My home broadband is, as I understand it, fibre to the local junction box (less than a mile away) and then very old copper to my house. When I first signed up a couple of years ago, I was consistently getting around 40Mbs down and 10Mbps up.
During this period ( the "golden age") , the line would occasionally "fail" but, as I'll explain, with minimal impact to me. I say "fail" because Ping and TraceRT worked, but more importantly, using a VPN (Witopia), I could happily "punch through" the problem and reliably get my full 40Mbps. The ISP engineer would eventually arrive out, test the line, agree that it could support 40Mbs, agree that there was no problem in my house, go away, do "someting" and my connection would go back to providing 40mbs without the VPN. Happy days, indeed,
Sadly, back in May. at 23:36 one night, my line went down and when it came back *three* minutes later, my max speed had gone from 40Mbps to 22Mps (with upload going from 10Mbps to 3.3Mbps). Aargh! Unfortunately, I had neither the time nor the energy to get into an extended row with my ISP and "settled" for 30Mbps down, 10Mbps up (which I verified independently).
And now my latest situation - as of a week or so ago, performance has collapsed. Some times my line supports 30Mbs/10Mbps, but for extended periods, I'm getting some data, but usually not enough to even load a web page. Unless, of course, I use my VPN. But not all of its setups work - I get a perfect connection using OpenVPN+TCP. UDP simply can't hack it.
So, my big question, please, is ...
Why is my TCP VPN working? I'm guessing that it's something to do with TCP error-correction, but I don't understand how that's so much more powerful than that of a a non-VPN TCP session.
(Subsidiary question, if it's not apparent from the main answer, what's the root problem?)
ISP - Sky Ireland.
PC - Laptop running Windows 8.1 (but I've got a consistent result from an Android phone).
Modem/Router - Sky QHub ER110 (and, previously, SR102).
If it helps, I am the only person in the house and I do not now, nor have ever, torrented or file-shared, My WiFi is WPA2-Personal and my password is 63 random characters.
Line monitoring - Every 10 minutes, a utility checks my line speed - JD Auto Speed Tester (https://www.gmwsoftware.co.uk/
Phone - while my broadband is misbehaving, the phone line and independent alarm system (both sharing the same copper as my broadband) is working fine. (The phone line shares a "master box" with the broadband whereas the alarm is wired-in upstream of that.)