Installing Network Cable
(continued)
Straight-Through/Crossover
(10BASE-T /100BASE-TX)
The most popular wiring used today, unshielded twisted-pair copper
cable, is used for 10BASE-T and for 100BASE-TX. As with 10BASE-T,
the transmit and receive data signals on each pair of a 100BASE-TX
segment are polarized, with one wire of each signal pair carrying the
positive (+) signal, and the other carrying the negative (-) signal. The pin
numbers used in the eight-pin connector for 100BASE-TX conform to
the wiring scheme already in use in the 10BASE-T standard, so a
100BASE-TX board can replace a 10BASE-T board in a Category 5
wiring system without any wiring changes.
The straight-through/crossover rule
that applies to 10BASE-T also applies
to 100BASE-TX. The 10BASE-T and
100BASE-TX cable and RJ-45 jacks for
Switch to Terminal connections must
be configured as straight-through. The
10BASE-T and 100BASE-TX cable and
RJ-45 jacks for Switch to Hub
connections must be configured as
crossover.
The two active pairs in a
10BASE-T network are pins 1
& 2 and pins 3 & 6. Use only
dedicated wire pairs (such as
blue/white & white/blue,
orange/white & white/orange)
for the active pins.
The two wires in each pair of the
cable must be twisted together for the
entire length of the segment and kept
twisted to within approximately 1/2
inch of any connector to ensure the
integrity of the signal-carrying
characteristics of the unshielded wire
pair.
Eliminating CSMA/CD collisions on the segment by installing full-
duplex cards at the network interfaces in a network with Category 5
cables already installed allows a minimum investment to effectively
double the network collision domain diameter.
Application behavior determines if a station can take advantage of the
increased network capacity of full-duplex. Typical applications do not
use bandwidth symmetrically. File transfers, for example, are
asymmetrical in nature; bulk data is transferred in one direction, with
short acknowledgments returned in the reverse direction. A station
which is only doing file transfers will not benefit from the doubling of
bandwidth offered by full-duplex switching.
When multiple applications are using the network simultaneously on a
single device, the benefits of full-duplex are apparent. Typically servers
handle simultaneous network traffic to and from multiple workstations.
While any given workstation is using the network asymmetrically, the
server can take advantage of full-duplex operation to simultaneously
handle transfers in from one station and out to another.
Transition Networks’
Pocket Switch
8
19
Install Transition Networks' Pocket Switch
AND Install Full-Duplex 10BASE-T Card in Server
For Collision-Free Full-Duplex Connection to Serve
Fu
ll D
uplex
Ethernet™
Lin
k
C
SM
A/C
D Collision Dom
ain
100 meters
20 Mb/s
100 meters
10 Mb/s
CSMA
/CD Collision Domain
100 meters
10 Mb/s
RJ-45
P
LUG
RJ-45
J
ACK
1
8
2 3 4 5 6 7
1
8
Straight-Through Cable
at RJ-45 Plug
Switch . . . . . . . . . . . . . .PC, transceiver,
NIC, printer
RJ-45 Male . . . . . . . . . . . . . . .RJ-45 Male
1 . . . . . . . . . . . . . . . . . . .1
2 . . . . . . . . . . . . . . . . . .2
3 . . . . . . . . . . . . . . . . . .3
6 . . . . . . . . . . . . . . . . . . .6
Crossover Cable
at RJ-45 Plug
Switch . . . . . . . . . . . . .Hub
RJ-45 Male . . . . . . . . . . . . . . .RJ-45 Male
1 . . . . . . . . . . . . . . . . . . .3
2 . . . . . . . . . . . . . . . . . . .6
3 . . . . . . . . . . . . . . . . . .1
6 . . . . . . . . . . . . . . . . . .2
