Dropped Connections

Thu Feb 28 16:46:01 2008

no
 having two stations with differing MTU
or automatic MTU calculation on either side of a vpn
can cause issues


Trace Carpenter wrote:
> You mentioned a "mismatched" MTU will cause problems.  Everything else 
> I've seeing says that the VPN MTU should be at least 100 bytes less 
> than the PPP MTU.  Are you saying that is incorrect and that they 
> should be the same?  Right now there are no registry entries below the 
> HKLM\SYSTEM\CurrentControlSet\Services\Parameters\ location, so they 
> would all have to be created. 
>  
> Thanks again for all your insight.
>
> --
> Trace Carpenter
> The Carpenter Group
> 445 E. FM1382, Ste. 3-373
> Cedar Hill, Texas 75104
> 972.617.7131 Main Line
> 972.617.9210 Private/Direct Line
> mail "at" tracecarpenter.com
> www.tracecarpenter.com
> www.carpenter-group.com
>
>
> > Date: Thu, 28 Feb 2008 11:31:52 -0400
> > From: edranem "at" dranem.org
> > To: carpenter_trace "at" hotmail.com; vnc-list "at" realvnc.com
> > Subject: Re: Dropped Connections
> >
> > yes that is likely the culprit
> > a mismatched MTU will cause drops and black screens and pauses
> >
> > data packet sent fragmentation issue
> > transaction never completes
> >
> >
> > steve
> > I wondered about that when I saw this:
> >
> > 
> http://support.microsoft.com/default.aspx?scid=kb;en-us;826159&Product=winxp 
>
> > 
> <http://support.microsoft.com/default.aspx?scid=kb;en-us;826159&Product=winxp>
> >
> > Is that what you're referring to? If so I suppose it would require that
> > we lay hands on every workstation in the organization all every 
> location.
> >
> >
> >
> > > Date: Thu, 28 Feb 2008 01:13:44 -0400
> > > From: edranem "at" dranem.org
> > > To: carpenter_trace "at" hotmail.com
> > > CC: vnc-list "at" realvnc.com
> > > Subject: Re: Dropped Connections
> > >
> > > it is a per station setting that needs to be adjusted
> > >
> > >
> > > Trace Carpenter wrote:
> > > > Thanks for the reply. Unfortunately Sonicwall doesn't have an option
> > > > to adjust the VPN MTU. The option is to enable Fragmented Packet
> > > > Handling. It has always been enabled and the "Ignore Don't Fragment
> > > > Bit" option is also checked.
> > > >
> > > >
> > > > > Date: Wed, 27 Feb 2008 19:07:54 -0400
> > > > > From: edranem "at" dranem.org
> > > > > To: carpenter_trace "at" hotmail.com; vnc-list "at" realvnc.com
> > > > > Subject: Re: Dropped Connections
> > > > >
> > > > > I have seen this due to non matching MTU settings
> > > > >
> > > > >
> > > > > 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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