VPN and Livebox

I am trying for several days to configure a VPN between my home and and another person.

At the other person is the VPN server running Windows Server 2000. The Internet connection is through a Livebox Inventel.

For my part I am trying to connect from a Windows XP Pro.

The connection among the local person is going very well. So the VPN server running smoothly. As against the connection from outside does not.

In part the Livebox router, I well forward on TCP port 1723 to the VPN server. Only by looking on the net I found contradictory information about how the Livebox would not VPN connections. But the Technical Service (Orange to present) I confirm that the VPN connection is possible, without giving me more details.

Could someone help me or simply resolve the issue by saying it is not possible with a Livebox.

VPN connection with LiveBox is possible.
Check the configuration LiveBox:
The following communication ports and protocols must be opened in the firewall (if a firewall is implemented on ADSL router):
ISAKMP: UDP port 500 (incoming1 and outgoing2)
ESP: IP protocol 50 (incoming1 and outgoing2)
Encapsulated ESP: UDP port 1972 (incoming1 and outgoing2)
HTTPS: TCP port 443 (outgoing2)

Thanks for your solution but how are you doing to inform the ESP protocol in the firewall of Livebox Inventel knowing it only offers TCP and UDP?