Patent ID: 7136362

Claim:
A method of operating a third generation mobile telecommunications system, in which packets, each having a source address and a destination address in its packet header, are addressed to a mobile node which is a user node having a home network and currently associated with a foreign network and which is communicating with a correspondent node which is another user node and has a correspondent node address, comprising the steps of setting up a home agent having a home agent address in the home network and allocating a Care of Address for the mobile node; receiving a packet at the home agent from the correspondent node, the packet having a packet header which includes the correspondent node address as the source address; and changing the packet header to change the source address from the correspondent node address to the home agent address, to change the destination address to the Care of Address, and to add a correspondent node identifier code, which identifies the correspondent node, and a mobile node identifier code, which identifies the mobile node.