What must all network devices do according to the CSMA/CD access method?

In the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol, all network devices are required to listen before transmitting. This principle ensures that a device checks the network to determine if it is clear for transmission. By 'sensing' the carrier, devices can detect whether any other transmission is occurring on the medium. This helps to minimize the chances of collisions, which happen when two devices attempt to send data simultaneously.

If a device finds the channel free, it proceeds to transmit its data. If it senses that the channel is busy, it will wait until the channel becomes available again before attempting to transmit. This initial listening phase is critical in maintaining efficient network communication and ensuring that devices do not interfere with each other’s transmissions, thereby enhancing the overall throughput of the network.