Cat 5 versus Cat 6 cables

Discussion in 'Tech Talk' started by Cinic, Mar 6, 2005.

  1. Cinic

    Cinic Spongy Member

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    Howdy,

    Most of the new computers that we've been getting for the office have gigabit ethernet adaptors. We recently got a deal from Dell on one of their gigabit switches and I'm not getting the throughput I had anticipated. In fact, it's nearly the same as when we had the 10/100 switch in the loop.

    My research has led me to believe that the wiring in the office is a suspect in the poor throughput. Most of it is fairly old and I'm pretty sure it's all Cat 5 and not Cat 5e or Cat 6.

    My question is this. Is it reasonable to believe that this could be the reason for the slow throughput? I'm thinking about getting a couple of cat 6 cables and running them between the switch and a couple of machines and testing the throughput. But I don't want to waste the time or money if this isn't a reasonable solution.

    Thanks for any help.

    John
     
  2. fastvfr

    fastvfr Ancient Tech

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    Category 6 (ANSI/TIA/EIA-568-B.2-1) was ratified by the TIA/EIA in June 2002. CAT-6 provides higher performance than CAT-5e and features more stringent specifications for crosstalk and system noise. All CAT-6 components are backward compatible with CAT5e, CAT5, and Category 3. If different category components are used with higher category components, then the channel will be limited to the performance of the lower category. Using all Category 6 components throughout the signal path should result in a Power-Sum Attenuation-to-Crosstalk Ratio (PS-ACR) that is greater than or equal to zero at 200 MHz.

    I use CAT5 Crossover cable to link two P4 machines with Gigabit NIC's, and I have set up several networks with Gigabit switches that have run happily on CAT5 cables...

    So that means that, somewhere, there is an older component holding your LAN speed down to its level.

    If ANY of the machines on your LAN have Base100 NICs, they will throttle the whole network accordingly.
     

  3. 0100010

    0100010 Millennium Member

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    Only "major" difference between cat5/e and cat6 : the pairs are segregated and twisted seperately in cat6.

    That being said, using cat5/e with gigabit hardware usually works just fine, as long as the pairing scheme is to spec.

    I agree with fastfvr - probably a non-gigabit device dropping your max throughput.
     
  4. Cinic

    Cinic Spongy Member

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    Correct me if I'm wrong, but are you guys saying that a non-gigabit machine anywhere on the network will drop the speed of the entire network? Even for a file transfer between two known gigabit machines?

    Interesting. I knew that this happened when you mix 'b' and 'g' wireless, but didn't realize it could happen with wired networks as well.
     
  5. fastvfr

    fastvfr Ancient Tech

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    That's what happens.

    As with most any other computer system, the whole is limited to the speed of the slowest link.

    Try detaching all sub-Gbps NICs from your loop and see what happens.
     
  6. Cinic

    Cinic Spongy Member

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    I'll give that a try.

    Is there any way to isolate the non-gigabit nodes from the switch and gain the speed with the rest of the capable machines? We have a plotter and a network printer on the network that don't have gigabit NICs. Also, the firewall that is plugged into the switch is 10/100. I still have the old 10/100 switch if that could be of any use.

    Thanks for the help guys.

    John
     
  7. chrismartin

    chrismartin

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    I don't believe that to be the case in modern switched networks, at least the way that it is stated. If that were the case, my core switch would be limited to 45Mb/s (I have an ATM card in my switch) and my other switches couldn't transfer faster than 10Mb/s, which is not the case. In my server room I have several SNMP environmental devices that are only 10Mb/s.

    If what you state were to be true there would be no such thing as a gigabit uplink port or even 100Mb/s uplinks either as that "uplink" would be limited to the slowest device.

    I do remember that 10/100 hubs that would throttle down to 10Mb/s if you had a single 10Mb/s devices on it. That led to hybrid switch/hubs that would segment the 10Mb/s traffic from the 100Mb/s traffic, basically turning the hub into two internal hubs on and internal switched backplane.

    On to the question, you need to make sure that your 1gig devices are properly negotiating 1000mb/s. I have several devices that will not auto-negotiate properly with one of my switches. I have to set the speed and such manually in order for it to be 1000mb/s.

    I have the Dell 6024 (16 ports fiber, 8 ports TP) I have the 10 Mb/s management port plugged into one of the 10/100/1000Mb/s TP ports. If the above posts were true, I would be running at 10Mb/s, which is not happening.

    I would check:

    1. Auto-negotiation problem
    2. Cross talk issue with the cable or other problems causing re-transmission issues.

    1. Is a simple software configuration of the switch. The switch will be able to tell you what speed each port is on and let you change it if needed.
    2. You can really only test with a good (expensive) cable testing tool or a different cable.
     
  8. gwalchmai

    gwalchmai Lucky Member

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    um, I have a mixed mode wireless network and I get 54mbs on the "g" nodes and 11 on the "b" nodes, so I don't think this is the case. Also, as noted, this flies in the face of switching technology, which should support the fastest speed between nodes.