This is making me pull my heair out so I am hoping someone can set me straight!
We were on ADSL Max on BT 20CN but was forced to upgrade to 21CN. We then took advantage of the upgrade and went from an 8Mb service to 20Mb service - at this point the circuit become unstable and I outline some more details below.
Since moving on 21CN, we have received multiple disconnects due to 'lost-carrier' as seen in our session history. A further diagnostics report run on the line has also shown that the we are on the absolute bare minimum of SNR Margin - averaging between 2-4db which is expected to cause disconnects. The current stats are SNR Margin of 3db, SYNC speed of 21Mb and the Loop Attenuation is 6db. We are physically close to the Exchange and the Line Attenuation of 6db seems to support that - however, the modem tries to sync at 21Mb every time you reboot BUT cannot remain stable and disconnects 11-20 times per day.
There is some other strangeness to share as well. I hope this helps in some diagnostics.
1. I have seen (when we first moved over to 21CN and upgraded to 20Mb) that the modem would sync at 17Mb and the SNR would be at 6db. So the connection does have the ability to sync at a lower speed BUT stable SNR. Why does it always revert back to the more usntable 21Mb on reboot? A BT Speed Test Results also said the Line Profile was set to 17Mb. So not sure why this is being ignored.
2. Overnight, there was a pattern forming that the circuit would break just before 2 hours (1h 59 mins : 58 seconds) 4 times on the trott. Does this not strike as odd? If the line was noisy why would it regularly break at a time just before 2 hours? During the day it would break but last longer or shorter. No huge pattern. I have spoke to the provider about duplicate logins, DNS and IP issues and they have triple confirm this not an issue with the connection.
3. Two Draytek 2830 Modems have been tried. 2 New filters have been tried. All cables have been replaced. The BT Master socket has been tried at the Engineer socket. No positive affect seen.
4. The SNR does rise when on the phone making a voice call - it raises from 2db to around 6db. This is indicative of a High Open which I understand needs an engineer to resolve. However, I am still baffled why the line was unable to just sync and stay synced at 17Mb @ 6db. If it can manage that, why not stay at that instead of going to the faster and more unstable connection.
My provider is (VERY slowly) arranging a SFI BT visit but its like pulling teeth. The reason I am posting here is that I just need some comfort from the expert community that this looks like a line fault rather then something else myself and the supplier is missing.
Thanks in advance.
Edited by Brad_Porter (Mon 26-Mar-12 14:30:43)