Sync speeds, Target SNR

[#1]

Hi all

I have been having issues now for around 2 years but nobody can help sort out my problems. Maybe someone here can help.

I used to have a pretty stable 72mbps down and 20 meg up. Target SNR's were around 1db. (This was with BT and around the time they lowered the SNR's to 1db on ECI cabinets.) 

Then things changed and my target SNR went back to 3db, This lowered my speeds to 65-67mbps down and 19.999mbps up. 

I then switched to plusnet and the line was great, 65mbps down, 19.999 up. Target SNR 3db on both up and down.

After around 12 months something happened and my line speed dropped, an engineer came out and said there was a problem with the port in the cabinet, he did what he called a "lift and shift" and again everything was good, for a few months. Then speeds start to drop. Every day I come home my router has reconnected multiple times. Engineer comes out and does a DLM reset, all fine again. This repeats around 3-4 times but not one of these engineers did a DLM reset afterwards.

Around a month ago it dropped below my guaranteed speeds so an engineer came out, literally just after lockdown. He tested the line, told me the max the line would support was 34 meg (I questioned this as when he arrived it was connected at 40 meg down. I requested he did a DLM reset, he said he did it and my line would max out at 36 meg now, but while he was chatting I pulled up the router stats and its actually connected at 50 meg down and 12 up. Better than it was but still not anywhere near it was.

So now i seem to be stuck at this 50/12-13 connection. I have noticed the SNR's in the router are always between 6 and 7db on both up and down. I have tried explaining this to Plusnet support and asking if my profile can be reset to 3db target, they tell me there is no restriction on my profile. So, why am I syncing with more SNR now than before, and why has my upload lost 7mbps, virtually half of it. 

Is it something to do with a stuck or broken profile? Should I be on 17a to get max speeds?

Thanks in advance

[#2]

Sounds like cable fill to me.

[#3]

Cable fill?

Does that mean that the copper is corroding/breaking down?

The pole that my line is connected to has a red D on it, apparently this means its unsafe to climb. All the engineers who visited looked at the pole but none of them have ever been able to climb it. 

[#4]

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@SpaceBallz wrote:

Cable fill?

Does that mean that the copper is corroding/breaking down?

---

I think @notmyname is referring to the fact that VDSL uses higher frequencies than ADSL on the copper section of the line, and is therefore more susceptible to crosstalk.

As more customers' switch to FTTC, the problem increases.

There are technologies (vectoring? GFast?) apparently designed to overcome the problem, but they are beyond my understanding!

[#5]

This exactly, aside from the "but they are beyond my understanding!" part.

You're probably the most intelligent member of this forum (no offence to anyone else)

[#6]

@notmyname Aw shucks, you're too kind - What can I say? The bar is low? Just kidding folks.

[#7]

Just thought I would update you all.

So after suffering slow speeds for a few months, low and behold last night when I got back from work I noticed the router stats were saying my max attainable was 13 meg higher than it was currently connected, and also my upload max attainable was near 5 meg higher. So I rebooted the router.

I am now connected at 67mbps downstream @ 3.1db SNR and 17.5mbps upload @ 5.6db SNR

So it seems my line has gone nearly back to what it was. 

What I dont understand is how can this not be a fault, that no engineers can find?

Losing so much down and upstream, to the point I was below the hand back threshold, (42mbps).

Anyway, its either fixed itself or someone who was recently working up the road has fixed it. 

Happy again. be a little happier if the upload went back to 19999.

[#8]

@SpaceBallz 

Happy again. be a little happier if the upload went back to 19999.

Why, are you uploading lots of data? Your upload is just a tiny bit lower than my fttc download!!

Re VDSL, issues can include many things,

crosstalk (between the wires) which cause your connection and others to slow down due to packet  errors packet.

Interference from many natural and unnatural sources.

Weather especially for overhead lines (trees touching wires, leaky junction boxes)

Radio signals don't really work too well on the existing telephone network, full fibre is a better, and we could have had this over 15 years ago!!

Google Thatcher Fibre killed

[#9]

Re upload.

I have 2 dedicated servers and 3 vps's which I use for various tasks. Sending files to them is where I suffer. One day I needed to upload a 30gb database backup to a server and after having virtually 20 meg upload slashed to roughly 12meg it really hurts on upload times.

As for the line it was great for a few days, Upload seems to have stuck at 17.1 @6db, downstream has lost the 3db sync speeds again, back down to 60 from 67. 5.1db on the downstream and its reporting a max attainable of 58. Seems my hike only lasted about 5 days.

I can see it going back down below 50 again soon. Whatever happened its un-fixed itself.