Networking —

Gigabit Ethernet

Gigabit Ethernet networking, which is becoming increasingly common as a backbone connection method and for a server to switch connectivity, is achieved using either copper-based media or fiber optic cabling. The two IEEE standards that specify Gigabit transfer are 802.3z and 802.3ab.

802.3z

Three distinct standards are specified under the 802.3z standard; they are referred to collectively as 1000BaseX.

The three standards are 1000BaseLX, 1000BaseSX, and 1000BaseCX. 1000BaseLX and 1000BaseSX use long wavelength laser and short wavelength laser, respectively. Both 1000BaseSX and 1000BaseLX can be supported over two types of multimode fiber62.5 and 50 micron-diameter fibers. Only long wave lasers support the use of single-mode fiber.

The 1000BaseCX standard specifies Gigabit Ethernet over STP cabling. Segment length of 1000BaseCX is extremely limited, reaching a maximum of 25 meters. 1000BaseCX is not widely implemented.

802.3ab

The 802.3ab standard specifies Gigabit Ethernet transfer over Category 5 UTP cable. To achieve the 1000Mbps speeds, each of the four pairs of wires in a twisted-pair cable can transmit 250Mbps. Table 5 summarizes the characteristics of the Gigabit standards.

Table 5 Gigabit Ethernet

Standard

Cable Type

Segment Length

Connector

1000BaseLX

Multimode/single-mode fiber

550/multimode 5000/single-mode

Fiber connectors

1000BaseSX

Multimode fiber

550 meters using 50 Micron multimode fiber

Fiber connectors

1000BaseCX

STP

25 meters

9-pin shielded connector, 8-pin fiber channel type 2 connector

1000BaseT

UTP

75 meters

RJ-45