See also this Community post.

In reply to a post by RobertoS:

I've just looked at the replies to your Community post. I'm most unimpressed by all the reactions - completely ignoring the power cuts you've had .

It depends on how large or small all those "little" drops in speed were when the power cuts were happening.

If any one of them dropped by between 10% and 20%, then it is likely to have been a DLM intervention. Smaller drops after a big drop could then be DLM making adjustments. But without the big drop, any small drops are more likely to be explained by crosstalk.

And, yes, crosstalk can knock 20% off your speed, or more, in little bits.

From across the various posts, it looks like the sync speed has dropped from roughly 80Mbps to 67Mbps, and if Matthew was right, then this is without DLM intervention. Over 18 months, I find that kind of drop entirely plausible.

As an example, my attainable dropped from roughly 90Mbps to 78Mbps over the course of around 30 months, on a cab that had already been stood for over a year. When DLM intervened (which happened twice) it temporarily dropped another 7Mbps.

The power cuts are something that *could* cause a problem with DLM, but it isn't guaranteed. If the whole area suffered from the power cut, then this might have been ignored: DLM has a mechanism to make allowances for wide-area events.
http://www.kitz.co.uk/adsl/DLM_system.htm#WideAreaEv...

The original support agent got his reasoning muddled, absolutely, but Plusnet seem to have played it straight otherwise - BT won't accept a report to just reset DLM. BT also won't accept a fault until the speed drops into the 10th percentile of speeds for similar lines (ie well below the bottom of the speed range, which is the 20th percentile), or the speed drops by more than 20% in a very short space of time. BT seem to have been getting stricter on this ... which means ISPs are too.

Even when an Openreach engineer turns up to investigate a fault that has been accepted, he isn't allowed to ask for DLM to be rest unless he has actually fixed a hard fault.

Some engineers will perform a reset as part of their investigations - especially if they feel that the "limited" way the line is now working is helping to mask the actual fault. But Openreach equally want to stop engineers from just resetting DLM, and then claiming to the householders that "There, it is fixed" only for speed drops to return when DLM intervenes again 48 hours later.

Leaving to a new ISP isn't likely to change any of these limitations.

Now it's funny you should mention the HG612:

https://drive.google.com/file/d/0Bzj4Ilqxsx4VaWx6Unh...

Attainable down rate 71300 yet line rate is 60996 (about 8pm tonight)

Looks like a cap to me...

My download speeds are in th 50s' now, and Plusnet are still fobbing off.

It depends on how the OP is measuring his ping. If he's using the BTW checker, then it's completely inaccurate.

There are also other factors (including which gateway the OP is on) which could be responsible for a latency increase.

I thought you had an ECI?
That difference between Attainable and Line Rate is about right for that caused by interleaving.

Are you on Windows? If so telnet into it. Instructions:-
************************************************************
Welcome Visiting Huawei Home Gateway
Copyright by Huawei Technologies Co., Ltd.
Login:admin
Password:
ATP>sh

BusyBox v1.9.1 (2014-01-21 16:44:38 CST) built-in shell (ash)
Enter 'help' for a list of built-in commands.

# xdslcmd info --show
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 15507 Kbps, Downstream rate = 60240 Kbps
Bearer: 0, Upstream rate = 15585 Kbps, Downstream rate = 53385 Kbps
...
...
**************************************************************

But give us the full output .

Don't hold your breath for PN to resolve this. I've been having issues with them for 18 months.
4 or 5 engineers, lots of swearing, still no resolution.
My fibre line speed drops by 50% for days at a time then spontaneously goes back up (using a Bipac 8800NL) or the whole thing will drop with no signal at all for hours or days (the record I think is 8 days without a service).

No resolution, constantly fobbed off, BT engineers haven't a clue what's going on. Nobody will actually step up and take proper responsibility for trying to get to the bottom of the problem.

My contract term is up in a few months and although I'm loath to leave PN as they're generally one of the better outfits and I've been with them for over 10 years, I will seriously consider upping sticks when the time comes. However inconvenient this will be.