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

  • Subject: Re: [Openvpn-users] Heavy packet loss with high traffic
  • From: James Yonan <jim@xxxxxxxxx>
  • Date: Mon, 20 Dec 2004 06:16:26 -0700 (MST)

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.


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