Acronym for Carrier Sense Multiple Access / Collision Detection

A set of rules determining how network devices respond when two devices attempt to use a data channel simultaneously (called a collision). Standard Ethernet networks use CSMA/CD. This standard enables devices to detect a collision. After detecting a collision, a device waits a random delay time and then attempts to re-transmit the message. If the device detects a collision again, it waits randomly (up to twice as long as the previous attempt) to try to re-transmit the message. This is known as exponential back off.

Some manufacturers don't (or didn't in the past) use exponential back off, so that in a mixed environment their cards would perform better (as measured by throughput). This however means that if you had a network of only their cards, as the network load goes up the network performance deteriorates quickly. Smart thinking...

CSMA/CD is a type of ContentionProtocol.

see also CSMA/CA