Patent ID: 7817649

Claim:
A method of performing a session based communication by a mobile terminal that operates as an inviter and an invitee of a SIP (Session Initiation Protocol) session, the method comprising: when the mobile terminal operates as the inviter of a first SIP session, sending a first session invitation message to an invitee mobile terminal through use of a SIP method via a server, the first session invitation message including at least one reason for the session invitation as description information and is used for establishing the first SIP session with the invitee mobile terminal via the server, receiving a response from the invitee mobile terminal that accepted the first session invitation message as a result of considering the description information, establishing the first SIP session with the invitee mobile terminal, and transmitting multimedia data to the invitee mobile terminal using real-time transport protocol (RTP) through the established first SIP session, wherein the description information is included in a SIP header or SIP body of the first session invitation message, and the description information is in the form of text; and when the mobile terminal operates as the invitee of a second SIP session, receiving a second session invitation message from an inviter mobile terminal through use of a SIP method via a server, the second session invitation message including description information and is used for establishing the second SIP session with the invitee mobile terminal via the server, sending a response to the inviter mobile terminal that sent the second session invitation message as a result of considering the description information, establishing the second SIP session with the inviter mobile terminal, and receiving multimedia data from the inviter mobile terminal using RTP through the established second SIP session, wherein the description information is included in a SIP header or SIP body of the second session invitation message, and the description information is in the form of text.