Ethernet | Electronics Seminar Topic
Ethernet
Ethernet is a family of frame-based computer networking
technologies for local area networks (LANs). The name comes from the physical
concept of the ether. It defines a number of wiring and signaling standards for
the Physical Layer of the OSI networking model, through means of network access
at the Media Access Control protocol (a sub-layer of Data Link Layer), and a
common addressing format.
Ethernet is standardized as IEEE 802.3. The combination of
the twisted pair versions of Ethernet for connecting end systems to the
network, along with the fiber optic versions for site backbones, is the most
widespread wired LAN technology. It has been in use from around 1980[1] to the
present, largely replacing competing LAN standards such as token ring, FDDI,
and ARCNET
destination and source address fields specified a
"packet type", but, as the paper says, "different protocols use
disjoint sets of packet types". Thus the original packet types could vary
within each different protocol, rather than the packet type in the current
Ethernet standard 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 specified the 10
megabits/second Ethernet, with 48-bit destination and source addresses and a
global 16-bit type field.
The first standard draft was first published on
September 30, 1980 by the Institute of Electrical and Electronics Engineers
(IEEE). It competed with two largely proprietary systems, Token Ring and Token
Bus. To get over delays of the finalization of the Ethernet "Carrier sense
multiple access with collision detection" (CSMA/CD) standard due to the
difficult decision processes in the "open" IEEE, and due to the
competitive Token Ring proposal strongly supported by IBM, support of CSMA/CD
in other standardization bodies
(i.e. ECMA, IEC and ISO) was instrumental to its success.
The proprietary systems soon found themselves buried under a tidal wave of
Ethernet products. In the process, 3Com became a major company. 3COM built the
first 10 Mbit/s Ethernet adapter (1981). This was followed quickly by DEC's
Unibus to Ethernet adapter, which DEC sold and used internally to build its own
corporate network, reaching over 10,000 nodes by 1986, far and away the largest
then extant computer network in the world.
