Research And Implementation Of NAT Traversal Technology Based On ICE

With the rapid development of the Internet, users’ demand for Internet-based applications continues to grow, and it is not uncommon that one Internet user has multiple network devices. However, the IP address space is limited, which cannot satisfy the large volume of networked devices. Although the emergence of NAT effectively alleviates the IP address shortage problem, it restricts the usage of peer-to-peer applications. Therefore, NAT traversal technology becomes extremely important. At present, there are various NAT traversal solutions suitable for different NATed environment, which are hard to fit all the diverse NATed environment. Therefore, a universal and standardized solution to NAT traversal is of important and practical significance.The Interactive Connectivity Establishment (ICE for short) technology takes the advantages of all the other kinds of NAT traversal technologies, which is suitable to nearly all NATed environment and is feasible and scalable. However, in the description of ICE’s NAT traversal algorithm, the RFC document does not define how to exchange SDPs (Session Description Protocol) that embed candidate addresses.According to the issue mentioned above, firstly, this thesis analyzes the main approaches to solve the NAT traversal problems in different NATed environment in detail, focusing on the client-based approaches.Next, this thesis mainly discusses how to integrate SIP and ICE to realize a complete NAT traversal solution, which is not covered in RFC5245. Both the theory and detailed design are presented.Finally, the NAT traversal system based on SIP and ICE is implemented using the PJSIP library, and deployed and tested in a laboratory environment. The testing result shows that the system can cope with nearly all types of NATed environment.