 summary of best practices to follow. Chapter 12, "Case Studies": Covers a few case studies of real-life SIP trunk deploy- ments, including the challenges faced and overcome. Chapter 13, "Future of Unified Communications": Shows some of the examples of how Unified Communications might develop in the next 40 years based on roadmaps of current products and technologies. Chapter 1 Overview of IP Telephony This chapter covers the following topics: History and overview of IP Telephony Basic components of IP Telephony Comparision of VoIP signaling protocols The technology of communications has always been a great area of innovation. Since the invention of the telephone in the 1890s to the latest advancements in Telepresence tech- nologies today, communications have been an important area of development. Since late 1990, the major development in communications has been the shift from many different protocols to the use of Internet Protocol (IP) for communications. Overall, this is known as IP Telephony. This chapter provides the introduction to IP Telephony and its essential components, including an introduction to the latest development in IP Telephony, Session Initiation Protocol (SIP) trunks. This chapter covers LAN solutions; WAN solutions; voice compres- sion technologies; multiple signaling protocols; quality of service (QoS), bandwidth requirement; Digital Signal Processors (DSP); Internet Protocol Public Branch Exchanges (IP-PBX); Cisco Unified Communications Manager (CUCM); Time-Division Multiplexing (TDM) to IP conversion gateways; dial plans; supplementary services, and SO on, and it provides some of the basic information that a service provider, systems integrator, and enterprise employees need to have to architect, design, and implement an IP Telephony system and SIP trunks. History of IP Telephony The first Voice over IP (VoIP) technology trials occurred in university and nontraditional company research labs in the late 1980s. Users wanted to take advantage of the growth in networked computer systems that 