A VoIP system for mobility voice security support using the VPN

Voice over internet protocol (VoIP) provided voice service using Internet. It receives footlights when it escapes an initial curiosity. Interest to VoIP increased, because it can transfer existing phone service and deliver voice data through Internet technology. Communication service providers introduce Next Generation Network and Broadband convergence Network with VoIP as an added service to the consumer. In addition, session initiation protocol (SIP) service can be applied even outside the Internet phone service. However, it is needed to ensure secrecy of VoIP call in a special situation. It is relatively difficult to eavesdrop in the commonly used Public Switched Telephone Network (PSTN) as it is connected with 1:1 circuit. In this paper, we propose a new model of Internet telephone for eavesdrop prevention enabling VoIP (using SIP protocol) to use the virtual private network (VPN) protocol and establish the probability of practical use comparing it with Internet telephone.