Why is it important for network devices to listen before transmitting in CSMA/CD?

In the context of CSMA/CD (Carrier Sense Multiple Access with Collision Detection), it is crucial for network devices to listen before transmitting to prevent data collision. The method works by requiring devices to sense the carrier signal on the network medium before attempting to send any data. If the medium is busy, the device will wait until it is free, thus reducing the chances of multiple devices trying to send data simultaneously.

When two or more devices transmit at the same time without prior checking, their signals can collide, leading to data corruption and requiring the involved devices to retransmit after a random back-off period. This kind of collision detection plays a vital role in maintaining the integrity of data being transmitted over a shared network medium.

By ensuring that devices only transmit when the line is clear, CSMA/CD effectively minimizes the likelihood of collisions. This mechanism is foundational for maintaining efficient communication in Ethernet networks, particularly in environments where multiple devices share the same communication channel.