FTTC - 4 minute long disconnection

[#1]

I've recently had a frequent disconnection problem fixed, and although no definite problem was found (just a few guesses), my line now seems a lot better with just the odd disconnection (maybe one per day or even less), that I'm told is normal. My router logs tell me that last night it disconnected again but didn't reconnect again for just short of 4 minutes. These longer disconnections were one of the problems I had before, so I'm worried again that things aren't right. The other disconnections I have had since things were "fixed" have only lasted a matter of seconds.
Is this something to be worried about? I still have an open ticket so I could add to that if PN think I have reason to. I don't want to over-react though if nothing is wrong. In case it was a known network problem, the disconnection was at 1:35am this morning and it reconnected at 1:39am. There is no evidence of a power failure in the house during the night, so that isn't the reason.
Thanks.

[#2]

I think this is normal on FTTC.  It takes a while for the modem to disconnect the session, so your router needs to wait for this time out to occur before it can reconnect.  Another more knowledgeable user may completely contradict me though!

[#3]

Thanks for the reply Kelly. It often only takes seconds though, so there must be some reason it's taken so much longer this time, and other times before I had it looked at.
People are always contradicting me by the way -  I'm used to that. 

[#4]

I wonder if it disconnected while the DLM changed things? I've noticed my ping has got even lower than the amazing 5ms it was at yesterday, to 0ms today! Does it disconnect for several minutes to make an interleaving change? It could be that some of my disconnections in the past were caused by DLM slowing things down and increasing the amount of Interleaving as there was a problem with my line.
It would be nice to know a few facts about how DLM works with fibre, as all I can do is use logical guesswork. It gets frustrating when even some OR engineers don't have a clue about it and tell me it's the same as ADSL (the same one who thinks my distance to the exchange is a factor in my speeds!).

[#5]

There's plenty of reports on thinkbroadband saying that the modem can often resync quickly enough for the router (and Plusnet) not to see a drop in the PPP session, if it takes longer (possibly when it's more than a simple resync, such as your suggestion about changing interleaving) than the PPP session will drop and it takes a bit longer for everything to reconnect.
I can't comment on what's normal for FTTC but I certainly don't see disconnections on anything like a daily basis, more like monthly in my case (and most of these are due to me rebooting my router as I think it benefits from a reboot after such a time).

[#6]

Thanks for the info w23, I haven't looked at thinkbroadband since getting FTTC installed so I'll have a read there later.
I wonder if all my disconnections since things being fixed (assuming they really have been) are actually the DLM. Things have been slowly speeding up and the pings get faster and faster. I can't imagine things will improve any more than this, so hopefully I won't get more disconnections from now on that aren't DLM related.

[#7]

If you've gone from lots of disconnections to a stable line then the DLM may well be gradually 'ramping up' your line, if things are slowly speeding up and pings improving then just be patient and see what you end up with.  If the disconnections stop then you're probably about as good as you'll get.
Just out of interest what kind of speeds are you getting (and do you know how far - by line route- you are from your cabinet)?

[#8]

Yes I agree to be patient and hope things are now ok. I'm still checking my router logs every day just to see how stable things are.
I didn't get an accurate number from the engineer for the length of my line, but he told me the route it runs underground, which would make it about 400 metres. I'm getting a max downstream of 73Mbps, upstream of 18Mbps (BT give a line speed of 77Mbps at the moment). So obviously very good and I'm very happy with it, providing it remains stable.

[#9]

That all sounds about right (certainly not bad) for around 400m, I'm a bit slower at 500m but I'm envious of your ping!!

[#10]

Yes I'm pretty impressed with my ping.