Post 21CN connection issues

My Mum was having issues with her internet last weekend (3rd and 4th August) and it was syncing at 512Kbps down. As I happened to be visiting I diagnosed the issue to be a dodgy phone cable and ordered a replacement which arrived on Wednesday, and as I also happened to be there that day, I replaced the cable and all was well (instantly back to an 8Mbps down sync speed).

As I noticed that BT 21CN was now available on her exchange and that she was already on a WBC line, I requested a regrade to the equivalent ADSL2 product; this regrade happened today.

Since then the router has been syncing at 16Mbps down (I can confirm this via the "Line Rate Data" section in the Zen portal), however there is (and this is where it gets vague as I'm not on site any more) either no, or a very flaky internet connection.

Looking closer at the "Line Rate Data" in the Zen portal, I can see that the router has been continually re-syncing every 5 - 20 minutes between 5:45AM and 11:46AM this morning (I'm not sure if it's still doing that, or whether the line data has a several hour delay on it) which might explain the apparent flakiness of the connection.

The router in question is a Netgear DG834Gv3 which this thread reports to have issues with ADSL2.

Is this flakiness and constant re-syncing part of the normal training process after a regrade, or is the router just having issues?

If it is I'll probably just replace it with a Technicolor TG582n from Zen to save her any more issues.

Constant resyncing is NOT part of the training process, so looks like router is misbehaving and constantly asking too much of the line

So would that suggest an issue with the router rather than an issue with the line?

Assume you have latest firmware 4.0.1. fixed issue with multiple disconnects with changing SNR.
unit supposedly CN21 compatible.

The firmware is version 4.01.06 (for UK), although I have just noticed there's a newer version 4.01.28 (for UK).

Edit:
And also a version 4.01.37 for what I assume is world wide, including the UK.

Edited by MrDoom (Sat 10-Aug-13 12:07:30)

Without seeing the full stats, the tendency would be to say the router may be over syncing.

Have seen some models do this, The BT DLM should kick in and raise target margin to avoid this in time.

An update after an hour long phone call.

I walked them through removing the Netgear DG834Gv3 and replacing it with our ancient US Robotics router (bought in January 2006 and has worked perfectly ever since; only ADSL or ADSLMax support though which is why it was switched out last week).

This has gotten their internet back up, but as the US Robotics router only supports G.DMT modulation, the line is only synced at 8Mbps down (curiously it's synced at 1Mbps up, where it only used to be ~700Kbps).

I'll order them a Technicolor TG582n to see if it fairs any better at providing ADSL2+ speeds.

Will the fact that the US Robotics is synced slower affect the result of the training period, and make BT permanently think the line only supports a slower sync speed?

Should not impact things if the line remains stable, and ISP can request reset if it does result in a badly banded connection