Patent ID: 6904466

Claim:
A method of mobile communications between a mobile computer capable of carrying out communications while moving over inter-connected networks and a correspondent computer, the method comprising the steps of: transmitting a packet directly to the correspondent computer from the mobile computer located at a visited site network outside a home network of the mobile computer, by encapsulating an inner packet having a home address assigned to the mobile computer at the home network as a source address, within an outer packet having a current location address acquired at the visited site network as a source address; storing cryptosystem parameter information necessary in forming a tunnel for transferring an encapsulated packet by encrypting the inner packet, at the mobile computer and the correspondent computer; notifying a change of the current location address of the mobile computer directly from the mobile computer to the correspondent computer by setting a new current location address as the source address of the outer packet in the packet transmitted by the transmitting step; updating the current location address used as a termination endpoint address of the tunnel in the cryptosystem parameter information stored at the mobile computer into the new current location address, when the current location address is changed to the new current location address; managing source addresses of the outer packet and the inner packet of the encapsulated packet received directly from the mobile computer respectively as the current location address and the home address of the mobile computer at the correspondent computer; and updating the current location address used as a termination endpoint address of the tunnel in the cryptosystem parameter information stored at the correspondent computer into the new current location address, when the change of the current location address to the new current location address is notified from the mobile computer.