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    DLM - why?

    This is a discussion on DLM - why? within the Sky Broadband help forums, part of the Sky Broadband help and support category; I have a very good line and am syncing: Down: 18493 kbps 7 - 9db Up: 1076 kbps 7 - ...

    1. #1
      stevvi's Avatar
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      DLM - why?

      I have a very good line and am syncing:

      Down: 18493 kbps 7 - 9db
      Up: 1076 kbps 7 - 8db

      I was waiting for Sky to put me on DLM to get upgraded from Max to Unlimited but got fed up with waiting so asked them to set my target noise margins at 7db with no caps on my download or upload (20Mb & 1.3Mb respectively) as this would give me my best possible speeds within their restrictions. Sure, if my router syncs at a low noise time I may get a bit more speed and have my SNR drop to below 7db at more noisier times which may, or may not cause instability (unlikely due to Sky's conservative limits), but I am more than happy to accept that situation. Sky duely "tested" my line and seem to have set my speeds to those shown above... which wasn't exactly what I asked for.

      I often get an SNR of 9db on my download at 18493 kbps sync rate but if I reboot my router I still get the same results. I have asked Sky about this and have got the reply:

      "We do not cap our speeds, the settings are automatically adjusted to offer you a stable error free connection."

      To me, it seems obvious that I have been capped at 18493kbps and their system refuses to let me sync above that. I am still awaiting a reply... and I've had to remind them that I am still waiting.

      Why on earth do they do this? Why implement DLM and all the hassle it it causing? Why not, as I proposed, set the target SNR and let the line sync at it's max rate?

      Any answers?

      Thanx.

      A


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    3. #2
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      Re: DLM - why?

      Noise varies during the day and they do not monitor the lines on a minute by minute basis so your router will sync at the best speed it can following a reboot.

      If there is then interference, the noise margin will lower until it either hangs on in there or looses sync and causes the router to re-sync at a slower speed.

      Mose people find it better to sync the router in the evening when it is noisier, this will then ensure that it will stay stable during the worst times but in the morning when the interference is less you may get a slightly higher noise marginm it will then drop again in the evening but it should stay within the 6.9db default.

      Sky set the target noise margin at 6.9db so as long as you are near this then you are not capped.

      If you were capped, you would have a higher noise margin.

    4. #3
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      Re: DLM - why?

      Sky's default SNR is 7dB exactly - ALL lines are set to this and are (usually) only set higher manually due to intermittency issues...that doesn't mean that the line will stay at 7dB at all times...
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    5. #4
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      Re: DLM - why?

      Quote Originally Posted by Smithy99 View Post
      Sky set the target noise margin at 6.9db so as long as you are near this then you are not capped.

      If you were capped, you would have a higher noise margin.
      As said, if I reboot my router when my SNR is 9db I still get the exact same 18493 kbps sync rate. Surely if I wasn't capped I should sync a little bit higher?

    6. #5
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      Re: DLM - why?

      it's an anomoly I think...the SNR will be set to 7dB, unless CST set it to 9dB for some reason...only way of confirming this is to speak to CST directly...
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    7. #6
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      Re: DLM - why?

      Quote Originally Posted by IWasNotTheEnemy View Post
      it's an anomoly I think...the SNR will be set to 7dB, unless CST set it to 9dB for some reason...only way of confirming this is to speak to CST directly...
      I don't think so. If I reboot when my SNR is 7db I get exactly the same speed and my SNR stays at 7db. It looks like that when CST sorted my higher speeds they decided my line would be unstable above that figure (I assume my SNR was at the lower end of it's range when they set the max rate) and capped it at that. I don't see why they need to do that as, assuming my line did become unstable the router would just reboot at a lower speed until it was stable... so why the need for DLM, which is causing so many people so much trouble, as it does exactly the same thing?

    8. #7
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      Re: DLM - why?

      assuming my line did become unstable the router would just reboot at a lower speed until it was stable... so why the need for DLM, which is causing so many people so much trouble, as it does exactly the same thing?
      That is exactly what I think. I don't see any need at all to cap a normal line. There are some lines which have very large swings in the noise margin which may need capped to give them some stability, but normally it should be left to the router to set the speed.

      TomD


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    9. #8
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      Re: DLM - why?

      18Mbps is still good though
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      Re: DLM - why?

      Quote Originally Posted by IWasNotTheEnemy View Post
      18Mbps is still good though
      Indeed it is and I did acknowledge this near the top of my my first post. I have no complaints about my line and very little "quibbles" (I love that word!) about how Sky have dealt with *my* situation. But why do lots of people have this constant problem with DLM and why do Sky still implement it as it does seem to cause more problems than it solves (in the realm of capping), especially when line instability can be easily solved by the router and Sky's conservative SNR target. Maybe I'm lax but I hardly think a router reboot every now and then is a big worry for most of us, especially as we only use our Sky broadband for pleasure and not business... ahem.

      Quote Originally Posted by Isitme View Post
      That is exactly what I think. I don't see any need at all to cap a normal line. There are some lines which have very large swings in the noise margin which may need capped to give them some stability, but normally it should be left to the router to set the speed.
      Although we're agreeing, even if lines have large swings in SNR then the router will still deal with the situation and sync at the best possible rate for the target SNR. OK.. I can see a situation where a router may have to resync a few times in a few hours but is that the end of the world?

      Again, I ask "Why DLM"?

      Answers on a postcard... or below

    11. #10
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      Re: DLM - why?

      Not an answer, but another "why dlm", why does dlm automatically set all lines to adsl2+ when it has been stated that it is only beneficial to lines with a line attenuation above a certain threshold ( cant remember the exact figure )


     

     
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