Kitz Forum
Broadband Related => FTTC and FTTP Issues => Topic started by: ktz392837 on November 25, 2017, 09:14:55 PM
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Had major problems with line due to weather (suspect many people in same area will have messed up lines also), 30 resyncs in short period of time and ended up 20Mb lost of download speed due to it now being banded.
It now syncs up at exact same speed each time with loads of margin to spare, very few ES and CRCs.
Upload was interleaved during same event but that has since been cleared so DLM does do something correct!
Will the DLM remove banding or am I better to report fault whilst the GEA(?) test is showing all the resyncs? Should I wait a few days - how long before reporting?
Thanks
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Banding has been known to stick for a long time. The only way some people have had success in lifting it is by applying a harsher manual banding of their own temporarily. This is possible on Broadcom chipsets (see the sticky forum thread in this section). This is also possible on some devices with a Lantiq/Infineon chipset (such as the DrayTek) by adjusting the SNRM target offset to +5.0 dB (maximum allowed).
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Thanks that was my concern however. Has banding ever been removed for anyone by doing nothing?
I do not see having to reduce the speed even further to be acceptable to me. It would be close to a 40/55Mb package rather than to 80Mb I should be getting and with no guarantee it would fix.
What would everyone else do? Wait or report as fault? Would a large excess of margin/big sudden drop of speed, ”proof" of the multiple resyncs be enough for a DLM reset?
Thanks
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In my experience the simple answer is NO.
Stuart
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Chrysalis had his banding removed, a couple of weeks after his line was improved...
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yes, banding was removed on my ECI line this past autumn.
I checked with openreach if it was manual intervention, it was not.
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This is interesting because on my line from an ECI cabinet it was not removed until BTOR took action to remove it over 12 months after it was implemented. There are reports of DLM not managing lines properly if a non-compliant modem is in use and I suspect this may well be the case for me and perhaps some others because although my banding has been removed interleaving is not and my line runs very very low error rates.
Also please do not suggest I lower my speeds to lower my error rates as I dont know that I can get them any lower ;)
Stuart
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No I suggest you just ignore it and worry about something else. Treat banding as permanent meaning you will never be disappointed when it stays around.
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Yes I guess it is not the end of the world but as it has taken 25% of my speed it should apply an appropriate discount to a lesser package.
I shouldn't be held to my 18m contract for such a big difference.
If BT can just hit some buttons to get the line working again they should just do it or better yet tell the DLM to remove banding if it can without any engineer intervention.
I will give it a few more days. I will then report to ISP if they try to fix great if not I will ask for a downgrade of package as I don't see why I should be forced into paying more than other customers getting the same speed.
Why doesn't the DLM sort it out? Half a job by BT again how difficult can it be? There must be a better way than what they have currently got? It is applying banding before it has even tried other solutions? What are the criteria to apply banding they are clearly wrong? Far too big of a hammer was used far too quickly.
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I think treating banding as normal is a very bad way to go. If a line is in serious trouble and cannot be made to run at the speed which is causing problems and all other causes have been eliminated then and only then banding is acceptable but if the speed drop is large (like the quoted 25%) then a reduction in the charges should be automatic. In my opinion banding is at least some times applied for a quick fix to save engineer time which should never be the case, in my case it was applied to try to resolve a problem but did not however the banding was never removed until I complained over the head of my ISP directly to BTOR over 12 months later after my ISP point blank refused to do anything.
Stuart
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What are the other solutions that are better?
1 - Ignore the conditions that triggered DLM and dont apply any stability action, granted this would probably be fine for many cases where we get DLM reacting to short lived events, but there would also be cases where lines have excessive dropouts and/or errors causing things to break.
2 - Apply interleaving, this reduces speed "and" increases latency so a bigger evil than banding.
3 - Apply banding, reduces speed but keeps existing latency.
Of course I have posted in the past of what I think should be happening, but it will never happen due to the cost constraints placed on openreach.
In an ideal world DLM would always be treated as a temporary bandage, and not a long term solution, however this would skyrocket costs to openreach treating every line that requires interleaving as faulty until a physical fix is applied, and in the current regulated environment isnt viable.
Thinking about this some more, speedtests need to become more relevant to reality. Most just test the burst speed, some now also test bufferbloat which is a step in the right direction, but I think tcp session creation time and dns lookup speeds need to be tested as well, both of these will primary respond to better latency rather than better burst speed, as burst speed is only part of what makes things fast, not everything.
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DLM intervention presupposes you have a fault of some sort. Automated actions are acceptable initially however these action may well just end up in covering up a fault which should be fixed and no one should be banded permanently just because they had a fault which may well have been fixed or gone away. I see no reason (cost apart) that a system like DLM could be designed to react in a better way to apply temporary fixes and then remove them some time later but monitor closely to make sure the line is still OK, then if not re-apply the temporary fix and flag it to be looked at by engineers who can then decide if the issue is real or simply the line cannot operate at the speed set. In the latter case the EU should be informed and receive a lower charge for their reduced speeds. The current DLM does not fix things it bodges them to cap costs.
Now I know this is unlikely to happen but jut imagine how popular a broadband provider would be if they had a system like this!
Stuart
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I dont believe DLM induced banding is permanent, just the conditions to remove are harder to reach than interleaving removal, which can lead to people thinking its permanent.
Stuart you need to understand how the entire system works.
Each provider relies on openreach, either directly or via a wholesaler such as BT wholesale.
The likes of talktalk (your isp) constantly lobby ofcom to reduce what they pay openreach for services, ofcom seems to sympathise with talktalk, and as a result openreach's revenues have dropped for rental over the past 10 years or so, even before inflation is taken into account. With openreach been forced to reduce revenue whilst keeping shareholders happy and investing in new technology, they clearly have to cut corners somewhere, and one such area is maintenance and line faults.
Talktalk would never do what you said, they only care about keeping costs down.
I remember reading a document in the early days of VDSL where it said CPs could request banding, in those instances it is permanent unless its specifically removed. I dont know if CPs can still do this and if they can do if talktalk use it as a policy to reduce costs of processing potential faults.
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I think Openreach has been kippered up with respect to parent company.
It's the same as British Gas, with Centrica selling on gas to BG, Centrica make all the profit while BG get lumbered with all the costs.
As for Banding, imagine if you bought a new car, after a weeks use, decided that it would only go 40mph every where >:D, one would be a little miffed if the garage turned round and said
thats normal, we'll look into the problem but it will cost you £500
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I think some people totally misunderstand DLM and why we need it. It's there for a purpose to maintain line stability especially in certain environments whereby our broadband requirements have changed and we no longer just use it for data. It is not there to cut costs by any means as running a DLM system in itself costs the carrier money to implement.
Openreach uses Tiered Rate Adaption (TRA) for its DLM.
The alternative is Automatic Margin Adjustment (AMA) which is used by BTw /TT/Sky and older legacy systems etc.
Both of these DLM types are DSL and NICC standards... and certainly not anything plucked out of the hat by BT/Openreach. :no:
A TRA based DLM is recommended in VDSL/NGA and mixed environments because of power savings. The reduction of power is of benefit to other users in the same bundle who will experience less cross-talk.
Its a bit more complicated.. but it goes back to the discussion last week with Chrys and Dynamic spectral masks.
Whilst power itself isn't managed as a DLM parameter, if TRA DLM is used then that is the speed used when the power management system uses when calculating PCB and PSD masks for individual lines on a particular DSLAM.
In simple speak - using banding together with DSM causes less crosstalk to neighbouring lines.
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Whilst the above is true... I do think the Openreach system can be a bit harsh when it comes to banding... or rather its removal.
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I am venting a bit, I guess I could be like some, stuck with a 1Mb connection and then I would certainly have something to vent about. I should count myself lucky.
Bad enough that ECI does not have Ginp, does not have 3db and does not have vectoring. It wouldn't matter as if it was all turned on tomorrow the stupid brainless DLM would not even try to use it as its a banded connection!
I hope at some point ISPs can remove banding. If it goes live tomorrow that would be great!
I should have a button to press on my ISPs control panel to reset my line perhaps with an area to give reason for reset request. I can do this a limited amount of times a year. Simples, would save BT money and give customers much more control.
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Whilst I don't think we ourselves will ever get the option, I totally agree that the ISPs should be able to.
The current system is an interim solution and only available to a couple of ISPs because its a manual process. Hopefully in time some sort of GUI will be built into the KBD/ BRAT tools or whatever they're called this week
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yes i forgot about that kitz but of course if i remember right from your earlier posts lines have to have had an improvement to qualify, but will openreach enforce that requirement?
Also agreed the power management stuff is essential, and so is the stability profiling when considering the cost efficiency approach to faults.
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I dont think its so much an improvement... rather what the DLM is limiting the speed to compared to what the line could achieve if there was no DLM. ie current sync v max attainable. Their terminology isnt actually very clear but it seems to be based around some sort of percentage AND the line must be stable for a period of time.