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(computer science)
A protocol for interconnecting computers and peripheral devices in a local area network.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


A local area network first described by Metcalfe & Boggs of Xerox PARC in 1976. Specified by DEC, Intel and XEROX (DIX) as IEEE 802.3 and now recognised as the industry standard.

Data is broken into packets and each one is transmitted using the CSMA/CD algorithm until it arrives at the destination without colliding with any other packet. The first contention slot after a transmission is reserved for an acknowledge packet. A node is either transmitting or receiving at any instant. The bandwidth is about 10 Mbit/s. Disk-Ethernet-Disk transfer rate with TCP/IP is typically 30 kilobyte per second.

Version 2 specifies that collision detect of the transceiver must be activated during the inter-packet gap and that when transmission finishes, the differential transmit lines are driven to 0V (half step). It also specifies some network management functions such as reporting collisions, retries and deferrals.

Ethernet cables are classified as "XbaseY", e.g. 10base5, where X is the data rate in Mbps, "base" means "baseband" (as opposed to radio frequency) and Y is the category of cabling. The original cable was 10base5 ("full spec"), others are 10base2 ("thinnet") and 10baseT ("twisted pair") which is now (1998) very common. 100baseT ("Fast Ethernet") is also increasingly common.

Usenet newsgroup: news:comp.dcom.lans.ethernet.
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The network technology that connects computers to each other and to the Internet via cables. Defined as the 802.3 standard by the IEEE, the Ethernet access method is the global standard. Companies have hundreds and thousands of PCs wired together via Ethernet, and almost every reference to "local network," "LAN," and "network ready" is Ethernet. All new computers have Ethernet built in, and old machines can be retrofitted (see Ethernet adapter). See LAN.

Ethernet Is Wired - Wi-Fi Is Wireless
Wired Ethernet and wireless Wi-Fi exist together in virtually every home and office. Desktop computers may be wired, but phones and tablets need Wi-Fi, and a wireless router supports both. See Wi-Fi and wireless router.

10/100/1000 Gigabit Ethernet
All new routers and Ethernet switches are 10/100/1000 "Gigabit" devices because the top speed is 1000 megabits (1 Gb). Older networking hardware maxed out at 10 and 100 megabits. If device speeds are not equal, Ethernet uses the highest common speed between them. See Gigabit Ethernet.

Above one gigabit, Ethernets do not mix. There is no such thing as a 10/100/1000/10000 port (see 10 Gigabit Ethernet).

Ethernet and TCP/IP Are Global
TCP/IP prepares the data that Ethernet transmits. Together, they comprise the global local area network (LAN) standard and more (see 100 Gigabit Ethernet and automotive Ethernet). For network details, see Ethernet and TCP/IP.

Invented by Robert Metcalfe and David Boggs at Xerox PARC in 1973, Ethernet first ran at just under 3 Mbps. Metcalfe joined Digital Equipment Corporation where he facilitated a joint venture with Intel and Xerox to collaborate further, and Ethernet Version 1 was finalized in 1980. In 1983, the IEEE approved the Ethernet 802.3 standard. See 100Base-T, Ethernet adapter, Ethernet switch and automotive Ethernet.


 TWISTED PAIR (Metal Wires)

    10Base-T        328 ft/100 m
   100Base-T        328 ft/100 m
  1000Base-T        328 ft/100 m

  MM=multimode fiber  SM=singlemode

  FOIRL MM             .6 mi/1 km
   10Base-FL MM       1.2 mi/2 km
  100Base-FX MM       1.2 mi/2 km
  100Base-FX SM         6 mi/10 km

Ethernet Uses a Star Topology
All computers connect to a central switch that lets each sender/receiver pair transmit at full speed (10, 100 or 1000 Mbps). Spare telephone wires are sometimes used, but often at lower speeds. For earlier topologies, see 10Base5 and 10Base2. See Ethernet switch, cable categories and twisted pair.

Ethernet Switch
This Omnitron switch has 16 10/100 ports and, like all Ethernet switches, automatically adjusts to the highest common speed between sender and receiver.

Ethernet Is Everywhere
Inside a home theater rack, this NETGEAR Ethernet switch communicates with the Omnitron switch (above) some 60 feet away. Here it connects to the Fire TV, Apple TV and Roku 3 streaming boxes, plus an Oppo Blu-ray player.
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