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Re: VPN over slow Internet connections
From: William Herrin <bill () herrin us>
Date: Thu, 21 Apr 2011 13:24:10 -0400

On Thu, Apr 21, 2011 at 12:55 PM, Ben Whorwood <bw-ml () mube co uk> wrote:
Can anyone share any thoughts or experiences for VPN links running over slow
Internet connections, typically 2kB/s - 3kB/s (think 33.6k modem)?

We are looking into utilising OpenVPN for out-of-office workers who would be
running mobile broadband in rural areas. Typical data across the wire would
be SQL queries for custom applications and not much else.

Some initial thoughts include...

 * How well would the connection handle certificate (>= 2048 bit key) based

Fine. The certificate isn't sent very often and is only 256 bytes when
it is sent.

 * Is UDP or TCP better considering the speed and possibility of packet loss
(no figures to hand)?

TCP is more likely to pass firewalls at the user's end, especially if
you put your VPN server on port 443. UDP will allow the user's various
sessions to recover from packet loss independently (i.e. faster). I
would pick UDP and provide an alternate TCP configuration for users
who experience trouble.

 * Is VPN over this type of connection simply a bad idea?

No worse than using this slow a connection in the first place. VPN
overhead is 5% to 10% tops. I would use a split tunnel though; let
general internet destinations go directly through the Internet
connection rather than through the VPN.

Bill Herrin

William D. Herrin ................ herrin () dirtside com  bill () herrin us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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