[OpenWireless Tech] openvpn bandwith throttling?

[Huub Schuurmans]

We are evaluating the use of a vpn-tunnel from the AP-owner machine to a
(remote) server on the Internet. We found that the available bandwith
suffers badly from the use of OpenVPN.
Has anybody experienced this before? Can we tweek openvpn performance by
changing parameters. We are running FreeBSD9.0 and used the default
OpenVPN-paramaters.
Bandwith at the server is about 100 Mbps, the internetconnection at the
AP-owner runs at 25 Mbps but with the openvpn tunnel in place this
reduces to only 8 Mbps. Even without encryption and compression bandwith
is only aroun 10 Mbps.

Kind regards,
Huub


Here are some technical details.

Bandwith from the server to the internet:
%fetch -o /dev/null http://ftp.de.freebsd.org/pub/FreeBSD/ls-lR.gz
/dev/null 100% of 25 MB 13 MBps

# AP-owner inet connection:
$ curl -o /dev/null http://ftp.de.freebsd.org/pub/FreeBSD/ls-lR.gz 100
25.6M 100 25.6M 0 0 6564k 0 0:00:04 0:00:04 --:--:-- 6650k
$ curl -o /dev/null http://ftp.nl.freebsd.org/pub/FreeBSD/ls-lR.gz 100
25.6M 100 25.6M 0 0 6739k 0 0:00:03 0:00:03 --:--:-- 6797k

# From the AP
# fetch -o /dev/null http://ftp.de.freebsd.org/pub/FreeBSD/ls-lR.gz
/dev/null 100% of 25 MB 843 kBps
# fetch -o /dev/null http://ftp.nl.freebsd.org/pub/FreeBSD/ls-lR.gz
/dev/null 100% of 25 MB 993 kBps

# Same, without encryption (only slightly higher)
# fetch -o /dev/null http://ftp.de.freebsd.org/pub/FreeBSD/ls-lR.gz
/dev/null 100% of 25 MB 1284 kBps

# Same, without compression  (only slightly higher)
# fetch -o /dev/null http://ftp.de.freebsd.org/pub/FreeBSD/ls-lR.gz
/dev/null 100% of 25 MB 1335 kBps

# Same with MTU 1400 (no effect)
# fetch -o /dev/null http://ftp.de.freebsd.org/pub/FreeBSD/ls-lR.gz
/dev/null 100% of 25 MB 1298 kBps