Information Technology Reference
In-Depth Information
For the most part, if your connections involve RJ45 jacks, you
should use a crossed cable when connecting two computers directly,
but you need a straightthrough cable for most other connections
between your computer and a network.
only for connecting two computers?
Although pointtopoint connections are efficient for tying two
computers together, this approach does not scale up well. For exam
ple, using this approach to tie 1 computer with 9 others would re
quire 9 cables, but connecting all 10 computers to each other would
require 45 wires. (
Computational aside:
To connect each of 10 com
puters to another, a cable could start at any of the 10 machines and
end at any of the 9 remaining machines. This initially suggests 90
cables. Each jack, however, serves as both a start and an end, so
only 45 cables would be required. Though smaller than 90, 45 ca
bles are still far too many to make this an efficient way to connect
computers.) Using pointtopoint communication to join many com
puters to each other would require a very large number of cables.
The size of cable jacks is also a practical issue that makes this tech
nique less appealing. Further, as the number of computers increases,
the bulk of the cables could become a problem. Clearly, pointto
point connections are not the bestsuited connections for linking a
large number of machines, and, therefore, they are not the most
common form of network connections.
Rather than using pointtopoint connections, computer and
communication networks typically employ one of three approaches:
star networks, Ethernet networks, or tokenring networks. Basic
configurations for these networks are shown in Figure 8.5.
Star Networks: In a
star network
, each computer is connected to
a central machine, and all therefore communications go through the
center. With 10 computers plus the central machine, 10 cables
would be needed. Also, regardless of how many computers were
