Patent ID: 6937590

Claim:
A method for supporting small group multicast in mobile IP in a mobile IP environment including a plurality of mobile nodes, a home network to which the mobile nodes belong, a home agent that is a router recognizing the current connection point of a mobile nodes on the home network to tunnel packets coming into the mobile node, a foreign network meaning a communication network other than the home network, a visited network meaning a foreign network to which the mobile node is currently being connected, a foreign agent corresponding to a router providing routing service on the visited network, and a care-of address meaning the end point of a tunnel toward the mobile node when the mobile node resides on the foreign network, wherein, in case where the home agent receives an implicit multicast packet to be transmitted to the mobile node belonging to the foreign agent, the home agent shifts the received multicast packet to an explicit multicast packet including the IP address of the mobile node registered as a receiving part of the multicast packet to transmit it to the care-of address, and in case where the home agent receives an explicit multicast packet to be transmitted to the mobile node belonging to the foreign agent, the home agent sends the multicast packet according to the care-of address shown in the received multicast packet.