The physical layer of Ethernet can work in either half-duplex or full-duplex mode.
Half-duplex mode
The half-duplex mode has the following features:
Data can only be sent or received at any time.
The CSMA/CD mechanism is used.
The maximum transmission distance is limited.
Hubs work in half-duplex mode.
Full-duplex mode
After Layer 2 switches replace hubs, the shared Ethernet changes to the switched Ethernet, and the half-duplex mode is replaced by the full-duplex mode. As a result, the transmission rate increases greatly, and the maximum throughput doubles the transmission rate.
The full-duplex mode solves the problem of collisions and eliminates the need for the CSMA/CD mechanism.
The full-duplex mode has the following features:
Data can be sent and received at the same time.
The maximum throughput doubles the transmission rate.
This mode does not have the limitation on the transmission distance.
All network cards, Layer 2 devices (except hubs), and Layer 3 devices produced support the full-duplex mode.
The following hardware components are required to realize the full-duplex mode:
Full-duplex network cards and chips
Physical media with separate data transmission and receiving channels
Point-to-point connection