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So Only a Week away now :D

Discussion in 'Networks & Internet Connectivity' started by gamesaregood, 24 Mar 2006.

  1. gamesaregood

    Mobster

    Joined: 17 Sep 2003

    Posts: 2,809

    Location: Suffolk

    Hello Everyone,

    So the time is almost here ... we are now only a week away until BTs ADSL MAX goes live :D and yet there is not really much details available yet as far as speed goes that I'm aware. Everyone knows of the checker in the FAQ and that its "upto 8mbps" but i was kind of hoping that by now BT would have updated theirs so we know for sure whats going to be available to us. Or is it going to be "sign up and we will see what we can do on your line" with no guarantee?

    Really hoping that this is going to allow a decent connection compared to my current 512kbps line :)

    Thanks,

    Michael
     
  2. ste_bla

    Sgarrista

    Joined: 9 Aug 2004

    Posts: 7,794

    Location: Milton Keynes

    Im pretty sure they arnt relaxing the limits for 1mb so therefor if your limited by db at the moment it wont make a difference

    Also you arnt automatically upgraded your isp has to ask for it to be done

    Ofcourse this is off the top of my head and could be wrong
     
  3. Phil99

    Capodecina

    Joined: 29 Oct 2004

    Posts: 10,900

    There wouldn't be much point with BT updating the checker for MaxDSL other than saying whether it's available or not - it's dodgy enough at the moment with basic boundries for 512kbps/1mbps/2mbps!

    If you go on to MaxDSL you'll get what the line can actually acheive, not what their database says you can acheive; so if your line can cope with 0.9mbps you'll get that, instead of dropping all the way back to 0.5mbps.


    [That was purely a made up example, I'm not sure what sort of steps BT are going to change the data rate at]
     
  4. Acolyte

    Mobster

    Joined: 18 Oct 2002

    Posts: 3,769

    Location: Bristol

    Nice, im good for 8 meg.

    28dB Atten
    29dB SNR

    and thats with it being synced at 2 meg already ;) :D
     
  5. garethrobinson1

    Gangster

    Joined: 16 Oct 2005

    Posts: 446

    Location: Essex

    You will only find out what speed your line can run at after the 10 day 'bedding in' period.

    During this period the DSLAM port will retrain with your modem several times a day to obtain a 'line rate', which is essentially the speed your modem and the DSLAM port is communicating at. This could be for example 6539kpbs one day, 5494kpbs the next and so on, until the 10 day period has ended.

    At the end of the 10 days the 'Maximum Stable Rate' is set by taking the lowest value that your line has been running at. The speed profile will then be mapped onto a Remote Access Server and that is the minimum speed your circuit will run at. However, if for any reasons line conditions improve, the circuit will increase in performance.

    The speed is upgraded in 500kbps increments so your circuit will only run at the nearest lower speed. For example, your line speed is read at 6846kpbs, your speed would be set at 6500kbps.

    You have to remember you're not buying a product based on speed, such as a 2mb, 4mb, 6mb or 8mb circuit. You're buying DSL Max which is the maximum speed your line can run at. This could be anything from 250kbps to 8000kbps.

    With regard to loop loss / margin (SNR), this basically goes out the window with DSL Max. It just doesn't function in the same manner as standard DSL. The margin is set to run at the lowest value possible (6dB) in order to maximise the bandwidth (frequencies) and only increased if there is loss on the line.

    By the way, if you're a gamer you probably won't want 'Interleaving' on either as it adds ~50ms to ping times. However, if your circuit suffers from dropping connection and/or packet loss then this will probably be turned on.

    Hope this helps.
     
    Last edited: 25 Mar 2006
  6. Phil99

    Capodecina

    Joined: 29 Oct 2004

    Posts: 10,900

    Now that surprises me...no benefit for people borderline on 1mbps afterall...maybe a slight (1 -> 1.5mbps) boost for people just unable to get 2meg though.

    Any idea the reasoning behind going with 500kbps steps rather than 200, or even 100? I wouldn't have thought the speed intervals would make any difference at all to the configuration or running of the BT equipment, yet it would definitely be beneficial to the user to have the closest possible speed the line can match.

    Also, if the line's minimum stable rate is 6490, will they be dropped to 6000 or will they have the choice to go with a slightly unstable line?

    Thanks for the info btw :)
     
  7. gamesaregood

    Mobster

    Joined: 17 Sep 2003

    Posts: 2,809

    Location: Suffolk

    Hello mate,

    Thank you for posting that reply, very interesting read :)

    So does this mean its possible that just by rebooting the router you could connect at a higher / lower speed? How would it affect if your router is up for say 10 days and conditions change? Would does this auto checking happen all the time?

    Thanks for your reply though mate :) just the kind of information i was after.

    Not that it prob changes anything:

    [​IMG]

    I think im right on the edge though, about 3km straight line distance :(

    Thanks again,

    Michael
     
  8. garethrobinson1

    Gangster

    Joined: 16 Oct 2005

    Posts: 446

    Location: Essex

    Yes this is something you can do, but try not to do it that often (more than say twice per day) as the more you reboot, the more likely the DSLAM port is to think there's a problem. This is because the there is a tool called 'DLM' (Dynamic Line Management) which monitors the 'MTBR' (Mean Time Between Retrains). So the more you reboot, the more likely it is that DLM will think there's a problem and might just end up downgrading your speed if anything.

    The 10 day 'bedding-in' period is purely to calculate your circuit's 'MSR' (Maximum Stable Rate). This is the minimum speed your line has run at over the 10 days. From here, the 'FTR' (Fault Threshold Rate) is calculated at 30% of the MSR. If your line speed falls below the FTR (unlikely on most circuits) then we can see there is a problem and will look for such things when customers report a fault on their DSL circuit.

    Yes this auto-checking happens every 15mins behind the scenes, but speeds will only change at each sync event eg. router reboot or USB modem being powered off when PC is turned off. When this happens, a new 'line speed' (between the DSLAM and your router) will be calculated. However, it will take 3 days of continous and reliable speed to upgrade the overall speed throughout the whole network, so will remain bottle necked on our Remote Access Server until these 3 days are up and everything has been running all fine and dandy.

    Everyone bangs on about distance from the exchange being THE contributing factor towards what speed you can get. This is true to some extent, but it's a very general point of view. Of course the signal gets worse as the line length grows, but we find the joints in the cable and therefore the route the cable runs has more of an influence. Looking at your screenshot, your margin is good at this means you will be able to obtain a higher speed with DSL MAX as it has more room to play with. It can lower the margin to 6dB and free up 23dB for extra bandwidth so theoretically you'll get decent speeds.
     
  9. CurlyWhirly

    Wise Guy

    Joined: 24 May 2003

    Posts: 1,429

    Location: UK

    garethrobinson1, just a little query if you don't mind :)

    I've just upgraded to an ethernet modem/router from a BT Voyager 100 modem.
    As I can now leave my modem/router on 24/7 is this going to help with the maximum speed that Max DSL will be able to offer me?
    In other words are routers generally better than modems for syncing with the new Max DSL DSLAM ports?

    My current S/N Ratio is 25.5 dB and Attentuation level is 56 dB.
    I know it's impossible to say for certain as there are so many variables but in your opinion does it seem possible that I may be able to double my current speed of 1 mbps to 2 mbps?

    I am 2.86 km from the exchange (straight line difference) if that helps :confused:

    I have been trying to get 2 mbps for the last couple of years but can't get it :(

    p.s. I also fitted a BT faceplate as well.
     
  10. garethrobinson1

    Gangster

    Joined: 16 Oct 2005

    Posts: 446

    Location: Essex

    Hi CurlyWhirly,

    The fact that you now have a router instead of a USB will most likely make little difference in determining your line speed. You have a 1mb circuit at the moment and obviously reasonably long line, but with a good margin of 25.5dB. This margin keeps noise from interfering with the DSL frequencies and what DSL MAX does is to decrease the margin in order to free up more frequencies for the DSL signal to use, thus increasing the overall line speed.

    I can't say for sure but looking at your current margin I'm pretty sure you'll be able to get over 2mbps with DSL MAX. :)
     
  11. tolien

    Caporegime

    Joined: 16 May 2003

    Posts: 25,368

    Location: ::1

    It isn't "DSL MAX" that does it, any xDSL kit should do it (including the LLU providers for the last umpteen years). It's just that BT kept the downstream sync rates constant.
    Your 500kbps is at odds with what the trialees have reported (and the information the AG folks got) too. Any relation to EmoHawk on ADSLguide per chance? :p

    So BT are going to kick the modem off and force it to retrain?

    Time'll tell.

    There's no new port involved - you'll be on the same port as you always have been.
     
    Last edited: 25 Mar 2006
  12. garethrobinson1

    Gangster

    Joined: 16 Oct 2005

    Posts: 446

    Location: Essex

    I'm talking about BT's configuration of ADSL circuit profiles on DSLAM ports. A standard DSL circuit will have a margin of say 35dB in or very close to the exchange and then decrease as line quality degrades and noise is introduced. (Under the current DSL speed profiles, the margin is set to the maximum possible to keep the noise clear of the ADSL frequencies.)

    The DSL MAX profile fixes the margin to 6dB initally and increases it if noise begins to creep in. I won't go into too much detail but changing from 35dB to 6dB allows 'BINs' to be freed up and the circuit can then take advantage of these extra BINs to increase the overall line speed / bandwidth.

    I don't know EmoHawk and don't read ADSLguide forums :) I've been supporting DSL MAX for BT Wholesale since the trials started (& xDSL for 6 years) so I know this from experience. The 500kbps change is carried out on the RAS, even though the actual line sync speed will actually be around 500kbps - 1000kbps faster. For example, a circuit syncing at 6000kbps (between modem & DSLAM port) is actually throttled at 5000kbps on the RAS.

    Yes, during the initial 10 day period. It has to do this to calculate the MSR and FTR.

    True, the port is physically the same on the line card. However, the DSL MAX profile is applied, which compared to the current DSL profiles is a different kettle of fish altogether ;)
     
  13. garethrobinson1

    Gangster

    Joined: 16 Oct 2005

    Posts: 446

    Location: Essex

    Sorry Phil, I missed your post first time round. :) There certainly are benefits for all customers using DSL MAX. The reasons I've described in the posts above illustrate this e.g. lower margin implemented to free up bandwidth. I think you'll be surprised at what your line will be able to achieve.

    BT's Remote Access Servers (RAS) have profiles created for each circuit speed: adsl500, adsl1000, adsl1500, adsl2000 etc etc up to adsl7150.
    Most of the speed profiles are changed in 500kbps increments, however there are a couple of lower profiles for those who are a very, very long way out: adsl135, adsl250. There is also only a 150kbps increment from 7000kbps to 7150kbps, which is the maximum speed the circuit will run at due to overheads.

    When the line speed between your modem and the DSLAM port is established, this information is passed on to the RAS which applies the appropriate profile. When I say appropriate I mean the next lowest speed setting.

    For example, line speed is at 6850kbps (modem to DSLAM port), the RAS will actually apply a profile of 'adsl6000'.

    DSL MAX operates from a 'stability over speed' stance so you won't be able to choose to have a faster connection and dodgy line :)
     
    Last edited: 25 Mar 2006
  14. CurlyWhirly

    Wise Guy

    Joined: 24 May 2003

    Posts: 1,429

    Location: UK

    Well if I only got 2 mbit I would be happy.
    I stream a lot of video and sometimes my connection isn't quite fast enough and on high bandwidth settings the video has to momentarily pause until the data stream catches up and hopefully with a 2mbit connection, this won't happen so often.


    This is good news as I would personally have a (slightly) slower but reliable connection than a (slightly) faster connection that regularly disconnects.


    Thanks for answering my query BTW :)
     
  15. CurlyWhirly

    Wise Guy

    Joined: 24 May 2003

    Posts: 1,429

    Location: UK

    Another query if you could? :o

    For the first 10 days while the 'bedding-in' period is taking place, is it going to be quite normal to be disconnected regularly as the line limits are reached or is this unlikely to happen?


    Even so, I'm glad I bought one anyway!
     
  16. tolien

    Caporegime

    Joined: 16 May 2003

    Posts: 25,368

    Location: ::1

    I'm talking about generic ADSL. Rate adaption's a well defined process, it's just taken BT this long to catch up.

    The target SNR margin is the same - the difference is that the downstream sync rate is currently tied (so the SNR margin will vary with how "good" the line is). With the Max services, the tie's removed, so the pair will push as hard as they can (with the control of the DLM kit for "stability").
    "Keeping the noise clear of the ADSL frequencies" is the modem/DSLAM's job, and should continue to happen with MaxDSL - the only difference being that both should be aiming for as close to 100% occupation as (stably) possible.

    If you think every line's sitting at an SNR margin of 35dB, you better get busy sending engineers out (to a few million lines). Doubt you'll ever see an SNR margin that high (and certainly not on any more than single digits of percent).

    The other way round. The sync rate is reduced to maintain the SNR margin above the target. "If noise begins to creep in", the SNR drops, so the sync rate is reduced (and correspondingly the stable rate will reduce).
    All standard ADSL/G.DMT stuff.

    Not quite. The bins always existed (and weren't necessarily occupied either), the modem just never used them (or used a reduced bit rate for each bin). The only way you're going to get full sync/ATM rate is 100% occupation, so shock horror, more bins occupied, and more bits per bin.
    Higher bin number == higher frequency == lower SNR, so higher occupation of those bins gives a reduced SNR. No surprises there.

    Oh well. I'll keep my skeptic hat on then.

    Broadband Assurance Tech Support?

    Curious, especially given the ISPs have (some) control over the "payload rate" (to use the STIN's terms), and it's not mentioned in (any) of the S(T)INs either (SIN 386 and STIN441, both version 2, for the interested).

    Odd that noone is warning about this (but are taking orders for IPStream Max). The STIN warns:
    Which sounds like it'll kick you off and rate adapt downwards if your connection becomes unstable, but nothing about kicking you off (on a regular basis) to "calculate the MSR and FTR".

    A profile isn't a port change...

    One thing's for sure, there's plenty FUD spreading about the Max services.

    The official sources certainly aren't saying that.
    You might get kicked off as part of normal SNR margin variation (ie you'll find your SNR margin drops about 1800 hours, and comes back up ~0600), but they ain't saying you'll be regularly kicked off to work out a maximum stable rate.
    There's the bit I quoted, or you can go read them for yourself on SINet. The numbers I mentioned earlier are the two you're looking for (or just search for "Max").
     
    Last edited: 25 Mar 2006
  17. garethrobinson1

    Gangster

    Joined: 16 Oct 2005

    Posts: 446

    Location: Essex

    I've run out of energy now, we could be here forever lol ;)

    Do I work in Broadband Assurance? No. Who do you work for? :)
     
  18. tolien

    Caporegime

    Joined: 16 May 2003

    Posts: 25,368

    Location: ::1

    We certainly could go on forever more.
    Personally, I'm happier with officially published facts (or peer reviewed statements in the case of AG, though there's plenty of BTw employees reading that site too) than the claims of a random individual.

    You might find that distasteful. That isn't my problem (and if you stick around long enough, you'll find I'm always this blunt too). :)

    That's an improvement.

    My profile claims I'm a student.
     
    Last edited: 25 Mar 2006
  19. garethrobinson1

    Gangster

    Joined: 16 Oct 2005

    Posts: 446

    Location: Essex

    lol I find you quite amusing mate :rolleyes:
     
  20. Phil99

    Capodecina

    Joined: 29 Oct 2004

    Posts: 10,900

    Long shot here....are you the Gareth from the BT Broadband Campaigners Tower visit?

    I think it was April 2004?