| 摘要 |
The present invention relates to a system having a mobile host ( 1 ) which can attach to different access networks ( 3 A, 3 B) for carrying on an active communications session with a correspondent host ( 2 ). The mobile host ( 1 ) has an identifier (NAI) which is independent of the access network ( 3 A, 3 B) to which the mobile host ( 1 ) is attached, but is assigned a communication address(IP Address) for carrying on an active communications session with a correspondent host ( 2 ), which address changes for example depending on the access network ( 3 A, 3 B) to which the mobile host ( 1 ) is attached. The system has a database (UNS User Name Service) which registers the association of the mobile host identifier (NAI) and the current communications address (IP address) of the mobile host ( 1 ). The correspondent host ( 2 ) is informed of the identifier (NAI) of the mobile host ( 1 ) when an active communications session is first established between the mobile host ( 1 ) and the correspondent host ( 2 ), and the correspondent host ( 2 ) accesses the database (UNS) to determine the current communications address of the mobile host ( 1 ). In accordance with the present invention, the mobile host ( 1 ) is engaged in an active communications session: detects when the communications address (IP address) of the mobile host ( 1 ) changes, for example as a result of attachment of the mobile host ( 1 ) to a different access network ( 3 A, 3 B): and upon detection of such a change of the communications address (IP address), sends a message (HANDOVER MESSAGE) to the recorded correspondent host ( 2 ), the message containing the mobile host's ( 1 ) identifier (NAI). The correspondent host ( 2 ) then uses the identifier (NAI) to access the database (UNS) to obtain the changed communications address (IP address) of the mobile host ( 1 ). The invention also provides related methods and mobile hosts.
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