Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). The name comes from the physical concept of the ether. It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model, through means of network access at the Media Access Control (MAC) /Data Link Layer, and a common addressing format.

Ethernet is standardized as IEEE 802.3. The combination of the twisted pair versions of Ethernet for connecting end systems to the network, along with the fiber optic versions for site backbones, is the most widespread wired LAN technology. It has been in use from around 1980 to the present, largely replacing competing LAN standards such as token ring, FDDI, and ARCNET.

History

Ethernet was originally developed at Xerox PARC in 1973–1975. In 1975, Xerox filed a patent application listing Robert Metcalfe, David Boggs, Chuck Thacker and Butler Lampson as inventors ( : Multipoint data communication system (with collision detection)). In 1976, after the system was deployed at PARC, Metcalfe and Boggs published a seminal paper.''

The experimental Ethernet described in that paper ran at 3 Mbit/s, and had 8-bit destination and source address fields, so the original Ethernet addresses were not the MAC addresses they are today. By software convention, the 16 bits after the destination and source address fields were a packet type field, but, as the paper says, "different protocols use disjoint sets of packet types", so those were packet types within a given protocol, rather than the packet type in current Ethernet which specifies the protocol being used.

Metcalfe left Xerox in 1979 to promote the use of personal computers and local area networks (LANs), forming 3Com. He convinced DEC, Intel, and Xerox to work together to promote Ethernet as a standard, the so-called "DIX" standard, for "Digital/Intel/Xerox"; it specified the 10 megabits/second Ethernet, with 48-bit destination and source addresses and a global 16-bit type field. The first standard draft was first published on September 30 1980 within IEEE. It competed with two largely proprietary systems, Token Ring and Token Bus. To get over delays of the finalization of the Ethernet CSMA/CD standard due to the difficult decision processes in the "open" IEEE and due to the competitive Token Ring proposal strongly supported by IBM, support of CSMA/CD in other standardization bodies, i.e. ECMA, IEC and ISO was instrumental for its success. Proprietary systems soon found themselves buried under a tidal wave of Ethernet products. In the process, 3Com became a major company. 3COM built the first 10 Mbit/s Ethernet adapter (1983), followed quickly by Digital Equipment's Unibus to Ethernet adapter.

Twisted-pair Ethernet systems have been developed since the mid-80s, beginning with StarLAN, but becoming widely known with 10BASE-T. These systems replaced the coaxial cable on which early Ethernets were deployed with a system of hubs linked with unshielded twisted pair (UTP), ultimately replacing the CSMA/CD scheme in favor of a switched full duplex system offering higher performance.