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Author Topic: Intense rain and the n+1th ‘hollow curve syndrome’  (Read 1342 times)

Weaver

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Intense rain and the n+1th ‘hollow curve syndrome’
« on: October 26, 2021, 04:10:01 PM »

Intense rain for well over a week, and squally winds. Janet said she saw some of the heaviest rain in her experience the day before yesterday. I slept through that, missed it. We have some happy visitors staying in one of Janet’s shepherd huts. They were warned in advance about the utterly vile forthcoming weather and don’t care, they have their books and have done a bit of cooking and been plying my wife with drink. We have a lounge / kitchen / bathroom for guests’ use in a very big shed that we built originally as an equipment store room.

My line #2 has once again developed a case of ‘SNRM hollow curve’ syndrome, which has knocked the highest downstream tones 49-95 down by four bits, from 11 bits to 7, so that’s something like 300k out of 2.7 Mbps, so now down to 2.4 Mbps after a forced resynch. The d/s SNRM started falling at 1800 UTC yesterday evening and continued falling until midnight. In the early hours I discovered the d/s SNRM was only at 0.5 dB, down from 3dB, with a vast error count downstream, so I forced a resync, back up to 3dB d/s SNRM, and all was again well. This hasn’t happened for a while now. Could it be due to intense rain, water getting in somewhere?

I’m talking to A&A about it, yet again. It’s the same old story. Send for OR engineer; he/she does tests, does nothing that ought by rights to be effective, but the problem is always fixed, by magic. And is fixed somehow either before engineer arrives, or during initial procedures, before test results come in. A visit has never failed to fix it. I can’t remember clearly, but I have some vague notion that A&A may have once fixed it remotely, presumably by the effect of firing up whatever remote tests they can initiate.


The CRC count is still really quite bad this afternoon, so I’ve had to raise the d/s target SNRM up to 6dB to fix it. So even more speed lost.
« Last Edit: October 26, 2021, 04:26:41 PM by Weaver »
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burakkucat

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #1 on: October 26, 2021, 04:30:56 PM »

Could it be due to intense rain, water getting in somewhere?

I suppose it could be a possibility.

A while back I speculated that a burst of AC, at a highish voltage, might fix it . . . purely because that is the one thing your lines never have - the ringing voltage is never applied to the pairs.

(If "The Cattery" was local, I would be willing to visit and give the pair a burst of AC.)
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Weaver

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #2 on: October 26, 2021, 04:42:10 PM »

I remember that we discussed this, and I myself was very much in favour of it; is it something an ISP can trigger remotely by happy chance ?
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burakkucat

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #3 on: October 26, 2021, 04:49:57 PM »

Perhaps A&A can give you a customised "Control Panel", one that has a button which causes the standard telephony ringing voltage to be applied to a nominated pair for, say, 60 seconds?
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Weaver

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #4 on: October 26, 2021, 05:07:44 PM »

Do they just need to call my modem? Or do I need a telephone to do it from my end?
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burakkucat

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #5 on: October 26, 2021, 05:20:34 PM »

Do they just need to call my modem? Or do I need a telephone to do it from my end?

Ideally the "Faultsman's Ring-Back" would do the job but as you don't have an active telephony service on each of the three pairs it can't be initiated from a telephone at your end.

If A&A have access to the Openreach test access matrix (TAM) at the NSBRD exchange, they should be able to remotely "do something".
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Weaver

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #6 on: October 28, 2021, 10:03:54 AM »

AA put the downstream target SNRM back down from 6dB to 3dB, which I assume wasn’t intentional, although they did say ‘got a bit more speed’. After that, the modem was reporting ~2k uncorrected downstream CRC errors per hour, which I decided was not good at all, so I put the d/s target SNRM back to 6dB. The downstream sync rate is now 1.8 Mbps, so it has lost about 900 kbps. This could be below the FTR now - I haven’t checked. I proposed to AA that we just keep an eye on it for a while.


Downstream sync rate down to 1.647 Mbps, so very much into faulty territory, as always happens: the problem just gets worse over time. Have told AA no engineer before the 8th because my dear wife is in self isolation before going into hospital next week.



Down to 400 k d/s with 13 dB d/s SNRM and many link retrains. Have switched line #2 off for the weekend, as it’s disrupting the quality of the entire bonded pipe since there are still ES in link #2. Will need to switch it back on later for a while so AA can see it.
« Last Edit: October 30, 2021, 01:54:13 PM by Weaver »
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Weaver

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #7 on: October 30, 2021, 01:58:19 PM »

A thought, would it work if one of you good friends phoned the number with a telephone ? The Black Cat has the numbers, which I think may have been updated in the light of new line changes a couple of months ago. I can dig them out from somewhere.
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burakkucat

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #8 on: October 30, 2021, 04:13:33 PM »

I can certainly initiate a call to each number but, as there is no associated telephony service on each line, I suspect the result will be that I hear a NU tone.

b*cat plods off to one of his telephones . . .
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burakkucat

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #9 on: October 30, 2021, 04:34:11 PM »

The results obtained --

Tel. No Ending        Service Identifier        Drop / Pair        Result

     70                     @a.1                   1 / 1             ET
     75                     @a.2                   2 / 2             ET
     14                     @a.3                   1 / 2             NU
     44                     @a.4                   2 / 1             ET

Where "ET" is Engaged Tone and "NU" is Number Unobtainable Tone.
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Weaver

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #10 on: October 30, 2021, 10:59:40 PM »

FYI, my friend, did we update your table a couple of months ago? Because I have a new line (poss #4 replaced, can’t remember) and line #3 is no more, only three in total now.

The drop + pair values are certainly correct, I see that.

I will recheck line 2 later on, as it’s disconnected now since it has become so bad, and Mrs Weaver, my assistant and chief cable puller, is heading for the Land of Nod. Or was until Beileag, sitting on a shelf by the bed, eating cat-crunchies, suddenly sneezed extremely loudly and made Janet jump out of her skin.
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burakkucat

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #11 on: October 31, 2021, 12:17:31 AM »

FYI, my friend, did we update your table a couple of months ago?

Yes, we did. The line which returned the NU (number unobtainable) tone was annotated with a "defunct" suffix.
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Weaver

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #12 on: November 08, 2021, 02:51:49 AM »

I never got this fault fixed, because Janet was going into hospital, so I couldn’t have engineers coming to the house, as there’d be no one to let them in.

And then guess what: on Friday night, line #4 went bad. Still usable, but now down to half speed downstream, with a high downstream SNRM too, of ~9dB; upstream is unchanged at the usual 0.39 Mbps sync rate. Upstream isn’t that great on that line, compensated for by line #1’s ~650 kbps. So now I’m running on 1.5 lines downstream with a downstream TCP payload throughput of about 3.8 Mbps which is very roughly ~1.0 OBs, where the new unit of downstream unveiled is one ‘Old (ADSL2) Burakkucat’.

Line #2 has been assumed unusable due to a high error rate and very low downstream speed (~400 kbps poss), so it has been unplugged for the last couple of weeks. Mind you, if it isn’t corrupting downstream packets at the moment, then its upstream would be worth having.

Will talk to AA this morning and finally give them the go-ahead to book engineers to come in asap, since Janet is now back home and recovering.
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burakkucat

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #13 on: November 08, 2021, 02:30:24 PM »

. . . a downstream TCP payload throughput of about 3.8 Mbps which is very roughly ~1.0 OBs, where the new unit of downstream unveiled is one ‘Old (ADSL2) Burakkucat’.

That DS throughput served me well for many a year. If it wasn't for TalkTalk's plans to get all their users onto VDSL2 connections then I would still be using the ADSL2 service.

Quote
Will talk to AA this morning and finally give them the go-ahead to book engineers to come in asap, . . .

The more I think about this recurring problem, the more inclined I am to believe that it is related to the absence of occasional bursts of AC (ringing current) through the multitude of crimps in the pair(s).

Quote
. . . since Janet is now back home and recovering.

That is good to know.  :)
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g3uiss

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Re: Intense rain and the n+1th ‘hollow curve syndrome’
« Reply #14 on: November 08, 2021, 04:36:02 PM »

I used to call that a wetting voltage, not heard that term for years
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