Method and system for transferring data in mobile IP

A method of transferring data in mobile IP of the present invention comprises the steps of: causing the home agent(HA) to store as a care-of-address of the mobile host (MH) an address of the foreign agent (FA) received from MH; causing a DNS server in the home network (HN) to demand the care-of-address of MH from HA in response to the request of the communication terminal about the IP address and the care-of-address of MH; causing HA to provide the DNS server with the care-of-address of MH upon receiving the demand; and causing the DNS server to deliver the IP address and the care-of-address of MH to the communication terminal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a block diagram showing an arrangement of a communications network for embodying the present invention. FIG. 2 is a diagram of a communication sequence according to the present invention. MH which has been moved from HN to FN demands to register the mobile IP of FA when MH found FA. In response, FA accepts and transfers the registration response of the mobile IP to HA. HA provides FA the registration response of the mobile IP corresponding to the registration request of the mobile IP from FA. The packet for the registration response of the mobile IP is then received by FA and transferred to MH. This allows HA to acknowledge COA of MH. When the communication terminal A supporting the route optimization wants to transfer the data to MH in FN, the following steps 1 to 6 are carried out. Step 1: The communication terminal A requests of a DNS server in HN the IP address of MT1.HOME1.com which is a domain name (FQDN) of MH and the IP address of FA or COA of MH. Step 2: In response, the DNS server requests of HA COA of MH. Step 3: HA provides the DNS server with FA 0 which is the IP address of FA as COA of MH. Step 4: The DNS server provides GA 1 as the IP address of MH and FA 0 as COA of MH. Step 5: The communication terminal A encapsulates the data to be transferred and GA 1 (the IP address of MH) with an IP packet of which the address is FA 0 and sends it out. Step 6: FA extracts the IP packet from its encapsulated form and delivers it to MH. According to this embodiment, HN needs not to transfer the data received from the communication terminal A to FN, hence allowing HA to handle less load of the data processing in mobile IP. Also, the transfer of data from the communication terminal A to MH is carried out directly from the beginning and its route will be always shortest. For registration of COA of MH, HA provides the DNS server with a TTL (time to live) indicative of a predetermined life time(expiration time). The DNS server stores the IP address of COA in a cache up to TTL. If the communication terminal A employs no route optimization, the encapsulation of data is disabled. Accordingly, COA is not stored in ARR (address resource record) but in other RRs such as TXT RR and used by only a communication terminal supporting the route optimization. This allows any communication terminal not supporting the route optimization to transfer data to GA 1 as the destination address in the conventional manner. The advantages of the present invention are as follows: (1) The home network needs not to transfer data received from a communication terminal to a foreign network, hence allowing HA to handle less load of the data transfer in mobile IP. (2) The data transfer from communication terminal to MH is carried out directly from the beginning and its route can be always shortest.