Why Industrial Networks Can’t Agree on Terms

Every industry has its own language. Meteorologists have haboobs (massive dust storms), horse racing has black type winners, and in France, cabbage can mean “sweetheart.” Industrial networking is no different, it’s filled with terms that mean wildly different things depending on whether you’re in IT or OT.

Let’s decode a few.

In the IT world, a Client requests something like a file, a web page or a transaction from a Server. The term dates back to IBM mainframes, where “terminal servers” connected simple terminals to a single giant computer.

Today’s cloud servers are infinitely more powerful, but the principle is the same: Servers store and serve; Clients connect and consume.

When networking hit the factory floor, the terms changed shape. Early systems like Modbus RTU used “master” and “slave.” The master requested data; the slave responded. That language may be fading, but those networks are still everywhere.

DeviceNet followed suit with its own spin, masters configure slaves and tell them what to publish and how often. When Modbus migrated to Ethernet (Modbus TCP), it adopted the Client/Server terms, aligning more closely with IT.

But here’s the twist: in manufacturing, the Server isn’t the big, powerful machine, it’s usually the tiny one. A valve block or motor drive might act as a Server, but it’s only serving a trickle of data to a Client (like a PLC) that’s actually running the logic.

Different technologies keep reinventing the dictionary:

• PROFINET uses Controllers and Devices.
• BACnet mixes Master/Slave and Client/Server.
• SNMP calls the Client a Manager and the Server an Agent.
• EtherNet/IP ditched IT jargon entirely, introducing Scanners (the ones who connect) and Adapters (the ones who respond).

Because manufacturing and IT evolved separately, and neither likes changing their vocabulary. The result: confusion, integration headaches and extra cost as engineers translate one dialect to another.

The bottom line? Whether it’s called a Client, Master, Controller or Scanner, it’s still just one device asking another for data. The names may differ, but the handshake remains the same.

And just like calling your sweetheart “cabbage,” it only makes sense if you speak the same language.