Information Technology Reference
In-Depth Information
It is quite important that you properly plan, specify, and implement a LAN
cabling system that will provide your organization with a reliable level of service.
The use of the appropriate component parts and good workmanship in your wiring
system will ensure that it can meet the performance standards that are expected for
the type of LAN you are installing. In addition, you should always plan for as much
future growth as is feasible, within obvious financial limits.
LAN wiring systems are in a constant state of change, as are all computer systems.
As with computer technology, some of the changes in LAN wiring technology are
evolutionary and some are revolutionary.
For example, accepted LAN wiring techniques, components, and practices tend
to
evolve
as manufacturers, installers, and users refine the existing wiring technol-
ogy. The introduction of tighter cable link performance standards and the trend
toward guarantees of component performance are perfect examples of evolutionary
change. Likewise, the introduction of new cable types, outlets, and patch panel
designs are also evolutionary. An
evolutionary
new product does not represent a
major technology shift; the refined product merely has an enhanced level of per-
formance or is more convenient to use.
On the other hand, some changes are revolutionary. A
revolutionary
change is
one that breaks with the past. In technology, this implies a product or method that
is no longer compatible with past items, but offers greatly increased capability. For
example, an increase in LAN speed is revolutionary. For the most part, the technol-
ogy required to increase from 10 Mbps to 100 Mbps (or to 1 Gbps or even 10 Gbps)
is a clear break from the previous practice, and is highly desirable, but no longer
compatible with the past. Revolutionary changes tend to be abrupt.
The main focus of a LAN wiring system design effort must be to keep up with
evolutionary changes in the wiring technology that will enhance the value of your
system, while attempting to plan for the next revolutionary jump in LAN technology.
When LAN wiring over-twisted-pair-wire first began, little was known about
the importance of wire performance. The initial interest in “twisted-pair Ethernet”
was to be able to avoid bulky coaxial cable systems and use one's existing telephone
wiring for the installation of the network, thus saving the enormous cost of
installing new cabling. However, we soon found out that the typical specifications
that were fine for telephone use were rather marginal for LAN frequencies that
needed much higher twists-per-cable-foot, as well as much better impedance and
crosstalk control. To make matters worse, deregulation of the telephone industry at
that time meant that cost-conscious installers sometimes used an even cheaper grade
