Patent ID: 7149225

Claim:
A method in an IPv6 mobile node, the method including: first generating a tag that uniquely identifies the IPv6 mobile node to an IPv6 gateway having an IPv4 gateway address and an IPv6 gateway address, the IPv6 gateway configured for transferring packets between an IPv4 network via the corresponding IPv4 gateway address and an IPv6 network; second generating a first IPv6 packet that specifies a request for a valid IPv6 care-of address that is reachable in the IPv6 network via the IPv6 gateway, the first IPv6 packet having an IPv6 source address field that specifies the tag and an IPv6 destination address field that specifies the IPv6 gateway address; first encapsulating the first IPv6 packet in a first IPv4 packet having an IPv4 header including a destination address field that specifies the IPv4 gateway address, a source address field specifying a mobile node IPv4 address for the IPv6 mobile node, and a transport header having a source port field specifying a prescribed transport layer port for the IPv6 mobile node, and a destination port field specifying a prescribed transport layer port for the IPv6 gateway used for identifying transfer of the IPv6 packet between the IPv4 network and the IPv6 network; first outputting the first IPv4 packet carrying the first IPv6 packet to the IPv6 gateway via the IPv4 network; receiving a second IPv4 packet carrying a second IPv6 packet that indicates an acknowledgement by the IPv6 gateway for the valid IPv6 care-of address; third generating a third IPv6 packet for a destination node reachable via the IPv6 network; second encapsulating the third IPv6 packet in a third IPv4 packet having the IPv4 header; and second outputting the third IPv4 packet onto the IPv4 network for transfer of the third IPv6 packet onto the IPv6 network by the IPv6 gateway.