Voice over IP (VoIP) technology is currently finding its place in the telecommunication market. It enables a telecommunication company to cut cost by allowing a single network to transmit both data and voice traffic. Voice Vox is the complete implementation of VOIP client and also describe how to build telecommunication applications using different layers of the Open Systems Interconnection (OSI) model. The book in your hand will lead you in details how you can develop a system based on all OSI layers. These layers are application, presentation, session, transport, network, data link and physical. In Voice Vox, the reader will find how to design the packets at different layers in order to effectively communicate with each other. At the application layer, Session Initiation Protocol (SIP) is used for establishing sessions between two parties using Asterisk as a telephone private branch exchange (PBX) server. At the session layer, the user can implement Real-time Transport Protocol (RTP) and Session Description Protocol (SDP) for real-time data transmission between two call parties. At the transport layer, the User Datagram Protocol (UDP) is used for the transmission of audio data.