| To succeed in the telecom market, the service provider must reduce the cost of construction and maintain as the competition of the telecom market is getting fiercer~[1]. This kind of pressure makes the Next Generation Network become the hot topic of research. As the next generation telecom switch equipment, the Softswitch is based on the VoIP technique, which makes the PSTN and Internet united to TCP/IP. The telecommunication based on Internet, respresented by VoIP, is facing a good opportunity for development as a typical type of Broad-Band application. In respect of VoIP technique and standard, SIP becomes the dominating protocol because SIP is more opening, easier to extend, closer to Internet than the other protocols such as H.323 and MGCP. After many years of development since SIP was first proposed in 1999, SIP has become mature. People in telecom industry have formed the view that the SIP product will dominate the future market of VoIP.~[2]On the other hand, with the construction of international information highway, the development of Internet, the popularity of Internet and the tempestuously increase of the number of computer, the traditional frame of the address of TCP/IP protocol architecture and the strategy of address distribution is not fit to the development of Internet. The address based on 32-bits is going to be used up, which prevents the development of Internet. According to the traditional strategy of address distribution, each computer will get an unique IP address. But some computers seldom connect to Internet. At the same time, some companies and organization applied more IP addresses for... |
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