The two terms that make up the title of this book, "carrier-grade" and " Voice over IP (VoIP)," mean many things to many people, and each term may have several meanings depending on the context. Furthermore, many people might consider the two terms to be mutually exclusive, making the phase carrier-grade VoIP an oxymoron. That used to be the case, but those days are over. The excitement that VoIP has generated and the resources that have been applied to developing technical solutions for VoIP have allowed it to become a serious alternative for voice communications. That is, VoIP is a serious alternative to the circuit-switched telephony that we have known for decades. Not only can VoIP technology now offer straightforward telephony services, but it can offer a lot more besides, and it can do it with the same quality of service (QoS) that we have become familiar with in traditional telephony.

The overall objectives of this book are to examine the technical solutions that make VoIP a reality and to illustrate how today's VoIP solutions can offer everything that traditional circuit switching provides, plus a lot more. This first chapter introduces the reader to VoIP in general and looks at some of the reasons why it is such a hot topic. Thereafter, a brief overview of technical challenges and solutions is presented. This chapter can be considered a glimpse of the topics that are covered in more depth in later chapters. Firstly, however, we need to understand what...