Hello,

I have discovered a weird issue with my download speed.

When I download files from the internet, the speed for one thread seems to be capped at max 10MB/s. But not always.

FTP - my 1st private server => 10MB/s
FTP - my 2nd private server => 7MB/s
FTP - ftp.bit.nl => 10MB/s
HTTP - Ubuntu MATE ISO direct download => 7MB/s
Speedtest - single thread => 10MB/s
Speedtest - multiple threads => 50MB/s (max speed)

The same download cap applies using Wi-Fi adapter on the same computer.
I tested FTP transfers using FileZilla and WinSCP with the same result. HTTP download and speedtest with Pale Moon.

So far I have tested :

- Safe mode with networking - same cap as above. (tested just FTP via LAN)
- Transferring file between two computers via local LAN maxes out the connection at 100MB/s.
- Booting another Windows installation from flash drive maxes out the connection at 50MB/s.
- Transferring multiple files at once from FTP maxes out the connection at 50MB/s. (but each thread / file is capped at the above speed)
- Another cable on another port on router makes no difference.

- Another computer (same model as the one with problem, also Win7) using the same router maxes out the connection at 50MB/s.
- Another computer (different model, Win10) using the same router maxes out the connection at 50MB/s.

My upload is only 3MB/s and this gets maxed out in each case.

To be honest, I am at a loss here. I have never seen such a weird issue (why are the capped speeds not the same ? ) and from the tests I conclude it must be a software problem.

Googling this issue is quite tricky and unfortunately led me nowhere.

Any tips ?

If anyone is searching for a solution, problem was solved by the command : netsh int tcp set heuristics disabled

Weird that the setting is enabled on the another laptop which is the same model and no throttling can be observed there.

Many thanks to Jerry Jongerius and his excellent article on this topic : https://www.duckware.com/blog/how-windows-is-killing-internet-download-speeds/index.html