Those of you who have been following my blog know that I love to write about what I classify as the soft sciences. By that I mean protocols, call flows, software, security, and other technologies that are for the most part, hardware and infrastructure independent. Does it make much difference if I run a SIP stack on a PC, virtual server, or smart phone? Not really. SIP acts like SIP no matter what platform is sending or receiving it.
So, it may come as a surprise that today I am writing about something that has little to do with source code or security certificates. I want to espouse on Ethernet cables.
Honestly, I didn’t give cabling a lot of thought until last week when I was speaking at an Avaya Users’ Group meeting in Tampa, Florida. After the president discussed old and new business, he opened the floor to the members to ask questions of their fellow Avaya users.
The questions were good. I took notes on several and chimed in where I felt I had something to add. However, the one that I found most interesting was this, “We are in the process of redoing our building’s LAN cables and I was wondering if people are installing Cat-5 or Cat-6.”
The answers varied quite a bit. Some folks already made the switch, a few decided not to, and some fell into the not-sure-what-we-will-do category.
For those of you who don’t have a plan (and I will assume that many of you are in that camp), allow me to spend some time introducing you to the Cat-5, Cat-5e, Cat-6, and Cat-6a Ethernet cables.
But first, this handy-dandy comparison table.
| Length (meters) | 10 Mb/s | 100 Mb/s | 1 Gb/s | 10 Gb/s | Power Over Ethernet | Frequency in Mhz | |
| Cat-5 | 100 | Yes | Yes | Yes | 100 | ||
| Cat-5e | 100 | Yes | Yes | Yes | Yes | 100 | |
| Cat-6 | 100 (55m for 10Gb/s) | Yes | Yes | Yes | Yes | Yes | 250 |
| Cat-6a | 100 | Yes | Yes | Yes | Yes | Yes | 500 |
The Differences
As the class of cable goes up, so does the speed and frequency of the wire. The biggest difference between Cat-5/5e and Cat-6/6a is the speed. Cat-5/5e tops out at 1 Gb/s and Cat-6/6a allows speeds up to 10 Gb/s.
The difference between Cat-6 and Cat-6a is that Cat-6 is only guaranteed for a distance of 55 meters at 10 Gb/s. Cat-6a can run at that same speed for up to 100 meters.
Physically, Cat-5/5e and Cat-6/6a differ in a number of ways. First, there are more twists per centimeter of wire in Cat-6/6a. Cat-5 and Cat-5e typically uses 1.5 to 2 twists per centimeter and Cat-6 and Cat-6a uses 2+ twists per centimeter. Twisting reduces interference between internal and external wires.
Second, Cat-6/6a use a thicker outside sheath than Cat-5/5e. This sheath protects against near end and alien crosstalk. Crosstalk is more likely as the frequency (Mhz) increases. Cat-6 and Cat-6a support higher frequency ranges so they have the thickest sheaths.
Lastly, a nylon spline (a longitudinal separator in the wiring) can also be used to reduce crosstalk. Cat-5e always has a spline, Cat-5 sometimes has a spline, and depending upon the manufacturer, Cat-6/6a may also have a spline. Since Cat-5e requires a spline and Cat-5 does not, Cat-5 has a thicker outside sheath than Cat-5e.
Cost-wise, Cat-6 and Cat-6a are about 10 to 20 percent more expensive than Cat-5/5e. So, cost is not a big issue considering the fact that you can obtain speeds ten times faster when you go to Cat-6/6a.
It’s important to know that Cat-6 and Cat-6a are backwards compatible and can be used with older Cat-5, Cat-5e, and even Cat-3 equipment.
Should You or Shouldn’t You?
If it were me, every new installation would use Cat-6a wiring. Running cable through a building is an expensive proposition and since most cable will stay in place for up to 10 years, I would future-proof my company by adding the fastest option available whether I was ready to rollout 10 Gb/s or not. Running cable twice in a short amount of time would be very foolish
However, I would not pull out perfectly good Cat-5e cable if I wasn’t ready to move to a higher speed. Wait until you need it before spending the money. Besides, by that time, there may be something even better that you can run.
Mischief Managed
This is an important topic that may not jump out at you as you look at upgrading your network switches and routers. However, as you saw, cable choice can make the difference between lightening fast and yesterday’s speeds.
Notice that I didn’t mention Cat-7 cables. For some folks, Cat-6a is ancient history. However, that wasn’t the original question and I need to leave myself something for a future blog article. Stay tuned.