After a period of instability with my Plusnet ADSL connection, stability has returned to normal and syncronisation has been held for 317 hours. However the period of instability lead me to closely monitor the line stats for the first time. It would seem that my connection is always set to the most cautious target SNR of 15dB despite the stability of the line.

The current line stats (at 317 hours) are as follows:

TX Blocks RX Blocks Corrected Blocks Uncorrected Blocks
10431644 218516506 51536 1256
Mode State Up Speed Down Speed SNR Margin Loop Att.
G.DMT SHOWTIME 448000 2464000 17.5 33.0

What this does not show is that the corrected blocks are incrementing quickly (about 300 at each page refresh) even when there is no traffic in or out. I would expect that the count of received blocks would include any corrected blocks but this only increments by about one block at each page refresh.

Am I misunderstanding something? Is this an issue that I should investigate further to try and get the target SNR reduced and hence a higher sync speed?

You should plug your router in to the BT test socket behind your m,aster socket (if you have one) and test from there, and see if the errors still go up at the same rate.

I rthink you probably have some kind of internal wiring fault. Have all your phones got filters, and have you disconnected your ringwire?

Thanks for the advice Lorian. I have already done all that you suggest and also checked the line with another router from a different manufacturer. I use an ADSL faceplate in the master socket which is only 2 metres distant from where the BT cable comes out of the ground. Internal wiring to the Draytek is all Cat5E.

However the rapidly increasing count of corrected errors has now stopped. The count has risen from 74 to 115 in 18 hours. This seems more normal to me.

More importantly line conditions are quite stable with sync at 3712 kbps at a S/N ratio of 21dB now having dropped to 19 dB overnight last night. The stable rate reported for my line by Plusnet has jumped from 2000 kbps to 3000 kbps which I have not seen at all in the 2 months I have been monitoring it.

I am hoping for further improvements if this stability continues, if/when the target S/N ratio is reduced by the equipment at the exchange.

Martin Goose wrote: However the rapidly increasing count of corrected errors has now stopped. The count has risen from 74 to 115 in 18 hours. This seems more normal to me.

Thats much better. Assuming your on ADSL Max then you could now raise a ticket with plusnet and say:

"I have recently fixed some local wiring issues, can you please ask BT to lower my target SNR".

They will probably say no, you need to reply inisisting they do, assuming you want some extra speed, of course.

If the line does go wrong again in future it will again automatically increase the target SNR anyway.

I am on one of Plusnet's up to 8Mbit offerings. I assume that this is ADSL max.

I do intend to get the target S/N ratio changed in due course but I am looking for a longer period of stability first. This is because I had a long running ticket (2 months) when stability was a problem culminating in Plusnet asking BT to act. I got away without a site visit (and possible hefty bill!) but things did improve, leading me to believe there was some issue that they found and corrected. I am very confident that I have no internal wiring or equipment issues as I have been thorough in my fault finding process.

Getting a better stable rate would be good. However, most of my big downloads are scheduled for 01:00 to 05:00 when Plusnet do not count it for charging purposes. Therefore, a higher stable rate is not a big issue. 3000 kbps is fine for my general use.

Thanks again for your advice (and for Vigorstats which I have used in the past!)

PS Have you considered open sourcing Vigorstats so that others can take it forward?