A duplex communication system is a point-to-point system of two devices that communicate with each other in both directions.
These two type of duplex communication systems available in Ethernet environment:
- half-duplex – A port can send data only at a time. In other words, it can't send and receive data at same time. Network hub runs in half-duplex mode in order to prevent collision in network. Since hub are rare in modern LAN, the half-duplex system is not widely use in Ethernet network anymore.
- full-duplex – All devices send and receive data on their port at the same time. There are no collision in full-duplex mode, but host NIC and the switch port must support the full-duplex modes. Full-duplex Ethernet use two pairs of wire at the same time instead of single wire pair like half-duplex.
Below example illustrates the concept:
Bubs can only operate in half duplex mode, the switch and the hub will negotiate to use half-duplex, which means the only one device can send data at a time. The workstation on the right side full duplex mode, so link between the switch and workstation will use full duplex, with both the devices sending data simultaneously.
Each NIC and switch port has duplex setting. For all link between host and switch, or between switch, the full-duplex mode should be used. So for all links connected to a LAN hub, in the time of half-duplex mode should be used in order to prevent a duplex mode mismatch that could decreases network performance.
In Windows, you can set duplex settings in the Properties of window of your network adapters:
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