This volume focuses on the real issues facing programmers and administrators who work with VOIP. VOCAL (the Vovida Open Communication Application Library) is an open source software project that provides call control, routing, media, policy, billing information and provisioning on a system that can range from a single box in a lab with a few test phones to a large, multi-host carrier grade network supporting hundreds of thousands of users. The book describes how such a phone system is actually built, and how too acquire the source code, install it onto a system, connect phones, and make calls. It covers the following topics: installing and configuring VOCAL 1.4.0 onto a single host and onto a multi-host network with phones and gateways; C++, C and Java architecture found within VOCAL; provisioning a VoIP system; SIP (Session Initiation Protocol), SDP (Session Description Protocol) and RTP (Real-time Transport Protocol) for call control and media; TRIP (Telephony Routing over IP), DNS SRV and ENUM for routing; MGCP (Media Gateway Control Protocol) and H.3 23 for call control and translation into SIP; COPS (Common Open Policy Service), OSP (Open Settlement Protocol) and RSVP (Reservation Protocol) for policy and Quality of Service; RADIUS (Remote Authentication Dial In User Service) for interfacing with billing servers; and SNMP (Simple Network Management Protocol).