In reply to a post by Gazanimal:

Did so, no change, but rebooted modem & now getting my usual 50mb/s down as before.
...............
IP Profile for your line is - 51.69 Mbps

Disconnecting and Reconnecting the PPP session was all that was needed to bring the amended Current Line Speed into effect, rather than risk a detrimental effect on sync speed. As it happens, you been lucky and gained a little bit in your profile 51.69 vs 50.6, but I seriously suggest you be careful about randomly rebooting the Modem.

I didn't random reboot the modem.

PlusNet support recommended it if my speeds didn't automatically increase after 40mins of waiting.

Sorry, I wasn't clearer. By "random" reboot I mean rebooting it just because something doesn't seem right. Rebooting the Modem on FTTC should be an absolute last resort if all other attempts to resolve an issue have failed.

Are you sure Plusnet didn't tell you to reboot the Router, as opposed to the Modem? That would have the same effect as Disconnect/Connect.
If they indeed tell you to reboot the Modem, then that was very wrong. That's the trouble with first line support, most of the time they haven't a proper clue.

There is far less to worry about in rebooting an Openreach FTTC modem than there has ever been rebooting a modem or modem/router on a BT Wholesale ADSLx connection.

The BT Wholesale DLM on ADSLx, whilst not as bad as it used to be, is still very unforgiving once it decides there is a problem. The Openreach one on FTTC rarely does anything worse than introduce interleaving and an 8ms addition to latency. It will remove them after a while if the problem was short-lived.

Obviously if there has been an ongoing degradation in the line characteristics the action may continue or even become more severe, but that isn't the scenario under discussion.

A few reboots of a modem will not cause banding to be applied - that is the nasty, but even if that happens it has been known to self-reverse.

The BT Wholesale ADSLx one will never remove interleaving automatically once applied.

Well I'm not agree with you Bob for the following reasons -
Until these last two posts users could be left with an impression that a reboot of the Modem any old time is fine
1) Most FTTC users cannot see their stats, but in particular the SNRM. If that happens to be below the Target SNRM of 6dB at the moment of reboot, you'll end up with a slower sync speed. The converse is of course true.
2) If you happen to have other issues with your connection (and possibly not aware) had a dropped connection, errors quite high, and so on - that reboot at just the wrong time can cause DLM to act.
3) So you think introducing Interleaving and increasing ping time by 8ms isn't particularly important - well a lot of Gamers would strongly disagree with you.
4) Depending on the circumstances, yes Banding could get introduced, and there's plenty moaning about that as well..

Whilst you say that ongoing degradation can result in the actions we've mentioned, if indeed they are short lived, the DLM actions can (and have been known) to self-reverse BUT on many occasions this can take weeks and weeks and weeks.

I don't agree that ADSLx DLM is less forgiving just because it won't remove Interleaving - I don't remember any cases with Interleaving BUT certainly with Banding it has been known to remove Banding.
HOWEVER with ADSLx, if one has had a problem or been a bit daft with reboots or whatever and the problems are fixed, the ISP can simply do an SNR Reset. Also Interleaving can be turned Off permanently which can be very important to Gamers.
That is NOT possible on FTTC, ISPs do not have that ability, it's down to OR - the only time a reset tends to get done is after a fault repair.

In reply to a post by RobertoS:

The Openreach one on FTTC rarely does anything worse than introduce interleaving and an 8ms addition to latency.

It isn't going to do that for a few modem reboots. Also note:-

In reply to a post by RobertoS:

As long as you don't do it loads of times in quick succession you can't do any harm.

I stand by what I said to the other posters.

Seeing as you went into minutiae, you don't mention the fact that sometimes interleaving and 8ms added to latency can be good for gamers, helping prevent packet loss and over-compensation by several game servers that slug very low latency connections.

I was trusting to the good sense of the people I was advising. I shall leave it at that, and let them judge our conflicting opinions.