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[Alex Atkin UK]

Didn't someone else have a Fritzbox 7530 recently that was unstable and got it replaced which fixed everything?

[Edinburgh_lad]

Didn't someone else have a Fritzbox 7530 recently that was unstable and got it replaced which fixed everything?

It's a red herring. I have the same problem as he does (almost exactly) and so it's unlikely that BobC's issues were the same as mine because of the router. Plus, I've also tested using other routers (Broadcom/Lantiq-based) and it makes no difference.

Here is my Fritzbox graph from Sunday 2 weeks ago and from this Sunday (I believe the discrepancy in the times errors occur is due to BST change, but this could be a red herring, too). Is it that all my neighbours are on the Internet around the same time, their browsing resulting in cross-talk and so errors? Is it some kind of interreference (someone's equipment) that's on on Sundays - the times of errors suggesting that and also that it's a system on a timer like a boiler or hot water tank? Or is it a high resistant fault that has never been fixed because the line is difficult to access and it's performing within parameters (3 disconnections a day according to Plusnet and OR is acceptable).  After the three drops today, preceded by an accumulation of errors, I have no errors on my Fritzbox counters at all despite being connected for 5 hours now.

So, in a nutshell, I have the same problem as BobC, including the fact that Min. effective data rate on my Fritzbox goes down to 3, whereas his is 6 kb/s.

BobC: what exchange are you connected to? Also, have you noticed that your 2.4GHz WiFi is also affected when these errors occur? Mine seems to be affected to the point where the router slows down big time, ping and jitter increase etc.

Another question to those reading the thread: what's the impact of an amateur radio station on VDSL signal?

[j0hn]

Is it that all my neighbours are on the Internet around the same time, their browsing resulting in cross-talk and so errors?

Crosstalk doesn't work like that. It's the sync from a neighbouring line that causes interference not the traffic they send.
As almost everyone leaves their modem/hub synced 24 hours a day then the crosstalk is always present.

It can be very noticeable when a crosstalking line gets activated for VDSL2 as the SNRM and the attainable drops. Next resync will be at a lower rate.

When 1 of these lines goes on holiday for a week and turns off their modem the SNRM increases as does the attainable rate, meaning you can sync higher temporarily.

Crosstalk is very much a lottery. The neighbour next door might have zero effect on your line as their pair may not be adjacent to yours in the bigger bundle. However someone from the next street down might be knocking 10Mb off your sync with crosstalk as your pairs run together for hundreds of meters.

[Alex Atkin UK]

I'm curious, how exactly does an idle line in sync cause the same crosstalk as a loaded line in sync?  Logically there should be less noise, same way a WiFi Access Point creates less interference if its idle than if its active.

[j0hn]

There are constant PTM packets being sent/received whether the line is being used or not.

It's the same reason that CRC/ES are the same for a line downloading at full rate as they are for a modem synced with no router connected.

The signal is always there. Power doesn't increase when traffic is being sent.

[Weaver]

In ADSL, with ATM, you’re sending idle cells all the time, is that that right? In VDSL, with PTM, That isn’t the case, so I believe, but I’m unsure.

[Alex Atkin UK]

Yes the signal is always there, but surely its not just constantly sending empty packets at max line rate, that would be hugely wasteful in electricity.

[j0hn]

In ADSL, with ATM, you’re sending idle cells all the time, is that that right? In VDSL, with PTM, That isn’t the case, so I believe, but I’m unsure.

I believe it's the same with PTM.

Yes the signal is always there, but surely its not just constantly sending empty packets at max line rate, that would be hugely wasteful in electricity.

It uses the same power whether data is being transferred or not. It's required to maintain sync.
It's a very small amount of power, often single digit mW.

[Weaver]

I desperately need to reread the docs about PTM framing and ADSL2 / VDSL2 specs again because I’ve forgotten important details. But I suppose when you have no PTM PDUs to send, at the physical layer you just send some arbitrary constellation of some sort over and over again, anything that doesn’t look like a valid start-of-frame.

[burakkucat]

I desperately need to reread the docs about PTM framing and ADSL2 / VDSL2 specs again because I’ve forgotten important details.

You're not the only one.   

Nowadays I rely upon forum members (say Reformed, for one example) to put right my incorrect memories.

[burakkucat]

Also, whilst wearing my moderators collar, I should mention that we have rather hi-jacked BobC's topic. 

If he should so wish, I could see about splitting off those posts which are not related to his (ongoing) problem.

[Alex Atkin UK]

It uses the same power whether data is being transferred or not. It's required to maintain sync.
It's a very small amount of power, often single digit mW.

Thinking about it more I guess this kinda makes sense, would need some complicated form of SRA that goes up and down on demand otherwise.

I still don't understand how the crosstalk would be the same though, how can it be equally as noisy when not transmitting data (above what's necessary to keep the link and PPP connection live) as it is when heavily loaded?  I mean there's been plenty of cases where people have said their line drops when loaded but is stable when idle or lightly utilised, which would surely run contrary to what you are saying?

[Reformed]

I still don't understand how the crosstalk would be the same though, how can it be equally as noisy when not transmitting data (above what's necessary to keep the link and PPP connection live) as it is when heavily loaded?  I mean there's been plenty of cases where people have said their line drops when loaded but is stable when idle or lightly utilised, which would surely run contrary to what you are saying?

It's the noise a line is receiving that's the problem, not what it's sending out.

[Edinburgh_lad]

So, I've done as someone suggested (I can't remember - I think it was Black Sheep - but thank you) and I dialled a number from my landline to my mobile. Immediately, the error count (ES) jumped up from 16 to 35 during the time I heard the ringing tone. However, the errors are on 'Central Exchange' part only on Fritzbox, which, I presume, means 'send' direction, rather than 'receive'.

[jelv]

What happens in the other direction (dialling your landline from your mobile)?