| 摘要 |
PURPOSE: A method for controlling a media channel by an SIP server and a communication system for implementing the same are provided to prevent illegal media transmission by taking a media flowing between user agents to re-transmit it and forcibly terminate the media when charging is terminated. CONSTITUTION: A UAC(User Agent Client)(201) transmits an invite message including an SDP to SIP server(210). The SIP server(210) changes address/port information of the SDP to its address and port information. The SIP server transmits the invite message including the changed SDP to a UAS(User Agent Server)(202). The UAS(202) receives the changed invite message. The UAS transfers a 2000K message including the SDP to the SIP server(210). The SIP server changes address/port information of the SDP to its address and port information. The SIP transmits the invite message including the changed SDP to the UAC(201). The UAC(201) receives the 2000K message. When the UAS(202) desires to transmit a media to the UAC(201), the UAS(202) first transmits the media to the address and port of the SIP server(210), and then, the SIP server(210) transmits the media to the original SDP address and port. When the UAC(201) or the UAS(202) transmits a bye message to the SIP server(210), the SIP server(210) closes its media port to cut off the flow of the media.
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