contention slot definition
(Or contention period). Minimum time a host
must transmit for before it can be sure that no other host's packet
has collided with its transmission. If the maximum propagation delay from one host to any other is T, then a host that starts to transmit at time t0 may collide with a host that starts just before t0 + T. The first host will not detect the collision until time t0 + 2T.