Networking —

Fast Ethernet

Many of the applications used on modern networks demand more bandwidth than what's provided by the 10Mbps network standards. To address this need for faster networks, the IEEE has developed the IEEE 802.3u specifications, of which there are three variations:

  • 100BaseTX

  • 100BaseT4

  • 100BaseFX

We have chosen to include information on it in this section to provide rounded coverage of this topic.

100BaseTX

100BaseTX is the most widely implemented of the Fast Ethernet standards. 100BaseTX uses two pairs of wire in Category 5 UTP cabling and can also use STP cable when a more resistant cable is required. 100BaseTX uses 100Mbps transmission and a total segment length of 100 meters.

100BaseT4

The advantage to 100BaseT4 is its capability to use older categories of UTP cable to perform 100Mbps transfer. In environments already wired with Category 3 or 4 cable, 100BaseT4 can be used instead of replacing the existing cable.

100BaseT4 uses all four pairs of wire of Category 3, 4, and 5 twisted pair and, as such, is prevented from using full-duplex transmissions. The other characteristics of standard 100BaseTX are in effect with 100BaseT4.

100BaseFX

The IEEE 100BaseFX standard specifies 100Mbps transmissions speeds over fiber-optic cable. 100BaseFX can use both multimode and single mode fiber. It has a maximum segment length of 412 meters when used over multimode fiber and 10,000 meters when used over single-mode fiber. Table 4 summarizes the characteristics of Fast Ethernet.

Table 4 Fast Ethernet

Standard

Cable Type

Segment Length

Connector

Topology

100BaseTX

Category 5 UTP

100 meters

RJ-45

Physical star

100BaseT4

Category 3, 4, 5 UTP

100 meters

RJ-45

Physical star

100BaseFX

Multimode/single-mode fiber-optic cable

412/multimode fiber-optic 10,000/single-mode fiber-optic

SC, ST

Physical star