Ethernet

Ethernet

Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). The name came from the physical concept of theether. It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model as well as a common addressing format and Media Access Control at the Data Link Layer.

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 used from around 1980^[1] to the present, largely replacing competing LAN standards such as token ring, FDDI, and ARCNET.

Ethernet was developed at Xerox PARC between 1973 and 1975.^[2] It was inspired by ALOHAnet, which Robert Metcalfe had studied as part of his Ph.D. dissertation.^[3] In 1975, Xerox filed a patent application listing Metcalfe, David Boggs, Chuck Thacker and Butler Lampson as inventors.^[4] In 1976, after the system was deployed at PARC, Metcalfe and Boggs published a seminal paper.^{[5][note 1]}

Metcalfe left Xerox in 1979 to promote the use of personal computers and local area networks (LANs), forming 3Com. He convinced Digital Equipment Corporation (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 Ethertype-type field. The first standard draft was first published on September 30, 1980 by the Institute of Electrical and Electronics Engineers (IEEE).^{[citation needed]} Support of Ethernet's carrier sense multiple access with collision detection (CSMA/CD) in other standardization bodies (i.e., ECMA, IEC, and ISO) was instrumental in getting past delays of the finalization of the Ethernet standard due to the difficult decision processes in the IEEE, and due to the competitive Token Ring proposal strongly supported by IBM.^{[citation needed]} Ethernet initially competed with two largely proprietary systems, Token Ring and Token Bus. These proprietary systems soon found themselves inundated by Ethernet products. In the process, 3Com became a major company. 3Com built the first 10 Mbit/s Ethernet adapter (1981).^{[citation needed]} This was followed quickly by DEC's Unibus to Ethernet adapter, which DEC sold and used internally to build its own corporate network, which reached over 10,000 nodes by 1986; far and away the largest extant computer network in the world at that time.^[6]

Through the first half of the 1980s, DEC's Ethernet implementation utilized a coaxial cable about the diameter of a US nickel, which became known as Thick Ethernet when its successor, ThinnetEthernet was introduced. Thinnet uses a cable similar to cable television cable of the era. The emphasis was on making installation of the cable easier and less costly.

The observation that there was plenty of excess capacity in unused unshielded twisted pair (UTP) telephone wiring already installed in commercial buildings provided another opportunity to expand the installed base, and, thus, twisted-pair Ethernet was the next logical development in the mid-1980s, beginning with StarLAN. UTP-based Ethernet became widely known with 10BASE-T standard. This system replaced the coaxial cable systems with a system of hubs linked via UTP.

In 1990, Kalpana introduced the first Ethernet switch,^[7] which replaced the CSMA/CD scheme in favor of a switched full duplex system offering higher performance and at a lower cost than usingrouters.