Last edited 04 Aug 2023


Ethernet is a standard for the technologies that make up a wired local area network (LAN). It was first developed in the 1970’s by Robert Metcalfe at Xerox and went on to be developed by Xerox, DEC, and Intel. It was standardised by the Institute of Electrical and Electronic Engineers (IEEE) as IEEE 802.3 in 1983.

Ethernet was originally conceived as a way of enabling computers to communicate over a shared cable. Ethernet originally used coaxial cable, but now commonly uses twisted-pair copper cable such as CAT5 or fibre optic cable.

The simplest Ethernet connects a number of devices on a single cable. Streams of data that are transmitted between devices are divided into ‘frames’ with a source and destination address. If more than one device is transmitting at the same time, and frames ‘collide’ and are corrupted, then they are re-transmitted. More complex variations allow devices to run with much reduced corruption, and full duplex modes allow devices to communicate simultaneously without ‘collision’.

Ethernet is now the most widely used standard for local area networks (LAN). Local area networks are networks used to connect a number of devices together that are located within a relatively small area, typically within a single building. This is as opposed to wide area networks (WAN) which are used to connect devices on a dedicated line across a large distance, such as across a city.

NB Guide to Controls (BG 83/2023) written by John Marrow and published by BSRIA in June 2023, states: ' Ethernet is a data transmission protocol, although is commonly referred to as a type of physical network structure or topology. In building IT networks, this often provides a backbone for all network devices to be connected to. Ethernet networks are usually described as either local operating networks (LANs), for example a small office of networked computers and servers, or wide area networks (WANs) consisting of groups of local area networks spread over a larger area or distance.'

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