Many security system integrators are installing network cable without following standard network cabling practice — so many, in fact, that it is not too uncommon to find kinked or stretched cables.
Category 5 and 6 network cable cannot be handled in the same manner as other types of cable, and can be damaged by handling that would not affect other cable types. Often, the weight of cable bundles in large control panels or equipment racks strains the network cables at their connectors. Solid copper wires wrapped around terminal screws can generally withstand much more weight than a standard network cable and its connector; yet, many installers handle both types of cable the same way.
Generally, installers believe that a network cable either works or it doesn’t — that’s not the case. A network cable can be faulty and still seem to be “working,” and this question arose from such a situation:
Q: A few of our cameras go offline once a week or so. Cycling the camera’s network port (a PoE port) rebooted the camera, but the camera would go offline again some weeks later. A consultant asked our integrator to check the network cable with a cable testing device, and some failed, was replaced, and the cameras using that cable no longer went offline. Our IT director hit the ceiling when he found out they didn’t certify the cable when they installed it. What kind of certification is he talking about? And why could we view and record video if the cable was bad?
A: The certification is of the cable itself using test equipment; and a cable can be faulty and still transmit data because the network switches can buffer data and retransmit packets that don’t get through on the first attempt, masking a faulty cable problem.
In copper twisted pair wire networks, copper cable certification is achieved through a series of tests in accordance with Telecommunications Industry Association (TIA) or International Organization for Standardization (ISO) standards. These tests are done using a certification-testing tool, which provides “Pass” or “Fail” information for each test. Certification is primarily done by installing contractors. It is this certification that allows the contractors to warranty their work.
I have talked to installers who “verify” their cabling by seeing if video gets transmitted over the network. If they can open a browser on a laptop and get a web page with video from the camera, they assume that all is okay — but it may not be.
For example, when using 10/100/1000 Mbps network interface cards and switches, a poor cable can cause the lower speeds to be negotiated between equipment because the cable won’t support the highest speed. The network will be “working,” but not at its intended bandwidth. That may not matter much for some access control systems, which generate very small amounts of network traffic most of the time, but it can have a critical impact on video systems.
In 2002 the Fiber Optic Association reported, “as much as 80-90 percent of all Cat 5 cabling was improperly installed and would not provide the rated performance. Contractors have told us that 40 percent of their Cat 6 installations pass certification tests. Untwist the wires too much at a connection or remove too much jacket and the cable may fail crosstalk testing. Pull it too hard (only 25 pounds tension allowed), or kink it, and [you] lose the performance you paid for.”
Good network cabling practice must be followed and that includes the practice of cable certification. A cable certification report should be part of the deployment documentation for any networked security system project. Many security system technicians are installing and servicing networks without sufficient training in networking design, installation and management. They do not certify the network cable they install.
On the other hand, I know of several security integrators who subcontract their large network cable installations to companies who specialize in that work. Their subcontractors use cable testing equipment and provide them with a cable test report certifying that the cable installation is sound. Their own technicians also certify the cable work that they perform themselves on smaller projects.
While network test equipment exists in the $4,000 to $12,000 range, a good network cable tester can be had for about $500.
It is worth mentioning that there are also cable testers that show the PoE power draw of installed equipment, which can be used to determine the total draw on a PoE switch. A complete examination of cable testing equipment is beyond the scope of this column, as is a discussion of cabling infrastructure standards and training.
Write to Ray about this column at [email protected]. Ray Bernard, PSP, CHS-III is the principal consultant for Ray Bernard Consulting Services (RBCS), a firm that provides security consulting services for public and private facilities. Mr. Bernard has also provided pivotal strategic and technical advice in the security and building automation industries for more than 24 years. He is founder and publisher of The Security Minute 60-second newsletter (www.TheSecurityMinute.com). For more information about Ray Bernard and RBCS go to www.go-rbcs.com or call 949-831-6788. Mr. Bernard is also a member of the Content Expert Faculty of the Security Executive Council (www.SecurityExecutiveCouncil.com).
