Ans2) In digital communication networks, contention is a media access method that is used to share a broadcast medium. In contention, any computer in the network can transmit data at any time. This system breaks down when two computers attempt to transmit at the same time. This is a case of collision.
To avoid collision, carrier sensing mechanism is used. Here each computer listens to the network before attempting to transmit. If the network is busy, it waits until network quiets down. In carrier detection, computers continue to listen to the network as they transmit. If computer detects another signal that interferes with the signal it is sending, it stops transmitting. Both computers then wait for random amount of time and attempt to transmit.
A collision can be detected by listening to the shared medium immediately after transmitting and identifying collision characteristics or by capturing data from the medium and performing error detection.