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Author Topic: HELP: Which Outdoor-DSLAM component lead to Supervectoring frequency breakdown?  (Read 1021 times)

Achimito

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Hi there,

I am living in Germany and German Telekom has diagnosed a "fault to earth" defect of their buried cable in our street last week. I had an excellent working Supervectoring line since I ordered it on November 13th 2018: Full-sync, 309 MBit line capacity on my brand new Fritz!Box 7590, excellent SNR margins of 11 and 12dB. German Telekom is going to repair the defective "fault to earth" part of their buried cable the upcoming week, i.e. a part of around 2m to 3m of the whole buried cable. So far so good.

BUT: Since May 16th 2019 the whole side of our street were hit by a sudden DSL-resync at the same time (16:39:59 o´clock). Since this time the Supervectoring frequency range above 17,7 MHz collapsed half-part. Please see attached image for details.

I have a dozen telephone conversations behind me since last week, but no so called "expert" at German Telekom knows what component in their Outdoor-DSLAM might have gone defective. All their remote management systems show no sign of any defect. So, they do not plan to repair their defective component in Outdoor-DSLAM.

Question to you guys: Which component in Outdoor DSLAM might have gotten hit by the "fault to earth" defect? I only know that I am connected to an Adtran Linecard 192.85. All neighbour hourses are affected by the defective frequency range above 17,7 MHz as well.

TIA for your advice,
Achim
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burakkucat

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Welcome to the Kitz forum.  :)

There may not necessarily be a fault with the DSLAM, its line-cards or their ports, but what is being seen may well be a result of the earth contact fault in the cable. I would suggest waiting until the faulty section of cable has been replaced and then check again.

You mention that your neighbours' and your own circuits all re-trained at precisely the same time. That, to me, is indicative of the DSLAM being re-booted or reset. It could well be the case that as the DSLAM re-initialised it detected the low insulation to earth on all the pairs and has cut-back the power, along with using a sub-optimum profile.
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Achimito

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Hi burakkucat,

first off, please excuse posting my first topic to the wrong sub-forum, as I am a newbie to this forum.

Thank you so much for your estimation. You know, I am very picky when it comes to my line stats which were in excellent condition before the fault occured, thus I got a bit nervous about the degraded frequency spectrum.

I will keep you posted if things won´t normalize after the faulty section of the cable will have been replaced by German Telekom.

Kind regards from Munich,
Achim
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Achimito

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So, German Telekom just claimed today that they got their cable fixed but the spectrum still looks the same, i.e. it is still poor and dagraded. What could still be the culprit component?

Please advise,
Achim
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burakkucat

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I must admit that the latest two plots (SNR and Bit Loading, both versus the sub-carrier index) do not look very good for the frequencies above the Profile 17a upper limit.

Does the Fritz!Box provide the Hlog and QLN plots, please? Sight of those two plots might be helpful.
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Achimito

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Unfortunately I am not aware that the FritzBox 7590 can be read out to show the Hlog and/or QLN plots. Do you happen to know a Broadcom based modem which is capable of Profile 35b and which lets dslstats read out the Hlog and QLN plots. I still have a ZyXEL VMG1312-B30A which is unfortunately not compatible with Profile 35b.

Do you have a recommendation for a dslstats compatible modem with Profile 35b support?

Thanks.
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burakkucat

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I am sorry but I do not know of any Broadcom chipset based device that is capable of Profile 35b support.

Perhaps other members might have a suggestion?
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re0

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I know the Zyxel XMG3927-B50A does support 35b, but I do not know the availability of the device in Germany (though, plentiful in Switzerland). This has access via SSH/TELNET - in-depth statistics available with "xdslctl", so can be configured to work with DSLstats.

They are various (a rather annoying list to compile) Zyxel modems available which support 35b. They usually sport Broadcom chipsets, but you'd probably have to do some digging and enquire with them to be sure.
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Achimito

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Thanks for the hint with the Zyxel XMG3927-B50A. I myself was only aware of the ZyXEL VMG8823-B50B which is mainly sold in Italy. I will look and see if I will be able to buy one of these ZyXELs.

To be honest, I am not yet sure whether I will stay with such a crappy German Telekom SVVDSL 250 line or whether I will downgrade to a better working VVDSL 100 line. Different German Telekom representatives just wrote me today that they are not willing to reboot or re-initialize the Outdoor-DSLAM and that they are definitely not willing to restore a full-power signal between 17,7 and 35 MHz. :no: I am really very disappointed about their decision and I will look whether I will unpack my good old ZyXEL VMG1312-B30A again to get a sync-loss-less VVDSL 100 line again up and running after changing my booked line rate and Profile with them.

I will keep you posted whether their will be any more positive German Telekom news in the future.

I highly appreciate all your help to me.
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re0

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It might be worth bearing in mind that a modem without G.fast support (which the Zyxel XMG3927-B50A has) may be cheaper than with. I do not have anything to hand to back this claim, but it should be a good assumption that a modem with 35b would be, at least in general, cheaper without G.fast support.

It is a shame that Deutsche Telekom are not being any more helpful. While there is a sizeable loss, it doesn't seem you are having stability issues or otherwise a degragded experience? If I experienced a loss like that, I'd likely push pretty hard to get it looked at rather than just downgrading. Although, short of emailing the CEO or another high up individual, you've had quite a bit of contact and it is down to judgement whether you wish to pursue it further.

Whatever you choose to do, good luck.
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Achimito

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Hi re0,

you can believe me that I already spent hundreds of hours with around 3 dozens of representatives of German Telekom. 26 trouble tickets of mine were closed so far. :'( I will see whether I and my neighbours will try more efforts at upper levels to get a flawless signal again... .

Thanks again for all your support and efforts you spent so far. I really highly appreciate that. Honestly.
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Achimito

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Hi there,

I don´t know whether I am currently dreaming or not, but someone from German Telekom just pulled out the DSLAM out of its failsafe mode after my waiting and begging from 16.05. to 03.07.2019. Please see attached screenshots for details.



I hope the DSLAM will stay in this condition for a long time... .

Kind regards,
Joachim
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burakkucat

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That certainly looks like an improvement. Let's hope it stays that way.  :fingers:
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