This has been the most unforgettable experience of my diplomatic career. A window of reform and opening-up, China-Singap......

基于会话发起协议（SIP）的IP网上话音（VoIP）具有诸多优势，目前发展较快，大有取代传统电话网络（PSTN）的趋势。然而，VoIP服务在可靠性和安全性......