FDDI Media
11-4
Cabling Types
To overcome this, a crossover must be placed between the FDDI TP-PMD ports,
forcing the transmit pins of one device to connect to the receive pins of the other
device. When two devices are being connected to one another using UTP cabling,
an odd number of crossover cables, preferably one, must be part of the cabling
between them. For ease of cable management, it is preferable to use
straight-through cabling for horizontal cable runs, and place any necessary
crossover cables in the wiring closet or data center.
Figure 11-3. Straight-Through vs. Crossover Cables
UTP Cable Quality
UTP cabling is produced in a number of overall quality levels, called Categories.
The UTP cabling used in FDDI installations must adhere to the minimum quality
characteristics detailed in the ANSI X3T9.5 TP-PMD specification. UTP cabling
that is Category 4 or lower is not capable of meeting the stringent quality
requirements of the TP-PMD specification, and should never be used in an FDDI
environment. Only cabling of Category 5 may be used for FDDI TP-PMD
installations. Descriptions of lower-quality cables may be found in the Ethernet
and Token Ring sections of this document.
Category 5
Category 5 UTP cabling is manufactured in the same fashion as standard
telephone installation cable, but the materials used are of higher quality and the
wires that make up the pairs are more tightly wound. This closer association
helps to reduce the likelihood that any one member of a pair may be affected by
external noise sources without the other member of the pair experiencing the
same event.
Tx+
Tx-
Rx-
Rx+
Tx+
Tx-
Rx-
Rx+
Path of Transmission
Path of Transmission
Crossover
Straight-Through
Tx+
Tx-
Rx-
Rx+
Tx+
Tx-
Rx-
Rx+
1845n06
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Страница 4: ...Notice ii...
Страница 22: ...Cabling Terms 2 8 Test Characteristics...
Страница 54: ...Ethernet Media 4 30 Connector Types...
Страница 72: ...Full Duplex Ethernet Network Requirements 6 8 Ethernet FOIRL Single Mode...
Страница 80: ...Fast Ethernet Network Requirements 7 8 Hybrid Installations...
Страница 130: ...FDDI Media 11 16 Connector Types...
Страница 136: ...FDDI Network Requirements 12 6 TP PMD STP...
Страница 170: ...Connecting and Terminating 14 20 FDDI...
Страница 192: ...Index 4...