Information Technology Reference
In-Depth Information
that allows multivendor interoperability with a high level of performance. Any item
that does not comply with the standards is an exception and may be a potential
problem for your network. This is, you see, also a way to hear “exceptional” that
says it is noncompliant. For the time being, you may be taking a risk if you choose
to use some of these better (but nonstandard) connectivity options.
What is specsmanship?
Specsmanship
is a term for the exaggeration or mis-
leading presentation of product specifications that sometimes occurs in the market-
place. Fortunately, the existence of recognized national and international standards
minimizes the occurrence of specsmanship, but it still occurs. Were there no stan-
dards, you can be sure that various manufacturers would make conflicting product
claims that would be impossible for the buyer to resolve. The tough standards for
telecommunications cabling make product differences clearly recognizable. All you
have to do is know which standard of performance you want the product to meet,
and then be sure that the products you use meet that standard. There is a continu-
ing controversy that involves connector performance.
The controversy concerns the relatively high NEXT of all modular connectors
and the measurable differences in longitudinal balance of some connector jack
designs. Several types of nonmodular connectors are available that have signifi-
cantly lower levels of NEXT than the popular 8-pin modular design. Some of these
connectors are used for field test instruments to reduce the contribution to NEXT
from the test set and are quite acceptable for testing the Permanent Link. However,
a compatible lower-NEXT modular connector style would be much more desirable
than attempting to replace more than a decade of installed modular connectors
with another connector. Several manufacturers are working on the improved prod-
ucts, and we're already starting to see clever plug and jack designs emerge, but the
issues of longitudinal balance and resonance phenomena are more subtle.
Resonance phenomena can cause short links (particularly under 15 m) to exceed
the allowable NEXT performance and is related to the return loss and/or balance
of the link.
Cable Plant Certification
In addition to using properly rated cable and components in your LAN wiring
installation, you should plan to test your installed wiring system to the expected
level of performance. Installing a cable plant or wiring system is a complex task,
particularly if you intend for it to support high-performance 100/1000 Mbps net-
works. Even 10 Mbps Ethernet and 16 Mbps Token-Ring had to have station cables
that met a certain level of performance to have been considered reliable. Most LAN
wiring is put to use immediately after cable plant installation.
