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OT: Re: [Openvpn-users] UDP Tunneling?


  • Subject: OT: Re: [Openvpn-users] UDP Tunneling?
  • From: "Renato Salles" <rsalles@xxxxxxxxxxxxxxxxxxxx>
  • Date: Mon, 10 Nov 2003 23:52:31 -0200 (BRST)
  • Importance: Normal

Just landed at my desktop this mail from James.
There are months that i'm searching for a VoIP app to use with OpenVPN.
Does anybody - and Jimmy also - has some links to point for?
Gnomemeeting? Never used but, could it be deplyoed in a "WAN/LAN"
environement also?


TIA,

RSalles


> Leo Vetterli <leo.vetterli@xxxxxxxxxxx> said:
>
>> Does anybody know if openvpn supports UDP Tunneling? I mean that the UDP
>> Protocol on a Sub-LAN is tunneled with Openvpn to the LAN?
>
> Absolutely.  People commonly tunnel NFS or VoIP over OpenVPN.  Since
> OpenVPN
> fully supports UDP as the tunnel carrier, when you are tunneling a UDP
> application stream, you get the clean encapsulation semantics of UDP over
> UDP.
>
> The one gotcha to keep in mind is that when OpenVPN encrypts and
> encapsulates
> a UDP packet, some security-related overhead is added to the packet size.
>
> The result is that the MTU is somewhat less than it would be over a direct
> connection with no VPN involved.  This can create a performance bottleneck
> or
> even lock up the connection if IP fragmentation is disabled by routers in
> the
> path.
>
> OpenVPN has a workaround for this: the --fragment option which does
> fragmentation internally.  This is really a last-resort for intractable
> fragmentation problems since it exacts a performance penalty.  Note that
> the
> --mssfix option does not work in this case -- it's designed to work only
> with
> TCP streams which are tunneled over OpenVPN.
>
> The best solution is to lower the UDP MTU used by the application which is
> being tunneled to a level just below the fragmentation threshold.
>
> James
>
>
>
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-- 
"A well-written program is its own heaven; a poorly-written program is its
own hell."
TAO of Programming - Book 4

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