Patent ID: 7464177

Claim:
A mobile network that is a first subnet that partially constitutes multiple IP networks, said mobile network comprising: a home agent server configured to manage identifiers of a plurality of mobile terminals, each of which is joined to said mobile network; a plurality of IP tunnel routers that include a first IP tunnel router connecting said mobile network to a network having a correspondent node and a second IP tunnel router connecting the mobile network to a second subnet that partially constitutes said multiple IP networks; and at least one buffer for temporarily storing IP packets, wherein when a mobile terminal of the plurality of mobile terminals moves to the second subnet, said home agent server is configured to accept destination information necessary for transmission of IP packets to said mobile terminal from said mobile terminal, and deliver IP tunnel setting information indicating said mobile terminal and said destination information to said plurality of IP tunnel routers, when the first IP tunnel router receives an IP packet from the correspondent node destined for said mobile terminal, said first IP tunnel router is configured to transfer said IP packet to said mobile terminal via said second IP tunnel router based on said IP tunnel setting information without transferring said IP packet to said home agent server, and when recognizing an occurrence of a handoff of said mobile terminal, said home agent server is configured to control each of said plurality of IP tunnel routers and said buffer so that each of said plurality of IP tunnel routers stores received IP packets destined for said mobile terminal in said buffer, when recognizing completion of the handoff of said mobile terminal, said home agent server is configured to control said buffer so that said buffer transfers the IP packets stored therein to said mobile terminal, and, when then receiving an IP packet destined for said mobile terminal, said home agent server is configured to control each of said IP tunnel routers so that each of said IP tunnel routers transfers the IP packet to said mobile terminal based on the IP tunnel setting information without transferring the IP packet to said home agent server.