Gigabit Ethernet - Computer Definition
Standardized by the IEEE (1998) as IEEE 802.3z, GigE is a backbone Ethernet solution that operates at 1 Gbps and is fully compatible with 10/100-Mbps Ethernet. GigE is available in both shared bus and switched versions, both of which support multiple ports that can run at 1 Gbps in full-duplex (FDX). Specifications include shared bus hubs, matrix switches, and transmission media. A GigE shared bus solution is a high-speed hub that uses CSMA/CD for medium access control (MAC) and can run at a speed of several Gbps. Switched GigE buffers incoming Ethernet frames, passing them to the output port when the shared bus becomes available. More substantial switched GigE products offer nonblocking matrix switching.Transmission media specifications include twisted pair (1000Base-T) and fiber optics (1000Base-LX and 1000Base-SX), and employs the same 8B/10B line coding technique used in ESCON and Fibre Channel. Although GigE is much like the predecessor 10/100-Mbps Ethernet versions, differences include frame size. As the clock speed of GbE is one or two orders of magnitude greater, issues of roundtrip propagation delay affect error detection. To avoid potentially disastrous collision rates, the minimum frame size is increased from 64 octets to 512 octets, which generally is equivalent in duration to transmitting a 64-byte frame at 100 Mbps.The larger minimum frame size provides the same time for the transmitting device to receive and interpret a collision notification.Although nonstandard, some manufacturers have increased the maximum frame size from 1,518 bytes to a jumbo frame size of 9,000 bytes, which improves throughput as there are fewer frame headers to be analyzed and fewer inter-frame intervals. GigE is found not only in local area network (LAN) backbones, but also is used by service providers in metropolitan area networks (MANs). See also 1000Base-LX, 1000Base-SX, 1000Base-T, 8B/10B, backbone, CSMA/CD, ESCON, Ethernet, FDX, Fibre Channel, LAN, LAN switch, MAC, and MAN.
StandardFiber TypeCore DiameterWavelengthDistance (Maximum) 1000Base-SX MMF 62.5
An Ethernet standard that transmits at 1 gigabit per second. Gigabit Ethernet (GbE, GE) connects PCs and servers in local networks and is commonly employed along with a mix of 10/100 Mbps devices. For example, a 10/100/1000 switch supports all three rates and adjusts to the highest speed between sender and receiver. All new computers and most network devices support Gigabit Ethernet. GbE transmits full duplex from point to point using Ethernet switches and half duplex in a shared Ethernet hub environment (see CSMA/CD). IEEE 1000Base-T (802.3ab) The 1997 standard (IEEE 802.3z) required multimode fiber or shielded copper cables, but two years later, 1000Base-T enabled GbE to run on ordinary Cat 5 copper and be readily used in existing networks. Four wire pairs each transmit 250 Mbps in both directions. TIA 1000Base-TX A competing standard created by the TIA that never caught on used simpler electronics but required Cat 6 cabling. However, 1000Base-T is often erroneously labeled 1000Base-TX. See Ethernet and 10 Gigabit Ethernet. COPPER CABLE Encoding Cable Range Standard Method Type (meters) 1000Base-T 802.3ab 4D-PAM5 Cat5-UTP 100 1000Base-TX TIA/EIA-854 4D-PAM5 Cat6-UTP 100 1000Base-CX 802.3z 8B/10B Cat1-STP 25 OPTICAL CABLE (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