EtherNet/IP and OPC UA

It’s a crazy time for manufacturing communications. We have more technologies to work with than ever before. We have more places to send data than ever before. It’s hard for the average automation professional who’s just trying to keep machines running to know how to use all these technologies.

There’s a lot of confusion over EtherNet/IP and OPC UA. Some think UA will replace EtherNet/IP. Some think that OPC UA is a companion to EtherNet/IP. And some think that they don’t need OPC UA at all.

OPC UA is really a different kind of technology than EtherNet/IP, and I always cringe when I hear OPC UA compared to it, PROFINET IO, or Modbus TCP. That wasn’t the case when PROFINET IO came out. I could tell people that it was the equivalent of EtherNet/IP for Siemens controllers. Same kind of technology. Basically, the same kind of functionality. Easy to explain.

I can’t do that for OPC UA. I could say that it’s Web Services for automation systems. Or that it’s SOA for automation systems, an even more arcane term. SOA is “https://docs.microsoft.com/en-us/previous-versions/aa480021(v=msdn.10),” basically the same thing as Web Services. That’s fine if you’re an IT guy (or gal) and you understand those terms. You have some context.

But if you’re a plant floor person, it’s likely that even though you use Web Services (it’s the plumbing for the internet), you don’t know what that term means.

And it’s just as likely that if you’re a plant floor person, you also say, “Why do we need another protocol? Modbus TCP, EtherNet/IP and PROFINET IO work just fine.” The answer is that it’s not like EtherNet/IP, PROFINET IO or Modbus TCP. It’s a completely new paradigm for plant floor communications. It’s like trying to explain EtherNet/IP to a PLC programmer in 1982. With nothing to compare it to, it’s impossible to understand.

In the automation world, the PLC networking paradigm is second nature. You have a PLC; it is a master kind of device, and it moves data in and out of slave devices. It uses very simple, transaction-type messaging or some kind of connected messaging. In either case, there is this buffer of output data in a thing called a Programmable Controller. There is a buffer of input data in a bunch of devices called servers, slaves or nodes. The buffer of input data moves to the Programmable Controller. The output data buffers move from the Programmable Controller to the devices. Rinse. Repeat. Forever. Done.

OPC UA really lives outside that paradigm. Well, actually, that’s not true. OPC UA lives in parallel with that paradigm. It doesn’t replace it. It extends it. Adds on to it. Brings it new functionality and creates new use cases and drives new applications. In the end, it increases productivity, enhances quality and lowers costs by providing not only more data, but also information – and the right kind of information – to the production, maintenance and IT systems that need that information when they need it.

And that’s the stuff that EtherNet/IP PROFINET IO, Modbus TCP and all the rest just can’t do. OPC UA is a perfect complement to EtherNet/IP and these other technologies, it’s not a replacement for them.

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