Application Research And Design Of H.323 In Softswitch

Along with the development of Voice over IP technology, the trend of circuit switching network evolving into packet switching network is obvious. As one of the pioneers in VoIP field, H.323 has become the most widely used VoIP protocol and the carriers have invested a lot on H.323 IP telephony. In the long-term evolution into next generation network, the investment shall be protected and the softswitch, which is the core device of next generation network, shall be compatible with the traditional circuit switching network and the H.323 IP telephony network. With the fast development of internet, Session Initial Protocol (SIP), as a VoIP protocol, has been popular in recent years. The interworking between H.323 and SIP should also be considered. The coexisting of PSTN, H.323 IP telephony network, SIP network is the real circumstance and the interworking between them is important.Beginning with the introduction of VoIP development status, the development trend of VoIP is analyzed. Then the architecture, the functions, the protocols, the applications, and the evolution strategy of softswitch and NGN is discussed. The application of softswitch in UMTS is also introduced. Then the architecture of H.323 system, the necessity and feasibility of implementing H.323 in softswitch, and the address resolution of interworking between SIP and H.323 are studied.With the research project of small to middle capacity softswitch, the application of H.323 in softswitch is analyzed and the design of H.323 module in call server is given, which includes functions classification, interface design, finite state machine implementation, data structure design, multi-protocol interworking design. As a result of the implementation of this design, the call server can provide interworking function between H.323 network and other major networks such as softswitch network, PSTN/ISDN, H.248 user network, SIP network.As the next focus of this research project, the design of the softswitch high-availability (HA) and the address resolution server are discussed.