Collision domain

A collision domain is a logical area in a computer network where data packets can "collide" with one another, in particular in the Ethernet networking protocol. The more collisions in a network the less efficient it is.

A collision domain can be a single segment of Ethernet cable in shared-media Ethernet, or a single Ethernet hub in twisted-pair Ethernet, or even a whole network of hubs and repeaters.

Devices with collision domains

Following the layers of the OSI model you can determine what devices extend or compound collision domains.

OSI Layer 1 Devices (hubs, repeaters) forward all data that is sent on the media and therefore extend collision domains.

OSI Layer 2 and Layer 3 Devices (switches,routers) break up collision domains.

Furthermore

Compare with broadcast domain.