| 摘要 |
A PTW (Push To Watch) server inside an IMS platform implements a SIP-based protocol to deliver real time media streaming contents inside a PLMN coverage area. The PTW server adopts alternative use and definition of the SIP MESSAGE request and a new mimic for the interaction scheme. Three different labels, respectively named: refer, ok, and bye are introduced in the header field "subject" of SIP MESSAGE to notify type and destination of the body content Three corresponding SIP MESSAGE(refer), SIP MESSAGE(ok), and SIP MESSAGE(bye) are used in the involved procedures. In "Session establishment procedure" the PTW server receives the INVITE request message from the inviter user and sends in correspondence as many SIP INVITE request messages as the number of the invited users each containing a list including the Public user identity of each user already in the session except the inviting. Then, based on the responses from the invited users, the PTW server sends to the inviter user as many MESSAGE(refer) as the number of invited users carrying in the body content the respective responses (e.g.: invited accepted or denied), and contemporarily sends to each invited user which has accepted the invite a MESSAGE(ok) containing in the body a list including the public user identity of each invited user that has accepted, except the recipient. The "Add user procedure" is quite similar to the preceding one but instead of INVITE the PTW server receives a REFER from an user which intends to add new users. In "Leaving session procedure" the PTW server receives the BYE request message from an user that intends to leave the session and sends in correspondence as many SIP MESSAGE(bye) to all the remaining participants; each message contains in the body content a list including the public identity of each participant which has left the session
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