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Cable Wars: Cat 6 vs Cat 7 vs. Cat 5e? 56

Posted by Cliff
from the if-you-gotta-go-copper dept.
stone22 asks: "My company has decided to install a gigabit link. This will be initially used only for testing purposes, and on the longterm as a backbone for our corperate network. We allready decided to use copper, but what standard ? I've heard about problems using cat 7 cables (cross talk, bulky cables, non-standard connectors) so I could really use some hints from all you cabling experts out there."
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Cable Wars: Cat 6 vs Cat 7 vs. Cat 5e?

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  • Fiber is better! (Score:4, Informative)

    by vertical_98 (463483) on Saturday October 05, 2002 @06:09AM (#4392622) Homepage
    While I can't insult you as well as the AC above, I do have to say that if you are seriously considering using this as a backbone pay the extra initial cash and lay fiber. You can go with MUCH longer runs, eliminate crosstalk, and generally find that life is much simplier. But if you have to have copper, Cat 5e UTP cable w/ RJ45s should be more than able to handle your GigE network.

    Peace.
  • Fiber rules...nuff said.
  • Sigh. (Score:4, Insightful)

    by Anonymous Coward on Saturday October 05, 2002 @10:38AM (#4393057)
    You can really tell that a bunch of sysadmins and not highly-paid wire jockies read slashdot... A cable is a cable, indeed. LOL.

    Seriously, in our lab tests, Cat 7 DID have some problems with a number of our servers- and this included non-home-grown stuff like NetApps and Suns. Cat 6 worked just fine. Check a couple of the links here for some more info.

    Cat 6 actually did provide us with better benchmarks, btw.

    http://www.siemon.com/white_papers/01-01-23-sff. as p

    http://www.networkmagazineindia.com/200205/krone 2. shtml

    The most disturbing thing here is the general downward trend of respect in the Slashdot community. And why did the first post get rated a "4" when it posted info from a NIC manual saying NOTHING of value about cables or comparisons?

    On the other hand, a search of Google probably would have found most of this out... but I suppose it's always nice to have a first-hand confirmation from someone who's actually looked at the question.
    • Re:Sigh. (Score:5, Interesting)

      by Dahan (130247) <khym@azeotrope.org> on Saturday October 05, 2002 @04:18PM (#4394279)
      Seriously, in our lab tests, Cat 7 DID have some problems with a number of our servers

      Maybe because there's no such thing as Cat7, despite what cable manufacturers might like you to believe? I could put crap on a string and call it Cat7 cable. Category 6 [tiaonline.org] cable is the latest standard for twisted pair cable. While Category 7 may be in the works, it's just marketing for now.

      And why did the first post get rated a "4" when it posted info from a NIC manual saying NOTHING of value about cables or comparisons?

      It made it up to 5, actually, because it was both informative and insightful. If you want to run GigE, you'll be using NICs and switches. In which case, RTFM for the NICs and switches and they'll tell you what kind of cable to use. What do you mean his post said "NOTHING of value about cables or comparisons"? His post explicitly said Cat5e is what you need if you want to go with copper, but he would recommend fiber:

      I would also say that fiber is a better backbone that Cu, and CAT 5e has always worked FINE with GigE - because that's what the fucking manual says.
      Sounds like you were more interested in bitching about his post than actually reading what he had to say.

      but I suppose it's always nice to have a first-hand confirmation from someone who's actually looked at the question.

      And isn't a first-hand confirmation from the manufacturer of the network equipment you'll be using even better than that?

      • someone mod parent up.

        Cat 7 *does not* exist. Anyone who pays extra money to have "Cat7" installed has been hood-winked or is a fool.
      • Actually... Cat5 NOT Cat5e is what's needed for GigE. 3 is better of course but isn't required.
  • Yeah, you point out the manuals and information and stuff like that. I'm sure that if he has the ability to post on /. that he has the ability to read.

    What if he's looking for user experiences in the real world (you have been in the real world right? You don't just stay in your parents' basement compliling kernels over and over again?).

    Manuals will tell you the how to, but not the how good.

    I guess he got his answer - ask the slashdot crowd and all the condescending assholes come out of the woodwork to parade their 133t status.

    And to stay on topic, I have found that cat5 is perfectly acceptable for gigabit ethernet, but I've only used it point to point, not as a backbone, and then only using a G4 tower and a Powerbook - obviously due to the aestheticly pleasing nature of these computers they can't be 133t, and hence my opinion doesn't count.

    Have a nice day.
    • and have you considered that this might be a small, non IT company that just wants a way to move big files around?

      What if they don't want to hire a sys admin? What if this guy has been given this job by his boss and has never done stuff like this before?

      Who knows.
  • by itzdandy (183397)
    go fibre, period, why would you run a backbone on Cu if their is any though of crosstalk?

    Cat6, Cat7? f*k them,
    Cat5e is the way to go, its in the spec for GigaEthernet, why not?

    but really, go fibre on the backbone
  • by Jahf (21968) on Saturday October 05, 2002 @02:17PM (#4393883) Journal
    This is one of the most worthless article I've ever seen.

    No, not because of the premise, I was actually curious what the answer was myself because I want to lay an inexpensive 1Gb network in my house at some point ("because I can").

    It is worthless because of all the people who ridiculed the poster with the various RTFM and "look it up on Google" responses. Most other responses were to use something (fiber) that the poster seems to have obviously ruled out (maybe cost, maybe convenience, doesn't matter), so those don't help much either but at least they were trying.

    He wanted to ask the opinion of his peers, not rely on what a manufacturer said or possibly out of date material. Most of the responses trashed him.

    Why do people bother to take the time to produce non-responsive or patronizing answers? If you don't like the question, or you think he should spend his time elsewhere to get the answer, then simply don't post.

    A lack of response is a much better way to get someone to go away than to waste your time writing and the time of everyone who pops in to see what the consensus was.


    • I'm sorry my advice to use fiber over copper, bothered you.

      I'm so sorry, I'll even explain to you why I gave that recommendation.

      Mr. stone22 is going to go buy Cat 6 or Cat 7 (or what ever the company wants to call it, 6e, 6xp) and pay some joe (or do it himself) to run copper. Two or 3 months from that time he is going to notice that a run is operating at less than GigE speed (maybe less than 100base speed). He is going to have to find out why. Did the joe who ran it drape it over a florescent light? Around an electrical junction box? Put a kink in the cable? The troubleshooting list goes on. He looks bad because the new network isn't working.

      If he lays fiber, half of his troubles go away. If he has to use copper he can then say to the powers-that-be, 'Yeah, we can use copper, but we will wind up paying more in the long run.'

      If you want to run GigE in your basement, use Cat 5e. It was good enough for GigE before Cat 6 was a reality. If Mr stone22 wants to connect his servers to his hubs, he can use Cat 5e also.

      So to answer the orginal question: I would use Cat 5e

      Sigh
      Vertical

      Lease this space. Low Monthly payment!
      • It was one specific answer that was the problem, and if the only issue had been people who posted a response that was not in answer to the specific question (ie, fiber when it wasn't a consideration), I wouldn't have cared. The problem was almost every response was negative or out of scope. It was not just about your post (you weren't the only person to post about fiber), which I understood before the clarification.
  • Cu vs Fibre (Score:3, Informative)

    by rerunn (181278) on Saturday October 05, 2002 @02:23PM (#4393904)
    Try here [networkmagazineindia.com]
  • Couple of points. (Score:4, Informative)

    by FreeLinux (555387) on Saturday October 05, 2002 @02:42PM (#4393982)
    First, you don't give enough information in the article for a really good answer. You say that you want to lay a backbone cable but, you don't give details like the distance it has to traverse or the environment it will be in. You also fail to say how many nodes might be directly attached to this backbone. These are important details in the decision process. That said, read on....

    I would have to agree with some of the other posts, you should use fibre. The other posts don't say why you should though so, here's why.

    First, fibre is not going to be a lot more expensive than good copper. Sure, it is a little more but, the extra cost is worth the benefits. Benefits include increased distance, no interference at all and, most importantly, room to grow.

    In laying a fibre cable, even a small one, you don't have a single data path, as you do with Cat 5-7. Even small fible cables usually bundle three or more pairs in the cable. That means that you can VERY easily double or triple your bandwidth in the future by lighting a second pair. Or perhaps you need a completely separate data path for some other service like maybe you want to interconnect a couple of legacy PBXs, or a video conferencing system, or a security system, who knows what.

    The next thing is that fibre gives you even more room for growth. Sure GigE is great but, will it meet your needs in the long term. Already 10GigE is a reality and 40GigE is well on it's way. These can easily be implemented in the future, if you have fibre. I doubt however that Cat 5-7 will ever run 10Gig and definitely not 40Gig.

    There is also a technology called Dense Wave Division Multiplexing (DWDM) that uses multiple lambdas or wavelengths on the same fibre pair. Using this technology it is possible to have 64 data paths on a single pair of fibre, that's 128Gbps aggregate bandwidth!!!!! That's all over fibre. With Cat 5-7 though, you will never have more than 1Gbps and only one datapath.

    Fibre is definitely the way to go for a backbone solution. I hope this helps.

  • Cat 5 is fine (Score:5, Informative)

    by Matt_Bennett (79107) on Saturday October 05, 2002 @05:02PM (#4394434) Homepage Journal
    I design and test the physical side of ethernet for a living, so I think I state with all honesty and some authority that using anything more than cat-5 cable is wasting money. Kinda like buying 94 octane when your car is designed for and runs fine on 87. It has more capacity than you will ever use. Ok, true cat-5 cable may be hard to find, so when I'm saying cat-5, I'm also mean cat5e. I agree with the other posters that fiber is the way to go for a backbone, but copper is quite a bit cheaper, and pretty reasonably priced. According to the Ethernet spec, fiber is actually held to a higher standard in terms of bit-error rate (fiber is 10^-12, where copper gigabit is 10^-10- I'm pretty sure, I have them in spreadsheets to check against, but anyway, fiber is better) On the other hand, on the interfaces I've tested, the BER on maximum loss (copper) cable is usually far better than 10^-10 so that isn't much to worry about.

    Be careful if you are thinking about installing fiber for possible use for 10GbE- there are a bunch of standards, and most of them seem to be incompatible with most current types of fiber, such as requirinig very small diameter single-mode fiber. At the moment the 10GbE world appears to be dominated by the long haul guys, not the LAN manufacturers, so cheap connectorization/fiber is not necessarily high on their priority list.

    Remember to keep the length under 100m (as it says in the spec) and don't go through a lot of patch panels (since each connector adds loss). If you are going for maximum length, be very careful how you cut and crimp the cable- the more you can maintain the twist in the wire the better, and the more matched each wire in the pair is, the better.

    Interesting fact: Since the loss of cat-5 cable is not well defined per unit length, The test cables (for 100Base-TX) are not specified in terms of length, they are specified in terms of loss. The maximum length cable that you test to is not a 100m cable, it is a 10dB loss at 16MHz cable. With good quality (cat5e) cable, that works out to around 135m.
  • Fiber or Cat 5E (Score:4, Informative)

    by JLester (9518) on Saturday October 05, 2002 @10:28PM (#4395393)
    You'd really be better off going with fiber for gigabit. Yes, Cat5e (and regular 5 if terminated correctly) will run gigabit, but there are some idiosyncracies that you might run into. Your NIC manuals should specify the requirements, I can't remember them off the top of my head. Also, we've found that different vendors support gigabit in slightly different ways on copper. We can't get SMC 1000-BaseT and Cisco 1000-BaseT to talk to each other. We ended up swapping out all our 1000-BaseT links to fiber and haven't had any troubles since.

    So, go fiber if at all possible. If you absolutely have to use copper, use 5E cable from a reputable vendor (Belden, Berk-Tek, Mohawk, etc.) and use GOOD jacks and patch cords. I prefer Panduit and spec it for all our jobs, but others also make good stuff. Don't scimp on the patch cords either, these cheapies that you find many times don't test real good. Go for 5E rated patch cords with the short plugs and gold contacts.

    Jason
  • I agree that Cat 6 is already superfluous for standard applications such as GigE Ethernet that operate in the 0-100MHz band (though theoretically it may give you somewhat more headroom against sloppy terminations in terms of overall testing qualifications).

    I guess higher-quality TP can be useful as a general-purpose wireline carrier for a wide range of analog/digital signalling (through the use of baluns and media converters). If I remember correctly, Belden had some nice info on this. With a good active balun you can carry up to 4 channels of baseband (and limited broadband A/V), USB, Firewire, whatever. Including home run distribution.

    When my house was built 2-3 yrs ago, Siemon's TERA System 7 (impressive 1GHz non-RJ termination system) was already being prototyped. Unfortunately, Alcatel's "draft Cat 7"-level cable (600MHz fully pair-shielded TP) wasn't available yet and I couldn't find anything else. So I went with Mohawk's 2nd-gen GigaLAN "Cat 6 plus" UTP (though Berk-Tek and others were close competitors) along with some Commscope 2+2 bundled cables. And mostly Siemon System 6 and Leviton for the termination (again, Hubbell, Panduit, etc, were all very similar). Note that back then Cat 6 hadn't officially been ratified yet.

    Tip #1: Terminating the 22AWG Mohawk UTP with its thick jacket and crossweb can be a pain on those closely-packed plates/panels.

    Tip #2: Try your local supply distributor (Anixter, Anicom, Graybar, etc) to see if they'll sell you these bulk spools for much, much cheaper than retail Cat 5 equipment. Places like DataComm Warehouse is also good, but they don't usually stock the more esoteric structured cabling parts.
  • asked. Don't be so mean to him, you have to start inexperianced once. Maybe he wants a second opinion because there might be a better solution than what he read about.

You can do this in a number of ways. IBM chose to do all of them. Why do you find that funny? -- D. Taylor, Computer Science 350

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