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Defense and Public Safety Technology Consulting Services



Category 5 Cabling and Beyond


The news on bandwidth.
The need for increased bandwidth never ceases—the more you have, the more you need. Applications keep getting more complex, and files keep getting bulkier. As your network clogs with more and more data, what was speedy not so long ago is pokey now. And you know it won't be long before the boss wants to know why you can't make the network go faster.

The good news is that the next generation of cabling is on the way. However, you must exercise care to ensure the cabling you install today meets your needs tomorrow.

Because unshielded twisted-pair (UTP) cable is by far the most common networking cable, that's where most of the research money is going these days. Let's take a brief look at where UTP technology is now and where it's headed.

The limits of Category 5.
Category 5 cabling is good, solid cable for 100-Mbps LANs. Right now there's a good chance you don't have anything in your network that Category 5 can't handle. Of course, that will change in the near future.

The Category 5 standard has been around since 1991, so it's had time to become well established in the industry. You'll find existing Category 5 installations everywhere you go. So the questions are: What can Category 5 cable do, and what can't it do?

It handles 100-Mbps Fast Ethernet very well. If you still have a lot of 10-Mbps equipment, chances are Category 5 cabling will serve you well for quite a while.

But if you're already running up against the performance limits of a 100-Mbps network, you'll probably be thinking about upgrading at least parts of it fairly soon. You're probably looking at full-duplex right now, and Gigabit Ethernet is on your horizon. That may mean upgrading your cable.

Category 5e: the new, improved Category 5.
One incremental improvement that has just been approved is Category 5e, or Enhanced Category 5. It's designed to make the world safe for full-duplex Fast Ethernet.

The main difference between Category 5 and Category 5e is that some of the specifications have been made a little stricter in the new version. With that improvement, you should be able to expect problem-free, full-duplex, four-pair Ethernet transmissions over your UTP.

In the near future, it's likely most installations will require Category 5e cabling and components. Many manufacturers sold Category 5e cable before the final standard was ratified, but the cable might not meet all the requirements. 

Category 6 and beyond: a look at the future.
You can't get real Category 6 cabling right now because the standard hasn't been created yet. But the standards bodies are working on it.

You can see some of the details of the proposed Category 6 standard in the guide below. One of the biggest improvements will be in bandwidth: Category 6 is expected to support a frequency of 250 MHz, two and a half times the specifications for either Category 5 or Category 5e.

Farther into the future, the TIA/EIA is looking at a Category 7 standard with a bandwidth of up to 600 MHz. We also know that Category 7 will use a new, yet to be determined, connector interface.

Industry Standards.
Now, here's where it gets confusing. The advantage of sticking to the industry standards is that you know your cabling will be compatible with standards applications. The disadvantage is the standards organizations seem to take their good old time ratifying them. The final standard may also be different than the proposed standard, but the differences are usually minimal.

You will often see cable listed as meeting proposed standards. For example, the proposed standard for Category 6 is 250 MHz, and the proposed standard for Category 7 is 600 MHz.

The important thing to remember is this: The proposed standards are improvements over Category 5 and Category 5e cable, and they should serve you well in terms of speed and headroom for future applications.

So do you have to rip out all your cable?
Not necessarily. You might be able to run Gigabit Ethernet over your existing Category 5 or Category 5e cable.

  Category 5 Category 5e Category 6 (proposed)
Frequency 100 MHz 100 MHz 250 MHz
Attenuation (min. at 100 MHz) 22 dB 22 dB 19.9 dB
Characteristic Impedance 100 ohms ± 15% 100 ohms ± 15% 100 ohms ± 15%
NEXT (min. at 100 MHz) 32.3 dB 35.3 dB 44.3 dB
PS-NEXT (min. at 100 MHz) no specification 32.3 dB 44.3 dB
ELFEXT (min. at 100 MHz) no specification 23.8 dB 27.8 dB
PS-ELFEXT (min. at 100 MHz) no specification 20.8 dB 24.8 dB
Structural Return Loss (min. at 100 MHz) 16 dB no specification no specification
Return Loss (min. at 100 MHz) no specification 20.1 dB 21.1 dB
Delay Skew (max. per 100 m) no specification 45 ns 45 ns
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