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    • clivep
    • By clivep 9th Sep 17, 1:41 PM
    • 124Posts
    • 36Thanks
    clivep
    TalkTalk SDLM - anyone with a long line NOT experienced a 30%+ reduction in speed?
    • #1
    • 9th Sep 17, 1:41 PM
    TalkTalk SDLM - anyone with a long line NOT experienced a 30%+ reduction in speed? 9th Sep 17 at 1:41 PM
    We had been with Sky for 12 months up to 2 months ago when we switched back to TalkTalk.

    Since the switch the best download speed we have managed is 2.6 Mbps (with the router in the test socket).

    With Sky the line was stable with a speed just under 4 Mbps (router not in master socket).

    Before Sky it was over 3.5 Mbps with TalkTalk (router not in master socket).

    Our long line means we are never going to get as high as 5 Mbps and have no chance of fibre for the forseeable future as we have an Exchange Only line.

    I've spent the last 6 weeks conversing with the OCEs on the TalkTalk broadband help forum trying to establish the cause of the speed reduction.

    Several different routers have been tried.
    I'm sure there's not a problem with our line.
    The OCEs have reported there's no line fault.
    TalkTalk Network Team can find no line fault.
    They are now suggesting an engineer visit to investigate further. If no fault is found (as we all expect) then this will cost me £65 and not gain any improvement.


    I now firmly believe that the reduced line rate I'm getting is purely down to the algorithm that the TalkTalk SDLM uses. I have asked the OCE to confirm this so we can save everyone the bother of further investigations but they are unwilling to do this.

    TalkTalk apparently rolled out their new DLM system nationwide in January. I've read many unresolved threads of people with no line faults having reduced speed since this was implemented.

    Those lucky enough to be closer to their exchange may not have experienced or be aware of a 1 Mbps reduction in speed but we are about 4km from our exchange so this makes a big difference to us.


    So my question is... Has anyone with a long stable TalkTalk line NOT experienced a 30%+ reduction in download speed with the TalkTalk SDLM?
Page 1
    • kwikbreaks
    • By kwikbreaks 9th Sep 17, 5:19 PM
    • 8,836 Posts
    • 4,415 Thanks
    kwikbreaks
    • #2
    • 9th Sep 17, 5:19 PM
    • #2
    • 9th Sep 17, 5:19 PM
    If it is the DLM then the way it will have reduced sync is by setting a higher default target noise margin. BT use a default of 6dB. To check reboot the router then look at the line stats reported.

    If you can't get any stats from the router or any other router you can borrow then you are pretty much in the hands of Talk Talk and you'll just have to wait out your minimum term and try swapping back.
    • clivep
    • By clivep 10th Sep 17, 12:47 PM
    • 124 Posts
    • 36 Thanks
    clivep
    • #3
    • 10th Sep 17, 12:47 PM
    • #3
    • 10th Sep 17, 12:47 PM
    The line was stable with Sky at a downstream sync rate of 4615 kbps and SNR margin of 3 dB.

    The current HG633 "super" router from TalkTalk is synced at 3039 kbps and a SNR margin of 8.3 dB. It also reports a Maximum downstream rate (kbit/s): 3524 but DLM is unwilling to increase the sync speed to this.

    The best of the 6 routers I've tried was the old HG523a which gave a sync of 3071 at 6.5 dB.

    OCEs have reoptimising the line several times but DLM does not attempt a faster connection with lower SNR margin despite me having a completely stable connection with no errors reported.

    TalkTalk advertise their broadband as "We’ll give you the fastest broadband your line can handle" which is clearly untrue as it's at least 30% slower than with Sky.

    I'm reading more and more threads about the DLM problem with longer lines that don't have line faults. I wanted to know if anyone with a long line HAD NOT been affected as it seems this is a known (but not admitted) consequence of their new DLM system they rolled out in January.
    • Mister G
    • By Mister G 10th Sep 17, 1:07 PM
    • 398 Posts
    • 247 Thanks
    Mister G
    • #4
    • 10th Sep 17, 1:07 PM
    • #4
    • 10th Sep 17, 1:07 PM
    I had similar problems with ADSL over a long line (5km).

    I found that the best solution was to get a router that you can 'select' the SNR on. I used a Billion 7800N which enabled me to set an SNR of 2dB. This gave me a reliable 2Mb instead of the 1Mb that the ISP supplied router gave.

    We've now got FTTC, so my line length has gone down to just over 1km. It does mean that my max VDSL speed is only 17Mb, but still a huge improvement.
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