Final answer:
Ethernet chooses CSMA/CD because it is simple, efficient, and quickly resolves collisions, making it better than Pure ALOHA, which has high collision levels, Slotted ALOHA, which reduces but doesn't eliminate collisions, and CSMA, which lacks collision detection.
Step-by-step explanation:
Ethernet uses the CSMA/CD (Carrier Sense Multiple Access/Collision Detection) protocol as it provides a reliable method for multiple network devices to share the same transmission medium, typically a bus or star topology. The key advantages of CSMA/CD include its simplicity, efficiency under low to moderate network loads, and its ability to rapidly resolve collisions that occur when two devices attempt to transmit simultaneously.
CSMA/CD works by having each device sense the carrier (the cable) before attempting to transmit. If the medium is free, the device can transmit. If a collision occurs, each device stops transmitting, waits for a random time, and then attempts to transmit again, hence the name collision detection.
In contrast, Pure ALOHA allows devices to transmit at any time but requires them to wait for a random interval if a collision occurs, which can lead to high levels of collision and thus reduced efficiency, especially as network traffic increases. Slotted ALOHA improves on this by dividing time into slots and requiring devices to start transmissions only at the beginning of a slot, reducing but not eliminating collisions.
The CSMA protocol is similar to CSMA/CD but lacks the collision detection feature. In CSMA, if a collision happens, it is not detected immediately, leading to the possibility of extended periods where no data can be successfully transmitted.
Overall, CSMA/CD's ability to detect and resolve collisions quickly often makes it preferential for Ethernet networks compared to these alternatives.