The diagram shows your network. Host X behind gateway A want to initiate a connection with a host Y machine behind gateway B. Gateway A cannot establish a VPN tunnel with gateway B directly due to political reason. Gateways A and B can only establish VPN tunnels with gateway C.
This configuration is known as what?

A.
Domain Based VPN

B.
Route Based VPN

C.
vpn_route.conf

D.
VPN Routing

E.
IP VPN Routing