Half-Duplex Gigabit Ethernet

Backward compatibility broke down when the 802.3 committee wrote the rules for gigabit hubs operating in a CSMA/CD environment. Some Ethernet protocol elements had to be changed to accommodate half-duplex Gigabit Ethernet.

Half-duplex Gigabit Ethernet is not used at the time of writing, but a description of the protocol elements is included for completeness. The discussion will uncover another reason that motivated vendors to implement only full-duplex Gigabit Ethernet—namely, the small diameter of a gigabit collision domain.

Modification to Frame Format for Half-Duplex Mode

Chapter 4, "The Classical Ethernet CSMA/CD MAC Protocol," presented one of the changes that was needed to implement CSMA/CD (half-duplex ...

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