Collision, in computer networking, is a condition that occurs when two or more computers on a network try to transmit signals at the same time.

What is Collision (in computer networking)?

Collision, in computer networking, is a condition that occurs when two or more computers on a network try to transmit signals at the same time. Handling collisions is one of the main functions of a networking access method.

For example, in Ethernet networks, collisions often occur when two or more stations attempt to place frames on the wire at the same time. To handle this situation, Ethernet makes use of the access method called Carrier Sense Multiple Access with Collision Detection (CSMA/CD) so that each station takes turns accessing the wire.

How Collision Works

When a station begins transmitting a signal and detects a collision, the station stops transmitting and issues a jam signal to tell the other station that a collision has occurred. Both stations then stop transmitting and wait a random interval of time before retransmitting their signals. The amount of time the stations wait before retransmitting increases with the number of collisions occurring on the network.

A collision can only occur at the physical layer in the OSI model. When multiple devices share a common media at the physical layer, which happens when you have multiple devices connected with a hub, there is a possibility that you will have a collision. The network area where a collision may occur is called a collision domain.