| In recent years, with the dramatic development of network and information technology, data and multimedia services have become more and more important, the integration of network and services has also become more and more urgent. Thus soflswitch technology has emerged. Many equipment manufacturers and operators support this technology, soffswitch product has become more mature and its performance has stabilized gradually.Meanwhile, the popularity of network application has also resulted in the shortage of IP address. Particularly, the shortage is serious in China. NAT technology is used to solve the problem through public and private IP address translation. A large number of enterprises and network service providers use this technology. To solve the problem of public network access to private network, a technology for NAT traversal must be used. Most of current NAT traversal algorithms depend on terminal equipments, so these algorithms can't solve the problem well. This thesis proposes the NAT traversal through proxy equipments to fix the deficiency.In this thesis, firstly we analyze the network structure and characteristics of the soffswitch system, then study the principle of NAT technology and its application in the field of security, finally analyze the traversal of a variety of NAT application networks, the advantages and disadvantages of other NAT traversal algorithms. For the characteristics of network equipments, we propose the NAT traversal through proxy equipments. In this project, we adopt the appropriate algorithm for different NAT application network, design an open structure to achieve the independence of services, and create a model called transparent traversal to avoid impacting the original network. Combining all the research results, we complete the NAT traversal system and integrate it with voice server of HUAWEI-3COM. Then we design a comprehensive test case for this system and test it. At last, the thesis points out the deficiencies and improvements of the design. |
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