[Smedy]

Hi,

I'm trying to troubleshoot a bad vpn connection (a 10/10mbit vpn tunnel) there seem to be a mtu issue or something. The client has issues with speeds using the vpn tunnel. There's no problem reaching 10mbit uploads but when it comes to download it hangs around 1mbit/s. I've tested tunnel myself and i am experiencing the same issue.

The tunnel is using openvpn and i do not have any access to the server side of the tunnel. The client is running windows and i've tested with 3 different versions of windows, 2 internet providers (one fiber technology and one docsis3.0), 5 different versions of openvpn and also various tweaks to the openvpn configuration, nothing fixes it.

When i'm trying to troubleshoot the mtu i can't find any issues, i can ping hosts using ping X.X.X.X -l 1472 -f successfully which indicates that mtu 1500 should work, no?

It seems like the first seconds of established connection the download speed go at 10mbit/s (full speed) but they drastically decreases down to around 1mbit per second and stay there. I suspect the ack queue stacks up at the higher speeds and that's why the download drops?

Any ideas?