OpenConnect connections unusably slow

Thomas Richter richter at
Thu Jun 13 03:31:34 EDT 2013

Dear openconnect developers,

our computing center recently switched from OpenVPN to open connect (or 
rather, anyconnect), and thus this required a change in my VPN tunnel 
configuration. I managed the configuration just fine, and the computer 
also connects to the system and establishes the tunnel, however, the 
connection as itself is incredibly slow, close to unusable.
Interestingly, this problem seems to be somewhat hardware related, and 
network related:

If I setup the tunnel within the network of the university over the LAN, 
things work fine. If I establish the link over Wifi at home, the 
connection is unreliable. Wireshark shows many http reconnection 
attempts, as far as I can tell. The connection is so slow that it is 
essentially unusable.

With the same wifi at home, but a different hardware, openconnect *also* 
works fine, so no problems there. Also, if I establish the tunnel by my 
own script, and not via the gnome network manager, things also work 
fine, though I here disable DTLS on the openconnect command line. Thus, 
it seems that DTLS or udp transport over my wifi seems to be the 
culprit, though I'm not quite sure.

The hardware of the problematic notebook is an intel iwl3945, the 
working notebook has a very old hostap-based wifi. OpenConnect version 
is 3.20, the one that comes with debian wheezy. I also tried to compile 
my own,  but apparently Debian made some patches and my own version does 
not play well with the libraries Debian installed.

Any hints or suggestions what else can be done to resolve the matter?

	Thomas Richter

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