Intriguing one this........
I moved from Be to PlusNet some months ago. On Be I'd been stable for years on a3dB profile, but with a non-standard (low) level of interleaving that was enough to contain occasional unidentified interference that would make the non-interleaved line unstable occasionally.
At PlusNet I soon found you needed interleaving had to be off otherwise upload speeds were very limited. It didn't make sense to me, but that's the way it was and you had to have interleaving on or off the same on both Up and Down (why?).
I let DLM do its thing and ended up with a 3dB profile which worked fine though speeds were nonetheless about 10% to 15% lower than with Be, both ways.
On Tuesday this week I noticed lots of service interruptions during the day; I also saw some BT guys working on my local cabinet when I passed it (just saying........
) it's some distance away and not visible from my house.
Late in the evening I had an interruption that didn't recover and after a couple of router reboots could see that it wasn't getting DNS so called PN. A few minutes wait (it was 11pm or so) and got someone helpful.
At first they thought a change of DNS would sort it but then realised I was connecting, and re-connecting, to the same overloaded "rack" - their word. So after some reconfiguration at their end and a router power cycle all was well again.
The tech said (I knew) there had been loads of resyncs during the day (one of which must have triggered the DND weirdness) and that he would monitor the line and call me the next day near the start of his evening shift if there was anything significant.
Well there was, loads more resyncs yesterday (Wed) and he duly called me about 5pm. I was running DSLstats (thanks
) and could see the noise margin varying through the day and resyncs when it got down to about 2. After multiple resyncs it went to 6dB but after a while (hour or so) reverted to 3dB again and the frequent resync cycle restarted.
After some discussion he said that it looked like DLM was trying to go lower than 3dB so he would make some changes to stop that, wasn't 100% clear to me what changes but I asked that interleaving stayed OFF if possible.
Another resync after his changes and I was back on 6dB but oddly at a much lower speed (13.6mbps) than during the day when on 6dB (about 15.5mbps and 17mbps on 3dB).
Then, strangely, about 2 hours later (about 8pm) the SNRM reported by the router jumped by 3dB to around 9, where it still is now over 14 hours later.
The connection speed is unchanged, no resyncs logged, and has been constant since 6pm yesterday.
This seems very odd and I'm not sure I believe the "DLM trying to go below 3dB" analysis at all.
Any thoughts from the gurus, other than some massive source of interference was switched off about 8pm last night and is still off?
I can also see on the SNRM graph a plateau of higher value (by maybe .4dB) from about 11:30pm to 7:15am which presumably represents some source of interference that was turned off for that time. Nothing in my house matches that for sure.
