65C/MT9 and IEEE 802, so experts from standard Ethernet and the application protocols above work closely together. This standard will define a TSN profile for industrial automation in which certain functions, configuration models with the associated protocols and options can be selected from a wide range of options. This is the only way to achieve a convergent network, i.e. different protocols use the same network.

 

In future, all components for setting up a TSN network must be standardized according to IEC/IEEE 60802 (TSN-IA). The specification is based on corresponding use cases, a first official version is expected in 2022.

Watch the video on TSN real-time communication on YouTube:

Watch video: PROFINET over TSN

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TSN in practice

Straight talk on the path to TSN: PROFINET and OPC UA

TSN unites existing IEEE standards that exclusively affect OSI communication layer 2. TSN isn’t a communication protocol; rather, it’s a basic technology that can be used in the coming years by both PROFINET and OPC UA as a kind of “turbo power.”

A sample model from the discrete industries

When machines communicate via TSN – Siemens demonstrates how it works

How might M2M communication with TSN look like in practice? Going beyond the theoretical, Siemens already has a trade show model that demonstrates this in practice using two robots with synchronized movements. Each of the robots communicates with a SIMATIC controller via PROFINET. Both controllers are synchronized via OPC UA PubSub (publish/subscribe) over TSN. Thanks to bandwidth reservation, data transmission in the TSN network is precisely predictable, independent of load.

 

To demonstrate how TSN communication and standard Ethernet communication can be used in the same network, data in the model is also transmitted from the controller to a cloud – like MindSphere – via a communication processor.

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Straight talk: Let us advise you on TSN

The development of industrial networks never stands still. What is Siemens doing with TSN? How will you and the top-two technologies OPC UA and PROFINET benefit from Time-Sensitive Networking? And how can you optimize your network with TSN? Our experts are happy to answer these questions and many more.

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