Yes, sounds familiar. At the time that I had all of that disconnecting problem, I tried to find out whether and how BT regularly received information about my line. It seems that, with my particular ISP, BT regularly relays data to my ISP as to how many connections and disconnections (referred to as 'log-ins' and 'log-outs') are occurring on customers' lines, and at what times of day. But my ISP uses this information purely, it seems, to keep an eye on the capacity usage of customers like me who are on capped accounts. This data is, in fact, made available to us customers via the ISP's website. What I found nauseating for so long was that, though notified by me about it, my ISP took no notice of my excessive disconnections for several months. During that time, I was getting around 1050 disconnections per month and, in fact, had largely abandoned Internet usage in the evenings. My SNR didn't get automatically raised by the DSLAM, presumably because my particular pattern of disconnections somehow didn't meet the 10 or 12 per hour criterion. Anyway, after very protracted arguments with my ISP, it was finally conceded - though not expressed as such by my ISP - that my disconnect figures were unusually high and then, not long after, it all changed - everything became stable and my SNR moved higher. So, I'm pretty convinced that, in my case, BT's DSLAM certainly didn't automatically adjust my SNR. In the end, it was clearly done by some sort of manual intervention.

My line's now very stable (though still not 100%, as evidenced by what occurred late last night). I guess that what happened yesterday was that, owing to there being less traffic around, the modem/DSLAM decided to try to run the line faster and dropped the SNR accordingly, but then got caught out by a bit of crosstalk or interference. After it reconnected, I noticed the SNR had gone right down to 6dB again (but has now crept up once more). So curiously, it rather looks as though the average SNR has been raised, but the target SNR (the point at which disconnection ensues) is still 6dB. Either that or interleaving has been applied. (I confess I know little detail of how interleaving affects stability).

As for the DMT utility that can be used with Speedtouches, I'm pleased to learn from you that it has a means for cancelling control of SNR by the router and reverting to DSLAM control. I'm looking forward to getting and using a 546v6. That model's not quite officially on the retail market yet.

Ah, I see. So, at the start, your DSLAM did what it was supposed to do and automatically adjusted the SNR upward, to 15dB. But then presumably, when you got your 516v6, you thought 15dB was overkill and so you used the 516 together with DMT to bring the figure down?

Yup, exactly as you describe

An old thread - time to put to bed