What is Ethernet? - Cable Categories

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It’s easy to get in the habit of thinking of Ethernet network cables as “just wires” (especially because they look a lot like telephone cables), but in truth Ethernet cables are subtler than simply an electrical conductor running from one PC to another. Inside the cable are actually four pairs of wires, twisted together very precisely. Network cables carry data imposed on radio frequency currents. These radio frequency currents run up into the hundreds of megahertz, and at those frequencies things like how sharp a bend you make in the cable matter a lot.

There are seven categories of unshielded twisted-pair (UTP) cabling recognized and defined by standards bodies, running from Category 1, which is simple telephone cable, to Category 6, which is capable of comfortably carrying network data at Gigabit Ethernet rates. A newer Category 7 cable can be backwards-compatible with Cat-5 and Cat-6, and features even stricter specifications. Currently, you’ll most likely encounter categories: 5, 5E, and 6. These are very much alike physically and mostly differ in the maximum data rate that they can carry:

· Category 5 cables are very common and work well for the older 10Base-T networks as well as modern 100Base-T networks.

· Category 5E cables can carry faster data streams, up to (barely) 1000Base-T. Category 5E patch cables are gradually replacing Category 5 cables in retail outlets.

· Category 6 cables are fairly new and can comfortably handle 1000Base-T connections at their top speed. These are slightly stiffer and still significantly more expensive than Category 5E cables.

If all you have are conventional 100Base-T network ports, you can do just fine with Category 5. Category 5E and 6 were created to support low-cost networks using Gigabit Ethernet technology, more precisely called 1000Base-T. Network ports for Gigabit Ethernet are more expensive and generally show up only on newer PCs. If you do decide to create a 1000Base-T network, you’ll be laying out more money for network add-in cards and switches anyway, so go the distance and buy Category 6 cabling. Category 5 cables won’t hack gigabit data streams; they will bring a 1000Base-T network down to barely more than 100Base-T speeds.

I’ve heard numerous reports that Category 5E cabling will allow slightly higher throughput than Category 5 for a 100Base-T network, but I’ve not found that to be true in testing network speed. My suspicion is that badly installed in-wall Category 5 was involved in some of these tests, with a much higher error rate than nice new lengths of Category 5E lying unstapled, unkinked, and otherwise unmolested on the test-room floor. The quality of cable installation matters!