软交换是下一代网络中的核心技术,SIP协议作为下一代网络最重要的协议之一,已经被广泛应用于VoIP系统中。 SIP协议无法支持SIP信令和媒体流的NAT穿越,从而限制了其在广域网上的应用和发展。虽然目前解决NAT穿越的方案已经很多,但都存在着一定的局限性。文中详细解释了NAT对SIP通信的影响,介绍了UDP打洞技术的基本原理,介绍了UDP打洞技术穿越锥形NAT的流程,以及Http代理网关方式穿越各种NAT的流程。文中通过比较各种NAT穿越方案的优缺点,提出一种综合UDP打洞与Http代理网关的NAT穿越方案。经过论证与实验,证明了该方案的可行性。%Soft switch is the core technology of next generation network. SIP protocol as one of the most important protocols in the next generation network,has been widely used in VoIP systems. SIP protocol can’ t support SIP signaling and media stream through NAT, which limits its application and development in the WAN. Although there are many NAT traversal solutions,every solution has limita-tions. In this paper,explain the impact of NAT on the SIP communication in detail,introduce the basic principle of UDP hole punching technology,the process of using UDP hole punching through the cone NAT and using the Http proxy gateway through various NAT. Compared the advantages and disadvantages of various NAT traversal solutions,present a NAT traversal solution which integrates UDP hole punching and Http proxy gateway technology. After the argument and experiment,it proves the scheme is feasibile.
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