Voice over IP (VoIP) is a methodology and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms commonly associated with VoIP are IP telephony, Internet telephony, broadband telephony, and broadband phone service. VoIP is undoubtedly a powerful and innovative communication tool for everyone, voice communication over the Internet is inherently less reliable than the public switched telephone network, because the Internet functions as a best-effort network without Quality of Service guarantee and voice data cannot be retransmitted. Because of the bandwidth efficiency and low costs that VoIP technology can provide, businesses are migrating from traditional copper-wire telephone systems to VoIP systems to reduce their monthly phone costs. VoIP Technologies introduces research strategies that address various issues with the aim of enhancing VoIP quality. VoIP solutions aimed at businesses have evolved into unified communications services that treat all communicationsphone calls, faxes, voice mail, e-mail, Web conferences, and more -- as discrete units that can all be delivered via any means and to any handset, including cellphones. VoIP allows both voice and data communications to be run over a single network, which can significantly reduce infrastructure cost. We hope that you will enjoy reading these diverse studies. This book will provide a lot of useful information about current VoIP technology research aimed at practitioners and researchers as well as advanced graduate students.