![]() ![]() Upgrading a Fast Ethernet backbone switch to a Gigabit Ethernet 100/1000-Mbps switch is straightforward and will enable you to connect high-speed server farms using Gigabit Ethernet network interface cards ( NICs). Gigabit Ethernet standards were developed only recently and are now beginning to be widely implemented in high-speed networks. The Gigabit Ethernet Alliance is an open forum for promoting cooperation and standards in industry implementations of Gigabit Ethernet. Gigabit Ethernet is defined by the IEEE 802.3z specification. ![]() Gigabit Ethernet might eventually be used for direct connections to high-speed user workstations, but at present this is a costly scenario to implement, and most applications can achieve sufficient bandwidth using only Fast Ethernet. This configuration can provide users with 1-Gbps access to application or file servers. High-speed server-switch connections for server farms connected to server backbones.An alternative would be to connect several 10/100 switches to one 100/1000 switch. Typically you might connect several 100/1000-Mbps switches to provide Fast Ethernet islands joined by Gigabit Ethernet backbones. High-speed switch-switch connections for network backbones.Engineers currently envision two main uses for Gigabit Ethernet in corporate networking environments: Gigabit Ethernet networks can function as shared-media half-duplex networks using 1000-Mbps hubs, but they are usually implemented as switched full-duplex networks using 1000-Mbps Ethernet switches. 1000BaseT: Uses twisted-pair category 5 cabling (four pairs of wires) over a maximum distance of 100 meters (maximum network diameter of 200 meters) and is intended mainly for connecting high-speed workstations to concentrators in nearby wiring closets.This version is used mainly for short cable runs of up to 300 meters (over 50-micron fiber) and up to 550 meters (over 62.5-micron fiber). 1000BaseSX: Uses short wavelength transmissions over multimode fiber-optic cabling.This version is used mainly for long cable runs of up to 5 kilometers. 1000BaseLX: Uses long wavelength transmissions over single-mode fiber-optic cabling.It uses Fibre Channel–based 8B/10B coding at a serial line rate of 1.25 Gbps. This version is used primarily for connecting switches and routers in wiring closets. 1000BaseCX: Uses 150-ohm balanced twinax cabling or shielded twisted-pair (STP) cabling over a maximum distance of 25 meters.Gigabit Ethernet can be implemented in four different cabling or physical layer (PHY) options: In standard half-duplex mode, Gigabit Ethernet supports speeds of 1 Gbps using CSMA/CD, but full-duplex versions support speeds of 2 Gbps for high-speed network backbones. Gigabit Ethernet uses the same standard 802.3 framing structure of standard Ethernet, with frames between bytes in length. When using switched full-duplex connections, these changes do not apply.īecause CSMA/CD is used, Gigabit Ethernet can be viewed as a relatively easy upgrade path for network administrators familiar with 10BaseT and Fast Ethernet technologies. Note that these changes to CSMA/CD occur only during half-duplex communication. The modifications can affect the performance of traffic involving smaller packets, but this is accommodated for by building a packet-bursting feature into Gigabit Ethernet that allows a station to take temporary control of the wire to send out a number of small packets. These modifications are performed to maintain a 200-meter-diameter topology for Gigabit Ethernet networks when a shared-media topology is used in half-duplex communications. From the point of view of the MAC (media access control) interface, the minimum packet size still appears as 64 bytes. Modifications to CSMA/CD for Gigabit Ethernet include extending the length of the carrier and slot times to pack out all frames to a minimum carrier length of 512 bytes. Gigabit Ethernet supports a modified Carrier Sense Multiple Access with Collision Detection ( CSMA/CD) media access method similar to those supported by previous versions of 10-Mbps Ethernet and 100-Mbps Fast Ethernet.
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