The 1980's ushered in the advent of the personal computer, and the domination of the massive mainframe as a business tool started to come to an end. However, most computer cabling was still a proprietary component controlled by the selected hardware vendor.

During this same timeframe, telephone cabling was a completely separate entity, typically dominated by two-pair, unshielded twisted pair copper (UTP) cable. This is still the type of cable being used in most residential houses today for their telephone applications.

Around 1990, as computer networking began to take off, the telephone and computer groups started to come together. Computer users wanted have more than one choice for their computer and network solutions. As end users started to exercise their options, more and more choices were becoming available. The end result was a proliferation of different computer networking solutions, each with their own proprietary cabling requirements. It was becoming clear that some form of cabling standardization was going to be required in order for the industry to advance faster and further along.

As a result, the computer industry, the telecommunications industry and large corporations agreed to form the Electronics Industries of America/Telecommunications Industries of America (EIA/TIA) as an independent standards body whose purpose was to define a common set of criteria for product specifications. This made it possible to purchase connectors, cabling and hardware from a wide variety of vendors and have all the different products work together.

One of the first and most important moves adapted by the EIA/TIA was in the early 1990s, when they approved 4-pair, Unshielded Twisted Pair as the cabling media of choice. The concept was to allow end users to install high-performance UTP cabling as their networking solution and expect it to support all or most present and future high performance computer networking applications in addition to supporting normal voice operations.

In order to delineate between different performance levels, "Categories" of performance were established for cabling specifications. CAT 3 was designed to support 10-BaseT (Ethernet), which was the dominant "desk-top" networking application at that time. In an Ethernet LAN environment, the backbone cable typically requires more bandwidth than the horizontal cables. Since CAT 5 was designed to support 100-BaseTX (Fast-Ethernet), an Ethernet LAN could use a CAT 5 cable as the backbone cable, and run 100-BaseTX as the backbone application. But in most cases, you will be better served using a fiber cable as the backbone cable, which would allow you to run 100-BaseFX now and any backbone application that may emerge in the future. Either way, a 10-BaseT LAN should have at least a 100 Megabit bandwidth or better as the backbone application.

Along with the product specifications, EIA/TIA established standard guidelines for installation methods and performance specifications. Among the most notable installation requirements was the rule of "homerun" cables. In order to assure future performance for new technologies and protocols, the cable was required to be unbroken (or spliced) from the Telecommunications Closet to the user outlet. The reason for this was because any time that you add an inter-connect point, you experience some loss of signal. Recently, because of the special obstacles that open office environments present, the cabling requirements have been addressed by TBS-75, which does allow for an interconnection point between the patch panel and the work-station. Please contact us for further information regarding cabling for open office environments.

Another notable cabling requirement that the EIA/TIA standards defined was the length of the cable from the closet to the wall outlet. Due to signal loss over distance, 90 meters was defined as the maximum length limit that a cable could be, and still meet specifications.

As technology progressed, and computer-processing speeds increased, the need for more bandwidth became apparent. Prices for 100Mb hubs and switches dropped, and more LANs were being designed to run 100-BaseTX to the desktop. It was only a matter of time before 4-pair, CAT 5 UTP became the widely accepted industry choice for horizontal cabling, due to its ability to support high bandwidth computer applications to the desk-top as well as voice applications. But what about the backbone in a Fast Ethernet environment? As mentioned before, the backbone is typically the workhorse of all LAN's, and should be designed with more bandwidth capabilities. Would a CAT 5 cable work as a backbone cable in a Fast Ethernet to the desktop LAN architecture? Fortunately, most LANs are now being designed with a fiber optic cable for the backbone, so implementing 1000-BaseT (Gigabit) as a backbone technology will not be a problem for most IS managers.

But more bandwidth to the desktop is still a problem, now and in the future. Moore's Law states that computer processing speeds will double every 18 months. New applications such as Voice over IP and Video over IP will require more network bandwidth. As prices for 1000-BaseT hubs and switches begin to come down, more IS managers will want to implement Gigabit to the desktop. But can the horizontal CAT 5 cabling that they have in place now support these faster application speeds? The answer is - possibly, but probably not without some fine-tuning.

The performance specifications for CAT 5 cabling requirements were set at a minimum rating of 100 Mhz. Not only would this provide enough headroom to run 100-BaseTX, (do not confuse Mhz with Mgb) but the cable rating that was required was thought to provide enough "Future-Proofing" for emerging technologies as well. But as 1000-BaseT was being developed and tested, some unforeseen problems began to appear, specifically with Signal to Noise Ratio.

Since crosstalk (or signal leakage) can occur with any electrical signal, this can affect any other pair of conductors that also might be trying to transmit a signal at the same time. It's sort of like two or more people trying to talk at the same time - not every one or every word is going to be heard or understood correctly. 100-BaseTX requires only 2-pairs (4 conductors) to operate; one pair to transmit, and one pair to receive. While this does indeed present some crosstalk issues and SNR concerns, as well as some other signal propagation problems, they are not nearly as significant as the problems that 1000-BaseT presents. 1000-BaseT requires all 4-pairs (8 conductors) to operate at full duplex, with all pairs transmitting and receiving simultaneously. This introduces some new SNR problems that were not addressed in the CAT 5 specifications.

Therefore, some additional testing parameters needed to be addressed and written into the EIA/TIA standards. These new standards are now called CAT 5E and have some new and significant testing parameters associated with SNR. Keep in mind that the 100Mhz requirement for CAT 5 did not change for CAT 5E. The main thing that changed was the additional testing parameters. Therefore, it may be possible that your old CAT 5 cabling system may be able to pass CAT 5E testing requirements without much modification. Therefore, if you are thinking about migrating your LAN from 100-BaseTX to the desktop to 1000-BaseT, you might want to think about having your present cabling plant retested and certified first. You may find that some or all of you present cabling plant will meet or pass all of the new testing requirements. And if you are designing a new cabling plant for your company, make sure that you specify that you want a cabling plant to at least meet or exceed CAT 5E specifications.

And not to add any more confusion to the mix, but not all CAT 5E cables are equal. During the two or so years that all the cabling manufacturers were lobbying for the new CAT 5 E specifications, they all jumped the gun. Wanting to be the first to come out with a CAT 5E cable, and not knowing ahead of time what the new CAT 5E specifications would require, many of the manufacturers produced some cables with a higher rating than the 100Mhz of the existing CAT 5 specifications. Most of these cables are in the 150Mhz range, and are still being manufactured and marketed as a CAT 5 E cable today. The benefit is a cable with more headroom than the minimum requirement of CAT 5E (100Mhz), but the drawback is a higher cost. Make sure that you know what you want, what you are getting and what you are paying for.

Remember, these standards are not like the UL or NEC electrical standards, since low voltage communications cabling does not present any hazard to life. Telecommunications cabling does not require inspection, and no one can shut you down for faulty installation methods (the only exception to this is if the cable jacket does not meet the required local, state and national fire code regulations as directed by NEC specifications). The EIA/TIA standards are just the industry recommended specifications in order to assure that all of your network components are manufactured to minimum tolerances, and are installed with some uniformity.

And finally, as you read this, the EIA/TIA committee is meeting once again to deal with the issue of CAT 6 cabling specifications. This cable will probably be rated somewhere between 200-250Mhz. Why is this much headroom needed? Well, 1000-BaseTX (Ten Gigabit) is just around the corner. And who knows what the future may bring? Remember Moore's Law…