Brief outage, now sync speed has halved

[#1]

On Tuesday my line dropped early in the morning and when I noticed I did my usual trick for these occasional drops (now fairly rare), which is to make a phone call (strange yes!). It dropped again in the afternoon and I did the same to recover it. After that it hasn't noticeably dropped. However on Weds it must have resynced and the sync speed has dropped to half what it was and SNR has doubled.
Rebooting the router doesn't change the sync.
Have I been shoved down a band or something? This isn't a stability issue as far as I'm concerned, just more of a blip. I wonder if the line drop was actually related to work on Tuesday as there was a notice of possible outage early Tuesday. Can't see it on the graphs below but the first drop appeared to be bang on 3am I think. Maybe coincidence.
Before this I was going to ask if I could go up a band as I'm currently getting around 6 to 7 max with a little SNR to spare, and it's been stable for a long time now.

[#2]

Quote from: deadkenny

On Tuesday my line dropped early in the morning and when I noticed I did my usual trick for these occasional drops (now fairly rare), which is to make a phone call (strange yes!). It dropped again in the afternoon and I did the same to recover it. After that it hasn't noticeably dropped. However on Weds it must have resynced and the sync speed has dropped to half what it was and SNR has doubled.

I recently came across a set-up where the trick was to receive a phone call to unblock an unresponsive internet connection - but the router log showed no loss of sync so goodness knows why that one works!  Deadkenny, you ought to consult your router log as this will tell you if a connection has been dropped without your noticing.  Routers are normally set to reconnect automatically if a connection is dropped.  Does making a phone call always cause your router to resync?

[#3]

Quote from: ReedRichards

Does making a phone call always cause your router to resync?

It will get it back in sync if it's lost it, pretty much most of the time, though it's been a long time now since I've last had this problem. Making or receiving a call when all is fine doesn't cause a problem. I've checked the logs and there's no loss then.
Usually when I've had this kind of a problem, I can pick up the phone and there's crackle on the line. Make a call and it goes, and all fine.
I've had this since I had the line some 10 years ago and I've had BT out a few times for various other issues, mentioned this and they've pretty much shrugged their shoulders. Getting them out when it's a very occasional issue (like now it probably won't occur again for months) is a pain as they'll not find a fault and charge me £100 or whatever it is. Last time I had them out I thought they'd finally fixed it as there was a fault on the pole over the road, but that fixed my major problem I had earlier in the year where I lost the phone line completely. I think this problem is somewhere else.
Anyway, the "call making fixing it" issue isn't really my problem at the moment. It's that my line got synced again and the logs aren't showing any other drops, but my sync speed is stuck at half speed now. I did reboot the router a couple of times over the past few days to try and improve it.

[#4]

It does sound like your sync speed has been banded because of the drops on your line (I'm in a similar situation myself, although my line is still dropping for some reason...). If your connection is stable for 72 hours I believe you can ask plus.net to remove the banding.

[#5]

Reboot your router (just once) and if the sync speed doesn't improve, please report it to the Faults Team.

[#6]

Done. No change. Ticket raised, after jumping through all the hoops.
P.S. I mentioned it on the ticket, but someone on DrayTek's forums said I should ask for INP to be enabled to counter spikes and remove the banded profile. Apparently my router should be fine with it, though I don't know what INP does.
The problem from what I can see is everything goes along fine but if there is a drop it shoves me back down a band even though it all comes up fine again.

[#7]

Yeah, you've been put on a 1-3Mbps banded profile. Your connection mostly stable, a few reconnections in the last seven days or so. Please leave everything powered up and plugged in, the Faults Team have your ticket and will be able to remove the banded profile in due course.

[#8]

Thanks.
Possibly some of those reconnects were me rebooting just to check, but I'm leaving it alone for now.
Is this likely to happen every time I get a connection drop though? This last one I'm not sure if was down to my line, maybe the inability of my router to recover after a blip, or just some noise on the line, but it was around the same time that a planned maintenance was announced with possibility of short outage ("Planned 21CN Broadband Network Maintenance - Tuesday 20th July 2.00am-6.00am"). If planned maintenance bumps my router offline, I shouldn't really be bumped onto a low band profile ?
That said, it could have been pure coincidence. There's still the odd thing that when it did drop, a phone call on the line got it back on line.

[#9]

Planned engineering works very rarely affect synchronisation which is the only thing that DLM monitors. You shouldn't normally be bumped to a banded profile due to a single drop, but DLM looks at the history of the line and assigns banded profiles, target SNR margins and interleaving on the basis if the performance.

[#10]

Hmm, from my point of view looking at my router graphs, it was going for several months at a decent speed with no obvious glitches, then suddenly a drop that didn't automatically reconnect, and another the same day for some reason, then reconnected at full speed and it promptly banded me the next day.
That said the graphs don't show up brief resyncs and the such. I haven't checked the logs in detail. As far as I'm concerned I have no problem with brief blips if it reconnects around the same speed. It's just when it bumps right the way down to 1-3Mbps when it doesn't appear to need to. In the past on resyncs it's just adjusted up or down as appropriate, so sometimes it will drop to 5Mbps, and later will go back to 6 or 7.
Anyway. Just have to see how it goes I guess.

[#11]

Okay, I'm being asked to do the connect to test socket, try another router and all that, and the talk is of escalating this to BT.
The problem isn't a line fault I think. It's just a banded profile thanks to a seemingly rare line drop. Unless the plan is to investigate why my line dropped? I don't mind, except for having to take time off for engineer visits and the usual threats from BT about charging me £140.
Anyway, can't do all the tests until I'm at home, but I've done all this a thousand* times before for previous issues.
* - obvious exaggeration but you get my point  

[#12]

I'll get this sorted for you...
Edit: Your line was erroring severely which is why the banding was applied. We need your equipment connected to the test socket as previously advised, even if this has been done before as we need to compare the line stats to ensure we work in the right direction here.

[#13]

Thanks.
Okay, I'll go through the hoops again.
It seemed to be fine once the line drop was recovered. Synced at normal speed and was going good until the next day then it banded me. Hadn't noticed any problems. But then as I say I usually have to do the line drop recovery by making a phone call, but that's been a problem on my line for years and it's fairly infrequent. Still, if that problem can be fixed once and for all that would be good.
When would the test be done, as I'm at work daytime? Though I'm at home until 11am tomorrow.