The Ethernet Confusion

I see more confusion on this issue than almost any other.  The question answered below is do I need Category 5e or Cat6 cable to run a Gigabit Network?

The confusion stems from the misunderstanding between common and similar sounding measurements. Those measurements are the MHz rating of Ethernet cable and the Rated Speed of an Ethernet network. The MHz rating on Ethernet cable pertains to the level of resistance to electromagnetic interference, which may or may not be present, and probably won’t be, in the atmosphere in and around your building. 10/100/1000BaseT is a measurement of the number of bits (measured in 1 million per second) that can be transmitted over properly installed data cable. (If you are not technical or do not care about technical details skip down to the last paragraph for the summary)

4 Pair or 8 individual wires make up Category 3, 5, 5e, 5E, or 6 Cable. Each cable pair is twisted in order to cut down on cross talk and electromagnetic interference. If present, electromagnetic interference will result in bits being lost by the network. Keeping in mind that network speed is measured in million bits per second, lost bits requires the resending of the bits, where possible, cutting down on your network performance. The tighter, or more twists per inch, on each of the four pairs inside the Category rated cable, the more the cable is impervious to electromagnetic interference, which may or may not be present, and probably won’t be, in the atmosphere in and around your building; hence it will have a higher MHz rating. A Properly installed and tested network cable includes an analysis of the Bit Rate Loss for each cable installed, which if certified will always equal “0” bits lost.

10/100/1000baseT Networks all transmit their data at the center frequency of exactly 31.25MHz. This is far below the MHz shielding rating printed on all Category 5 or better cable. In fact 10/100/1000 was designed to run over Category 5 cable.
What to do if you have no idea how well your cable has been installed or you have concern about electromagnetic interference? For about $15.00 per cable run, you can have a professional “Certify” your cabling. Objectively knowing what your network cable can handle in terms of network speed and knowing if you have bit rate loss problem, will allow you to eliminate suspected problems and focus on real performance issues.

Warning! Do not purchase the cheapest Category “X” wire you can find over the internet, regardless of its rating. Unscrupulous Category “X” wire manufacturers do exist overseas. Saving a few hundred dollars on the cable is one of the worst things a company can do, unknowingly causing thousands of man hours spent trouble shooting network issues that will not be eliminated until the network cable is replaced.

All this technical analysis is necessary to understanding the different measurements, but what does practical experience teach us? I recently spoke with a cabling professional with 15 years experience installing and testing data cable and asked him how many times has a properly installed cable failed the Bit Rate Loss Test? He said “NEVER”.   This statement tells me that even 15 years ago when Category 5 was the most common cable being installed we were not having electromagnetic interference that affected the transmitting of data.  So it seems that Category 6 is solving a nonexistent problem.

The bottom line is Category 6 cable is not necessary to run a 1000baseT network. If you have the budget by all means install Cat6 and only sleep soundly after you have the installation certified. For those of you without the budget, install Category 5e, have it certified and sleep as soundly as if you had installed Cat6 knowing with certainty that you will also be able to run 1000baseT to the desktop.

Please call with any questions you may have.

Craig Hodges, Telecom Amb.
586-330-9252 DID/Cell


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