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We are about to put in the wiring in an expansion of our office building and the vendor is proposing we use Cat 6 cabling because it is "faster." Gigabit works fine over Cat 5e which is what our existing building has run throughout it and according to Wikipedia we would need Cat 6a to be able to actually support 10 GB though it may work over shorter distances with Cat 6 (how long is shorter distances exactly?).

People talk about the increased speed/bandwidth of Cat 6 cable over Cat 5e but I believe what they are talking about is that Cat 6 supports 250 MHz vs Cat 5e support for 100 MHz. My understanding is that this does not at all translate into any difference in MBps which is what I normally think of in terms of speed.

If I setup a test with two computers at a distance of 100 ft that transfer data between each other using Cat 6 and then again using Cat 5e I don't believe I would see the time to transfer a 10GB file vary at all due to the cable used.

To further confuse the issue variance by MHz doesn't seem to be a reliable measurement of performance even when comparing cabling as the Cat 5e 350 MHz debacle illustrated.

I will be the first one to admit that I am not expert in this area but I am struggling not to make this decision based on what I see as cable suppliers use of fear mongering to convince me to purchase something that provides us no real benefit other than protecting myself by making the choice that no one will question in the future.

Are there other benefits that I am not considering or things that I have misunderstood which make a compelling case for Cat 6 instead of Cat 5e?

duffbeer703
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Chris Magnuson
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  • Time is limited with everyone, but I think it could be of value if you were to scientifically conduct the test that you mention - String together two machines with each of the cables (machine-terminated, of course) and see if you actually do get a difference. I'm betting you won't, too, but the proof is in the pudding, as they say. – Matt Simmons Feb 22 '11 at 16:44
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    The proof is not in the pudding, it is in *the eating of* the pudding, i.e tasting it. – DutchUncle Feb 22 '11 at 17:14
  • Frankly, based on what you've said here (and to be fair we're only hearing half the story) then I'd fire the vendor if they told you that the same signal down a CAT6 wire will somehow be faster than the same signal down a CAT5e cable but can't quantify how and offer you proof - unsupported statements like this mean they're either trying to rip you off or they're dangerous idiots who shouldn't be allowed near your network cabling. – Rob Moir Feb 22 '11 at 17:30
  • @Robert The problem is, in terms of the frequency a signal can be sent in MHz Cat 6 is technically faster than Cat 5e and so the statement that Cat 6 is faster than Cat 5e is technically correct if not relatively meaningless. – Chris Magnuson Feb 22 '11 at 17:43
  • Sure. But that isn't important - the question is a) do they know that or is it just a salesperson who's big mouth is doing all their thinking for them and b) if they know that, do they actually really *believe* that means the connection itself is faster (in which case they're incompetent) or do they know it makes no difference to the network throughput and they're just trying to rip you off. Which brings me back to firing them because you don't want to work with conmen and fools and they're clearly at least one of those. Just imho of course. – Rob Moir Feb 22 '11 at 19:33

6 Answers6

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I'm no expert either but I'm on board with what you've stated in your question. My opinion is that the vendor is giving you a snow job in order to make more money off of the job by selling you CAT6 cable. My recommendation is that unless you plan on moving to 10GbE (CAT6a cable needed) in the near future then stick with CAT5e. GbE (1000BASE-T) will happily run on CAT5e or CAT5 cable.

joeqwerty
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    Completely agree. There are practically no use cases for 10Gb/s to the desktop in the typical office environment (in fact, in a lot of offices (mine included), there's no cause for 1Gb/s speeds). In 5 years? Yeah, we might all be doing multiple realtime video/audio streams from our desks, but I don't think we'll have many use cases for 10GbE. – Matt Simmons Feb 22 '11 at 16:37
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    Not to mention that there is no advantage of cat6 over cat5e. You need *cat6a* cables to safely run 10gig. – chris Feb 22 '11 at 16:44
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    +1 The cost differential is so astronomical right now that the market is a cesspool of vendor corruption. – squillman Feb 22 '11 at 17:23
  • +1 to sqillman for using the term 'cesspool', second only in my heart to "wretched hive of scum and villany" – Matt Simmons Feb 22 '11 at 19:18
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    I think we may have to consider that the vendor may genuinely believe what they are saying based on what they themselves have been told. Not every bit of misinformation is a deliberate attempt to mislead the customer. – John Gardeniers Feb 24 '11 at 04:05
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Read the wikipedia articles on this stuff.

There is no real advantage of cat6 over cat5e. Specifically, both can run gig ethernet the same distances and when you go to 10gig ethernet, neither is 100% guaranteed to work.

If you want to be able to run 10gig ethernet over copper, you need a 100% cat6A cable plant, not just cat6. With cat6, you can run up to 55meters "in a favorable alien crosstalk environment" which means you don't have lots of cables right next to each other. I've run 10gig over cat5e without problems on 100foot runs.

Cat6a is hugely expensive and difficult to work with. Cat6 is almost as expensive and nearly as hard to work with (thicker, harder to bend, etc)

Whatever you do, make 100% sure that the installation is tested with proper equipment after it is installed. Just because all the parts are marked as "cat5e" or "cat6" or "cat7a" or whatever, doesn't mean anything. It all needs to be put together correctly for it to actually perform to the specified ratings.

chris
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  • How did you do 10Gb/s over cat5e? – Matt Simmons Feb 22 '11 at 16:45
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    Plug it into the switch and the network port on the device. – chris Feb 22 '11 at 16:47
  • Interesting! What did the actual throughput end up at? – Matt Simmons Feb 22 '11 at 16:58
  • When you're working with networking cables, it either works or it doesn't. If it doesn't, it either doesn't work at all or it works poorly and you get errors, and if you get errors, the throughput falls so far through the floor that it is nearly unusable. So a bad cable that links up will be 1/100th as fast as the rated speed if you put lots of data through it. tl;dr --> as fast as if I had used fiber. – chris Feb 22 '11 at 17:05
  • But I was lucky. Some of the luck was that I was careful in crimping the ends (a cable tester actually said the cable tested as cat6) and I was lucky that the alien crosstalk around the cable wasn't enough to cause errors. – chris Feb 22 '11 at 17:06
  • So any twisted pair cable capable of 500Mhz operation should allow 10GbE? (like this: http://www.blackbox.com/Store/Detail.aspx/CAT5e-Industrial-Patch-Cord-500-MHz-Stranded-24-AWG-PVC-Industrial-to-Industrial-Gray-3-ft-0-9-m/EVNSLI01%C4%820003) – Matt Simmons Feb 22 '11 at 17:33
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    If it isn't cat6a you've got no promises from anyone. This includes cat6 or cat5e or even cat5. A single run is far more likely to work properly than 50 cables in a conduit all running 10gigE because of alien crosstalk issues. But in practice, cat5e usually works. The question here, of cat5e vs cat6, though, is simple -- no value in 6 vs 5e at all. Zero. Zip. Nada. Zilch. Just more money for the cable guys. – chris Feb 22 '11 at 17:48
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Unless you really need to push a lot of data right now, I think in the future with the trends for selling laptops and handheld devices convenience will trump speed as long as it's "good enough" and you'll see improved use of wireless, if for no other reason than cutting down one more wiring run that has to be done to each workstation (and people keep wanting to move them around anyway). I remember it wasn't all that long ago people were pushing for fiber to the desktops for better speed and future-proofing.

But that's purely my own speculation. For all I know there will come a time when you install a faceted dome that hones in and shoots data using lasers straight to your devices. Just don't stand between the dome and the device or you'll get a slight warming sensation.

Bart Silverstrim
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Generally speaking the better cables will reduce noise on the line. This is not that much of an issue unless you are pushing the distance limits. You can do 10GBit over telephonwire if it is less than a meter.

It is when you get above 50m or so that the cable types will start to have an actual effect on your performance. What you will typically see when you run ethernet too far is (in roughly this order)

  1. Increased packet loss due to corrupted frames
  2. Autoneg gives you a lower link speed than the cards are capable of
  3. Autoneg fails, forcing you to hard-configure the link speed
  4. Random link failures, typically short (5-10 seconds)
  5. Total link failure

Note that you don't get any slow "degradation" of speed like you would expect in an analog system.

If you are rolling out 1G Cat 5e is fine for the vast majority of installations. If you are rolling out 10Gbit the 33meter limit is pretty hard. Note that this is reduced further by the patch cables. I typically recommend people to use SM fiber instead of copper if they are rolling out 10Gig. It is not a large price difference and distance is suddenly a non-issue.

pehrs
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I too never saw any benefits other than stronger cable when dealing with Cat6 over Cat5e.

I guess it can make a big difference if your cables are laying next to neons and ventilation docks (in a suspended ceiling for example). In that case maybe the Cat6 get less interference and so better performance on the network.

But that's just a guess.

Alex
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    Sorry Alex, but I've got to disagree. Both are twisted pair. You do get better separation between the pairs with CAT6 (due to the plastic spine that used to be included, but frequently isn't now(http://www.addison-tech.com/english/faq13.htm)), but that is only relevant to in-wire crosstalk. To avoid external interference in a noisy environment, use a shielded cable (which is also available with CAT5(e). – Matt Simmons Feb 22 '11 at 16:41
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    None of those features actually make anything work faster. Just like plumbing -- if your pipes are plastic or copper or gold, or steel, they all flow the same volume of water for the same inner diameter pipe. Sure, some of them have higher melting points or corrode faster, but that's not relevant to the question at hand. – chris Feb 22 '11 at 17:30
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None of the answers here really address the question.. probably because it was poorly worded. The subject is "what can I get beyond Cat6" and the question is "is Cat6 faster than Cat5e"?

Cat6 supports a higher maximum bandwidth, meaning its theoretical maximum throughput is higher. This is like putting 6in plumbing vs 4in plumbing.

It won't change how fast current network cards are transmitting. A 1Gbps card will still be 1Gbps on Cat6. A 100Mbps card will still be 100Mbps.

But, back to the original subject - future proofing - Cat6 does give more capacity so that future network devices will be able to go beyond 1Gbps. Whether or not 10Gbps home devices will become reasonable is another question. But, if they do, Cat6 is your best bet to support them.

Also, note that if you're looking for 10Gbps support - get Cat6a cable. Whether you want to do the whole house that way or just a few strategic runs is another thing to consider. 5e is cheap and easy (and usually sufficient) 6a for a 'basement to office' or '1st floor to second floor' run could be a good future proofing option.

Thomas Harris
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