Ethernet

Ethernet is a large and diverse family of frame-based computer networking technologies for local area networks (LANs). The name comes from the physical concept of the ether. more...

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It defines a number of wiring and signaling standards for the physical layer, two means of network access at the Media Access Control (MAC)/Data Link Layer, and a common addressing format.

Ethernet has been standardized as IEEE 802.3. Its star-topology, twisted pair wiring form became the most widespread LAN technology in use from the 1990s to the present, largely replacing competing LAN standards such as coaxial cable Ethernet, token ring, FDDI, and ARCNET. In recent years, Wi-Fi, the wireless LAN standardized by IEEE 802.11, has been used in addition to or instead of Ethernet in many installations.

History

Ethernet was originally developed as one of the many pioneering projects at Xerox PARC. Ethernet was invented in the period of 1973–1975. Robert Metcalfe and David Boggs wrote and presented their "Draft Ethernet Overview" some time before March 1974. In March 1974, R. Z. Bachrach wrote a memo to Metcalf, Boggs, and their management, stating that "technically or conceptually there is nothing new in your proposal" and that "analysis would show that your system would be a failure." In 1975, Xerox filed a patent application listing Metcalf and Boggs, plus Chuck Thacker and Butler Lampson, as inventors (US4063220: Multipoint data communication system with collision detection). In 1976, after the system was deployed at PARC, Metcalfe and Boggs published a paper titled Ethernet: Distributed Packet-Switching For Local Computer Networks.

The experimental Ethernet described in that paper ran at 3 Mbit/s, and had 8-bit destination and source address fields, so Ethernet addresses were not the global 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 standardized the 10 megabits/second Ethernet, with 48-bit destination and source addresses and a global 16-bit type field. The standard was first published on September 30, 1980. It competed with two largely proprietary systems, token ring and ARCNET, but those soon found themselves buried under a tidal wave of Ethernet products. In the process, 3Com became a major company.

Read more at Wikipedia.org