Patent ID: 7805519

Claim:
A method for scaling a display size between different types of user agents by using a session initiation protocol, the method comprising: exchanging session initiation protocol messages, including media information when performing a call setup for setting up a media session, between the user agents; determining one of the user agents to scale the display size, in response to the exchanged media information; scaling, by the determined user agent, the display size on the basis of the media information, and sending video data subject to the scaling to the other user agent; the media information includes at least one of a type of media intended for communication, a display standard of the user agent sending the media information, and performance of a central processing, unit of the user agent sending the media information, the step of determining one of the user agents to scale the display size includes: determining, by a user agent server receiving an INVITE message from a user agent client, whether the type of the media included in the media information is processable at the user agent server; as a result of the determination, if the type of the media included in the media information is processable at the user agent server, comparing the display size and the performance of the central processing unit of the user agent server with the display size and the performance of the central processing unit of the user agent client, respectively, and differently setting a value of a scaling 13 flag parameter based on a result of the comparison; sending, by the user agent server, the scaling 13 flag parameter to the user agent client, the scaling 13 flag parameter being included in a service description protocol of a Response message; and if it is determined from the value of the scaling 13 flag parameter that the user agent server and the user agent client have different display sizes, scaling the display size on the user agent side where the performance of the central processing unit is better.