CSMA/CD is a media access control (MAC) method designed to control the number of collisions that occur on a network. In its most simple form it operates as follows:
1. A station that wishes to transmit on the network checks to see if the cable is free.
2. If the cable is free, the station starts transmitting.
3. However, another station may have detected a free cable at the same instant and also start transmitting. The result is a "collision."
4. Once the collision is detected, all stations immediately stop transmitting.
5. Stations then wait a random length of time before checking the cable and then retransmit