VNC Fails through a VPN router on Windows 98

Moderator: stephen

VNC Fails through a VPN router on Windows 98

Postby stephen » Sun Oct 05, 2008 8:01 pm

I have a Windows 98 PC with VNC Installed.
I can remotely connect to the PC from the internal LAN
However when trying to connect remotely over a VPN
I can get to the password prompt, enter the password, press OK. but the screen display does not happen.

you can use the
netstat -s
command to view the TCP parameters

this problem is discussed here
maybe tcp/ip stack issue with size of packet too big
try dr tcp,139023769,139146171,00.htm
Quoted from above web site
You'll make the changes in the system registry. Start the Registry Editor by selecting Run from the Start menu, typing regedit in the Open text box, and clicking OK. When the Registry Editor opens, navigate through the left pane until you get to the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP\Parameters key. In the right pane, look for the value named GlobalMaxTCPWindoSize.

If the value exists, it's probably set to 1500, which is the default value for the key. To change the value, double-click it. You'll then see the Edit String screen. Enter the value of that you found out was best through your ping tests above in the Value Data field and click OK.

If the value doesn't exist, you'll need to add it. Select New | String Value from the Edit menu. The new value will appear in the right pane, prompting you for a value name. Type GlobalMaxTCPWindoSize and press [Enter].

Double-click the new value. You'll then see the Edit String screen. Enter a new value in the Value Data field and click OK. When you're done, close Regedit. Your registry changes will be saved automatically. Reboot your workstation.

LAN = MTU 1500
WAN = MTU 1500 if ADSL PPP over ATM (PPPoA)
WAN = MTU 1492 if ADSL PPP over Ethernet (PPPoE)
VPN = MTU 1492 or less depend of the VPN and encapsulation
1300 (in bytes)

The choice recommended for both straight IPSec and IPSec through NAT. Using this value guarantees that the client does not fragment packets under normal circumstances.

I think the problem is related to the TCP-IP MTU Packet Size and packet fragmentation

This site has tips on changing the MTU Size in Windows 98
manually changing the MaxMTU in Windows 98

HKEY_LOCAL_MACHINE HKEY_LOCAL_MACHINE System CurrentControlSet Services Class NetTrans

This site has some tips on getting VNC working through a Linksys router
can't get vnc to work, with lynksys router

This site has some net Tools that may help diagnose the problem.
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