ADSL2+ - crazy noise margin values

[#1]

To cjags
Have you seen my thread on similar subject ?
http://community.plus.net/forum/index.php/topic,104125.0.html
It appears DLM may have removed the banded profile today on my line after all the repeated attempts by PN to set it up last week.  Although the target noise margin has actually risen to 9dB for the moment, it's now almost inevitable it will drop to 6 and then 3dB this coming week.  

[#2]

That is similar.
Plusnet have been resetting my target SNR to 6db since February.  It works for a while, then mysteriously, dissappears and I am back to target 3db or even 1db which basically, is not stable.  The last settings Plusnet applied were Profile: WBC 160K - 24M Medium delay (INP 1) 6dB Downstream, UC Medium delay (INP 2) 6dB Upstream (ADSL2+) which was done on 26th April.  It lasted until yesterday (19th May) which is the longest so far.  They just need to find some way to make it permanent.

[#3]

fyi, the target noise margin on my line snapped back to 3dB at 6am this morning on the final day of training since the last SNR reset.
http://community.plus.net/forum/index.php/topic,104125.msg893424.html#msg893424

I've come to the conclusion PN's efforts over the past month to raise the target noise margin and/or apply a banded profile are a waste of time. Eventually, it would seem DLM will undo it all as there is no means for the ISP to make the settings permanent (ie. override DLM)

[#4]

I'm with you on that one. It has been happening to me since Feb.
While 3db is fine for ADSL2+, the problem I have is the SNR frequently drops 3db for a few mintues so a target SNR of 3db means a lot of trying to run at 0db which causes SNAFU.  Target SNR of 6db is great because it then only drops to 3bd which is fine.  Trouble is, Plusnet can't make this stick   I have tried a new router but that has the same problem.  Latest attempt by Plusnet is to put a speed cap on my line, seeing how an SNR cap can't be made permanent.  So much for 21st century network

[#5]

Quote from: Bullet

How long does it typically take for the 6.0/3.0 profile to be re-applied ?

Plusnet can usually get the target put back to 6db within 1 working day.
But no guarantee how long it will last.

Quote

Also, have you gone for uncapped upload ?

Yes and it made no difference to the line stability or download speed.

[#6]

Thanks for providing this information.
From your first post you state that the target S/N appears to be lowered after a couple of days (or is it actually longer and staged, i.e. 9 to 6 and then 6 to 3 over a week etc ?
Not a fix, or even a workaround really, but if you were to reboot your router (multiple times) every say 2-3 days (without disconnecting first), then my guess is you could trick the exchange into thinking that there was a fault and it would no longer try and lower the S/N margin to 3 for several days or more. Of course this is a pain and would further limit your sync connection speeds. It might just be a little less frustrating.....
[Moderator's note by Dick (Strat):  Full quote of preceding post removed, as per Forum Rules ]

[#7]

HI zzZzz and cjags,
There's one more way I can modify your lines to try to keep them fixed. Give me an hour or two and I'll get them done and get back to you here.
Jojo

[#8]

Quote from: Bullet

From your first post you state that the target S/N appears to be lowered after a couple of days (or is it actually longer and staged, i.e. 9 to 6 and then 6 to 3 over a week etc ?

On my line, the SNR (reported by the modem) varies by +/- 3db over the course of a day.  The line can work at 3db, but if 3db is set as the target (seems to be the default for ADSL2+), eventually, the SNR drops to 1db, 0db, or lower and that is the end of the connection.
Even if the SNR goes back up to 3db, the connection doesn't usually recover and a modem reboot is needed.  This usually reconnects at 3db which is usable (for a while).
I then ask Plusnet to put the target SNR back to 6db which they do and within 24 hours (or by Monday if it fails over the weekend) the SNR goes back to 6db (+/- 3db).  However, this is not permanent and can drop back to 3db at anytime (although 7 in the morning seems to be favourite).
The drop back to 3db is instant and not staged.  I am using routerstats lite to record the SNR and connection data and can see when the target gets reset.  The SNR will be plotting at 6db +/-3db then will suddenly drop to 0db or lower, then come back and plot at 3db +/- 3db.
There is a corresponding blip in the connection speed.  At the time the SNR drops to 0, the connection speed drops to 0 as well, then when the SNR goes back to 3db, the connection speed goes up (a lot).

[#9]

Hi cjags,
the current target is 6dB. and the line is banded at 4-9M and the target downstream SNR is set to 6dB, although I can see there have been fluctuations between 2dB-9dB over the last couple of weeks. This could be put down to interference maybe. There is another banding level above what you're on if you're looking to get a bit more speed.
Jojo

[#10]

9MB is fine so 4-9 will be OK as long as I don't get stuck at 4.
I think 11Mb is the fastest I can reliably get without the connection becoming unstable.

[#11]

Quote from: Bullet

I `think` if there are a sufficient number of disconnects then ADSL2+ will start setting a higher S/N margin and will want to keep it for a period of time.  What I don't know is how long this is. I'm just going to leave the router alone and let it and the exchange sort themselves out.

I don't know either.
My experience of the exchange giving a higher SNR after several disconnects has only been with ADSL.
Back then the lower SNR/Profile would last around 14 days.

[#12]

At the moment I've got 3 days connected, with 2 days prior to that when I manually disconnected and then restarted the router.
So it looks like ADSL2+ does not kick in a re-sync, following a high number of disconnects for 5 days or more ?
I'll update this post when my router does a re-sync as a result of a lowered S/N ratio.
Presently I have S/N up/down margins of 7.0/9.0 (up normally being 6.0 etc) and down following the completion of the training period was 3.0
(Plusnet staff, please don't do anything to my line please)

[#13]

OK cjags we'll leave it there for now.
No worries Bullet, just let us know if you need us to do anything.
Jojo

[#14]

It was going so well but bang on cue at 7am something happened.  Why is it always around 7am?

[#15]

I seem to be having the same problems even after upgrading my router