Networking – Does the category of RJ11 modem cable matter


I have a VDSL2 connection and of course a modem. I have a Cat5 DSL RJ11 cable and I was wondering how to tweak the performance. Would it be possible to use a Cat6 or Cat7 DSL RJ11 to gain more performance from the connection? I cannot find any RJ11 DSL cables that are Cat6 or Cat6. All of them seem to be Cat5. My ethernet cables are all Cat7, though. The connection is about 100/40Mbits right now. What would be the best way to tweak and enhance the performance? Should I somehow obtain a new faster RJ11 cable, or?

Best Answer

  • A network will function at the speed of its slowest component.

    As Michael Kjörling noted, a standard cat 5 cable can handle a bandwidth of up to 1 Gbit/s. However, if your internet connection is carried via DSL, then the amount of data being sent by your ISP will be a fraction of this figure. In this case, you will not notice any significant speed increase from using a 'higher' category cable.

    If you are using your router to send data between computers or devices on your network, the 'slowest component' rule still applies. You are - in this case - limited to the rate at which device A can send data, the maximum bandwidth of your router and the rate at which device B can receive data, as well as the maximum bandwidths of cables in between. To check the maximum data throughput of each device, compare against the relevant IEEE Ethernet standard (full list here). For wifi devices, check this list.

    Lastly, the cat 5e standard brought in controls on crosstalk (where the electrical signals in a wire interfere with other wires which are close by). If your cable happened to be routed near other data wires, then it could be the crosstalk that is slowing down your network. This would be important for offices and such, but for a normal home environment I don't think this would be an issue.

    In short, a cat 5 cable is generally good enough!

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