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Re: [Openvpn-users] Heavy packet loss with high traffic


  • Subject: Re: [Openvpn-users] Heavy packet loss with high traffic
  • From: Eric Hokanson <hokanson@xxxxxxxxx>
  • Date: Mon, 20 Dec 2004 10:20:56 -0700

On Mon, 20 Dec 2004 06:16:26 -0700 (MST), James Yonan <jim@xxxxxxxxx> wrote:
> On Mon, 20 Dec 2004, Eric Hokanson wrote:
> 
> > I have a WinXP box at home running OpenVPN 2.0rc4 which is connect to
> > a high speed university network.  This network blocks all udp packets
> > and most tcp ports.
> >
> > At my work place across town, I have a Linux box also running OpenVPN
> > 2.0rc4.  It is connected directly to the Internet with a high speed
> > connection.
> >
> > I have a tcp tunnel between the two machines with all my home traffic
> > being sent through to my work machine.  This way I was hoping I could
> > play games and stream video, etc.  When the connection isn't stressed
> > it appears to work great and a ping from my home machine to a reliable
> > site produces hundreds of pings with a 0% packet loss.  When I start
> > to send a high volume of packets through, such as an online game or
> > video stream, the first 5 seconds or so work great then I suddenly
> > start to get massive packet loss.  I've tried disabling encryption,
> > authentication, and compression with no change.  I've also tried
> > lowering my sndbuf size to reduce latency with no change.  I see no
> > obvious problems in the log window.  Below is part of my WinXP
> > configuration in case you spot anything abnormal.  Anybody know how to
> > fix this problem?
> 
> Keep in mind that a lot of games as well as video streaming use UDP-based
> application protocols.
> 
> Because transmit throttling is not built into UDP, the application must
> deal with it by reducing its transmit speed to a level which the link can
> support.  Otherwise, if apps transmits UDP data at LAN speeds, a high
> percentage of packets will end up being dropped at the local VPN gateway.
> 
> James
> 

Humm, you are correct, these are probably all using UDP but I'm sure
my connection can handle it.  My ping from home to work over the
tunnel is between 5 & 10ms and I can easily download files from the
Internet over this link at 200-300 KB/sec.  Is there some settings I
can change to prevent dropped packets?

-- 
Eric Hokanson
www.allthingsgeek.com