Carrier Sense Multiple Access / Collision Detect.
The low level network arbitration protocol used on Ethernet. Nodes wait for quiet on the net before starting to transmit and listen while they are transmitting. If two nodes transmit at once the data gets corrupted. The nodes detect this and continue to transmit for a certain length of time to ensure that all nodes detect the collision. The transmitting nodes then wait for a random time before attempting to transmit again thus minimising the chance of another collision. The ability to detect collision during transmission reduces the amount of bandwidth wasted on collisions compared with simple ALOHA broadcasting.