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Answering the Top 7 Questions About Profinet

We get a lot of questions here at PI North America from end users, distributors, system integrators, and device vendors. Here are our answers to the questions we get asked most.

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Isn’t Profinet a Siemens product?
No, Profinet isn’t ‘just Siemens,’ as many questioners ask. Yes, Siemens is a strong supporter and adopter of the Profinet technology. As are many other automation device vendors. Profinet is an open standard defined in the IEC and the technology is not owned by any single company. Development on the Profinet standard—along with all other technologies under the Profibus and Profinet International (PI) umbrella—is performed by working groups staffed by volunteers from many different companies.

Is Profinet a closed network?
Profinet is not a closed network. Profibus, as a serial fieldbus for example, was a closed network. By closing the network, Profibus was able to ensure determinism. Despite being an Ethernet-based protocol, the choice was made early-on to keep a Profinet network open. With the widespread adoption of Ethernet and now Industry 4.0, today we are able to appreciate what a wise decision that has become. Profinet utilizes standard unmodified Ethernet, meaning any Ethernet-based protocol can utilize the infrastructure. Inherent Profinet mechanisms ensure the determinism required for industrial automation.

Does Profinet require special hardware?
Since Profinet is based on standard unmodified Ethernet, no special cables or switches are required. However, using the same cables and switches built for office environments on a factory floor is a recipe for trouble. Profinet cabling is merely Ethernet cabling that is shielded and ruggedized against tough conditions. We recommend end users install managed, purpose-built switches in their networks. These offer ruggedized hardware and advanced features helpful to running and maintaining an industrial Ethernet network.

Isn’t Profinet very complicated?
If you have ever set up a Profibus network, then setting up a Profinet network is basically the same. If anything, it is likely easier than Profibus since you do not have to worry about network segmentation, signal repeaters, or termination resistors. Profinet is just Ethernet. With Profinet there are no dipswitches to set, you simply assign a name to the device you are installing. The controller assigns the IP address. Configuration and parameterization of devices proceeds as it always has.

Is it true that Profinet traffic is not routable?
It is true that most Profinet traffic is not routable. This is by design. Profinet utilizes UDP/IP and TCP/IP where it makes sense. And skips them where it doesn’t. Automation traffic is often little pieces of data. It is bits and bytes exchanged quickly and deterministically between controllers and devices. The use cases for routing these little pieces of data across the Internet are uncommon, if non-existant. There are other protocols better suited at moving information as such, for example OPC UA. Conversely, protocols with large packet sizes, and reliance on UDP/IP or TCP/IP, are not optimized for moving automation traffic deterministically on the factory floor. For installations that do require some basic routing in their Profinet networks, devices exist to seamlessly couple different subnets together.

Is Profinet secure?
That fact that most Profinet traffic is not routable is an inherent security measure. For a nefarious actor to manipulate Profinet traffic, they would need to do so from inside your network. If a hacker is already in your network, then you likely have bigger problems to worry about. Profinet Security Classes are in place to deal with aspects of authenticity, integrity, and confidentiality. End users can choose the level of security appropriate for their installation. In general, network security should be approached holistically with a defense-in-depth strategy.

Is Profinet ‘old’ technology?
Profinet is based on Ethernet, which was invented in the 1970s and has come a long way since then. It certainly seems like wireless is taking over as the primary way to move data in the consumer world, particularly with the upcoming versions of 5G cellular. While most Profinet installations utilize Ethernet, many also seamlessly employ Wi-Fi, Bluetooth, and, eventually, 5G. Ethernet works very well for its purpose and has improved along the way. This appears to be true for the future as well. Today, industrial Ethernet bandwidth can scale from 10 Mbps to 100 Mbps to 1 Gbps and beyond. Soon, Time-Sensitive Networking (TSN) stands to make Ethernet robust for even the most heavily loaded networks.

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