BB woes continue

So my BB woes continue. Over the last 3-4 weeks my BB has been glitchy, I've been on a fast path 24M 6BdB profile, it never disconnects but it would just stop. So I contacted CS and they dropped me onto an interleaved 8M 15dB profile.

Not only does my connection speed drop from 7Mb down to 5Mb, the reliability gets even worse, the lines drops and resyncs half hourly but then it sometimes drops and resyncs every minute. I also noticed that after the change my upstream attenuation and snr margin also now drop to 0dB periodically.

So I ring up CS again and they put me onto an 18dB profile, now this does stabilise the line but instead of dropping every half an hour it now stays up for 7-10 hours.

The line shows no faults and CS seem to think that it's quite acceptable to keep on increasing the SNR margin which I'm obviously not happy, even more infuriating is that I've been running at 7Mb for quite a few years until the problems with the line started some 2 years ago.

Back in July last year, I had a new router (replaced my Netgear DG834N with a DGN1000), new face plate (replaced my ADSL Nation with a BT faceplate), new external junction box and a line fault fixed which I'd been trying to get fixed for the previous year fixed.

Anybody got any ideas or words of wisdom especially as why increasing the SNR margin made the line less stable and why now on the higher margin both the upstream attenuation and SNR margin periodically show as being 0 in the router stats , the provider is Talktalk and I have to admit their general BB service has been pretty dire. Never used to have any problems like this with BT.

Try monitoring the line with RouterStats. http://www.vwlowen.co.uk/internet/files.htm

Here's a quick trace I've just done

http://img.photobucket.com/albums/v280/IAmATeaf/snr-...

Noise has got worse? Tested from the test socket? Tried with the old dg834N?

Why the old router, the 834 may perform better, i.e. problem has been there ages, but the 834 handled it better?

My previous problem was that not only was a lot of noise on the line, the 834 when synced would also add to the noise on the line. Had an engineer out who fixed the noise on the line, replacing the 834 with a DGN1000 resolved the noise that the router was introducing.

What I don't understand is why does increasing the noise margin actually make the problem worse?

Looking on the graph the suggestion is that this is not just random noise, as the noise spikes are consistently high, but something that is producing noise perhaps at random times, but of a high amplitude.

A router introducing noise that affects ADSL is rare, how sure are you that this was NOT the problem you have now? It maybe that the problem went away for a while and is now back.

Increasing target margin should make you more immune to noise spikes, but only if the margin is high enough that the spikes leave some usable signal, in your case the spikes are bigger than the target, so its not helping.

Time to power down the house, and have just one mains plug to run the modem and a laptop running off battery to test it. Then see if the situation improves.

Also any chance of a longer plot, as the time shown is just around sunset, at the point where security lights may be flickering on, and they are great RF noise producers, and the sun setting increases the amount of noise affecting ADSL too.

Have you done the basics - i.e. checked for noise on the PSTN line and tested using the test socked with no other equipment connected??

I've checked the basics and this line is only used to ADSL, so there's a faceplate with the router and a single handet (which I forgot to mention but it was also replaced last June) with no extensions.

I'll try and get a longer plot this evening.

I know I'm repeating what I said above but when I was on a 6dB SNR margin, the internet was intermittent but the router never ever resynced and TT could see that there were errors but since increasing the SNR margin which they hoped would get rid of the errors it's just made things a whole lot worse.

I'm currently on a SI158M1M (or something similar) profile which has made the line unusable but I was previously on SF624M1M where I'd have intermittent slow downs and pauses but the router never ever resynced.

Yes - BUT is there noise or crackling on the line - especially when the problem occurs??

The Talktalk names mean nothing, unless we know what inpulise settings etc are involved.

You can tweak a line to make it more or less sensiitve to noise, and not by just changing the noise margin.

If old profile was better, why not request a move back to it?

There's no noise or crackling on the line, this was resolved for me back in June last year.

I have requested being put back onto the initial profile but I've been told that they are still investigating and whilst they do this they want it left on the 15dB profile.

Any chance of some stats from your router ,or a DMT graph of the ADSL tones they may give a clue what is going on, But the fact that you still are seeing disconnections whilst on a very high (any over 12db) and different ADSL modes Then it suggests a fault , maybe it's not with the line plant, maybe it's the equipment in the telephone exchange at fault ,do you know if that was this checked when the engineer repaired the line fault ?
I would make a formal complaint to the senior manager of your ISP Do this via letter sent to sign for, keep a copy of your letter ,As their overseas support is a complete waist of time , have you managed to speak with anyone English yet ? assuming that they still employ English call center staff, who may actually be trained and have some degree of knowledge ,unlike their counterparts that don't deviate from the script

Edited by tommy45 (Wed 02-May-12 13:36:18)

I've done some longer plots, unfortunately they are in the evening again, I have noticed that it starts drop the connection only in the evenings, then at around 4:30am it seems to stabilise. If the connection get used then you get the graphs below.

http://img.photobucket.com/albums/v280/IAmATeaf/sync...
http://img.photobucket.com/albums/v280/IAmATeaf/sync...
http://img.photobucket.com/albums/v280/IAmATeaf/snr-...
http://img.photobucket.com/albums/v280/IAmATeaf/snr-...

These are pics of the actual router stats, the 2nd pic also shows the upstream SNR margin and attenuation which both randomly drop to zero:

http://img.photobucket.com/albums/v280/IAmATeaf/rout...
http://img.photobucket.com/albums/v280/IAmATeaf/rout...

Am going to find out how to do a DMT graph.

EDIT: I've just checked and the DMT tool doesn't work with the DGN1000

Edited by deleted (Thu 03-May-12 20:56:28)

I think and I'm hopeful I may have found the problem, well a problem at least. The junction box where the line from the pole hits my house had come loose and flopped down so that water could run along the wires and enter the junction box. So I've gone and borrowed a neighbours ladder and re-secured it so that water can't run into it.

I didn't open the box up but am hopeful that if any water did manage to get in it will naturally drain away or at least dry over time. Just a case of waiting now to see if my Rod Hull-esk endeavours up a ladder were worth it.

Water ingress is a problem where there is more than one line running through the cable, you may pick up the battery off another line. If only one line, then the problem may be due to corrosion in the connectors. So your remedial work to the junction box is unlikely to cleared the problem.

Ask if TalkTalk will run a CIDT test on your line, when the router is in sync, does this pass ??

I adjusted the junction box on Saturday and now since Sunday the line is now stable with no drops or re-syncs, the only problem is that due to the earlier problems the SNR margin has been increased to 12dB and TT now won't drop it down back to 6dB as they claim that it's their automatic system that has managed to stabilise the line. They also reckon that if the line is stable then their system will automatically drop the SNR margin in 3dB chunks so there's no need to do anything.

I'll ask if they performed a CIDT test.

One question, why would setting the modem to G.DMT make the line more stable?

I was told to leave the modem set to Auto, the line is supposed to be ADSL2 but when playing around I've found that setting the modem to ADSL2 means there's no sync at all, ADSL2+, modem syncs but my upstream attenuation and SNR margin keep on dropping to 0 and the line will drop and re-sync every few hours. If I set the modem to G.DMT then no more fluctuations on my upstream and the line never drops.

What does all the actually mean? I know the obvious answer to keep the modem set to G.DMT but I'm curious

Very unusual for it not to connect on ADSL2, which is often the best setting on dodgy lines.

G.DMT (ADSL) is more stable than ADSL2+ because ADSL2+ uses twice the frequency range, the same as G.DMT plus the same number above those. Those higher frequencies have two problems.

First, they attenuate more, which is why on long lines they become useless and there is no speed gain, and second they are more prone to interference. Noise.

As a general rule the higher the speed the more errors there will be, on G.DMT or ADSL2+, and more noise almost by definition means more errors.

High error rates can trigger a disconnection and reconnection.

In reply to a post by RobertoS:

Very unusual for it not to connect on ADSL2, which is often the best setting on dodgy lines.

G.DMT (ADSL) is more stable than ADSL2+ because ADSL2+ uses twice the frequency range, the same as G.DMT plus the same number above those. Those higher frequencies have two problems.

First, they attenuate more, which is why on long lines they become useless and there is no speed gain, and second they are more prone to interference. Noise.

As a general rule the higher the speed the more errors there will be, on G.DMT or ADSL2+, and more noise almost by definition means more errors.

High error rates can trigger a disconnection and reconnection.

Brickwall time I think.

They don't seem to be able to connect the fact that I stopped water getting into the outside junction box a week Saturday and seem to think that it was their actions on a week Sunday that helped to resolve the problems and now don't want to drop my SNR margin back to 6dB. 6dB is what the lines been running at for years without problems but that seems to be largely irrelevant.

Think I'm going to give up before I go mad.

In reply to a post by IAmATeaf:

They don't seem to be able to connect the fact that I stopped water getting into the outside junction box a week Saturday and seem to think that it was their actions on a week Sunday that helped to resolve the problems and now don't want to drop my SNR margin back to 6dB. 6dB is what the lines been running at for years without problems but that seems to be largely irrelevant.

Think I'm going to give up before I go mad.

This is, unfortunately, a reasonable approach for them to take - and an example of what happens when too many people have hands on. Quite naturally they will want theirs to be the solution, and I don't suppose they'd bother to look at the history of your line -even if they had it to hand.

Good luck in your fight

I've given up to be honest, 12dB is what the line will stay on is what I've had back. Doesn't matter about past history, after the fault the line has been regraded by them to have a 12dB margin.

If it wasn't a business line I'd have voted with my feet a long time ago.