BaseT Media Types

Three media types are supported by 100BaseT at the OSI physical layer (Layer 1), as shown in Table 3-11.

• 100BaseTX— Based on the ANSI Twisted Pair-Physical Medium Dependent (TP-PMD) specification. The ANSI TP-PMD supports UTP and STP cabling. 100BaseTX uses the 100BaseX signaling scheme over 2-pair Category 5 UTP or STP cabling.

The IEEE 802.3u specification for 100BaseTX networks allows a maximum of two repeater, or hub, networks and a total network diameter of approximately 200 m. A link segment, defined as a point-to-point connection between two Medium Independent Interface (MII) devices, can be up to 100 m.

• 100BaseFX— Based on the ANSI TP-PMD X3T9.5 specification for FDDI LANs. (FDDI LANs will be discussed in detail in Chapter 7, "FDDI.") 100BaseFX uses the 100BaseX signaling scheme over two-strand multimode fiber-optic (MMF) cable. The IEEE 802.3u specification for 100BaseFX networks allows DTE-to-DTE links of approximately 400 m, or one repeater network of approximately 400 m in length.

• 100BaseT4— Allows 100BaseT to run over existing Category 3 wiring, provided that all four pairs of cabling are installed to the desktop. 100BaseT4 uses the half-duplex 4T+ signaling scheme. The IEEE 802.3u specification for 100BaseT4 networks allows a maximum of two repeater, or hub, networks and a total network diameter of approximately 200 m. A link segment, defined as a point-to-point connection between two Medium Independent Interface (MII) devices, can be up to 100 m.

Table 3-11. 100BaseT Media Type Characteristics

Characteristics

100BaseTX

100BaseFX

100BaseT4

Cable

Cat 5 UTP, or Types 1 and 2 STP

62.5/125 micron MMF

Cat 3, 4, or 5 UTP

Number of pairs or strands

2 pairs

2 strands

4 pairs

Connector

ISO 8877 (RJ-45)

Duplex media-interface

ISO 8877 (RJ-

connector (MIC)

45)

Maximum segment length

100 m

400 m

100 m

Maximum network diameter

200 m

400 m

200 m

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