Patent ID: 8886923

Claim:
A system comprising: a multi-mode device; and a Mobile Internet Protocol (Mobile IP) home agent having a public IP address, wherein the Mobile IP home agent comprises a virtual-private-network (VPN) function co-located at the public IP address; wherein the multi-mode device communicates with the Mobile IP home agent at the Mobile IP home agent's public IP address to establish a VPN tunnel extending between the multi-mode device and the Mobile IP home agent, wherein the multi-mode device receives from the Mobile IP home agent an assignment of a given public IP address for the multi-mode device to use in communicating with the Mobile IP home agent via the VPN tunnel; wherein the multi-mode device thereafter conducts a Mobile IP registration with the Mobile IP home agent via the VPN tunnel, including (i) sending to the Mobile IP home agent via the VPN tunnel a Mobile IP registration request having a source IP address equal to the given public IP address that the Mobile IP home agent had assigned to the multi-mode device to use in communicating with the Mobile IP home agent via the VPN tunnel, and (ii) receiving from the Mobile IP home agent via the VPN tunnel a Mobile IP registration reply having a destination IP address equal to the given public IP address that the Mobile IP home agent had assigned to the multi-mode device to use in communicating with the Mobile IP home agent via the VPN tunnel, the received Mobile IP registration reply further specifying as a Mobile IP home address of the multi-mode device the same given public IP address, established as the Mobile IP home address for the multi-mode device; and wherein the multi-mode device thereafter exchanges encrypted packets with the Mobile IP home agent inside the VPN tunnel, wherein the encrypted packets do not include separate IP headers for (i) the VPN tunnel and (ii) Mobile IP communication.