自1995年以色列VocalTec公司推出"IPhone 1.0"開始，VoIP技術持續演進，百家爭鳴。如今網路頻寬大幅提昇，VoIP相關技術門檻也陸續被克服，IP電信應用服務也因而將成為網路服務提供業者之基本門檻。本所在IP電信領域累積多年的研發技術，同時持續充實VoIP佈建實務經驗，本文即以電信等級之網路電話系統為目標，先以剖析基本VoIP技術原理、系統服務元件、佈建架構以及相對應技術，再從實務經驗中，逐步分析、擴充既有之VoIP系統，以期讓自有之IP電信技術更進一步提升。

Ever since the first release of "IPhone 1.0" from the VocalTec, an Israel software company, in 1995, VoIP technology was continuingly developed. Now, with the Internet access bandwidth be improved and related issues be conquered, IP telecommunication would become more mature to be the basic service for the internet service provider. ICL has been involved in the telecommunication technology for years, as well continuingly accumulating the deployment experience. The goal of this article is to help upgrade an enterprise VoIP system to the Carrier-Grade IP telecommunication system. In this article, the fundamental VoIP technology would be introduced first, following with the system service component, deployment architecture, and related technologies. Finally, out of our experimental experience, we analyze how to improve the existing VoIP system toward a carrier-grade IP telecommunication system.