Information Technology Reference
In-Depth Information
The demanding cable performance that is required by modern LAN applica-
tions can no longer be met by such simple testing methods. To truly test a LAN
wiring system to meet one of the more rigorous performance categories requires the
use of very sophisticated test equipment.
Specialized field testers have been developed to reduce the cost of testing. These
testers are far less expensive to purchase than the ultrasophisticated laboratory RF
network analyzers (these test all sorts of electronic networks, not local area com-
puter networks). Yet, the field testers yield useful results that closely match the
measurements to the LAN category standards, produce quick pass/fail indications,
and print full reports.
These field testers are also very easy to use. They can run completely auto-
mated tests, store the results, and pinpoint problem locations on the cable under
test. Most of the testers will operate for several hours on battery power, so you don't
even have to find a power outlet.
Although these testers provide many advantages, they are still much more
expensive than the simple wiring verification tools, and they require additional
skill to operate properly. Consequently, you should expect to pay extra for having
your cable “scanned” with one of these field testers. The cost of the tester, the
skilled operator time, the preparation of reports, and the possible retesting should
be considered when budgeting for the additional cable scanning step. You should
allow a budgetary cost from 5% to 15% of the installation cost per drop to certify
to Permanent Link standards. The cost variation is to allow for special circum-
stances, such as an unusually difficult and expensive per-drop cost. If the scanning
is done by a separate contractor, you should allow an additional factor for prob-
lem determination or visual inspection. Scanning is best done before personnel
have moved into the office space. Although scanning involves only a brief visit to
each workstation outlet, labor costs will be higher if furniture (and people) have to
be moved.
If your intention is to install a full Category 5e or 6 wiring system, then you
need to plan for a complete certification scan. The component standards and instal-
lation practices are simply too tough to not test completely for proper performance.
If you have an existing facility that is supposed to meet Category 5 and you have
not previously tested it to 100 Mbps, then a new scan would be appropriate. To
recertify Category 5 links for Gigabit Ethernet, you should test to the limits in TSB-
95, as the full Category 5e limits should not be required. Prior to the release of the
testing procedures and limits in TSB-67, standard practice was to use Category 5
cable and components, install using the best current practices, and test using what-
ever cable scanners were available at that time. The older EIA/TIA-568 standard
specifically excluded installed cable and connectors from its scope.
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