Re: Dropped Connections

Thu, 28 Feb 2008 09:00:49 -0800 

the stations mtu typically need to be smaller then the vpn

so the data packet fits within the transmitted ethernet packet


Trace Carpenter wrote:
OK, I think I understand where the confusion came in now. I see that you mean that both stations need to have the same MTU sizes, but does the VPN MTU need to be 100 bytes smaller than the PPP MTU on both stations? Oh and one last question. The Sonicwall defaults to an MTU size of 1500. Does that enter into the equation when I set the sizes on the workstations? Thanks again. 

--
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
[EMAIL PROTECTED]
www.tracecarpenter.com
www.carpenter-group.com


> Date: Thu, 28 Feb 2008 12:45:22 -0400
> From: [EMAIL PROTECTED]
> To: [EMAIL PROTECTED]; vnc-list@realvnc.com
> Subject: Re: Dropped Connections
>
> 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
> > [EMAIL PROTECTED]
> > www.tracecarpenter.com
> > www.carpenter-group.com
> >
> >
> > > Date: Thu, 28 Feb 2008 11:31:52 -0400
> > > From: [EMAIL PROTECTED]
> > > To: [EMAIL PROTECTED]; vnc-list@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: [EMAIL PROTECTED]
> > > > To: [EMAIL PROTECTED]
> > > > CC: vnc-list@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: [EMAIL PROTECTED]
> > > > > > To: [EMAIL PROTECTED]; vnc-list@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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