Ethernet Definition

Ethernet is by far the most commonly used local area network (LAN) architecture.

A LAN is a network that connects computers and other devices in a relatively small area, typically a single building or a group of buildings.

Ethernet features high speeds, robustness (i.e., high reliability), low cost and adaptability to new technologies. These features have helped it maintain its popularity despite being one of the oldest of the LAN technologies.

A key feature of Ethernet is the breaking of data into packets, also referred to as frames, which are then transmitted using the CSMA/CD (carrier sense multiple access/collision detection) protocol until they arrive at the destination without colliding with any other packets.

The currently most commonly used form of Ethernet is 100Base-T, also referred to as fast Ethernet, which can accommodate data transfer speeds of up to about 100Mbps (million bits per second). The newer gigabit Ethernet supports data rates of one gigabit (1,000 megabits) per second.

Fiber Ethernet uses optical fiber cables to carry data. Optical fiber allows transmission over very long distances (over 2,000 meters), has a very large capacity and is completely immune to electrical interference. However, it is relatively expensive.

Wireless Ethernet transmits and data via a low-power microwave radios built into computers and other devices. It allows communication within a radius of approximately 100 meters.

Construction of an Ethernet network is relatively simple. For example, in the case of a basic, wired Ethernet, the hardware requirements include a network interface card (NIC) for each computer, a hub or switch, and some Cat 5 cables to connect the computers to the hub or switch. Expansion is also easy, and can be conducted by adding additional hubs and/or switches. The software is generally built into the operating system, so that all that is necessary is a few configuration steps, including assigning IP addresses for the network hosts.

Each node (i.e., computer, printer, hub, switch or other device) on the network has a hardware address, also called the MAC address. The address for any computer running an Unix-like operating system on an Ethernet can be found by using the ifconfig command with its -a option as follows:

/sbin/ifconfig -a

Ethernet was originally invented at the Xerox Palo Alto Research Center (PARC) in the early 1970s in order to interconnect that organization's innovative Alto desktop computers, and it was then further refined in cooperation with Digital Equipment Corporation (DEC) and Intel Corporation. It was named by Robert Metcalfe, one of its developers, after the passive substance called ether that was once thought to pervade the universe.

The word Ethernet is a trademark owned by Xerox Corporation. Consequently, it is typically written with an initial capital letter.

Other LAN architectures include token ring and FDDI (fiber distributed data interface).

Created October 7, 2005.
Copyright © 2005 The Linux Information Project. All Rights Reserved.