Where is the 'decision' to re-sync made?

I'm on a fairly long (730 metres) FTTC connection (55/10) and started having constant disconnections/re-syncs last year. At worst it was several times a day with anything up to 10 minutes downtime.

I was told that tests showed the problem lay in my premises, it will cost £xxx if an engineer comes out etc. but nevertheless I did have an engineers visit and an external joint was replaced and the rest of my line checked and found to be in order. Things didn't improve.

I finally replaced the Plusnet Hub One with a Fritz!Box 7530 and with the default settings got an immediate improvement.

Various changes that I've tried made little difference except for one which I don't entirely understand.

In the connection settings there is an option entitled, "Delay disconnection by provider to the period between" with a drop down box after it to allow a choice of a 2 hour period. I have mine set at 3-4 i.e. between 03:00 and 04:00 hrs. I'm guessing that by "provider" it means of the connection to the cabinet and not Plusnet.

Every night at about 03:15 hrs the router log shows "Clearing internet connection briefly to prevent the internet service provider from disconnecting you in the immediate future." followed by "Internet connection cleared." and then "Internet connection established succesfully." together with my new IP address gateway IP and other info.

If I untick this option then my connection drops once or twice a week and the re-connection takes anything up to 10 minutes If I have the option enabled the new session is started with 1-3 seconds.

The downside for me seems to be that the downstream SNR rises slowly day by day. At the moment it is wavering between 14 - 16 dB and my download speed has dropped from around 45Mbps to about 36 Mbps, this being nearly 9 days after a re-sync.

Have my observations lead me to a false conclusion that I can control whether my line re-syncs or not ?

p.s. apart from the obvious fact that I can re-boot the router to force a re-sync

Edited by longedge (Tue 15-Sep-20 09:19:50)

Clearing internet connection - is it just dropping the PPPoE connection, or both PPPoE and sync. Sync should only take 1 to 2 minutes to negotiate, some providers can be slow on the PPPoE side, have seen this take longer times like 5 minutes sometimes.

A remote DSLAM (in cabinet) can drop line to force resync if errors seen are too high and the modem can too. The ISP Plusnet have no direct contract over sync.

If you are succeeding in making the modem hang onto a signal without resyncing, its possible the modem is doing this by ignoring high error counts and a side effect of this may be the DLM system that relies on reports from the DSLAM will see the higher error figures and force more harsh training parameters when you resync.

You stated

"my download speed has dropped from around 45Mbps to about 36 Mbps, this being nearly 9 days after a re-sync."

If the sync speed was 45 Mbps to drop to 36 Mbps you would need a resync.
If the 45 Mbps is actual download speeds, you might be having lots of retransmissions going on reducing throughput or the ISP may be slower.

Thanks for that, yes it's just a new PPoE session every morning around 03:15.

Re the speed of re-sync, the engineer said that as my cabinet/connection has vectoring enabled re-sync takes a little longer. In practice starting a new session never takes longer than 3 seconds whereas a re-sync is never less than 7 minutes.

The last time I watched what was happening after a re-sync, I saw a downstream SNR of 4 dB briefly which has risen over the 9 days to 15 dB currently. It goes up and down by 1 or 2 dB all the time but the trend is always upwards and the highest I have seen is 16 dB.

Having seen the 4 dB, I wondered if there was a fault of some sort at the cabinet. The engineer said during his visit that he had spoken with a colleague and my line settings had been changed to prevent SNR from dropping below 6 dB.

I'm pretty sure that my TBB speedtest results dropped during the current sync period once the SNR got to around 10-11 dB i.e the drop occurred without a re-sync.

Truth be told I cope perfectly well with things as they are and it's just me trying to understand what's happening.

p.s. My router currently shows in the error counter ES - router 8 cabinet 867 and SES router 1 cabinet 0. Corrected DTU in the router is currently 2 per minute and 0 uncorrected over the last 15 minutes. So errors don't appear to be a problem.

Edited by longedge (Tue 15-Sep-20 12:06:08)

Ask on https://forum.kitz.co.uk/

In reply to a post by longedge:

Re the speed of re-sync, the engineer said that as my cabinet/connection has vectoring enabled re-sync takes a little longer.

This is indeed true.
Sync usually takes around a minute but this roughly doubles with Vectoring enabled.

How old is your modem? I was seeing similar a couple of weeks ago. I was using a 10 year old Huawei Openreach device. Swapped to Vigor 130 and line stability returned.

In reply to a post by clmfsh:

How old is your modem?

Not sure what your point is but the Fritz!Box is 4 or 5 months old and the last Plusnet Hub One I was using was a couple of years old. The Plusnet Hub One/BT HH5 is adequate but only in ideal conditions.

In reply to a post by longedge:

In the connection settings there is an option entitled, "Delay disconnection by provider to the period between" with a drop down box after it to allow a choice of a 2 hour period. I have mine set at 3-4 i.e. between 03:00 and 04:00 hrs. I'm guessing that by "provider" it means of the connection to the cabinet and not Plusnet.

Every night at about 03:15 hrs the router log shows "Clearing internet connection briefly to prevent the internet service provider from disconnecting you in the immediate future." followed by "Internet connection cleared." and then "Internet connection established succesfully." together with my new IP address gateway IP and other info....

Have my observations lead me to a false conclusion that I can control whether my line re-syncs or not ?

As it's a German router manufacturer - that feature is related to:

https://community.ui.com/questions/automatic-wan-ppp...
https://translate.google.co.uk/translate?hl=en&sl=de...

On some providers, their PPPoE connection is terminated after 24 hours. It's better to have this happen in the middle of the night instead of during the day when the connection is more actively used - and restart the 24 hour countdown.

Yes indeed just as I described but what I don't understand is why this (i.e. forcing the start of a new PPoE session once a day) prevents a re-sync as it appears to do.

The session is always dropped and re-started in less than 3 seconds whereas a re-sync takes anything up to 10 minutes.

As a side issue, there is something very strange about my speedtest history. It goes up to 21/8/20 and then the topmost result is replaced each time with the last test result so currently a gap of almost a month when in fact I run a test at least once every day. Are the results held locally so something wrong on my system?