Dropped Connections

[Alex Pelts]

Most likely you VPN MTU does not match your network MTU. VPN MTU has to 
be smaller than network MTU by enough bytes so VPN packet is not 
fragmented. VNC seems to transmit in large packets which are fragmented 
and VPN packet is spit to 2 Ethernet packets. This causing VPN packet to 
be dropped and connection becomes very bad.

Decrease you VPN MTU to the point that this will stop happening. Usually 
  around 100 bytes smaller than regular MTU. IF 100 bytes does not help 
keep decreasing in 10 bytes decrements.

Alex


Trace Carpenter wrote:
> For years I've been battling a problem that no one seems to be able to solve.
> 
> When using RealVNC we commonly encounter a dropped connection with the error
> message "Connection reset by peer (10054)."  When testing with TightVNC the
> error still occurs, but he message displayed by that program is "Error waiting
> for server message."
> 
> According to much of what has been written by James Weatherall, the problem is
> usually attributed to a lack of bandwidth and it is suggested that a rate
> limit on mouse pointers be inacted. In our case, we commonly see it when going
> across a 100Mbps LAN at all three of our locations and when transversing a VPN
> tunnel between the LANS.  The VPN tunnel is a dedicated tunnel running between
> Sonicwall TZ170s and the pipe between the locations are T-1 so bandwidth seems
> to be an unlikely culprit.
> 
> In a testing situation I have often left VNC sessions open for >24 Hours which
> have been stable when no one is using either computer.  The problem seems to
> occur most often when you have a session going between your workstation and a
> remote server, AND you are working on other things at the same time.  For
> example, while working on the remote machine you open another window on your
> local machine to enter some data and then go back to the remote machine
> window.  It is at that time you will see the failure.
> 
> All machines are current class machines running at least 1.5 Gigs of memory
> and Windows XP Professional.
> 
> There seem to be a few other threads with this exact same problem that have
> been tested in the same manner and have gotten the same error messages from
> the different VNC flavors, but I have yet to find a response to their request.
> Hopefully I've included enough details to help resolve this.
> 
> Any insight would be greatly appreciated.
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