Foreword

This is the year of VoIP! So was last year, and the year before that, and the year before that.... Okay, so what's the real story? Is VoIP really going to happen? The answer is that VoIP has been slowly happening all this time. Bit by bit, industry by industry, this technology has been creeping into homes and businesses everywhere.

As a technology, VoIP is a pretty simple ideause packet-switched data encapsulation instead of the tried-and-true time-division multiplexed (TDM), circuit-switched methods that telephony has used since its creation. Since its creation? Is that an exaggeration? TDM telephony today is essentially just an electronic version of the "cord board" that the old-time operators used to connect one caller with another. Advances in packet communication technologies are now making that model obsolete, permitting more efficient use of bandwidth resources while providing mobility and the integration of voice, presence, and other information.

If VoIP is so great, why has it been so slow to catch on? First, as currently standardized, VoIP is more complicated to administer and set up than a traditional telephone line. Second, while VoIP's technical merits are impressive, TDM technology is globally deployed. "Copper may be buried, but it's not dead," the saying goes. In order to be successful, VoIP must be interoperable with this established technology. Finally, until recently, VoIP was more expensive to deploy than traditional telephony. Today, thanks to competition enabled by open standards and more recently open source technologies such as Asterisk, the cost of a VoIP system is not only competitive with TDM, but in many cases less expensive (as well it should be).

The key to evaluating when VoIP may or may not help you, and to having successful VoIP deployments where it does help, is understanding the technologies, protocols, and tools (including open source platforms such as Asterisk, for which I can't resist including a second, shameless parenthetical plug). It is the goal of this book to educate and inform you, to put control in your hands, and to save you from as much frustration as possible!

Original author and maintainer of Asterisk

Founder and president of Digium

Mark Spencer