[clug] VPN over Wireless

[Stephen Hodgman]

Hello All,
I am having some difficulties running VPNs over wireless links and 
wanted to know if anyone can offer help please.

I am using WinXP clients making a PPTP connection over Telstra NextG 
wireless and ADSL links  to a Snapgear Firewall box.  The Snapgear is an 
embedded Linux unit that offers simple VPN/Firewall  services.  What I 
am finding is that the XP clients connecting via ADSL get very good 
connection times.  Over wireless though it is terrible.

I have recently trialled Netspeed's Longreach Wireless as an alternative 
and had similar difficulties.  On this I have tried decreasing the MTU 
and found it does improve the service but it is still not real good.

What I was interested in was anyone else's experience and/or some 
explanation as to why the wireless links should be so temperamental.  I 
would have thought the VPN was just a TCP connection and it should 
handle traffic as normal.  e.g. On the Netspeed link, I can do sustained 
FTP downloads and have no difficulties.  If it do an "ls -lRt" on a 
terminal session over the VPN on wireless it clags and kills the link 
almost immediately.  What is the difference?  I see there would be some 
"vpn padding" around the data but it must be very susceptible to timing 
issues.

Anyway, if anyone can offer suggestions on how to improve the link I 
would be most grateful.  I am stuck with the client systems and 
protocols for now so I would like to really make the best of it.
Thanks,

-- 
Stephen Hodgman
Namadgi Systems
+61 (0)407 182 355 (mobile)
+61 (0)2 6285 3460 (Office)
+61 (0)2 6285 3459 (Fax)