A Layman's Guide to Network Cable Types - Deciphering CATs, UTPs, STPs and other bits of Alphabet Soup
By Lee Penrod Copyright (C) 2010 Directron.com.
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Although wireless network technology has improved greatly over the last few years, nothing beats the reliability and performance of a good wired network in your home or business. One challenge that a lot of people face is what kind of cable they need when buying bulk cable for a project such as in home network cable installations, drop ceiling cable installations, or simply creating a custom patch cable. The goal of this guide is to provide a easy explanation of the cable types that anyone can understand.
Part One: Basic types
Although, in truth there are over a dozen types of network cable types in the field, the fact is there are really only 3 types of network cable used commonly in home and small business network installs: Category 3 (CAT3), Category 5 (CAT5), and Category 6 (CAT6).
- CAT 3 Cable: These days CAT3 cable isn't used that much. Category 3 cable is primarily for phone wire installation in homes and businesses, however it can be used for other purposes such as alarm system installs or other means. Bulk CAT3 cable may have 2, 3 or 4 pairs of wires inside it. Generally we stock 3 pair and 4 pair CAT 3 cable at Directron. When hooking up a single phone line 2 wires are needed [ 1 pair ]. Generally older buildings used 2 pair CAT 3 cable for phone installs so you could have two phones at each wall plate or could support two line phones. The benefit of three pair or four pair cable is that you have extra pairs behind the plate in case of problems with one of the wires and also it allows for a 3rd/4th line if needed. That said, for the most part, 4 pair CAT 3 cable is not used very much in new construction. When using 4 pair CAT 3 cable, the price difference isn't that much compared to CAT 5 cable, maybe a maximum of $20 on a plenum 1000 ft roll. For most contractors they prefer to just buy all of the cable for the job as CAT 5 or CAT 6 and just use that for phone line runs as this allows them flexibility in switching a phone jack into a network jack and potentially higher bulk purchase discounts. The most cost savings with CAT 3 cable comes with 2 Pair and 3 Pair CAT 3 cable which use much less copper than CAT 5. Four Pair CAT 3 is cheaper than CAT 5 primarily because CAT 3 has fewer twists in it. Fewer twists = less copper per foot. Obviously, if you have less pairs in the cable, you go down even more because there are less copper wires in total.
- CAT 5 Cable: Category 5 network cable is pretty much the most widely deployed type of network cable today. Currently, you'll be hard pressed to find actual CAT 5 cable as it has been pretty much replaced by CAT 5e [CAT 5 Enhanced]. We'll talk more about what this means in the next part. CAT 5 cable can be used for Phone line use, 10 base-T Networks or 100 base-T Networks (10/100) . CAT 5 cable can also be used for Gigabit networking, however quality may vary depending on the age of the cable. CAT 5e is more regularly recognized for support of 1000 base-T networks [ Gigabit Ethernet ].
- CAT 6 Cable: Category 6 network cable is quickly becoming the main choice for residential and business installs for new construction. Category 6 cable is specifically designed for 1000 base-T [ Gigabit Ethernet ] or higher speeds *(Note 1). That said, CAT 6 cable works just fine for pretty much any use you would expect from a CAT 5, CAT 5e, or CAT 3 cable including phone line usage or slower network standards. Although both Category 6 cable and CAT 5e both can run Gigabit network, CAT 6 has some additional benefits we'll discuss later in this article as well.
Each of these three basic types has a enhanced version, as well as several sub types which we will explore further in the next part.
Part 2: Cable MHz ratings and Enhanced
As far as network cable goes, some ratings are not all they are cracked up to be. One misunderstood rating factor is MHz number (bandwidth). To understand that a little better we need to look at a little table-
|Standard||MHz Rating||Highest Network type||Comment
|CAT 3e||16MHz?||10||RARE, Not official|
|CAT 5||100MHz||100||No longer recognized|
|CAT 5e||350MHz(or 400MHz)||1000||Not Recognized|
|CAT 6e||550||1000* (note 2)||Not Recognized|
Note 1: Category 6 cable can support 10 gigabit Ethernet ( 10GBe ), however not necessarily at full maximum length between connections (100 meters [328 ft]). In a really good interference free area standard CAT 6 may only be able to sustain about 37 m (121 ft) of distance while a poor area may only survive half of that. 10 GBe ethernet is very susceptible to both crosstalk ( the bleeding of signal from one wire to the next) between pairs as well as external interference such as that caused by electric motors, fluorescent lights, and other electrical equipment.
So what does not recognized mean?. As we all know from buying computers or processors in the past, MHz numbers are a selling point. Cable manufacturers long ago realized this, so they began testing their cable for the maximum bandwidth it could sustain. The problem with that is that the network standard organization basically outlines the specifications of what should be in the cable, and the minimum tested bandwidth of the cable (including procedure to test) to say it's Category X.
Huh?. Ok so what does that really mean? Well it means that if you buy a Category 5e cable it had to meet a couple of criteria to be called a 5e cable. The main thing it had to have in it was better insulation and materials to cut down on cross talk. It also had to be tested to be able to sustain 100MHz of bandwidth. Basically when you buy a 5e cable that's really all you're guaranteed. 350MHz basically began as a marketing gimmick. You have a few engineers sitting around, they make minor changes X,Y and Z to the cable design and they find that they can push a few more MHz out of the cable and charge more. For a short time, 350MHz or really any rating over what was required of the standard organization was really a mark of quality. You purchased a higher number, and potentially got better cable. The problem with that is in the beginning this was done with a guarantee from the manufacturer. That didn't last long at all. The problem with that is very few people have a $4,000 - $15,000 cable certifier to take with them to do a basic network job and it costs pretty much nothing to print a couple extra numbers on the cable covering.
At the worst end of the spectrum the MHz numbers are simply one more thing to print on the cable. At the best end it may mean a very minor improvement in performance of your network for long cable runs. Bear in mind, today you'll find almost all 5e is already marked 350MHz. For the manufacturer of the cable, there is no incentive not to say 350MHz (or even some higher number) on the cable, however there is a negative for them if they don't do it. That's not to say that all cable marked 350MHz won't pass a 350MHz test with an expensive meter, but it does mean you should take such claims with a grain of salt. After all, unless the quality of the cable is poor overall, it's going to provide the connectivity level stated in the table. For this and other reasons, we keep an eye on the quality of our bulk network cable and won't sell cable with shoddy construction. We suggest you do that same.
Note 2 - CAT 6, CAT 6E and CAT 6a are actually all very similar. In the notes above I mentioned the issues of not recognized claims. Well, at least for my own personal experience I do have to at least give a nod to CAT 6E ( CAT 6 550 MHz ). Basically it's like this, with 10GBe you have limited distances with standard CAT 6 because of crosstalk (signal bleed) issues between pairs and because of external interference. (This is issue is typically called alien interference) CAT 6a is the official answer to this problem. It contains additional measures in it to reduce crosstalk between pairs and has to pass a higher bandwidth test of 500MHz.
In this author's personal experience with cabling I have found that a primary difference between CAT 6 cable and CAT 6e / CAT 6 550MHz is the addition of a spline in the network cable. This spline separates the pairs in the network cable which cuts down on cross talk quite a bit. This spline gives the cable a bit of heftier feel to it as well. Although as with standard CAT 6 you are only really subject to the 37m rule for 10GBe, my feeling is that with good solid core Category 6 550 MHz cable with a spline you can probably push it further. I'm not willing to go out on a limb and say you can get the full 100m, however I would encourage you to test it in your application if you are needing a significant number of 6a runs (especially short ones) and there is a large price difference.
Now that you have an idea of Category ratings, and MHz ratings, we need to get down to some more nitty-gritty details.
Part 3: STP, UTP, Leave me be
Ok now that you have a idea of what Categories are, and a little bit about MHz ratings, lets tackle a little basic knowledge. Network cable typically comes in two basic types UTP (Unshielded Twisted Pair) and STP (Stone Temp- I mean Shielded Twisted Pair).
UTP vs STP is actually fairly easy to understand. The short answer to the cable buyer is buy UTP. There are extremely few situations where UTP is not appropriate for normal installations. The long answer is, if you are running through terrible conditions UTP may not be good enough.
UTP - Unshielded Twisted Pair. Unshielded twisted pair cable is a basic term referring to the how the cable is constructed. The cable consists of a few basic parts: Pairs of wires (Typically 4 pair except in CAT 3), a piece of twine [sometimes called a rip cord], and a outer sheathing of insulation. Some types of cable such as CAT 6e / CAT 6a, outdoor cable, or armored cable may contain additional pieces such as a dividing spline, a water repelling gel/coating, a braided armor coating or other parts.
STP* - Shielded Twisted Pair. Shielded twisted pair takes the design of UTP cable and alters it a bit. Instead of having the pairs covered in a outer covering, the pairs are covered in a plastic covering (typically clear), then that covering is covered with a metal foil not unlike that used in coax cable. An un-insulated metal drain wire runs the length of this foil material and the whole thing is then wrapped in another thicker insulation. At either end of the cable when doing a run the drain wire must be attached to a ground in order for the shielding to work. The shielding on the cable pretty much eliminates external interference from typical industrial sources
Note 3: There are actually two types of shielded cable: STP and FTP, however manufacturers don't universally call them the same things. FTP means Foil Twisted Pair. The complicating thing is there can be shielding on the inside on the individual pairs, or shielding on the outside like I described or both. Most of the shielded cable what we sell is technically FTP cable. The manufacturers however denote it as STP cable with FTP shielding or in some cases just mention STP not FTP at all. If you need cable with both kinds of shielding (sometimes called S/FTP compared with (S/UTP or F/UTP) for our kind), please contact our sales department if you can not find it online. Cable with this kind of double shielding is typically overkill for most situations and is considerably more expensive. The primary use for double shielded cable would be for experimental types of data networks such as 100 Gigabit ethernet. This kind of double shielding is part of the specification for Category 7 / 7a which more or less doesn't exist yet.
Part 4: PVC Jackets, Plenum Rated, Outdoor, and More
One more thing to think about when buying cable is: Where is the cable going to go? Although this should be one of the easier questions to answer (either by knowing your house, doing a site survey, or looking at blue prints), the area that the cable will go in contributes to what kind of cable covering is needed. There are a few choices here depending on the situation.
- PVC: Probably the most common kind of network cable is PVC. PVC is commonly used as the covering for patch cables, and is often used for bulk cable. The biggest issue with PVC covered cable is that when burned it releases a toxic smoke. For this reason most local fire codes prohibit PVC covered cable from being used in air handling spaces. Generally it's acceptable to use PVC cable for in wall installations though, however you should check your local fire codes.
Plenum: Plenum rated cable (often called Plenum cable for short), is network cable that has a covering that burns without toxic smoke. The name comes from the air handling space typically found in construction known as a plenum. In construction plenum refers to the separate space provided for air circulation, heating, and venting. In a standard commercial building, the plenum is the space between the drop ceiling and the structural ceiling. In residential installations the plenum could be in a few places such as as the floor when floor level air circulation is used or the ceiling.
Collectively PVC and Plenum rated cable are the most common coverings for network cable. In the picture at the top of this part you'll see the two different coverings. Don't be fooled by the color difference, they both come in a variety of colors. The main difference is in the construction of the covering. In general it's not necessarily easy to tell the two apart by eye, however in my experience usually plenum cable will have a slightly different feel to it. It may be slightly more glossy/waxy than PVC cable and generally it doesn't hug the pairs as much (because of how it's applied) so the covering may appear smoother. In general most Plenum rated coverings are somewhat softer than standard PVC and as such it is a bit easier to tell the difference when stripping a small section of the cable. As far as external markings go, plenum cable is typically screen printed with either Plenum or CMP (Communications Plenum) along the cable itself when possible.
Note: Plenum isn't a substance. A plenum rated cable may actually be coated with a number of different things. Generally plenum rated cables are coated with a flame retardant low smoke PVC or Teflon (FEP).
Armored Cable, Outdoor Cable, Aerial Duct Cable, Direct Burial: For extreme environments there are a number of solutions available. In general these types of cables have the following possible additional characteristics:
- Flooded Core / Poly-Filled: Almost all outdoor cable and most other kinds of armored cable has this. Basically this means that a water resistant gel encases the pairs and this helps prevent water from directly contacting the wire and corroding it in the event it contacts water. (or at least greatly slows down the corrosion process)
- Teflon Tape: This feature is found on some kinds of outdoor cable. Basically if the wire has this feature then the pairs are wrapped in Teflon tape before getting the outer coating. This is usually done in conjunction with Poly Gel, and is just another layer of water protection.
- Drain Wire/Shielding: Some outdoor cable contains shielding like I described in the STP section in part 2. It functions basically the same way, however it is applied in addition to other water resistant features such as poly gel, Teflon tape, or other means.
- Armor Coating / Toughened outer insulation- In general outdoor cable overall is going to have a much tougher than normal outer covering. Typically this is not plenum rated [for obvious reasons-if your air handling space needs armor you've got some serious issues]. Toughened outer insulation is primarily there to help prevent abrasion damage to the cable and in the case of direct burial, prevent the outside from coming in.
Now as we've learned most of the ins and outs of cable, we need to cover one more topic.
Part 5: Stranded vs Solid Core
When selecting network wire, we have one more issue to cover- Stranded vs Solid Core.
When buying network cable you can buy either kind, however neither one is appropriate for all kinds of situations. Solid Core wire has a solid 22-24 gauge copper wire. Stranded wire has many small threads of copper twisted together to add up to 22-24 gauge.
In general wall jack (keystones), and patch panels were designed with solid core wire in mind, and as such termination will be easier and more reliable with solid core wire. (Yes you can find keystones / patch panels for stranded, but they are less common and most keystones / panels don't even mention wire type in the specs). Standard network cable connectors for patch cables (commonly called RJ45 connectors / 8P8C connectors) are really more designed with stranded cable in mind and will terminate more reliably with it.
So why the difference? Solid Core wire has very good attenuation properties (it's easier to send a signal over). As such, solid core is best for long runs. What solid core wire lacks somewhat is flexibility. Solid Core wire can be bent, however not as much as stranded wire and as such stranded is much better for patch cables where flexibility is very important. Excessive bending or very sharp angles with solid core wire risks breaking a wire.
So basically - Use Solid Core wire in your walls and building wiring, and use stranded where you have to make extreme bends or in patch cables.
Conclusion So I went over a lot of things in this article. Lets distill it down to a few points.
1) For networking PCs in a normal office environment use CAT 5e / CAT 6 / CAT 6e UTP network cable. You can use CAT 3 or your standard network cable if you need to run phone lines.
2) Use solid core cable in the walls / ceiling and buy a small amount of stranded if you want to make your own patch cables (or just purchase cables).
3) Buy CAT 6e / CAT 6a cable to future proof your network. You may or may not need 6a for 10GBe depending on length of runs.
4) Only buy shielded if your networking environment is extreme.
5) Use Outdoor cable if you plan to directly bury the cable, run it exposed to the elements, or expose it occasionally to moisture.
I hope that this article has helped you with your bulk cable purchases. Good luck.
Last updated: 5/03/2010
More Works by Lee Penrod: | How to Install USB | Understanding Memory and CPU speeds: A Layman's guide to FSB | What is PCI Express? | 1.5V AGP Guide | What is a KVM? | Hooking up a Neon Light | Mod Dictionary | Lee's Blog |
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