Patent ID: 7406064

Claim:
A communication system including a plurality of packet routers and a server connected over a network to first and second terminals, wherein the server includes a memory for storing the match between the address in the home network and the address of the movement destination of the terminal managed by the server itself, and at least one packet router among the plurality of packet routers includes: a transmit section for sending to a first terminal, information on a network where at least one other router among the plurality of packet routers is connected, and information on the network where its own packet router is connected, and the first terminal includes a transmit section to send two care-of addresses generated respectively from information on a network connected to the first packet router and information on a network connected to another packet router, and the server or the second terminal that has received the two care-of addresses includes: a transmit section to send packets with duplicate contents to the two care-of addresses that have been received.