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Ethernet is the most widely used local area network (LAN) technology. The original and most popular version of Ethernet supports a data transmission rate of 10 Mb/s. Newer versions of Ethernet called "Fast Ethernet" and "Gigabit Ethernet" support data rates of 100 Mb/s and 1 Gb/s (1000 Mb/s). An Ethernet LAN may use coaxial cable, special grades of twisted pair wiring, or fiber optic cable. "Bus" and "Star" wiring configurations are supported. Ethernet devices compete for access to the network using a protocol called Carrier Sense Multiple Access with Collision Detection (CSMA/CD).
In 1979, Digital Equipment Corporation (DEC), Intel, and Xerox joined for the purpose of standardizing an Ethernet system that any company could use. In September 1980 the three companies released Version 1.0 of the first Ethernet specification called the "Ethernet Blue Book", or "DIX standard" (after the initials of the three companies). It defined the "thick" Ethernet system (10Base5), based on a 10 Mb/s CSMA/CD (Carrier Sense Multiple Access with Collision Detection) protocol. It is known as "thick" Ethernet because of the thick coaxial cable used to connect devices on the network. The first Ethernet controller boards based on the DIX standard became available about 1982. The second and final version of the DIX standard, Version 2.0, was released in November 1982.
In 1983, the Institute of Electrical and Electronic Engineers (IEEE) released the first IEEE standard for Ethernet technology. It was developed by the 802.3 Working Group of the IEEE 802 Committee. The formal title of the standard was IEEE 802.3 Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications. IEEE reworked some portions of the DIX standard, especially in the area of the frame format definition. However the 802.3 standard was defined in a manner that permitted hardware based on the two standards to interoperate on the same Ethernet LAN.
In 1985, IEEE 802.3a defined a second version of Ethernet called "thin" Ethernet, "cheapernet", or 10Base2. It used a thinner, cheaper coaxial cable that simplified the cabling of the network. Although both the thick and thin systems provided a network with excellent performance, they utilized a bus topology which made implementing changes in the network difficult, and also left much to be desired in regard to reliability. Also released in 1985 was the IEEE 802.3b 10Broad36 standard that defined transmission of 10 Mb/s Ethernet over a "broadband" cable system.
In 1987, two standards were released. The IEEE 802.3d standard defined the Fiber Optic Inter-Repeater Link (FOIRL) that used two fiber optic cables to extend the maximum distance between 10 Mb/s Ethernet repeaters to 1000 meters. IEEE 802.3e defined a "1 Mb/s" Ethernet standard based on twisted pair wiring. This 1 Mb/s standard was never widely used.
In 1990, a major advance in Ethernet standards came with introduction of the IEEE 802.3i 10Base-T standard. It permitted 10 Mb/s Ethernet to operate over simple Category 3 Unshielded Twisted Pair (UTP) cable. The widespread use of UTP cabling in existing buildings created a high demand for 10Base-T technology. 10Base-T also permitted the network to be wired in a "star" topology that made it much easier to install, manage, and troubleshoot. These advantages led to a vast expansion in the use of Ethernet.
In 1993, the IEEE 802.3j standard for 10Base-F (FP, FB, & FL) was released which permitted attachment over longer distances (2000 meters) via two fiber optic cables. This standard updated and expanded the earlier FOIRL standard.
In 1995, IEEE improved the performance of Ethernet technology by a factor of 10 when it released the 100 Mb/s 802.3u 100Base-T standard. This version of Ethernet is commonly known as "Fast Ethernet". Three media types were supported: 1) 100Base-TX operates over two pair of category 5 twisted pair cable, 2) 100Base-T4 operates over four pair of category 3 twisted pair cable, and 3) 100Base-FX operates over two multi-mode fibers.
In 1997, the IEEE 802.3x standard became available which defined "full-duplex" Ethernet operation. Full-Duplex Ethernet bypasses the normal CSMA/CD protocol to allow two stations to communicate over a point to point link. It effectively doubles the transfer rate by allowing each station to concurrently transmit and receive separate data streams. For example, a 10 Mb/s full-duplex Ethernet station can transmit one 10 Mb/s stream at the same time it receives a separate 10 Mb/s stream. This provides an overall data transfer rate of 20 Mb/s. The full-duplex protocol extends to 100 Mb/s Ethernet and beyond. Also released in 1997 was the IEEE 802.3y 100Base-T2 standard for 100 Mb/s operation over two pairs of Category 3 balanced cabling.
In 1998, IEEE once again improved the performance of Ethernet technology by a factor of 10 when it released the 1 Gb/s 802.3z 1000Base-X standard. This version of Ethernet is commonly known as "Gigabit Ethernet". Three media types are supported: 1) 1000Base-SX operates with a 850nm laser over multi-mode fiber, 2) 1000Base-LX operates with a 1300nm laser over single and multi-mode fiber, and 3) 1000Base-CX operates over short haul copper "twinax" shielded twisted pair (STP) cable. Also released in 1998 was the IEEE 802.3ac standard that defines extensions to support Virtual LAN (VLAN) tagging on Ethernet networks.
In 1999, the release of the 802.3ab 1000Base-T standard defined 1 Gb/s operation over four pairs of category 5 UTP cabling.
The current IEEE 802.3 standards may be ordered from the following web address: http://standards.ieee.org/catalog/IEEE802.3.html. The following standards were available as of March 1999:
IEEE has formed an 802.3ad Working Group to develop a new standard regarding "Link Aggregation" or "Trunking". A draft of this standard is expected in 1999. Refer to the 802.3ad web page for the current status of this standard.
IEEE has formed a study group to explore 10 Gb/s Ethernet. Refer to the 802.3 Higher Speed Study Group web page for the information on this activity.
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