In Ethernet networks, the term for when two devices transmit on a shared medium is a ______.

• A. Collision
• B. Broadcast storm
• C. Unicast collision
• D. Collision domain

Answer: (A)

Two devices transmitting at the same time on a shared Ethernet medium cause a collision. In classic Ethernet (coax or hubs, operating in half-duplex), devices listen before sending using CSMA/CD. If two stations start transmitting simultaneously, their signals interfere and the frames become corrupted. The network cards detect this collision, send a jam to ensure all participants notice it, and then each transmitter waits for a random backoff period before trying again. This behavior limits how many devices can send at once on the same wire, and it’s why switches are used today—to create separate collision domains and prevent collisions. A broadcast storm is unrelated—it’s a flood of broadcast traffic, not the actual event of two devices transmitting at once. A collision domain is the network segment where such collisions could occur, not the event itself.