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Ability to Reset Openreach FTTC Broadband DLM Profiles Arrives

Monday, February 5th, 2018 (11:28 am) - Score 31,523

At present if an ISP feels that the Dynamic Line Management (DLM) profile for a UK Fibre-to-the-Cabinet (FTTC / VDSL2) based broadband line needs a reset then it usually requires an Openreach engineer visit, but progress is being made on a new remote reset solution.

The DLM system is used to control the performance and stability of related lines, which in practice means that your speed may go up or down depending upon how stable / error prone DLM thinks the line is. Broadly speaking the DLM system on Openreach’s FTTC network works pretty well, although sometimes a connection’s profile may become stuck at a lower level or other problems can occur that might benefit from a profile reset.

Unfortunately ISPs have not previously been able to perform remote resets on FTTC circuits, which is partly because to do so would require an engineer visit (attracts a cost). Last year we mentioned that Openreach were working to improve DLM by tweaking how it works and also offering an “interim” solution for resetting the caution counters (technically a DLM reset), which would allow ISPs to “request a caution counter reset on a number of their lines each day“.

Since then several ISPs (e.g. Plusnet) have started offering the option of a remote DLM reset as part of a trial with selected customers. The reset seems to take place in phases and has in a few examples helped to return some FTTC lines back to a higher speed. Today Openreach issued an interesting update to tout an “interim” solution that “will allow [ISPs] to request a DLM reset and replaces the ability to request caution counter resets” (here).

The briefing itself isn’t public, although ISPs inform us that it does indeed extend the trial from a caution counter reset to a full DLM reset, which should fix banding problems and some other issues with DLM profiles; assuming of course that the original underlying problem has been resolved first. We understand that this change will come into play from the 19th February 2018.

Using this approach means that each day an ISP can submit a list of circuits to be reset, which is then applied overnight by Openreach. A limit of 1000 circuits per day per ISP remains in place, although we’ve not seen any complaints about this restriction. Obviously this is something that ISPs don’t expect to use a lot but it’s a useful tool for them to have and could save on engineer visits, as well as satisfying some users.

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By Mark Jackson
Mark is a professional technology writer, IT consultant and computer engineer from Dorset (England), he also founded ISPreview in 1999 and enjoys analysing the latest telecoms and broadband developments. Find me on Twitter, , Facebook and Linkedin.
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28 Responses
  1. James says:

    Incredible to think this wasn’t a thing until now.

  2. adslmax says:

    I am the lucky one that Plusnet has done a remote DLM reset as part of a trial with selected customers with BTw. My line was banded at 74Meg for almost 64 days before DLM has resetted and removed banded.

    1. AndyH says:

      Plusnet did not do a DLM reset.

    2. adslmax says:

      @AndyH. Yes PN did told me in fault team that BTw has resetted my line vis remotely DLM reset as part of the trial and this is why they did for me because of stuck caution couter that has banded my line for 64 days with no fault of mine due to Western Power loss and intermitted that caused my DLM to banded my line a day after.

    3. AndyH says:

      There is no option for ISPs to reset DLM at the moment. This won’t be introduced for another couple of weeks and BT Wholesale will introduce it some point after.

      The trial is for the line caution counter to be reset, so that you can move up a profile step/s (as long as your line doesn’t get error beyond the thresholds).

      There are some key differences with the caution counter reset (it is far less intrusive) as opposed to a full DLM reset.

    4. BooseyLad says:

      You okay @AndyH?

      I apologise on behalf of adslmax not nailing the detail between “cause & effect” on what PN did to resolve his issue, and causing you to feel so distressed that you needed to correct him in a beratel tone, jerk!

  3. Ixel says:

    This is a huge step in the right direction, I never thought I’d see this day coming. I expect some reputable ISP’s like AAISP will be using this option every so often if a customer reports that their connection is banded or has been stuck on interleaving for some time.

    Are there still certain requirements for being eligible to submit a request DLM reset though I wonder? From what’s said here I assume the only thing that now applies is the limit of 1000 connections per ISP per day and that it’s at the ISP’s discretion to grant a DLM reset for the connection.

    1. AA-Andrew says:

      Yes, we’ve been requesting this for years and years and years 🙂

    2. Chris C says:

      The obvious question is why has it took them several years to implement it.

  4. adslmax says:

    Here is my line stats before DLM Banded and after resetted DLM by PN:

    1st Remote Defect Indicator/DLM resync: 26th Nov 2017 at 12:55pm (line banded enabled)

    Downstream Upstream
    Line attenuation (dB): 11.4 0.0
    Signal attenuation (dB): Not available on VDSL2
    Attenuation rate (kbps): 89238 30218
    Connection speed (kbps): 74000 19999
    SNR margin (dB): 9.9 15.1
    Power (dBm): 12.5 -0.9
    Interleave depth: 16 1
    INP: 49.00 0
    G.INP: Enabled Not Enabled

    2nd Remote Defect Indicator/DLM resync: 29th Jan 2018 at 6:10pm (after 64 days stable & DLM resetted)

    Downstream Upstream
    Line attenuation (dB): 11.3 0.0
    Signal attenuation (dB): Not available on VDSL2
    Attenuation rate (kbps): 83026 27648
    Connection speed (kbps): 69594 19999
    SNR margin (dB): 6.2 15.2
    Power (dBm): 12.5 -1.3
    Interleave depth: 1363 1
    INP: 3.00 0
    G.INP: Not Enabled Not Enabled

    3rd Remote Defect Indicator/DLM resync: 1st February 2018 at 1:45pm (after 3 days stable & restored)

    Downstream Upstream
    Line attenuation (dB): 11.3 0.0
    Signal attenuation (dB): Not available on VDSL2
    Attenuation rate (kbps): 82489 27617
    Connection speed (kbps): 79999 19999
    SNR margin (dB): 6.7 15.1
    Power (dBm): 12.4 -1.3
    Interleave depth: 8 1
    INP: 48.00 0
    G.INP: Enabled Not Enabled

    1. AndyH says:

      Thanks for that, I’m sure we’ll all sleep better tonight knowing your line is back to normal.

    2. Thomas says:

      @AndyH This is an ISP review blog/ news site. I’m not sure what you are expecting here? Maybe you should go back to The Sun comment area 🙂

  5. Marty says:

    Hopefully it makes a difference on those ECI cabs However still waiting for the fix to be applied.

    1. MrMike says:

      I’ve been banded for many months now with 8ms interleaving enabled on the downstream and a much slower download cap than the line is sync’d at. Router stays connected for weeks at a time. Been a never-ending process to get through the front-lines of support at BT to try and request a DLM reset. Hopefully they will submit one for me soon if they can remote request one.

  6. Andy Mitchell says:

    About dam time! My line keeps getting DLM’d to bang on 60000kbps because I reboot my router every 14 days. How it can’t tell that it’s a routine reboot is beyond me.

    1. Tom says:

      It worries me that you have to or want to reboot your router regularly. Why?

    2. Simon says:

      Do you have a HH6? that does it every 14 days.

      if not – why ?

    3. GNewton says:

      @Tom: Ideally you should be able to switch off your modem/router at nighttime, or when you are on holidays, or out of town for a few days, without having an effect on your line. I am not sure whether Openreach’s DLM can cope with it.

    4. AndyH says:

      @ GNewton – Ideally according to who? The energy consumption of a modem/router is tiny compared to many other domestic appliances. It costs between £7 and £11 a year on average for a router to run 365 days a year.

    5. Norbert says:

      I was working with guy who is turning off his modem every night or day when he is outside to save electricity. His IP has changing every time so he had to ask to update company firewall rules update to keep remote access working. Finally we created Jenkins job for that.

    6. GNewton says:

      @Norbert: He should use a static IP address.

    7. AN other says:


      Multiply that across the millions of routers across the UK that don’t need to be on 24/7 and it comes to a tidy sum and an awful lot of wasted energy. Anyhow back to the matter in hand BT’s FTTC DLM was designed by an imbecile and fails to have considered the usage and fail scenarios properly IMHO. The end customer should have the ability to reset it by request through several possibilities such as email, text message, tone command string from phone or router request for reset. Given the terrible and aged state of BT’s copper/aluminium network this should have been foreseen at the outset. BT stop sweating your unfit network and foisting it on the public, it’s rubbish we want FTTP and it’s better reliability.

  7. adslmax says:

    If HH6 do this every 14 days of rebooted and cause DLM to act then surely Openreach or BT should know this and adjusted to DLM system to ingorne HH6 rebooted every two weeks or any power cut or power loss intermitted in same area etc.

    1. Jonny says:

      A router reboot every 14 days shouldn’t cause DLM issues. Similarly, power failures should result in a dying gasp message being sent back to the DSLAM to provide some context of the sync loss.

      I believe the 14 day Hub 6 reboots aren’t happening anymore – mine has several weeks uptime for example.

  8. Shoei says:

    The usual advice for rebooting the modem or modem/router is to power off for 30 minutes, DLM samples the line every 15 minutes and marks two consecutive ‘off’ states as a power fail. Power fails don’t provoke hostile DLM action so a minimum 30 minutes off should be safe.


    As far as I know the ‘last gasp’ message is detected by the cabinet but is not used by DLM. When there is an intermittent fault or power outage, DLM assumes every transient must be a noisy line, which would be fine if it didn’t spend months and years pondering whether to resume normal service.

  9. Optimist says:

    Good to see the ISPs taking their own advice

    “Have you tried turning it off and turning it back on again?”

  10. daniel badman says:

    anyone know if zen will be offering this from the 19th my lines been stuck at 29 meg for almost 3 months no fault online erros are few but dlm is just completely stuck and i no my line can get 40meg very frustrating

  11. David says:

    This is still in a Trial phase with selected customers, the only change is that from the 19th of Feb, Openreach will be performing a full DLM reset rather than a caution counter reset.

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