networks//network protocols//Ethernet

Ethernet is the dominant wired link technology, carrying frames between neighbors on a shared or switched medium over copper or fiber. It is the layer many protocols ride on, and no automation protocol in itself (protocol stack).

Ethernet is the dominant wired link technology, carrying frames between neighbors on a shared or switched medium over copper or fiber. It is the layer many protocols ride on, and no automation protocol in itself (protocol stack).

On top of it travel TCP/IP and, on top of that, Modbus TCP, EtherNet/IP, PROFINET, OPC UA or MQTT. A device that has Ethernet tells which connector it has and nothing about 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).

A MAC address names a network interface on the local link and is used by switches; an IP address names a host across networks and is used by routers. Neither says anything about the device inside: a Modbus unit identifier or a PROFINET device name is yet another address, at the application layer.

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