This book helps readers to see SIP in a broad communications context, assess what SIP can do and deliver, evaluate SIP's fit with other standards and systems, and plan new SIP-enabled services. The Session Initiation Protocol (SIP) is the signalling protocol that will deliver IP multimedia services for the third generation of mobile systems. It will merge together the cellular and Internet worlds. It will provide ubiquitous access to the services it enables, and make us a truly mobile population for the first time. These are not small claims, which might explain why some people have started looking to SIP as an all-purpose solution to building the telecom future. In fact, SIP is a powerful but limited protocol, with a well-defined scope.This book describes it in the context its framers intended, and meticulously explains how to use it as a transformative tool for telecom services. Written by one of the earliest contributors to SIP development in the IETF, "SIP Demystified" takes a long look at the "what's" and "why's" of today's most talked-about protocol, helping readers to move past the buzz, get poised for 3G, and start developing tomorrow's applications. You must read this book if: you're a telecom engineer, manager, or developer who wants to survive professionally in a converged world; you want a smooth transition from switched circuits to the connectionless paradigm; you want to be first to market with SIP services; you want to know how SIP interacts with other protocols; you need to find out what architectures support SIP; you have questions about QoS, security, and authentication; you want to evaluate SIP products, such as gateways, proxy servers, application servers, SIP phones, instant messaging, and presence applications; you're an industry analyst predicting and rating coming hot products and services; and, you're a curious noncombatant who can't get enough insider details on how the newest technologies work. "SIP Demystified" gives you jargon-free explanations of the concepts that set SIP apart from other protocols and the reasons the standard was drafted - so you can decide what to do with it.