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(computer science)
A protocol for interconnecting computers and peripheral devices in a local area network.


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.


The most widely used local area network (LAN) technology. Defined as the 802.3 standard by the IEEE, the Ethernet access method is used to connect computers in a company or home network as well as to connect a single computer to a modem for Internet access. All new computers have Ethernet built in, and old machines can be retrofitted (see Ethernet adapter). Almost every reference to "network ready," "LAN" or "LAN connection" implies Ethernet. See LAN.

Ethernet Is Wired - Wi-Fi Is Wireless
Ethernet uses cables to connect computers; Wi-Fi is its wireless counterpart, and both technologies are used together. See Wi-Fi and wireless router.

10/100 and 10/100/1000
A 10/100 Ethernet port transmits 10 and 100 Mbps, while the maximum speed of a 10/100/1000 "Gigabit" port is 1 Gbps. Ethernet uses the highest common speed between sending and receiving devices. Although wide area networks (WANs) may employ 10 Gigabit Ethernet (10 Gbps), there is no such thing as a single 10/100/1000/10000 port that supports all four speeds (see Gigabit Ethernet and 10 Gigabit Ethernet).

Ethernet and TCP/IP Protocols
Ethernet and TCP/IP work together and comprise the primary communications protocols in a local area network. For 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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