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[Weaver]

Started last Thursday evening around 19:15 very suddenly, packet loss on one line out of three, as indicated by loss of responses to PPP LCP "ping" Echo Requests issued by the ISP's CQM system. See attached image, the red 'dripping blood' hanging down from the top is the indicator.

Why should it start so suddenly, and what might be behind it?

[Weaver]

This line is approx 4.55 mi long ( est. ) by road. The BT DSL availability website gives the line length as ~6200m.

[Weaver]

I have been very out of it, so I will ask my wife to email Andrews and Arnold support tomorrow to get the ball rolling. I did a ‘copper line test’ at the weekend, which did not reveal the source of the problem.

[Weaver]

I've done obvious things such as power-cycling the modem. I haven't left it turned off across a DLM fifteen minute boundary period.

[Chrysalis]

The simple thing to do if you suspect the line is the cause is to monitor the error stats on the modem.

[Weaver]

I have plenty of spare preconfigured modems as well, that might be worth trying, just as a rule-out.

[kitzuser87430]

@weaver...is that the phone number in the top RHS of the graph?? We do know you only have dsl on the line but......

Ian

[Weaver]

It is. (There's no voice service on the line. (I think.) It used to be an option as to what Andrews and Arnold would do with voice, but now I don't really understand what the story is. AA are desperate to stop all voice services and prevent users getting charged for any such thing.)

[Chrysalis]

weaver I wonder if this is related? decided to have a read of revk's blog and seems they have had to do some work to relieve capacity issues.  Although the most recent post suggests it is now resolved.

http://www.revk.uk/2016/03/growing-pains-next-step.html

[Weaver]

There was a nasty two hour outage, not properly warned, early that Thursday morning. Then that evening one line went suddenly bad and has remained bad every since. Why it has stayed bad, and why only the one line, these are perplexing questions. The lines seem to all go to the same BRAS in ?Falkirk, so no obvious difference there.

Is it my imagination or is there some sort of repeating temporal pattern in the dripping blood?

[Weaver]

There have been a few errored seconds per day some days, which is most unusual. The other two lines are zero errored seconds in each day, as expected.

[Weaver]

Had two faults this year so far, 1) piece of wire or solder or something fallen down somewhere it shouldn't be in exchange, and 2) knackered wiring shallowly buried near the fank at Harrapul, possibly after a lorry went over it, shorting wires out against one another or something, iirc.

[Weaver]

Andrews and Arnold had a brief look at the line this morning. Did an SNR reset to 6dB d/s instead of my dangerous 3dB, a change that has had no effect on the dripping blood at all.

And it didn't explain why the sudden change last Thursday evening, when it worked fine on a really really low target SNRM before then, just like the other two lines.

The problem is that I don't think anything is showing up in BT's tests.

Here's the CQM graph for last Thursday 2016-03-24. Scroll to the right to see the sudden onset of the problem:

[Weaver]

We agreed that the d/s target SNRM 6dB was a waste of time, I think it's back to 3dB now. Listened to the line on a POTS phone, was all good.

Then swapped lines @a.1 and a.3 over at the wallsocket link stage, to see if the visible dripping blood would move from 1 to 3. An equipment rule-out.

Agreed to leave it in swapped over state until tomorrow morning when we reconvene.

[Weaver]

The dripping blood 'moved' when the lines were swapped over. Thank goodness. Now hopefully we can make some actual progress tomorrow.

It's my fault that this has gone on so long, I have been  really out of it, very ill with overwhelming fatigue, and so I didn't notice the dripping blood until Sunday and then there was the bank holiday. AA didn't pick up on my requests for support delivered by Twitter, so I lost more time as I had to get my wife to email tech support which again I did belatedly because I was so under the weather.