IMS CSCF Design And Reaserach On S-CSCF Selection

3G IP Multimedia Subsystem (IMS) is an essential part of the core network in the 3rd Generation mobile communication's scope. IMS is supposed to implement the integration of multimedia services such like voice, video, message and data, the integration of multiple wireless access of 2G , 3G or WLAN, and the integration of mobile communication and traditional fixed communication including telephony and internet. CSCF is one of the most important functional entities among those, and take the responsibility of processing signaling messages for controlling the user's multimedia session.I-CSCF is one category of CSCF which is defined as the contact point of multiple operator domains. The core function of I-CSCF is the S-CSCF selection function. In abnormal cases S-CSCF reselection procedure will be done. The recognition mechanism of initial registration is the very related issue to a valid S-CSCF selection. Since there is no such effective mechanism in the early IMS security as in the fully compliant IMS security, and the fact of invalid S-CSCF reselection procedure's consequence of invalid authentication, 3GPP now restricts that the S-CSCF reseletion can't be used in the early IMS security. However, this restriction will lead to some great problems of service reliability.After briefly introduced the background, basic concepts, network architecture, essential protocols of IMS and the authentication mechanism of IMS security, this paper mainly introduced an generic function structure design of CSCFs; made an analysis of the S-CSCF selection function of I-CSCF; and then gave an example of I-CSCF design based on a security architecture which is different from fully compliant IMS security and early IMS security, while taking effectively, safety and efficiency into account. This paper also descoveryed a bug of initial registration recognition in fully compliant IMS security, meanwhile introduced and compared several alternative methods which are pushing...