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Author Topic: ADSL Line Outages - Equipment or Line  (Read 1402 times)

burakkucat

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Re: ADSL Line Outages - Equipment or Line
« Reply #15 on: February 08, 2019, 05:23:55 PM »

Annoying utter nonsense.  :o

I'm sure A&A will ask the relevant question of BTW, if you mention it them.  ::)
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aesmith

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Re: ADSL Line Outages - Equipment or Line
« Reply #16 on: February 08, 2019, 05:53:59 PM »

We've not got another engineer appointment booked.   The trouble I think is that BT isn't looking at this as a whole.  They checked today when the line was in it's failed state, confirmed no PPP session established or even trying to establish, confirmed that clearing a session on other ports immediately reconnects.  From that they conclude it must be at my end.  Concluding "I would say the fact we are receiving no PPP requests from this EU is contributed to the poor quality copper line and resetting the CPE/ port temporarily resolves this as the ADSL sync re-trains"

I think it's got A&A at a bit of a loss as well.  However we'll see what comes of the engineer visit.  Next stage might be another change of CPE,  A&A are suggesting trying a D-Link modem.  Although not sure what that proves, if it works OK have we just proved that a couple of months ago the line became incompatible with anything except D-Link?
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ejs

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Re: ADSL Line Outages - Equipment or Line
« Reply #17 on: February 08, 2019, 06:37:35 PM »

In some episodes the router SNR has dropped down to near zero or even sub zero, this drop happening instantaneously but followed by small variations around that value for the remainder of the outage.

In the past, I've had periods where the DSL has remained connected but not in any particularly useful state. But this was always very obvious from looking at graphs of errors and usually also visible, perhaps to a smaller extent, on the SNRM graphs. Usually I'd have a very slow connection with very high packet loss rather than no connection at all. I think it's a possibility that some sort of noise spike leaves the equipment at one or other end of the connection stuck in a not useful state, but doesn't drop the DSL link, and therefore a manual retrain fixes it. What looks like a vast amount of noise could be an ordinary amount of noise affecting a bad line/wiring.
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aesmith

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Re: ADSL Line Outages - Equipment or Line
« Reply #18 on: February 08, 2019, 07:17:31 PM »

The thing that strikes me is that it happens from one minute to the next, with no apparent warning or periods where it looks like it might have nearly failed.  One minute zero or near zero CRCs, next minute there are 4,000 and it stays at 4,000 per minute until the reset.   See attached from this morning covering the end of one episode when I manually re-trained at around 06:00 then the clean spell before the start of the next outage at 06:50.
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ejs

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Re: ADSL Line Outages - Equipment or Line
« Reply #19 on: February 08, 2019, 07:33:17 PM »

If you enabled "sesdrop", perhaps it would retrain automatically after a short time.
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aesmith

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Re: ADSL Line Outages - Equipment or Line
« Reply #20 on: February 08, 2019, 07:46:44 PM »

Cheers, will give that a try.
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aesmith

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Re: ADSL Line Outages - Equipment or Line
« Reply #21 on: February 19, 2019, 12:45:44 PM »

BT engineer on site yesterday, and over the phone he told me he'd fixed a couple of issues on the physical line, and changed equipment at the exchange.  He reckons the underlying fault is our neighbours electric fence, which of course we know about but which hasn't caused this particular type of failure before.   However in a sense it's a "get out of jail free" card for BT.  At least this time he confirmed that he'd measured the same error rates on a number of other lines on that main cable.   Interesting also that he reckoned the interference could have caused damage at the exchange, I wonder how they'd deal with that if it was the case.
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noddy

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Re: ADSL Line Outages - Equipment or Line
« Reply #22 on: February 21, 2019, 11:29:27 AM »

BT engineer on site yesterday, and over the phone he told me he'd fixed a couple of issues on the physical line, and changed equipment at the exchange.  He reckons the underlying fault is our neighbours electric fence, which of course we know about but which hasn't caused this particular type of failure before.   However in a sense it's a "get out of jail free" card for BT.  At least this time he confirmed that he'd measured the same error rates on a number of other lines on that main cable.   Interesting also that he reckoned the interference could have caused damage at the exchange, I wonder how they'd deal with that if it was the case.
I was going to say that CRC graph looks just like ours when the fencing is on in the summer months :(
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aesmith

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Re: ADSL Line Outages - Equipment or Line
« Reply #23 on: February 21, 2019, 11:49:57 AM »

Yes and no.   When the line is in it's normal state, ie after all DLM stuff has been reset, we get around 60-70 CRCs per minute, dropping to zero when the fence is off.  See attached.  There's no change in SNR with the fence on or off, and that error rate doesn't affect throughput.  This has been the case since Nov 2016.

The more recent fault symptoms of 3000+ CRCs per minute and complete failure at the PPP level do not appear to relate to when the fence is switched on or off.  For example the outages often start late at night or in the small hours.   And they are cleared immediately on a retrain.
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parkdale

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Re: ADSL Line Outages - Equipment or Line
« Reply #24 on: February 21, 2019, 05:57:29 PM »

My Dad had this fault on his circuit, and would clear if you rebooted it.... :-\
Several tests later by me and changing the modem to a 8324 did not make any difference.
Rang up provider and they found the UG section of the cable had been damaged by contractors at some point.
So OR located and dug up the affected part and all is well now.
During all this the phone/ voice part did not show any noises.
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aesmith

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Re: ADSL Line Outages - Equipment or Line
« Reply #25 on: February 21, 2019, 06:49:07 PM »

That's interesting.  Maybe this latest work will resolve it, the guy definitely found and fixed two copper line faults.  It's not failed since, but then I think it went just over a week without fault after the lift and shift.
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Chrysalis

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Re: ADSL Line Outages - Equipment or Line
« Reply #26 on: February 22, 2019, 07:59:22 AM »

the symptons you describe may well get resolved by change of modem, sometimes ive had a modem which doesn't like the line behaviour, bitswapping will seize up, then errors skyrocket until a resync which wakes up bitswapping again, this wad in my adsl days granted but symptoms match
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aesmith

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Re: ADSL Line Outages - Equipment or Line
« Reply #27 on: February 22, 2019, 02:03:49 PM »

That sounds plausible as well, maybe both Billion and Zyxel were affected because both have Broadcom chip sets.
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