Your forum username:
Do you already have an account?
Forgot your password?
  • Log in or Sign up


    Welcome to Sky User - The Unofficial Support Forum for everything Sky! - Proudly helping over 65k members.


    Advertisement

    Results 1 to 5 of 5

    Information on ADSL, and ADSL2+

    This is a discussion on Information on ADSL, and ADSL2+ within the Sky Broadband help forums, part of the Sky Broadband help and support category; Right, what I am about to write is just the very basics of the differences between ADSL (G.DMT) and ADSL2+. ...

    1. #1
      indefatigable's Avatar
      indefatigable is offline Sky User Member
      Exchange:
      Broadband ISP: BB tech Support + Max
      Router: Sky Hub SR101
      Sky TV: Sky+HD 2TB
      Join Date
      Apr 2007
      Posts
      568
      Thanks
      2
      Thanked 12 Times in 12 Posts

      Information on ADSL, and ADSL2+

      Right, what I am about to write is just the very basics of the differences between ADSL (G.DMT) and ADSL2+. I do not know the technical differences, but hopefully, what I write will help a little.

      ADSL(G.DMT) is basically the original broadband service. It offers speeds of upto 8Mbps. On ADSL, you will not get above 8Mbps

      ADSL2+ is a newer technology which can offer speeds of upto 24Mbps.

      There is also an intermediate technology, called ADSL2, which offers speeds of upto 12Mbps

      All of these are dependant on your telephone line length, and quality.

      In terms of Max Package, if you line can only support sub-8Mbps speeds, your line will be put on ADSL. You will not see a performance increase by being put on ADSL2 or ADSL2+, and it may even adversly affect your line. You would more than likely see a performance decrease due to errors building up on your line.

      I am only putting this up because there are many posts here, and a lot of calls at sky where people think that ADSL2+ will give them a better service, even though they can only get 2mbps maximum down their line. Its just not true.

      Also, remember that all Sky packages offer speeds upto the package limit i.e. upto 8mbps, upto 16mbps. You are not guaranteed to get the full speeds.

      hope this clears up some confusion


    2. Advertisement
    3. #2
      mossywell's Avatar
      mossywell is offline Sky User Member
      Exchange: LSMEPK
      Broadband ISP: Max
      Router:
      Sky TV:
      Join Date
      Sep 2006
      Location
      London, UK
      Posts
      789
      Thanks
      0
      Thanked 11 Times in 4 Posts

      Re: Information on ADSL, and ADSL2+

      Thank you for that. I'd also add that even if the speed is under 8 Mbps, there is still a reason to go Max: unlimited downloads.

      I have a question for you: when deciding whether to go G.DMT or ADSL2+, I assume that you use a simple formula such as:

      If Attenuation > X
      G.DMT
      Else If Line Errors > Y
      G.DMT
      Else
      ADSL2+
      End If

      (Put another way, you only get ADSL2+ if your attenuation is lower than X and your errors are lower than Y.)

      Would you be so kind as to let you know what X and Y are, as we often get asked by users on Skyuser whether it is worth them asking T3 to go from G.DMT to ADSL2+?
      IQ album "Dark Matter" artwork reproduced with permission. See www.gep.co.uk/iq for more information.

    4. #3
      IanMax's Avatar
      IanMax is offline Sky User Member
      Exchange: Peartree
      Broadband ISP: Max
      Router:
      Sky TV:
      Join Date
      Jan 2007
      Posts
      188
      Thanks
      0
      Thanked 0 Times in 0 Posts

      Smile Re: Information on ADSL, and ADSL2+

      Quote Originally Posted by indefatigable View Post
      ADSL(G.DMT) is basically the original broadband service. It offers speeds of upto 8Mbps. On ADSL, you will not get above 8Mbps

      ADSL2+ is a newer technology which can offer speeds of upto 24Mbps.

      I think the correct term is that ISP's say adsl ( g.dmt ) is upto 8mbps but in actual fact adsl ( g.dmt does go higher if the line is good.

      Obviously the upto 8mbps is 99% true as an isp will never give you more than 8mbps on an 8mbps package.

      just for fun.

      /usr/sbin/adslctl: ADSL driver and PHY status
      Status: Showtime Channel: INTR, Upstream rate = 768 Kbps, Downstream rate = 10208 Kbps
      Link Power State: L0
      Mode: G.DMT
      Channel: Interleave
      Trellis: ON
      Line Status: No Defect
      Training Status: Showtime
      Down Up
      SNR (dB): 7.6 13.0
      Attn(dB): 28.0 18.0
      Pwr(dBm): 19.8 6.9
      Max(Kbps): 10752 1280
      Rate (Kbps): 10208 768
      G.dmt framing
      K: 320(0) 25
      R: 12 16
      S: 1 8
      D: 64 8
      ADSL2 framing


      As you can see i am using g.dmt and getting 10mbps.

      ISP's and bt always say upto 8mbps so if you get 8mbps your happy and the 'upto' part always allows an isp to state to people who dont get anywhere near 8mbps to say 'no sir this is an upto 8mbps connection'

      Ian
      Bt phone socket and wiring help > http://www.skyuser.co.uk/forum/cabling-faceplate-help/

      Router stats and help on understanding them > http://www.skyuser.co.uk/forum/router-stats/

    5. #4
      Saturday's Avatar
      Saturday is offline Sky User Super Mod
      Exchange:
      Broadband ISP: Sky Broadband Unlimited Pro
      Router: Sky Hub SR102
      Sky TV: Sky+HD box
      Join Date
      Sep 2006
      Posts
      6,086
      Thanks
      20
      Thanked 52 Times in 47 Posts

      Re: Information on ADSL, and ADSL2+

      Therein lies the problem of using an imprecise term such as G.DMT.

      If you are a Connect customer on "G.DMT" then you are on BT's version of ADSL known as ADSL Max which is a broad product set title given to a range of BT Wholesale ADSL products that are rate-adaptive, and are deployed over IPStream and Datastream. Theoretical sync is ~8000kbps.

      If you are a Sky LLU customer on "G.DMT" then you are on a later annex of ADSL (or more accurately ITU G.992.1) which has characteristics in common with ADSL2 offering a theoretical downstream sync of ~12000kbps.

    6. #5
      indefatigable's Avatar
      indefatigable is offline Sky User Member
      Exchange:
      Broadband ISP: BB tech Support + Max
      Router: Sky Hub SR101
      Sky TV: Sky+HD 2TB
      Join Date
      Apr 2007
      Posts
      568
      Thanks
      2
      Thanked 12 Times in 12 Posts

      Re: Information on ADSL, and ADSL2+

      i think i need to make an adjustment to waht i was saying. It is true that you can get upto 12mbps on ADSL (G.DMT). It was explained 2 different ways to me, and it turns out Sky dont use ADSL2 any more, just ADSL and ADSL2+

     

     

    Tags for this Thread

    Posting Permissions

    • You may not post new threads
    • You may not post replies
    • You may not post attachments
    • You may not edit your posts
    •  
    SkyUser - Copyright © 2006-2017. SatDish and NewsreadeR | SkyUser is in no way affiliated with Sky Broadband / BSkyB
    RIPA NOTICE: NO CONSENT IS GIVEN FOR INTERCEPTION OF PAGE TRANSMISSION