No technical support

[Mr+Slant]

If its right on the edge of the allowable errors per day/hour then worst case it'll bounce back and forth between banding levels every night on DLM. I ended up manually setting a noise margin of 7dB which meant it more or less stayed at 74Mbps rather than bouncing between 74 and 66Mbps. A few months later g.INP got applied to the line and that was enough to get full sync back on a 3dB margin.

Night time is always going to be worse if the cable is above ground due to the Heaviside layer in the ionosphere bouncing more HF radio interference around which will reduce the noise margin. That's one of the reasons you see more of these sort of issues in winter.

In my previous property the "problem" re crosstalk was simple enough - the (new) neighbours had chosen VDSL services whereas the previous neighbours had a Virgin service. Both pairs ran side by side from the cabinet so crosstalk increased by a large amount.

Edit - this will probably assist in understanding how DLM works on Openreach VDSL services : https://kitz.co.uk/adsl/DLM.htm

[jamesn123]

---

@Eeeps wrote:

---

I can't see that aditional crosstalk can cause drop from a steady 79 to 63 overnight.

This definitely looks like a fault to me which DLM is trying to compensate for.

---

Thats exactly what crosstalk can do. DLM will step in when the error limit or drop limit is reached and bring down the margin to the next suitable level. Depending on line length and quality this could be a drop of anything from a few mbps to 16mbps as you see. 

[Kristof]

Update. 

It is hard to blame those advisors because they have no tools to deal with any problems, but the incompetence of the whole system is just shocking.

I was messing around with sky hub port forwarding because it wasn't working properly due to this line fault, and I was frequently rebooting sky hub due to changes in my router for a few days.

Yesterday, I received a text message from Sky with broken web link. So I called Sky to find out what was going on.

Guy, who sounded like he was sleepy or drunk, couldn't figure out what this was; he said it was more like a scam message.

Anyway, back to my little work on port forwarding later on. actually get something working this time. I was chatting with someone on Skype chat at the same time. I managed to verify my account after a 1-hour response gap, etc., and was asking about this message once again.

 This advisor identifies the message, and he was explaining to me that the messages I received were regarding the original, unplanned visit that was booked and closed prior to the appointment I arranged on the phone. But Sky just decided to send me a not-working link to it just to make me wonder what this is about. Common sense.

Of course, when I asked the advisor what the point of this kind of communication with customers was, he couldn't answer and just went on and on about the subject of that message.

In the mean time, he told me that "the unassigned openreach visit has done all the external checks and they couldn't detect a fault, including checking the network side of things such as DLM," and this is why the next step is an "assigned openreach visit to your property."

So first, he admitted that it was me who booked a BT engineer on the phone. But then he said they actually checked their side first before I book enginneer, and because everything is fine, the fault must be in my house, so that's why a BT engineer is coming to fix this at my house. WOW !!!

While I was trying to explain to him that this was not the case, he insisted that BT need too check my socket because it appears that there is a fault in my home (BT replaced the socket 3-4 times in the last 2 years because of the same logic).

Anyway, I kind of had enough of this conversation, and I just had to reboot Sky Hub again. The speed went up to 73 mbps. This clearly indicates that whatever Openreach was doing, they discovered and fixed the problem. At least it looks that way.

The unfortunate aspect of this story is that it occurs on a regular basis, every few months. Sky never learns from it, never admit any fault so far, and I need to go through the same process of incompetence every time DLM goes crazy. Last time, when speed dropped 100 kb below my minimum speed, my advisor told me there was nothing Sky could do about it. Right now i still waiting for the BT engineer to test my line and prove nothing wrong here. Pathetic.