Abstract: A method quickly resuming a downlink service in a hard handover in a cellular mobile communication system. To provide the fast downlink service to an MS during a hard handover from an OBS to an NBS, the NBS receives handover user information from the OBS, and generates an MS temporary ID using the handover user information to identify the MS. If user data is generated for the MS before a connection is established for traffic transmission between the MS and the NBS, the NBS transmits the user data to the MS on an HCCH using the MS temporary ID.

Abstract: Disclosed is an apparatus for converting internet protocol addresses, including: an address allocating unit for allocating a first private IP address and a second private IP address of a first IP address format to a first terminal and a second terminal upon an access request of the first terminal; an address generating unit for generating a first public IP address of a second IP address format from a hardware address of the first terminal; an address acquiring unit for acquiring a second public IP address of the second IP address format corresponding to a domain name of the second terminal from a domain name server; a storing unit for storing a mapping table where the first private IP address and the second private IP address correspond respectively to the first public IP address and the second public IP address; and a control unit for providing the first private IP address and the second private IP address to the first terminal.