Your browser isn't supported
It looks like you're using an old web browser. To get the most out of the site and to ensure guides display correctly, we suggest upgrading your browser now. Download the latest:

Welcome to the MSE Forums

We're home to a fantastic community of MoneySavers but anyone can post. Please exercise caution & report spam, illegal, offensive or libellous posts/messages: click "report" or email forumteam@. Skimlinks & other affiliated links are turned on

Search
  • FIRST POST
    • DonnyDave
    • By DonnyDave 10th Jul 17, 6:57 PM
    • 1,561Posts
    • 435Thanks
    DonnyDave
    Ofcom’s apathetic stance on DSL SNR margin
    • #1
    • 10th Jul 17, 6:57 PM
    Ofcom’s apathetic stance on DSL SNR margin 10th Jul 17 at 6:57 PM
    Having switched my landline telephone and ADSL service I have discovered that my new provider offers a minimum downstream SNR margin of 6dB. Previously, with BT, I had 3dB, and it ran with that for quite a number of years.

    Consequently, of course, the data sync speed is somewhat reduced. I am not at all happy because I naturally never gave SNR margin a second thought and the promotional literature from ISPs, including this one, made no mention of the SNR margin.

    This raises a number of points:
    1. Ofcom does not stipulate that providers must make mention of SNR margin in sales literature. General Condition 23 obligates service providers to advise of the minimum contract term, payment terms and cancellation terms, but not SNR margin.

      The response I received from the regulator goes on to say “If this [the SNR margin] is something of particular interest to a consumer, we would expect them to raise this with the service provider concerned before agreeing to the contract.”

      So, according to Ofcom, it’s down to the consumer to ask – it’s my fault for not asking! But it’s not something like a new car that I’m looking to buy – where I might have a requirement for a particular style of wheel trim, for example. In essence, I naturally assumed the service would have a 3dB minimum margin – why would I not?

    2. An axiom of any free market is that traders must set out information on their products, including properties and specifications. This is so as to differentiate them from those of competitors in the eyes of the consumer.

      But the telecommunications regulator sees no reason why consumers would wish to know the minimum SNR margin, which varies by provider. A knock-on effect is that this factor can have no influence on prices because consumers aren’t informed. So a service with a 3dB minimum will, all other things being equal, go for the same price as one with a 6dB. Of course it can’t be equal because the speed will be slower for the latter, and I will come on to this below.

    3. As well as modulation scheme, there are several factors that determine the sync speed on a DSL line:
      • Line length and quality, including whether any of it is aluminium. Essentially, I assume, this determines attenuation.
      • SNR margin.
      • Any noise which is present, which may be compensated by increasing the SNR margin.

      I am not familiar with the requirements Ofcom sets out to ISPs on how they must indicate broadband speeds. The reason that it is not possible to present a single figure that is reasonably accurate is due to unknown variables.

      Where there is a function consisting of one or more unknowns it is imperative to assimilate all those that are known, extending ambiguity in the computed output to the unknowns only. Ofcom does not agree.

    4. The response from Ofcom says that for providers using the Openreach network to offer their services, such as my provider, the standard minimum downstream SNR “seems to be 6dB”.

      It may be of interest to note that the consumer retail divisions of both BT and TalkTalk offer a minimum noise margin of 3dB. This surely means that not only may their retail customers have this at disposal but that the same exchange hardware which supports other ‘virtual’ operators (like mine) could potentially provide the same margin to those operators.

      If the network operators are really supplying other communication providers with 6dB or above then I have to wonder whether this is anticompetitive behaviour. Even if it is not, why has Ofcom not intervened to see that they do offer a 3dB profile?

      It must be said, though, that any notion of this being anticompetitive is somewhat mitigated by each individual ISP failing to give open declaration in its literature (as detailed in point 2)! Consumers aren’t generally aware so show only indifference.

    I must stress that references herein relate to the minimum possible downstream SNR margin of a service. This might not be the same as the default or standard offered. It is accepted that the margin may need to be increased due to noise. The debate could perhaps be extended to the minimum upstream SNR margin, also.

    The variances in speed we are talking about are not insignificant. To give my experience as a guide: with BT I had a SNR margin of 3dB and downstream sync speed of between 12Mbps and 13Mbps. My line, I estimate, is about a mile and a quarter. Initially with my new provider I had a 12dB margin which gave a speed of around the 7Mbps mark. This having been reduced to 6dB now means the line speed is reliably 10Mbps or just above.

    While I didn’t expect it to be absolutely the same as with BT – because it is provided by TalkTalk MPF – I really didn’t foresee this fly in the ointment!

    This is anything but a new technology still in its infancy. By now I would have expected these sorts of issues to have been ironed out.


    The ASA CAP is currently running the Consultation on speed claims in broadband advertising which closes in a few days’ time.
    Dave
    Say no to 0870!
Page 1
    • Mister G
    • By Mister G 10th Jul 17, 7:47 PM
    • 348 Posts
    • 224 Thanks
    Mister G
    • #2
    • 10th Jul 17, 7:47 PM
    • #2
    • 10th Jul 17, 7:47 PM
    You could always get yourself a router that allows you to 'adjust' the SNR yourself.
    • lee111s
    • By lee111s 10th Jul 17, 7:50 PM
    • 2,724 Posts
    • 1,896 Thanks
    lee111s
    • #3
    • 10th Jul 17, 7:50 PM
    • #3
    • 10th Jul 17, 7:50 PM
    It's down to each ISP how they want to run their network.

    A target margin of 3db is more likely to cause a circuit to have more errors/drop outs and result in DLM taking action by banding the line, applying interleaving etc than a one with 6db. Less faults means less Openreach engineer visits, less costs and ultimately less complaints from customers as the vast majority of joe public want a stable connection for their daily internet usage.

    6db is the industry standard, with some ISP's offering 3db on lines that can handle it, but even then it's managed by DLM and of the line is unstable or has a large number of errors which can cause issues with throughpt, then the margin would be increased.

    99.99% of customers aren't interested in the inner workings and finer details of their internet connections and thus it wouldn't make sense for ISP's to add in all of the technical specifications of any type of xDSL/GPON/DOCSIS technology to their terms and conditions or conditions of sale.

    That said, you can buy routers with Broadcom chipsets, such as Billion routers, which allow you to configure the SNR from your end.
    • Mister G
    • By Mister G 10th Jul 17, 7:53 PM
    • 348 Posts
    • 224 Thanks
    Mister G
    • #4
    • 10th Jul 17, 7:53 PM
    • #4
    • 10th Jul 17, 7:53 PM
    Indeed. I ran a Billion 7800N for a number of years with an SNR of 1.5dB on a line of some 5km. It enabled me to get speeds of 1.5Mb instead of the 0.75Mb the ISP wanted to supply.
    • lee111s
    • By lee111s 10th Jul 17, 7:57 PM
    • 2,724 Posts
    • 1,896 Thanks
    lee111s
    • #5
    • 10th Jul 17, 7:57 PM
    • #5
    • 10th Jul 17, 7:57 PM
    Indeed. I ran a Billion 7800N for a number of years with an SNR of 1.5dB on a line of some 5km. It enabled me to get speeds of 1.5Mb instead of the 0.75Mb the ISP wanted to supply.
    Originally posted by Mister G

    Yup, my 4.5km line is happy bumbling along at 2dB SNR.
    • DonnyDave
    • By DonnyDave 10th Jul 17, 8:32 PM
    • 1,561 Posts
    • 435 Thanks
    DonnyDave
    • #6
    • 10th Jul 17, 8:32 PM
    • #6
    • 10th Jul 17, 8:32 PM
    So with respect to the router that one can configure the SNR margin, how does that work?

    If the ISP has set the profile of 6dB then are you saying it is possible to force the DSLAM to operate at a lower margin with a modem/router equipped for such a task?
    Dave
    Say no to 0870!
    • lee111s
    • By lee111s 10th Jul 17, 8:56 PM
    • 2,724 Posts
    • 1,896 Thanks
    lee111s
    • #7
    • 10th Jul 17, 8:56 PM
    • #7
    • 10th Jul 17, 8:56 PM
    Yes.

    The SNR is set during the initial conversation between the modem and the DSLAM.

    The modem can say to the DSLAM it wants to connect with a SNR either x+ or x- db than the DSLAM has as the target.
    • DonnyDave
    • By DonnyDave 10th Jul 17, 9:07 PM
    • 1,561 Posts
    • 435 Thanks
    DonnyDave
    • #8
    • 10th Jul 17, 9:07 PM
    • #8
    • 10th Jul 17, 9:07 PM
    I am just reading this page: http://www.increasebroadbandspeed.co.uk/SNR-tweak

    It explains how the modem measures the SNR and reports it to the exchange. The DSLAM at the exchange then decides on the sync speed based on the SNR and the SNR margin that it is set for.

    The page above, near the top, talks about having the modem report the SNR as being higher than it actually is. I can see clearly that this will have the desired effect.

    lee111, is this the same as what you are saying when you said "The modem can say to the DSLAM it wants to connect with a SNR either x+ or x- db than the DSLAM has as the target"? Or to put it another way, the modem can't say to the DSLAM that the SNR margin will be xdB, but it can misrepresent the actual SNR.
    Dave
    Say no to 0870!
    • lee111s
    • By lee111s 10th Jul 17, 9:14 PM
    • 2,724 Posts
    • 1,896 Thanks
    lee111s
    • #9
    • 10th Jul 17, 9:14 PM
    • #9
    • 10th Jul 17, 9:14 PM



    Here's mine.

    Default is at 6, I have mine set to "-4" in the router, so the target set by the DSLAM is 2dB. Current margin is at 2.5dB
    • DonnyDave
    • By DonnyDave 10th Jul 17, 9:23 PM
    • 1,561 Posts
    • 435 Thanks
    DonnyDave
    Default is at 6, I have mine set to "-4" in the router, so the target set by the DSLAM is 2dB. Current margin is at 2.5dB
    Originally posted by lee111s
    Thanks. I will read up on these routers.
    Dave
    Say no to 0870!
    • lee111s
    • By lee111s 10th Jul 17, 9:26 PM
    • 2,724 Posts
    • 1,896 Thanks
    lee111s
    They're decent.

    Mine has held a 2db connection for over 60 days.

    Roll on the local powe company sorting out the power for our fibre cab.

    2.2meg throughput is depressing!
    • DonnyDave
    • By DonnyDave 11th Jul 17, 12:51 AM
    • 1,561 Posts
    • 435 Thanks
    DonnyDave
    Following the guidance here under the heading You can tweak some Broadcom-based routers using telnet I have now managed to adjust the SNR margin on my connection.

    My router is a USRobotics USR9108 and is over 10 years old. Granted, if I power it down it will forget it and will therefore need reprogramming, but I am pleased to have a rate of 12203k and margin of 1.8dB. Speedtest.net just returned a result of 10.54M!

    I will see how it goes, obviously, noting whether there are errors that might suggest an increase in margin would be worthwhile.

    What about the upstream margin? Is it possible to adjust that? I guess maybe not as it's the receiving end that determines the SNR and that is obviously the exchange end.
    Dave
    Say no to 0870!
    • lee111s
    • By lee111s 11th Jul 17, 8:49 AM
    • 2,724 Posts
    • 1,896 Thanks
    lee111s
    As far as I know you canmt adjust the upstream noise margin.

    What sort of upstream connection rate you getting?

    Even on my long line I get around 800kbps sync upstream.
    • Chrysalis
    • By Chrysalis 11th Jul 17, 9:20 AM
    • 1,948 Posts
    • 893 Thanks
    Chrysalis
    It would be too confusing for most people, estimating a speed is seen as reasonable tho.

    With FTTC services openreach are currently rolling out lower SNR margins to their hauwei cabinets, no plan in place for ECI cabinets tho as those cabinets are still waiting for G.INP which is likely required to be working before lower SNR margins come.

    Every single isp selling FTTC uses openreach FTTC so would all be the same in that respect.
    • DonnyDave
    • By DonnyDave 11th Jul 17, 12:26 PM
    • 1,561 Posts
    • 435 Thanks
    DonnyDave
    As far as I know you canmt adjust the upstream noise margin.

    What sort of upstream connection rate you getting?

    Even on my long line I get around 800kbps sync upstream.
    Originally posted by lee111s
    Upstream it syncs reliably at 1019k. At the present moment the SNR margin on that is 10.7dB.
    Dave
    Say no to 0870!
    • lee111s
    • By lee111s 11th Jul 17, 12:28 PM
    • 2,724 Posts
    • 1,896 Thanks
    lee111s
    You won't get much better than that anyway.

    Max is 1152 if I'm not mistaken.
    • DonnyDave
    • By DonnyDave 11th Jul 17, 12:38 PM
    • 1,561 Posts
    • 435 Thanks
    DonnyDave
    With FTTC services openreach are currently rolling out lower SNR margins to their hauwei cabinets, no plan in place for ECI cabinets tho as those cabinets are still waiting for G.INP which is likely required to be working before lower SNR margins come.

    Every single isp selling FTTC uses openreach FTTC so would all be the same in that respect.
    Originally posted by Chrysalis
    I was wondering about FTTC VDSL. From what little I've read G.INP is the buzzword.

    But VDSL still has an SNR margin so isn't it possible for the savvy user to drive it down in order to get faster sync speeds?

    I suppose the issues that result in errors on VDSL are greater as it is more complex and utilises frequencies that go higher than ADSL.
    Dave
    Say no to 0870!
    • DonnyDave
    • By DonnyDave 11th Jul 17, 1:00 PM
    • 1,561 Posts
    • 435 Thanks
    DonnyDave
    Is there a guide somewhere that explains what the entries in the router's System Log mean?

    One says:

    syslog: proxy.c:211 INFO:Outgoing Call from: 12@89.163.146.196

    What does this mean?
    Dave
    Say no to 0870!
    • lee111s
    • By lee111s 11th Jul 17, 2:13 PM
    • 2,724 Posts
    • 1,896 Thanks
    lee111s
    You'd need to check with the router manufacturer as every router will report differently on the logs.

    As for FTTC, Openreach have built something into the DSLAM that prevents the router setting the target margin.
    • DonnyDave
    • By DonnyDave 11th Jul 17, 2:24 PM
    • 1,561 Posts
    • 435 Thanks
    DonnyDave
    As for FTTC, Openreach have built something into the DSLAM that prevents the router setting the target margin.
    Originally posted by lee111s
    Is it something the ISPs don't like? Is it best not to mention it to them?
    Dave
    Say no to 0870!
Welcome to our new Forum!

Our aim is to save you money quickly and easily. We hope you like it!

Forum Team Contact us

Live Stats

3,006Posts Today

8,462Users online

Martin's Twitter
  • Byebye! I'm about to stop work & twitter, to instead spend glorious time with Mrs & mini MSE. Wishing u a lovely summer. See u in 10 days.

  • WARNING Did you start Uni in or after 2012? The interest's rising to 6.1%; yet it doesnt work like you think. See https://t.co/IQ8f0Vyetu RT

  • RT @JanaBeee: @MartinSLewis Boris is the anomaly (coffee), the others are versions of normal (beer). Lots of same candidates = vote share d?

  • Follow Martin