Mobile communications system conforming to mobile IP, and home agent, mobile node and method used in the mobile communications system

A home agent used in a mobile communications system conforming to Mobile IP, wherein a mobile node belongs to the home agent, and the home agent has a global IP address that is a home address common to a plurality of mobile nodes, the home agent comprising:

• an interface unit configured to route a received packet according to a transfer table that includes a correspondence among a home address of the mobile node, a care of address of the mobile node, and a communication session identification number for identifying a communication session opened by an application of the mobile node, with respect to each of the plurality of mobile nodes, wherein a transfer destination of the received packet is identified by a combination of the care of address and the communication session identification number;
• and
• a location information management unit configured to manage the transfer table,
• wherein the transfer table is updated based on change information from the mobile node indicating that at least of the home address of the mobile node, the care of address of the mobile node and the communication session identification number is changed.

A mobile node used in a mobile communications system conforming to Mobile IP, wherein the mobile node belongs to a home agent having a global IP address that is a home address common to the mobile node and one or more of other mobile nodes, the mobile node comprising:

• an interface unit configured to send and receive a packet;
• a detection unit configured to detect a change in at least one of a home address of the mobile node, a care of address of the mobile node and a communication session identification number for identifying a communication session opened by an application of the mobile node, wherein the mobile node sends change information indicating the change detected by the detection unit to the home agent when the application generates a communication socket,
• wherein a packet transferred from the home agent according to a transfer table is received by the interface unit,
• wherein the transfer table includes a correspondence among the home address of the mobile node, the care of address of the mobile node, and the communication session identification number, with respect to each of a plurality of mobile nodes, and
• wherein a transfer destination of the packet is identified by a combination of the care of address and the communication session identification number.

A method used in a mobile communications system, conforming to Mobile IP, comprising:

• a home agent having a global IP address;
• and
• a mobile node belonging to the home agent,
• wherein the global IP address is a home address common to a plurality of mobile nodes,
• wherein the home agent prepares a transfer table,
• wherein the home agent routes a received packet according to the transfer table, wherein the transfer table includes a correspondence among a home address of the mobile node, a care of address of the mobile node, and a communication session identification number for identifying a communication session opened by an application of the mobile node, with respect to each of the plurality of mobile nodes, wherein a transfer destination of the received packet is identified by a combination of the care of address and the identification number,
• wherein the mobile node detects a change in at least one of the home address of the mobile node, the care of address of the mobile node and the communication session identification number, and sends change information indicating the change that is detected to the home agent, and
• wherein the home agent updates the transfer table according to the change information.