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Ethernet is the most widely-installed local area network (LAN) technology. Now specified in a standard, IEEE 802.3, Ethernet was originally developed by Xerox and then developed further by Xerox, DEC, and Intel. An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. The most commonly installed Ethernet systems are called 10BASE-T and provide transmission speeds up to 10 Mbps (megabits per second). (Faster ethernet technologies, such as 100BASE-T and Gigabit ethernet are also available now.) Devices are connected to the cable and compete for access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol.
CSMA/CD works like a dinner party in a dark room. Everyone around the table must listen for a period of quiet before speaking (Carrier Sense). Once a space occurs everyone has an equal chance to say something (Multiple Access). If two people start talking at the same instant they detect that fact and quit speaking (Collision Detection.) The CSMA/CD mechanism is invoked for every transmission on the network. The mechanism is designed to enforce fair access to the shared medium so that all stations get a chance to use the network.
Further Study:
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