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Keeping Ahead of Cabling Problems

Cabling remains a key component of any infrastructure, and ignoring best installation practices and details can create issues that just won't go away. This is particularly troublesome for businesses requiring real-time communications.

Let's look at this from the perspective of a flaky smartboard setup within a campus environment.

The symptom is intermittent loss of sound and picture on smartboards installed in classrooms across a school campus approximately two years ago. One teacher noted that her classroom smartboard has experienced sound and picture loss since day one, yet the company that handled the installation never responded to her complaints. The same issue has affected two additional smartboards elsewhere on campus.

After first looking at the software, I began digging into the cabling. I found that the maximum length supported for the HDMI cable from the workstation adapter to the projector was 16 feet. The HDMI cable is thick, and the fitting was tight -- too tight.

As a fix, I loosened the mounting screws, slid the mounting plate towards the wall, and backed about a half inch off the HDMI cable so it no longer popped out of the connection. Reducing the cable length by that half inch solved the problem. I then adjusted the projector image.

Here are a few of the factors I take into account when planning cable installations. Cable Length & Location - The IEEE standard designating segments of 100-meters long is not a mandate. Therefore, as appropriate, I plan, design, and install cable plants that limit the distance of endpoint drops to 150 feet, while not installing to the maximum Ethernet cable length of 328 feet.

Sure, I go over the 150-feet limit at times, but limiting drop length forces other considerations, such as locating closets or intermediate distribution frames (IDFs) at central locations and thereby reducing the overall length of drops to be cabled in that area. This forces an architectural discussion, too, because placing IDFs at extreme locations, such as the far end of a building and opposite ends between floors, is very costly. The 150-feet length is my ideal, and it especially pays off in a project's early planning stages when you can still influence the location of closets and IDFs.

Next on my list is to get that plant above the ceiling and away from all the stuff that hums: lighting, HVAC gears, electrical wiring, etc. Anyone installing cable plant should know this ideal and strive to minimize exposure.

Wi-Fi - Install Cat 6 or Cat 6A for wireless access points (WAPs). Wireless LANs will continue to evolve, and when budgets are tight I'd rather limit the use of higher-cost Cat 6A to the WLAN and install Cat 6 for all the endpoints.

Connecting Closets/IDFs - Build a fiber backbone plant, and stave off so many issues. Fiber electrically isolates power transients -- in other words, power surges don't traverse fiber, so power hits that affect local gear won't travel to the fiber-connected switch stack. Copper is noisy, and that won't change. Aggregating fiber also improves network resiliency and increases internal network bandwidth, which provides a positive impact for applications and overall user experience. Uplink the switches using fiber and the same benefits result. Aggregate ports to the server and remote users will appreciate the improvements, too.

Field Crimps - Toss out any field-crimped patch cords or connections; they don't hold up. And, work to standardize your patch cords and arrange your real estate. In other words, do some housekeeping. Space patch panels and switches by alternating them in racks and cabinets. You may not be able to achieve all one-foot patch cables to connect patch panel port to switch port, but you won't need anything beyond three feet. Patch cables account for too much extra footage, and when sites look unkept it's usually because they are. What's really annoying is running down long patch cables and trying to trace them to the right port.

Knock-Off Products - Insist on faceplates, inserts, patch cords, and other materials from the same manufacturer. Manufacturers will reward you with certified installers who will certify your cable plant with a meaningful guarantee. Reputable cable contractors all have their favorite manufacturers, and that's fine; it's their way of standardizing their inventories and keeping their costs in check while delivering a quality cable plant. Beware of contractors who use knock-off and inferior cabling products to lower the cost of their bids.

Power - The juice to get your gear running is changing, and you really need to think about how you are going to deliver 15, 30, 60, or even 100 watts to devices. You have to ask yourself, "What cable do I use? Why? How do I get it installed, and how much is it going to cost?" The Internet of Things will bring new things and new requirements for gear. You don't want someone who thinks they know how to install cable because what you really need is someone who will show you how and why -- and that's the key difference.

The IEEE standard designates the following:

But these standards don't stop at length of runs, and planned and efficient IDFs that are well managed. They require other considerations, such as for temperature. The Telecommunications Industry Association (TIA) recommends that no cable that delivers Power over Ethernet (PoE) and data exceeds an increase of 15 degrees Celsius from the ambient temperature around that cable.

Siemon, a network cabling solutions provider, notes the following about 802.3at PoE Plus:

PoE is replacing local power, but it is important to note the requirements and concerns. PoE devices such as WAPs may necessitate grouping the cabling destined for these devices by themselves or simply not including them in the same bundle as other endpoint drops. TIA found that reducing allowable bundle sizes -- of 52 cables for Cat 5e, 64 for Cat 6, and 74 for Cat 6A --by thirds or halves, reduces the temperature.

In short, reduce the bundle size and you can still plan the powered devices and then group the devices and even group the drops separately to minimize temperature increases. This protects your investment and hedges against poor performance.

Here's a cable primer from Belden to assist in distinguishing cable types:

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