poc session includes an identifier in order to notify that an answering subject is the poc box 1210 instead of the poc client b 1201 s 104 information on the identifier can be transmitted to the cf x 1000 first and then to other poc clients belonging to a conference in various message forms a method of transmitting the identifier information of the poc box service to each poc client may vary depending on a type of the session or participation in the session and may use a sip response signal or real time transport protocol rtp control protocol rtcp message s 105 and s 106 c 1 a detailed sdp mime message format of the sip message for transmitting the identifier information of the poc box service will be described below with reference to fig7 after receiving the 200 ok response from the pf b 1200 the cf x 1000 transmits a media burst control protocol mbcp granted and taken messages using a mbcp for managing a media burst s 107 s 108 s 109 and s 110 and thus a multimedia stream is transmitted s 111 and s 112 at this time only specific media can be transmitted to the poc box 1210 according the setting of the poc client if the media type set by the poc client is audio the audio is stored in the poc box 1210 if both audio.