This book explains why people and companies are using SIP equipment and software to efficiently upgrade existing telephone systems, develop their own advanced communications services, and to more easily integrate telephone network with company information systems. This book provides descriptions of the function parts of SIP systems along with the fundamentals of how SIP systems operate. It identifies and explains what key services are possible through the use of SIP and how existing phone systems can be upgraded to SIP capabilities. It describes why it is easy to integrate SIP with information systems along with how to develop new advanced revenue producing services. The reader will learn the basic SIP system development and installation process and how to manage SIP systems. Explained are the typical costs of SIP systems and how SIP technology is changing to meet future multimedia communication needs.