Hi. Firstly I realise this may be classified as a homework question, so please move it if necessary. Problem For a lab using PLCs, I'm supposed to answer this question: What is the difference between Ethernet, Profibus and Profinet? My attempt This is for a control subject, but due to my course structure I may not have done the subjects that contain the prerequisite knowledge. I have searched the web for over 3 hours for information, using anything from Wikipedia to FAQs of Siemens. This is what I have got so far: Ethernet: a computer networking technology that was originated designed for office use. It features a star topology and uses twisted pair wiring. In industrial automation, it is typically used for communication between PLCs and HMIs. Profinet: an open standard for industrial Ethernet with adaptations for improved real-time applications. It can directly connect PLCs and IO devices. Profibus: a fieldbus system for real-time distributed control. It is used for process and field communication in cell networks with few stations and for data communication. It connects PLCs, sensors, actuators and other automation devices. Further help required Well, I'm just not happy with what I've got. My explanations of Profinet and Profibus seem almost the same, and neither mention physical differences with Ethernet (such as wiring form, performance parameters and whatever that's applicable). I've also found some contradictions between sites, with some saying that Profinet is Profibus on Ethernet (which I don't really understand), and others saying that Profinet is a total revolution from Ethernet and so on. If anyone can fill in the gaps, correct my mistakes and/or give me pointers on where I can find more detailed and reliable information, I would be very grateful.