2.3 Gigabit Ethernet
2.3.2 Gigabit architecture
Gigabit Ethernet merges aspects of 802.3 Ethernet and fiber channel, a gigabit technology intended for high-speed interconnections between file servers as a LAN replacement. The fiber-channel standard details a layered network model capable of scaling to bandwidths of 4 gigabits per second (Gbps) and to extend to distances of 10 km. Gigabit Ethernet borrows the bottom two layers of the standard: FC-1 for encoding/decoding and FC-0, the interface and media layer. FC-0 and FC-1 replace the physical layer of the legacy 802.3 model. The 802.3 MAC and LLC layers contribute to the higher levels of Gigabit Ethernet. The Figure illustrates the merger of the standards to form Gigabit Ethernet.

The fiber-channel standard incorporated by Gigabit Ethernet transmits at 1.062 MHz over fiber optics and supports 800-Mbps data throughput. Gigabit Ethernet increases the signaling rate to 1.25 gigahertz (GHz). Further, Gigabit Ethernet uses 8B/10B encoding, meaning that 1 Gbps is available for data. The 8B/10B encoding is similar to 4B/5B discussed for 100BASE-TX, except that for every 8 bits of data, 2 bits are added, creating a 10-bit symbol. This encoding technique simplifies fiber-optic designs at this high data rate. The optical connector used by fiber channel, and therefore by Gigabit Ethernet, is the switching controller (SC) style connector. This is the push-in/pull-out, or snap-and-click connector used by manufacturers to overcome deficiencies with the snap-and-twist (ST) style connector. The ST style connector previously preferred was a bayonet-type connector that required finger space on the front panel to twist the connector into place. The finger-space requirement reduced the number of ports that could be built into a module.