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Appendix A
Data Cabling Techniques
The following sections detail cabling techniques and port specifications for
IEEE 802.3 media. For comprehensive treatment of these topics, refer to the
original IEEE specification.
10BASE-T
UTP (either RJ45 or Telco [RJ21]) links support transmissions up to 100
meters [328 ft.]) at 10 Megabit data rates.
A serious problem exists concerning identification of modular cable. There
are various grades of voice-quality and data-quality cables available. These
can appear to be similar externally, although their high-speed data
transmission characteristics are radically different.
The identification problem is exaggerated by the fact that some suppliers
have sold purportedly data-quality cables manufactured with voice-quality
cabling. If any voice-quality cabling is used in a 10BASE-T network system,
data movement is slow, collision-prone or non-existent. To confuse the issue,
the Link indicator on the interface will usually indicate a valid link in such a
case.
For the foregoing reasons, it is absolutely vital that you use only Level 3, 4 or
5 cabling with 10BASE-T connections. As a rule of thumb, if a cable type is
flat, it is usually untwisted, and will cause problems. If a cable is more or less
round in section, it will typically work.
