Getting a decent buy on the right wiring with which to build or expand your network can be difficult. Because wiring is the bedrock of optimal network performance, it's important that the proper type and best quality wiring be used, installed and tested by experienced technicians. Today's network wiring carries a contemporary mix of analog and digital signals: Ethernet, Fast Ethernet, Gigabit Ethernet, KVM (keyboard, video, mouse), VoIP (voice over IP) telephone data and supply voltage, critical security information and other signals.
Network wiring's value-add is coming into focus for savvy IT planners who see it through a lens that reveals the nature of a critical investment. Sorting out the claims and terms bandied about the cabling community is no easy task though. Fortunately, there are basic standards and practices to help you select and deploy the right wiring solution.
Performance Standards
Familiarizing yourself with network wiring requires entrance into the realm of UTP (unshielded twisted pair) wiring. Four-pair UTP has been the medium of choice for large and small networks for many years, and the cable manufacturing community has been exceptional in its role as a catalyst for higher speeds and increased bandwidth in networks.
But as so often happens, confusing hype inevitably creeps in, and some less-than-great players emerge. One solid rule of thumb: Avoid off-brand UTP. These may be the leftovers from a major player's production line or, worse yet, obsolete wire that's been repackaged and marketed to the unfamiliar as a high performer. Today's UTP of choice is Category 5E cable, with the venerable Category 5 now widely considered legacy.
For those new to UTP, the first point of confusion is often the difference between the various cable categories. All UTP categories have a foundation in IEEE, ANSI and TIA/EIA (Telecom/Electronic Industry Association) guidelines and standards. One of the most referenced standards governing UTP is the recently adopted TIA 568B and its various TSB (Telecommunications Systems Bulletins) supplements. TIA 568B defines the differences between wire categories and outlines performance parameters, and physical and network characteristics. TIA 568B incorporates all the previous TIA 568A TSB supplements and reflects evolutions in speed, bandwidth and testing.
A quick Web search will turn up many detailed excerpts from TIA 568B and related documents, so get familiar with the basics before spending a bundle on new wiring. (For a look at where cable's been, see sidebar, "Wiring Then and Now").
Even today's Cat 5E UTP products have wide variations in actual performance ratings. All such products meet the TIA 568B standard's minimum requirements, and many claim to exceed the basic metrics. UTP cabling marketers like quoting performance figures--and higher numbers are billed as better. Increased headroom, only one of the phrases used to tout UTP, means the product's been consistently tested to perform beyond the basic 100-MHz requirement.
A quick comparison at our Real-World Labs® in Syracuse, N.Y., turned up three Cat 5E samples with varying bandwidth ratings: 155 MHz, 200 MHz and 350 MHz. Also common are manufacturer-generated terms like Cat 5E Enhanced and Cat 5E+. Both signify higher-performing Cat 5E UTP products. Some vendors call basic Cat 5E wiring Cat 5e, while higher performing UTP is dubbed Cat 5E. UTP that far surpasses current requirements for Gigabit Ethernet is usually sold as the cabling that will future-proof your network, but you must guess whether your future enterprise profile will require (or would ever have a prayer of using) such awesome bandwidth capacity.
Regardless of promised bandwidth, all legitimate Cat 5e cable will meet a plethora of basic requirements, including measurements of ELFEXT (equal-level far-end crosstalk) and return loss.
Check the Label
Aside from electrical performance, cable composition is a required consideration. Any UTP available today should be registered with Underwriters Laboratories (UL) or another NRTL (Nationally Recognized Testing Laboratory). NRTL facilities work under the auspices of OSHA (Occupational Health and Safety Administration) to ensure that consumer products, including UTP, meet basic safety criteria in their makeup and operation. Any UTP product that's been tested by an NRTL will have one or more symbols on the wire and packaging to signify minimum safety standard compliance.
Some UTP products produced offshore and sold in smaller catalogs or by clearinghouses have never been safety tested--avoid these despite any potential savings they may offer.
Jacket Required
Cable jackets come in two varieties: plenum rated and nonplenum rated. Plenum-rated UTP wiring is intended for use where wire is installed freely (not in conduit) in return-air spaces (open spaces in ceilings and under computer floors that are part of the HVAC system in a facility). This type of wire usually costs about three times as much as nonplenum UTP because it's far less combustible and its structure includes components like Teflon.
Nonplenum cable is installed where plenum UTP is not required and is made with less expensive PVC (polyvinyl chloride) as the main jacket ingredient.
Specifying the correct type of cable before investing is crucial. Don't pay for plenum-rated cable if it's not needed. Likewise, don't set up a fire hazard in the form of nonplenum cable if it will be installed in return-air environments. Most UTP product lines offer both jacket types.
A less common jacket type is outdoor, direct-burial Cat 5E. These products are armored and rodent-resistant for use outdoors in special applications and are developed from the widely used high-pair-count voice distribution cables that typically run underground to most commercial buildings.
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