Carrier-Sense Multiple Access with Collision Detection

In the Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) method, each computer on the network senses any signal passing on the cable. The computer can only transmit if the cable is free. If two or more computers send data at exactly the same time, it will result in data collision. When a collision occurs, the two computers involved stop transmitting and then attempt to re-transmit after a certain period of time. The collision detection method is only effective up to 2,500 meters.

With more traffic, collisions tend to increase, which slows down the network. So, CSMA/CD can be a slow access method.

Carrier-Sense Multiple Access with Collision Avoidance

In the Carrier-Sense Multiple Accesses with Collision Avoidance (CSMA/CA) method, each computer signals its intent to transmit before it actually transmits data. This way, the computer can avoid collisions. CSMA/CA is a slower access method and is less popular than CSMA/CD.