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What Kind of Ethernet (Cat-5/e/6/a) Cable Should I Use?

Not all Ethernet cable is created equally. What’s the difference, and how do you know which you should use? Let’s look at the technical and physical differences in Ethernet cable categories to help us decide.

Ethernet cables are grouped into sequentially numbered categories (“cat”) based on different specifications; sometimes the category is updated with further clarification or testing standards (e.g. 5e, 6a). These categories are how we can easily know what type of cable we need for a specific application. Manufacturers are required to adhere to the standards which makes our lives easier.

What are the differences between the categories and how can you know when to use unshielded, shielded, stranded, or solid cable? Keep reading for “cat”-like enlightenment.

Technical differences

The differences in cable specifications is not as easy to see as physical changes; so let’s look at what each category does and does not support. Below is a chart for reference when picking cable for your application based on the standards for that category.

As the category number gets higher, so does the speed and Mhz of the wire. This is not a coincidence, because each category brings more stringent testing for eliminating crosstalk (XT) and adding isolation between the wires.

This does not mean your experiences have been the same. Physically you can use Cat-5 cable for 1 Gb speeds, and I have personally used cable longer than 100 meters, but because the standard has not been tested for it, you’ll probably have mixed results. Just because you have Cat-6 cable, doesn’t mean you have  1 Gb network speeds either. Every connection in your network needs to support the 1 Gb speed and in some cases, the connection will need to be told in software to use the available speed.

Category 5 cable was revised, and mostly replaced with, Category 5 Enhanced (Cat-5e) cable which did not change anything physically in the cable, but instead applied more stringent testing standards for crosstalk.

Category 6 was revised with Augmented Category 6 (Cat-6a) which provided testing for 500 Mhz communication (compared to Cat-6′s 250 Mhz). The higher communication frequency eliminated alien crosstalk (AXT) which allows for longer range at 10 Gb/s.

Physical Differences

So how does a physical cable eliminate interference and allow for faster speeds? It does it through wire twisting and isolation. Cable twisting was invented by Alexander Graham Bell in 1881 for use on telephone wires that were run along side power lines. He discovered that by twisting the cable every 3-4 utility poles, it reduced the interference and increased the range. Twisted pair became the basis for all Ethernet cables to eliminate interference between internal wires (XT), and external wires (AXT).

There are two main physical differences between Cat-5 and Cat-6 cables, the number of twists per cm in the wire, and sheath thickness.

Cable twisting length is not standardized, but typically there are 1.5-2 twists per cm in Cat-5(e) and 2+ twists per cm in Cat-6. Within a single cable, each colored pair will also have different twist lengths based on prime numbers so that no two twists ever align. The amount of twists per pair is usually unique for each cable manufacturer. As you can see in the above picture, no two pairs have the same amount of twists per inch.

Many Cat-6 cables also include a nylon spline which helps eliminate crosstalk. Although the spline is not required in Cat-5 cable, some manufactures include it anyway. In Cat-6 cable, the spline is not required either as long as the cable tests according to the standard. In the picture above, the Cat-5e cable is the only one with a spline.

While the nylon spline helps reduce crosstalk in the wire, the thicker sheath protects against near end crosstalk (NEXT) and alien crosstalk (AXT) which both occur more often as the frequency (Mhz) increases. In this picture the Cat-5e cable has the thinnest sheath, but it also was the only one with the nylon spline.

Shielded (STP) vs. Unshielded (UTP)

Because all Ethernet cables are twisted, manufactures use shielding to further protect the cable from interference. Unshielded twisted pair can easily be used for cables between your computer and the wall, but you will want to use shielded cable for areas with high interference and running cables outdoors or inside walls.

There are different ways to shield an Ethernet cable, but typically it involves putting a shield around each pair of wire in the cable. This protects the pairs from crosstalk internally. Manufactures can further protect cables from alien crosstalk but screening UTP or STP cables. Technically the picture above shows a Screened STP cable (S/STP).

Solid vs. Stranded

Solid and stranded Ethernet cables refer to the actual copper conductor in the pairs. Solid cable uses a single piece of copper for the electrical conductor while stranded uses a series of copper cables twisted together. There are many different applications for each type of conductor, but there are two main applications for each type you should know about.

Stranded cable is more flexible and should be used at your desk or anywhere you may be moving the cable around often.

Solid cable is not as flexible but it is also more durable which makes it ideal for permanent installations as well as outdoor and in walls.

Now that you know which type of cable you should use, have a look at our guide to making your own Ethernet cable.

 

Justin is a Linux and HTPC enthusiast who loves to try new projects. He isn't scared of bricking a cell phone in the name of freedom.

  • Published 08/16/11

Comments (25)

  1. vistual

    Thanks for the great info., Justin.
    So,”unshielded, shielded, stranded, or solid” ASIDE, can this be translated to …
    one would be better off buying the “better” grade cable to ensure that they’re getting the most of of their connection?

  2. xilmiki

    Great Thanks for this.

  3. Peter

    @vistual – Generally yes, and the most long term benefit from their network. The cost of the cable itself is generally a tiny fraction of any network project, and the last thing you want to have happen is to cheap out on the cable now, and have to do it all over again in a few years because your network can no longer handle what you’re throwing at it. The cost difference between a spool of Cat5e and Cat6 is about $30. That is nothing compared to the cost of running the cable in the first place, and far, far less than the cost of having to run it a second time.

  4. Mehlrodze Brzonowicz

    Don’t forget the FIRE rating of the cable sheath!! In many locations any cable not certified as “CM rated” cannot legally be put through walls, cable not certified as “CMR rated” cannot legally be put up through risers, cable not certified as “CMP rated” cannot legally be put throughor air plenums without using conduit, and the electrical inspector CAN order the cable removed. Some locality’s inspectors can declare the building unsafe for occupation until the cable is removed.
    Most important, don’t jeopardize safety by using unsafe cable.

  5. Tiffini

    Good point MB!!!

  6. MaxB

    You didn’t mention crossovers

  7. kb

    is there at CAT 6E?

  8. Peter

    To add to what Mehlrodze said, I would strongly advise against the suggestion in the article that you can run any type of Ethernet cable outdoors. Stringing Ethernet (unshielded or shielded) between buildings or on poles is extremely dangerous unless you take precautions to ground it and make it safe from lightning strikes. Once you add in that cost, you might as well run fiber. Stringing a 50 foot cable from your house to garage might seem safe, but its really not. If you have to run cable outdoors, bury it in conduit (and do yourself a favor and pull a second strand so you don’t have to dig it up if the first one fails).

    Also, as far as using shielded cable, I’ve run unshielded cable in some pretty hostile EMR areas without any issues. (Near large transformers and electrical panels, and among high voltage electrical machinery with no problems. Of course YMMV.) Shielding cable doesn’t make it acceptable for outdoor aerial use either.

  9. Peter

    @MaxB – Hardly anyone needs crossover cables any more. If you use a straight through in a situation where you need a crossover (or visa versa), most modern networking gear can detect that and switch the traffic for you.

  10. Carl

    Good info. But what about Cat7 and Cat7a?
    http://en.wikipedia.org/wiki/Category_7_cable

  11. Mark

    Excellent! I was looking for this info!

  12. শাওন

    WOW! thanks a bunch!!

  13. Wayne Riker

    I’m keeping this for reference. However, there’s no mention that shielded cabling may require special NIC cards that support shielded cabling, that goes for switches and routers, too. I’d like to see the tech and science for this. I think it has to do with proper grounding to the NIC jacks.

  14. Scott

    As far as using shielded cable, it really isn’t necessary in the home, even if you do run it inside of walls. An improperly grounded shield can cause problems, and most home-use equipment isn’t set up to support shielded cable or connectors. Try not to run your cable close to and parallel with power lines. When you have to cross a power line, as might happen when you’re running cable in the attic or crawlspace, do it on as close to a 90-degree angle as you can get.

  15. Ron

    Shielded and unshielded cables have different impedence. The jacks must match the type of cable you use. Most commercial switches have ports that support grounding of the screened cables as long as proper screened patch cords are used.

    For outdoor cable make sure to use a cable filled with a water blocking agent (icky pic) or aqua-phobic powder. Water will change the characterist impedence. If the cable is not place in conduit above ground the use a UV protected jacket cable. There are also cables for direct bury under ground.

    The reason that screened or shieded cable is not normally needed is because Ethernet uses differential signaling. As one conductor of a pair goes high the other conductor will go low. External noise will effect both conductors equally, there will be minimal difference between conductors of the signal pair.

  16. appuru

    so i have cat6 cable…could i crimp the cat6 cable using the cat5e connectors? i’ve been wanting to do this for a while, but have been hesitant b/c i read somewhere that the cat6 cable is too thick for the cat5e connectors… TIA

  17. Christian Meland

    This was interresting !

  18. Jerry Nissen

    This was great! Thanks…… do more of this…..

    jerry

  19. Katie S.

    GREAT article on cables…need to forward this to my professors!

  20. Justin Garrison

    @appuru The Cat-6 cable probably will not fit into the Cat-5 connector. Part of the shielding that is thicker is also the sheath on the individual wires. Because of that the Cat-6 cable may not fit into the Cat-5 connector.

  21. Paul Gadebusch, III

    This is a great primer for cable. All the differnces explained clearly and the graphics make it clear for the novice.
    Not all connectors are he same. Cat6 solid core can sometimes be pushed into the cat5 connector, twisted core bends to easily.

  22. CH

    How does the nylon spline reduce crosstalk?

  23. astral_cyborg

    Another great article. Simple to understand and very informative. Thank you.

  24. DLS

    Great post, thanks Mr. Garrison :)

  25. Edward Allen Weissbard

    Good info, that’s again!

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