Download speed limited/shaped/throttled?

Hi,

I've had an unusual problem with my broadband speed since the start of January ,and I'm hoping someone might have encountered it before or identify the issue...

My ip profile is 5500kbps. If I use p2p I can get 500 kB/s, so my connection works and gives decent speeds. However, if I try to download a file (I've tried itunes, ubuntu, zen test files, and many microsoft downloads, among others) in firefox or IE my download speed is limited to ~50-100 kB/s. If I set a second file downloading it too will download at this speed. The same for a 3rd file etc. If I use a download manager which splits the file up into sections, I can download the file at 500+kB/s.

As a test to eliminate the operating system, I used an ubuntu live cd and tried downloading the files here:

http://www.microsoft.com/downloads/details.aspx?Fami...
I start the 1st file it goes to 100-120kB/s
I start the 2nd file, it goes to ~100kB/s, the 1st remains the same.
I start the 3rd file, it goes to ~100kB/s the other 2 remain the same.
I start the 4th file, it goes to ~100kB/s, the other 3 remain the same.
I close them down individually and their speeds don't increase.

So the speed was a bit faster but the behaviour was the same.

I've tried different computers, different routers, different filters and RJ11 leads, different ISPs (I moved from O2 to Andrews and Arnold last week) and have the same problem. AA tech support are currently working on the problem, but I wanted to see if I could get some extra help as it seems to be an unusual problem.

Cheers in advance.

Sounds like per connection limit - as the P2P will no doubt be many connections making up the full line rate.

Very strange though.

Matt

Have you tried connecting to the test socket behind the ADSL faceplate?

Yeah, sorry forgot to mention I'm plugged into the test socket.

When using p2p the max single peer connection download I noticed was 130kB/s. It's hard to tell if this was 'limited' or not.

Unless you have odd extension wiring, that probably rules out your end being the problem.

Any LLU available at your exchange?

The only extension I have is one of those leads to extend the length of the cable to the phone. I've tried with and without this plugged into the filter (in turn plugged into the test socket) with no effect.

No LLU in my exchange unfortunately!

MTU and RWIN values may be relevant -

http://www.dslreports.com/tweaks
http://www.speedguide.net/analyzer.php?

will show you what's happening. A small RWIN value limits the rate a TCP/IP stream can achieve.

agreed - reminds me of the days of so called bandwidth optimisers for modem connections that killed bandwidth on broadband.

Andrews and Arnold tech support reported a fault to BT, who sent an engineer out to fix it. Turns out the was a major service failure and my connection seems to be sorted now.

Thanks for your advice guys!