See 802.3z in Computer
An IEEE standard for Gigabit Ethernet over optical fiber and shielded twisted pair (STP). It provides for full-duplex transmission from switch to end station or to another switch and half-duplex over a shared channel using the CSMA/CD access method. 802.3ab is the counterpart standard for Gigabit Ethernet over Category 5 copper wiring. See Gigabit Ethernet.