To serve as a single comprehensive source of information and as reference material on SIP technology. To deal with an important and timely topic of emerging technology of today, tomorrow, and beyond. To present accurate, up-to-date information on a broad range of topics related to SIP technology. To present material authored by the experts in the field. To present information in an organized and well-structured manner. Although the handbook is not precisely a textbook, it can certainly be used as a textbook for graduate courses and research-oriented courses that deal with SIP. Any comments from the readers will be highly appreciated. Many people have contributed to this handbook in their unique ways. The first and the foremost group that deserves immense gratitude is the group of highly talented and skilled researchers who have contributed 24 chapters. All of them have been extremely cooperative and professional. It has also been a pleasure to work with Ms. Nora Konopka, Ms. Jessica Vakili, and Richard Tressider of CRC Press, and we are extremely gratified for their support and professionalism. Our families have extended their unconditional love and strong support throughout this project and they all deserve very special thanks. Syed Ahson Redmond, Washington Mohammad Ilyas Boca Raton, Florida © 2009 by Taylor & Francis Group, LLC Editors Syed A. Ahson is a senior software design engineer with Microsoft in Red- mond, Washington. As part of the Mobile Voice and Partner Services group, he is busy creating new and exciting end-to-end services and applications. Prior to working at Microsoft, he was a senior staff software engineer with Motorola, where he contributed significantly in leading roles towards the cre- ation of several advanced and exciting cellular phones. Dr. Ahson has exten- sive experience with Wireless Data Protocols, Wireless Data Applications and Cellular Telephony Protocols. Prior to joining Motorola, he was a senior soft- ware design engineer with NetSpeak Corporation (now part of Net2Phone), a pi