VoIP is a technology that mostly utilized in IP phone, and relevant value-added services. The most advantage of VoIP is that can make use of the global IP internetworking environment, to provide the more and more、the better and better services than tradition PSTN network. The IP phone using VoIP technology is the result of the combination of such chief technology, the packet technology on network taking IP as its sign, and the integrating technique of services on network taking real-time media transmission ...