Invest in a Cable Tester

Industry giants Agilent Technologies, Fluke Networks and Textron are among the current players at the front line in the cable-tester field. Their marketing strategies all emphasize the fact that testing turns up problems that might otherwise go unnoticed. A UTP cable run that looks good might have any number of problems waiting to spring, and the more critical the machine connected to the network via that cable, the more serious the consequences.

Cat 6: It's All in the Details

Like most standards, the recently approved Category 6 wiring standard involves a wealth of technical minutiae. And though groups like the IEEE, the International Organization for Standardization (ISO) and the Telecommunications Industry Association (TIA) define the details of every wiring standard, UTP manufacturers and testers do an excellent job of boiling those details down to a level that the general IT population can digest. You have to be familiar with the terminology in order to purchase the right tool for the job. For example, the newest wiring testers--all Category 6--are referred to as Level III testers, whereas Cat 5 testers were Level II (or IIe). The higher level promises tighter test specs and increased performance metrics. You or your installer should be testing Category 6 wiring with a Level III tester. Accept nothing less, or the results will be meaningless against the Category 6 standard.

Category 6 testers incorporate tests from previous standards to ensure backward compatibility for testing legacy cables while meeting the challenge of higher performance measurements. Cat 5e cable testers were designed with gigabit in mind, so they swept a frequency range of 1 MHz to 100 MHz. Category 6 testers provide sweeping to 250 MHz, which means a higher-performing cable when combined with the rest of the metrics, including signal-to-noise ratio. The new top end of 250 MHz means a wider pipe is guaranteed, as compared with legacy standards (see "Cat 5e and Cat 6 Comparison," below, for the differences between Category 6 and the now-legacy Category 5e measurement criteria).

Universal AppealThe concept of Permanent Link testing is a critical part of Category 6 testing. It takes into account not only the horizontal cable run but the behavior of patch cords at either end, for a more complete picture of overall end-to-end run performance. For best results, make sure the tester you select has Universal Permanent Link testing capability. This means your tester will function with any true Cat 6-compliant jack. Otherwise, you may need to purchase additional pieces, such as an adapter, to function with your specific brand of jack.

Also, remember that when you put your new Cat 6 wiring into service, you must use Cat 6 patch cables as well. Mixing legacy patch cables with new wiring has always been a problem, so beware.

Know What You Need

Level III testers must cover the basic requirements of the Category 6 cable standard. Beyond the basics, though, it's important to be aware of how manufacturers' product features differ. It's just like buying a car: Armed with knowledge of the standard features and various options, you will be better equipped to define your needs before you entertain the tester sales folk.

Most testers will live up to their basic charter of evaluating cable with a predefined battery of tests. But you may be more concerned with testing speed and ability to store large numbers of reports for later download, for instance, while someone else's priorities may be ease of use and battery life.If you are not the one who scans the cable, have a sit-down with a rep from your installation crew to define what you need in a tester to fit your specific setup. This is also a good time to check that your installation crew knows how to use the tester.

Early Adopters, Take Note

A number of cable manufacturers started selling

Cat 6 cable long before the standard was ratified, hoping that the promise of increased bandwidth and headroom on the wire would rally customers to take a chance--and many of us did. The problem is that much of this cable was installed before the availability of test equipment that could accurately measure cable performance at Cat 6 specs. Even worse, some cable manufacturers may have guessed wrong about what the final Cat 6 specification would be. If you were an early adopter of Cat 6 when only Category 5e cable testers were available, consider retesting your cable with a post-standard Category 6 tester. And heed this warning: The same phenomenon is beginning to occur with respect to Category 7 (and the distant Category 8, for the truly adventurous)--a standard that may never see the light of day. Know the current standards and be wary of those marketing something that does not yet exist.

The tools don't stand by themselves, as many of us have learned the hard way. When it comes to bandwidth and speed, the wire, jacks, patch panels and patch cords are far from the whole story. In addition to having the appropriate tools, make sure you have trained installers with knowledge of standards to test and certify the wiring plant for rated performance. If you have the tools and the know-how, you'll be able to rest easy.Lee Badman is a network engineer at Syracuse University. Write to him at [email protected].

Post a comment or question on this story.