The book explains how SIP is a highly-scalable and cost-effective way to offer new and exciting telecommunication feature sets. From an examination of SIP as a key component in the Internet multimedia conferencing architecture… to a look at the future direction of SIP, practitioners get the knowledge they need to design "next generation" networks and develop new applications and software stacks.This newly revised edition of the ground-breaking Artech House bestseller, SIP: Understanding the Session Initiation Protocol offers a thorough and up-to-date understanding of this revolutionary technology for IP Telephony. Essential reading for anyone involved in the development and operation of voice or data networks, the second edition includes brand new discussions on the use of SIP as a wireless communications protocol and mobility technology. Professionals find details on the latest application areas such as instant messaging.