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Connecting to a Remote Computer
Virtual Private Network - Remote Desktop Protocol
Note: you must have Remote Desktop enabled on the remote computer.
CP>System>Remote and have VPN configured on the remote device you are dialing
i.e. a VPN enabled router or a Remote Access Server (with the router set to pass
through VPN connections - ports 1701,1723,47)
- In 'Network Connections' create a new connection selecting the VPN option in
the wizard.
- Make sure you are connected to the Internet then dial this connection. You
should now be able to access your remote computer.
- After you have a connection to the remote computer start the Remote Desktop
session. Go to Start>Programs>Accessories>Communications>Remote Desktop. Enter
the details of your remote computer then connect.
- You will see the remote desktop as if you were sitting in front of it and be
able to do everything on the remote computer.
Known Problem
Connects and then drops within 15 seconds.
FIX
Depending on the route taken to get to the gateway, there may or may not be
"black-hole" routers in the path. The solution was to add two registry keys to
the Windows XP box (These keys should be valid all the way back to NT 3.51).
The keys should be added to...
HKEY LOCAL MACHINE\System\Current control set\Services\Tcpip\Parameters then
follow the details below.
Add -
Value Type: REG_DWORD - Boolean
Key Name: EnablePMTUBHDetect
Valid Range: 0,1 (False, True)
Set To: 1
Description: Setting this parameter to 1 (True) causes TCP to try to detect
"Black Hole" routers while doing Path MTU Discovery. A "Black Hole" router does
not return ICMP Destination Unreachable messages when it needs to fragment an IP
datagram with the Don't Fragment bit set. TCP depends on receiving these
messages to perform Path MTU Discovery. With this feature enabled, TCP will try
to send segments without the Don't Fragment bit set if several retransmissions
of a segment go unacknowledged. If the segment is acknowledged as a result, the
MSS will be decreased and the Don't Fragment bit will be set in future packets
on the connection. Enabling black hole detection increases the maximum number of
retransmissions performed for a given segment.
Value Type: REG_DWORD - Boolean
Key Name: EnablePMTUDiscovery
Valid Range: 0,1 (False, True)
Set To: 1
Description: Setting this parameter to 1 (True) causes TCP to attempt to
discover the Maximum Transmission Unit (MTU or largest packet size) over the
path to a remote host. By discovering the Path MTU and limiting TCP segments to
this size, TCP can eliminate fragmentation at routers along the path that
connect networks with different MTUs. Fragmentation adversely affects TCP
throughput and network congestion. Setting this parameter to 0 causes an MTU of
576 bytes to be used for all connections that are not to computers on the local
subnet.
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