When twisted-pair or fiber optical media is used, data can flow from station to station, station to switch, or switch to switch in full-duplex mode.
For full-duplex operation, the CSMA/CD protocol is not applied; there are no collisions.
The parameters relevant for full-duplex operation are the interframe gap, the minimum MAC frame size, and the maximum MAC frame size.
Backward compatibility with half-duplex interfaces was established by introducing an Auto-Negotiation function that enables nodes to agree on using capabilities that both support.
Special PAUSE frames tell a partner to temporarily stop sending frames.
The MAC control sublayer was created to perform PAUSE functions (and other functions that might be defined in the future). ...