networks//network protocols//Ethernet

The dominant wired link technology: frames between neighbors on a shared or switched medium, over copper or fiber. Ethernet is **not** an automation protocol; it is the layer many protocols ride on (protocol stack).

The dominant wired link technology: frames between neighbors on a shared or switched medium, over copper or fiber. Ethernet is not an automation protocol; it is the layer many protocols ride on (protocol stack).

On top of it travel TCP/IP and, on top of that, Modbus TCP, EtherNet/IP, PROFINET, OPC UA or MQTT. Saying a device "has Ethernet" says which connector it has, not what it can say.

From about 2000 Ethernet became dominant in factories too, but office Ethernet never prioritized low latency, low jitter, synchronization or fast recovery. The industrial variants that add those properties are a family of their own (industrial Ethernet), and the office switch and the plant switch are different products (industrial switch).

Many digital field devices have no Ethernet at all and speak serial buses instead (RS-485, CAN).