Ethernet Physical Properties Half and Full Duplex Ethernet

Half-duplex mode fundamentally operates Ethernet in the classic carrier sense multiple access collision detect (CSMA/CD) mode. Ethernet hubs are a good example of a device requiring half duplex. Half-duplex Ethernet has the follow characteristics:

• Unidirectional data flow.

• High potential for collisions.

• Operates on shared media devices such as a hub, or a workstation.

• Operational efficiency is rated at 50 percent to 60 percent of the total bandwidth of the link.

Full-duplex Ethernet allows for a station to simultaneously transmit and receive data. Ethernet frames are transmitted and received simultaneously on two pairs of unshielded twisted-pair (UTP) or a single pair of fiber. Full-duplex Ethernet is essentially Ethernet without CSMA/CD. Full-duplex mode basically doubles the bandwidth of Ethernet! To run full-duplex Ethernet, both Ethernet devices must be capable and configured for autonegotiation or full duplex. Figure 1-11 illuEtrates a Sommon Ethernet network and the duplex setting of the links.

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