What is Carrier Sense Multiple Access/Collision Detect (CSMA/CD)? - Definition from Whatis.com

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Carrier Sense Multiple Access/Collision Detect (CSMA/CD)

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Carrier Sense Multiple Access/Collision Detect (CSMA/CD)

Carrier Sense Multiple Access/Collision Detect (CSMA/CD) is the protocol for carrier transmission access in Ethernet networks. On Ethernet, any device can try to send a frame at any time. Each device senses whether the line is idle and therefore available to be used. If it is, the device begins to transmit its first frame. If another device has tried to send at the same time, a collision is said to occur and the frames are discarded. Each device then waits a random amount of time and retries until successful in getting its transmission sent.

CSMA/CD is specified in the IEEE 802.3 standard.

Related glossary terms: MDI/MDIX (medium dependent interface/MDI crossover), 802.3, Ethernet Glossary, Quad FastEthernet (QFE), 10BASE-2, coaxial cable (illustrated), Power over Ethernet (PoE), Ethernet point-of-presence (EPOP), DVMRP (Distance Vector Multicast Routing Protocol), 1000BASE-T

Contributor(s): Steinar Forshaug and Tom Wade

This was last updated in August 2000

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