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Letter to the Editor: UTP and STP on even ground

A column in the last issue written by Richard Smith and headlined Will that be STP or UTP? (see July/August CNS, p. 26) indicated that STP cabling is significantly better at being immune to alien cros...


September 1, 2007  


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A column in the last issue written by Richard Smith and headlined Will that be STP or UTP? (see July/August CNS, p. 26) indicated that STP cabling is significantly better at being immune to alien crosstalk.

Properly installed STP should at all times provide better immunity to electromagnetic interference (EMI) including alien crosstalk than UTP. Fluke Networks would like to stress to readers that we maintain a neutral stand on whether UTP or STP is inherently better at supporting 10GBASE-T.

We believe that both types of cabling are capable of transmitting 10GBASE-T in a very reliable fashion if correctly installed and pass the performance requirements of the applicable standards (IEEE std 802.3an or TIA TSB-155). The latter can be verified in advance of any deployment by using the correct field certification tests.

While STP cabling does have certain design traits that can offer greater immunity to alien crosstalk, there are tradeoffs.

Those same design traits make the installation process for STP more demanding and more time consuming, which require greater workmanship and experience. For example, special care must be taken that the screen or shield fully surrounds the wire pairs from end to end; the screen is properly grounded at both ends of the link; and the integrity of the screen is maintained over the entire length of the cabling link.

Many UTP cabling installations we have tested have fully met the guidelines outlined in the proposed Cat 6A standard.

UTP offers some advantages in that it is the more economical system and more familiar to installers in North America. However, the increased diameter size of some UTP cabling does require adjustments in installation in terms of handling, bundling and pathway design.

Those who argue that STP passes testing requirements by a wider margin should take note that this offers no real advantage in the support of 10GBASE-T.

If a link is certified including tests for alien crosstalk, and it passes both the certification and AXTALK tests, there is no measurable difference in performance whether it passes with a good margin or an exceptionally good margin.

The current standards do not address, of course, any future network application that may be developed to run over twisted pair cabling.

When it comes to installations, the critical factor is not whether you choose UTP or STP. Whatever the choice, success ultimately relies upon using the proper installation and testing procedures. From the perspective of Fluke Networks, UTP and STP are equally valid choices for 10GBASE-T.

Brad Masterson

Product Manager

Fluke Networks Canada