Voice over IP, or VoIP, is a family of technologies that enables voice applications and telephony to be carried over an Internet Protocol (IP) network such as the Internet. These technologies include protocols, hardware and software standards, and computer programs. VoIP is employed in telephony applications, from analog phones to next-generation IP phones and wireless headsets, and in desktop voice chat services, from web-based party-line chat services (like Yahoo! Chat) to the well-known Skype desktop voice-calling service.
VoIP has become an important technology that is integrating pervasively into the popular culture. It is employed daily to drive new engines of commerceeverything from business-class VoIP-powered calling services to simple desktop chat tools such as Apple's iChat. Other high-profile companies like eBay, Microsoft, Google, and AT&T offer applications and services that utilize VoIP, too.
These big companies have recognized that the popular culture is moving to VoIP services en masse, even as the telecom industry is being set on its ear by scrappy young VoIP startups like Vonage, Packet8, and SpeakEasy.net. VoIP services deliver telephony applications less expensively than the old phone companies can hope to. This is because VoIP is free of the continually burdensome legacy technology investment the old phone companies must make to keep the "old" global phone network running. VoIP is also free of the endless government regulations and tariffs imposed upon the old phone companies.
In a nutshell, the way society looks at the voice network has changed. VoIP is the enabler of the change, and tomorrow's global voice network is the Internet.
This book contains only a small subset of VoIP knowledgeenough to serve as an introduction to the world of VoIP and teach you how to use it to save money, be more productive, or just impress your friends. My friends love my on-hold music when they call my house; I love that when people call my house, the call is connected to my notebook PC via Skype, no matter where I am in the world. You'll learn how to do all of this and more. I hope this book gets your mental gears turning and that your VoIP hacks are as enjoyable to implement and customize as they were for me to write!
For more VoIP theory and detailed reference information about Voice over IP, check out these great O'Reilly titles: