| With the development of the Next Generation Network technology, VoIP as a network service has become the most promising technology. VoIP is a service for sending voice, video and data communications over the Internet based on packet switch technology, which can meet various requirements of the people. The realization of VoIP system involves a series of questions, such as: the voice compression coding, the signaling dispatch, passing through NAT and firewall and so on. This dissertation takes the project of VcomOffice2008 video conference of DaLian vcomb Digital Technology Co.Ltd as a background, takes on the basis of the core protocol of session initial protocol in NGN. We design a VoIP communication module which is set into VcomOffice2008.This dissertation is focus on the VoIP technology, introduces SIP and SDP protocol knowledge, compares analysis between the SIP protocol and the H.323 protocol, analyzes the reasons why we select SIP and the advantages of selecting the SIP as the signaling dispatch. It analyses the architecture and network levels of NGN. This dissertation analyzes the VoIP architecture based on its technology. It provides VoIP system module in NGN, designs the SIP server module in VoIP. At NGN, this dissertation designed a software solution to the problem through NAT. In the realization of passing through NAT module, it analyzes the STUN protocol, designs modules of identifying NAT styles. It is an important point that we select the revising SIP and SDP message as the traversal's basis to implement pure software passing through NAT. It not only provides the rate of successful traversing NAT, but also saves the resources. It suits for the application of NGN.Finally, the dissertation has been tested for the system, compared with the current system. the designed system has basically been able to complete the expected functionality. At last, the dissertation did the summary to the full text in the conclusion part, and point out a direction with next subject. |
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