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    on GDMT rather than ADSL2

    This is a discussion on on GDMT rather than ADSL2 within the Sky Broadband help forums, part of the Sky Broadband help and support category; Hi, I've just moved into a new property. The house has had a new BT line to the telegraph pole ...

    1. #1
      nicke1's Avatar
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      on GDMT rather than ADSL2

      Hi,

      I've just moved into a new property. The house has had a new BT line to the telegraph pole installed.

      My issue is that I can only connect on GDMT. My router will not sync using ADSL2.

      On GDMT I sync at 8mbps, attenuation of 28 and SNR of 8.

      I should sync on ADSL2 at around 14-16mbps I think.

      I've already been through hell with Sky and have probably spent over 10 hours on the phone, tickets closed, the usual run around. Before the issue can be escalated I had to try another router which also, as expected, has the same issue.

      Has anyone experienced this problem? Any tips on what causes it or how it gets resolved; who looks at it, etc. etc.

      The ticket has now supposedy been escalated but I'd like to be armed with as much info as possible since given the previous hassle I've had with support I doubt the issue will be resolved painlessly.


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    3. #2
      Smithy99's Avatar
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      Re: on GDMT rather than ADSL2

      Can you post your router stats. With a SNR of 8 then you are not being capped, at least not by much and your line will not sync much higher than it is without problems.

      Are you sure you are on the Sky Max package?

    4. #3
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      Re: on GDMT rather than ADSL2

      To sync at anything approaching 14meg, you need to have a much higher noise margin, so at 8meg it would need to be around 13dB. How are you connected? do you have a master socket with a test socket? If you do try and connect there.

    5. #4
      nicke1's Avatar
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      Re: on GDMT rather than ADSL2

      Are you sure this is the case on ADSL2?

      I've looked at the stats as the Customer Solutions person has made changes and synced my router at different speeds on GDMT.

      E.g. attentuation and noise are always around 28/29 and 7/8 regardless of whether I'm synced at 5mbps or 8mbps.

      I must be able to get ADSL2. The house I have moved into is next door from my previous property where I could get ADSL2 and with an attenuation of 34 and SNR of 7 - this typically synced between 9 and 10 mbps.

      A new line has been installed at the new property and has a clear run to the pole whereas the line at the old house went through a large tree hence my assumption that I should get better speeds.

      (I'm already in the test socket of the master socket)

    6. #5
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      Re: on GDMT rather than ADSL2

      If you are in the test socket and there is no noise on the voice line with a corded phone then I don't think you are going to get any better, certainly not much anyway.

      Can you post the full router stats?

    7. #6
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      Re: on GDMT rather than ADSL2

      Given that no-one else has made this point already I am now questioning my own understanding of this but I always assumed that Sky chose whether you were on G.DMT or ADSL2+ in their setup.

      I had heard tales of those whose exchanges had Easynet DSLAMs which were full and therefore they couldn't get ADSL2+ and had to wait on G.DMT until extra capacity was arranged. Surely if the OP is connecting via G.DMT, this must be because Sky have set him up that way. To get him on G.992.5 (ADSL2+) Sky must change a setting their end. I cannot believe his router will decide which protocol to use depending on line quality. I have much greater attenuation than him yet I get G.992.5.

      With an attenuation of 28dB, 8meg is possible but that is the theoretical max for G.dmt in any case. Assuming the same attenuation on G.992.5 the range of line speeds runs from about 10 to 16 meg.
      For more info see this article on Wikipedia: http://en.wikipedia.org/wiki/File:AD...ttenuation.gif

      Or do I have it round my neck?? Happy to be enlightened.
      Last edited by Ratcliffes; 15-01-09 at 08:10 PM.

    8. #7
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      Re: on GDMT rather than ADSL2

      That is my understanding as well although Sky will not want to put them on ADSL2 if the line can only just handle it. GDMT works better for the marginal lines.

      They will want to keep the capacity for other users.

    9. #8
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      Re: on GDMT rather than ADSL2

      Erm - there seems to be a bit of confusion in this thread.

      By default, Sky don't set an ADSL mode on Sky Max. The DSLAM and the router negotiate which mode to use (provided the router is set to multimode) or the router determines it (if set to a specific mode).

      Other LLU products (Base and Mid) are generally configured G.DMT, but. with the advent of DLM, this seems to be changing and most customers have/will end up on ADSL2+ as the line goes to default, like Max.

      If Sky cap the line, they generally cap to G.DMT. If this is done then no amount of fiddling with the router will get it to sync on any other mode. If the connection is set to default the router can be made to sync G.DMT, ADSL1 or ADSL2+. Only a LLU connection can be capped, Connect (non LLU) doesn't work like that.

      On LLU, whether the connection is configured on G.DMT or default, it uses the same physical resources i.e. nothing to do with "keeping ADSL2+ capacity for others".

      If there are no LLU connections available then customers are offered Connect. Connect also uses G.DMT but runs a different DLM type process controlled at the exchange. This is a BT product.

      HTH


      Quote Originally Posted by nicke1 View Post
      My issue is that I can only connect on GDMT. My router will not sync using ADSL2.
      If you can only sync on G.DMT then either:
      • you're not on Max, you're on Connect - post your stats
      • you're not on Max, you're on Mid
      • you are on Max but Sky have restricted your ADSL mode to G.DMT
      • you are on Max but your line is incapable of supporting ADSL2+ (rare but not unheard of)


      Quote Originally Posted by nicke1 View Post
      I should sync on ADSL2 at around 14-16mbps I think.
      Maybe. Your attenuation should support that, but it also depends on your line quality. Your noise margin synced at 8meg doesn't look promising for 14-16meg

    10. #9
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      Re: on GDMT rather than ADSL2

      we do set adsl mode on Max - either gdmt or adsl2+...

      if a line is seen to be long it'll be on gdmt by default...
      -------------------------------------------



      Useful Sticky: - How To Obtain Your Router Stats, BT Speed Test, Check For Test Socket

    11. #10
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      Re: on GDMT rather than ADSL2

      Quote Originally Posted by IAmNotTheEnemy View Post
      we do set adsl mode on Max - either gdmt or adsl2+...
      Yes, but setting to ADSL2+ is actually saying "allow" ADSL2+ i.e. it is not set to anything - it allows all modes. Hence why a customer on ADSL2+ can set their connection (via the router) to G.DMT or ADSL2 as well. If Sky setting to ADSL2+ locked it to this then that wouldn't be possible.

     

     
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