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[mikeb]

My friend has been having problems with her fttc connection (with talktalk) since she moved in almost a year ago. Never had adsl on this line before, so don't know if that was reliable. The connection will drop, sometimes for a few minutes, sometimes for hours at a time. We've tried a few different routers, and the problem persists. She phoned talktalk who ran the standard tests and then arranged an engineer visit. He came yesterday, presumably from Open Reach. Not sure what he did exactly, just told my friend that he'd 'changed some settings' and then left.

Anyway, it doesn't seem to be any better, in fact it's worse now, speed seems to be capped at about 4mb. The serving cabinet is right outside the property, probably about 30ft max of copper to the socket, and the attenuation figures seem to match that. Interleaving is now present on the line as well, although it may have been the for a while. These are the current stats from the talktalk router:

 Line Quality

Upstream line rate (kbit/s):         800
Downstream line rate (kbit/s):     4198
Upstream noise safety coefficient (dB):    25.8
Downstream noise safety coefficient (dB):   33.4
Upstream interleave depth:           37
Downstream interleave depth:        485
Line standard:                           VDSL2
Upstream line attenuation (dB):       0.1
Downstream line attenuation (dB):   4.2
Upstream output power (dBm):      -4.5
Downstream output power (dBm):   13.9
Channel type:      Interleaved
DSL up-time:       0 days 3 hours 30 minutes 47 seconds

[WWWombat]

An attenuation of 4.2dB is a short line - perhaps 50-80m. It ought to be capable of an 80/20 sync easily (if she paid for the higher package), and 40/2 should be a stroll in the park. The connection ought to stay up for months at a time.

The high noise margin, 33dB, suggests the line can do much more, but has been banded by DLM - presumably in an attempt to get a stable line. If it keeps disconnecting, even at such low speeds, it suggests some physical problem, but perhaps intermittent (and hard to find).

The engineer may have been Openreach, but could have been a subcontractor. However, TalkTalk employ their own "bright spark" engineer whose job is to check for internal problems (eg extension wiring in the house) but who cannot alter Openreach's network outside.

Can you describe the wiring in the house? Does your friend have extensions? Is the router plugged into the master socket? Via a built-in filter, or a plug-in variety? Has she tried running from the test socket?

[mikeb]

She's on the 40/2 package, and it used to sync at 38mb and worked perfectly fine when it was actually synced, but it's always been up and down.

Consumer side wiring is dead straightforward - a single master socket with built in filter, no extension wiring or sockets. Pretty sure we tried going straight in the test socket with an external filter months ago, and it was exactly the same.

As you can see from the stats it's only been synced up for 3 hours or so this morning, so it doesn't look any more stable despite the dlm/speed limiting.

[WWWombat]

Pretty sure we tried going straight in the test socket with an external filter months ago, and it was exactly the same.

The same speed-wise? Or stability-wise?

Assuming it was the same stability-wise (ie bad), this problem looks to require attention from an Openreach engineer ... so it will be worth finding out who attended before.

If it was an Openreach engineer, you would expect him to have run a variety of tests, both run remotely (started from his mobile) and from a handheld test unit ... which may have led to a physical fault that needed fixing ... which, in turn, could have led to a DLM reset being performed. The latter is, as far as I'm aware, the only "settings" that an Openreach engineer would attempt to make changes to.

Currently, a DLM reset could go one of two ways - one to an "open" profile without interleaving, and the other to an interleaved profile ... and this might explain why you now see interleaving present. But I would also have expected a DLM reset to have lifted the banding limitation ... so it isn't immediately obvious what has happened there.

Meanwhile, a "bright sparks" engineer might have played with the router somewhat, and "changed settings" there ... which would likely have no effect whatsoever on this fault. A result of "changed some settings" makes this one sound more likely ... but shouldn't have caused interleaving to be added.

Do you have any statistics from before the visit?

I'm not very au-fait with the TalkTalk router, so others will have to advise whether more information can be extracted to help diagnose.

[mikeb]

The same in terms of lack of stability. When it was up it was used to happily sync at 38mb with a good 6db margin as far as i remember. I don't have any more detailed old line stats. It worked fine while it was up, but then it would loose sync and couldn't resync at all for a while (between minutes and days). It still appears to be doing that, but now even when it is synced, it's been forced down to an artificially low speed (presumably a result of dlm kicking in at some point).

I wasn't present when the 'engineer' attended, but it  sounds very much like a talktalk person rather than openreach/BT (sounds like he logged into the talktalk router and possibly tweaked settings, which I doubt a BT engineer would do).

To me, everything points to a line/cabinet issue, but as it's intermittent, it might seem fine when an openreach engineer comes out.