[GLLUG] Openvpn overhead?

Tim Woodall t at woodall.me.uk
Wed Apr 4 18:58:48 UTC 2018

Hi all,

I have a wifi link between two (debian) firewalls that are in separate
premises. I'd like to put a wired link in but that requires getting some
permissions so it won't be quick (although it's simple to do)

Over the wifi link I can scp data at at least 1MB/s which isn't great
but it's not too bad. iwconfig says the connection is at 150Mb/s so in
theory I should be able to do 10x that. (One end is an access point into
a 100Mb ethernet link while the other end is a USB wifi dongle so I'm
not expecting 15MB/s)

Over that wifi link I then run a udp openvpn link. I've tried both tun
and tap devices.

When I copy over the openvpn link I get around 100KB/s.

If, while the copy over the openvpn link is running, I the do another
copy over the wifi link the wifi copy runs at around 800KB/s and the
openvpn copy drops to about 10-20KB/s

Does anyone have any ideas why the openvpn link is so slow? I've
reducing MTU in case it was fragmentation problems.

I am using IPv6 rather than IPv4 if that makes a difference.


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