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Re: [Openvpn-users] tcp over tcp with udp problem?


  • Subject: Re: [Openvpn-users] tcp over tcp with udp problem?
  • From: "James Yonan" <jim@xxxxxxxxx>
  • Date: Wed, 5 Nov 2003 23:03:13 -0000

Michael Hale <michaelh@xxxxxxxxxxxxxxxx> said:

> Hi I was wondering if the way openvpn is implemented, if it suffers 
> from the problem of tcp running over tcp 
> (http://sites.inka.de/sites/bigred/devel/tcp-tcp.html)?  It seems like 
> running with the udp connection would solve this problem, but I wanted 
> to ask the people who wrote this software explicitly just to make sure 
> ;-)

As a tunnel transport, UDP is almost always a better choice from a performance
perspective, though TCP can work reasonably well if the network is not
congested.  As the network becomes more congested and the percentage of
dropped packets goes up, a TCP tunnel's performance will drop off more sharply
than a UDP tunnel, because of the reliability layer collision which is cited
in the article.

OpenVPN originally supported UDP only, but TCP support was eventually added
due to overwhelming popular demand.  Of course things didn't stop there...
soon we were tunneling over HTTP.  I suppose it's just a matter of time before
someone suggests tunneling IP over SMTP :)

James


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