Video communication is being popular by spreading broadband networks. Realization of this kind of communications is important to deploy IPv6. However, many almost of commercial videoconference systems do not work in IPv6 networks. We developed an application gateway called as “PTGATE” to extend available scenes of videoconferences. PTGATE has three functions: IPv4 over IPv6 tunneling to use videoconference systems for IPv4, multicast tunneling over unicast networks, and error recovery using FEC. By using PTGATE, the current resources of videoconferences correspond to various network environments. In this paper, we describe the overview of PTGATE and its evaluation. Also, we show practical experiments of PTGATE using actual networks.