Wikipedia
A collision domain is a network segment connected by a shared medium or through repeaters where simultaneous data transmissions collide with one another The collision domain applies particularly in wireless networks, but also affected early versions of Ethernet A network collision occurs when more than one device attempts to send a packet on a network segment at the same time Members of a collision domain may be involved in collisions with one another Devices outside the collision domain do not have collisions with those inside Only one device in the collision domain may transmit at any one time, and the other devices in the domain listen to the network and refrain from transmitting while others are already transmitting in order to avoid collisions
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