Ethernet

Layer 2 protocol that runs at 10 Megabits/s Half-Duplex with CSMA/CD, which stands for Carrier Sense Multiple Access with Collision Detection.

Half- and Full-Duplex

Half-Duplex means that bi-directional communication is possible but only in one direction at a time.

Full-Duplex, in opoosition, means that bi-directional communication is possible, in more than one direction at a time (simultaneously, like a phone call).

CSMA/CD

CSMA/CD comes into play when two devices transmit at the same time and frames can collide. CSMA/CD is constantly listening in on the wire for collitions. When this collition happening, it sends out a jamming signal to all devices, and asks to devices to stop transmitting for a random period (everyone can receive different times), then the chances are lessened that they will retransmit at the same time, and hence the collision avoidance comes in.