Media Access Control (MAC)
Gigabit Media Independent Interface (GMII)
IEEE 802.3z physical layer
(C) Herbert Haas
Gigabit Ethernet has been defined in March 1996 by the working group IEEE
802.3z. The GMII represents a abstract interface between the common Ethernet
layer 2 and different signaling layers below. Two important signaling techniques
had been defines: The standard 802.3z defines 1000Base-X signaling which uses
8B10B block coding and the 802.3ab standard uses 1000Base-T signaling. The
latter is only used over twisted pair cables (UTP Cat 5 or better), while
1000BaseX is only used over fiber, with one exception, the twinax cable
(1000BaseCX), which is basically a shielded twisted pair cable.
BTW: The "X" stands for block coding.