[Openvpn-users] Re: Tcp tunnel bridging performance ?

[JPM <jpm_tmp2@xxxxxxxxx>]

James Yonan <jim <at> yonan.net> writes:

> 
> On Mon, 31 Jan 2005, JP M wrote:
> 
> > Hi, list.
> > I am happily using openvpn + shorewall on a debian
> > 'testing' box. I am using bridging in the old openvpn
> > 1.5 way.
> > Among other uses I have 2 tunnels to connect wireless
> > machines to my Lan. I normally use UDP tunnels.
> > Trying to stream data (videolan) over the tunnels, I
> > come to the conclusion that udp over udp is not
> > reliable enough, while udp streaming over a tcp tunnel
> > is the solution.
> 
> I'm not sure that running video over TCP makes sense because 
> any frame drops/retransmits will kill the real-time experience.
> 
> That's why people run video (or VoIP) over UDP -- because you would rather
> lose a few frames and preserve the real-time experience.
> 
> > Unfortunately, I observe a massive performance hit
> > (throughput at least divided by 4) with the tcp
> > tunnels. I tweaked the usual mssfix, but it did not
> > seem to help much -or not long ??. 
> 
> mssfix doesn't really do anything when the tunnel itself is using TCP as a 
> carrier.
> 
> James
>
James,
thanks for your answer. 
I have narrowed the so-called performance issue to Samba<->windows : using http
over openvpn tcp, I can achieve downloads on my lan at roughly 2/3 of the rate I
experience with a udp tunnel. That seems fair enough. (No mssfix statement in
the conf file, tun-mtu 1500, tun-mtu-extra 32.)
Now, when I am doing a samba file transfer over a tcp tunnel, the xfer rate is
low, but I have noticed that when I start a vlc udp unicast at the same time (on
the samba server box, to the client), the samba file transfer speeds up to
perform somewhat like the http transfer. 
I have cleared shorewall's rules on the router and put interfaces in forwarding
mode, fiddled with the samba conf, no change. 
I am baffled. Does anyone know what is going on ?


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