contention slot

In a communication system where only one node at a time may transmit successfully on a shared channel, the contention slot or contention period is the time a node must wait before it can be sure that no other node's transmission has collided with its transmission.

If node A starts to transmit at time t0 and then another node starts to transmit just before it recieves A's transmission at time t0 + T, then the transmissions will collide but node A will not detect the collision until time t0 + 2T. The contention slot, 2T, for nodes seperated by the maximum propagation delay thus determines how much data the node must be prepared to re-transmit in the event of a collision.