An Ethernet standard that transmits at 1 Gbps. Used mostly to connect high-end workstations and servers as well as for network backbones, Gigabit Ethernet transmits full duplex from point to point using switches and half duplex in a shared environment (CSMA/CD) using a hub.
The first IEEE Gigabit Ethernet standard (802.3z) was defined in 1997 for use over multimode optical fiber and two years later for copper cables.
1000Base-T and 1000Base-TX
In 1999, the IEEE 802.3ab standard (1000Base-T) enabled Gigabit Ethernet to run over Category 5 copper cable and be readily used in 10/100 Ethernet networks without changing cables. The TIA/EIA later introduced 1000Base-TX, which did not catch on. It required Category 6 cabling, but greatly simplified the circuitry by using a different transmission method. In 1000Base-T, each of four wire pairs transmits 250 Mbps in both directions. In 1000Base-TX, two pairs transmit at 500 Mbps, and two receive at 500 Mbps.
The maximum distance between nodes is based on the type of transceiver and cable used as outlined below.
8B/10B Encoding
Fiber Modal
Diameter Bandwidth Range
(microns) (MHz-km) (meters)
1000Base-SX (802.3z)
62.5 multimode 160 220
62.5 multimode 200 275
50 multimode 400 500
50 multimode 500 550
1000Base-LX (802.3z)
62.5 multimode 500 550
50 multimode 400 500
50 multimode 500 550
9 singlemode --- 5000
1000Base-CX (802.3z)
Shielded twisted 25
pair copper
1000Base-T Encoding
1000Base-T (802.3ab)
Category 5 UTP 100
1000Base-TX (TIA/EIA-854)
Category 6 UTP 100
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