Title: Asterisk: The Future of Telephony
Author: Jim Van Meggelen, Jared Smith & Leif Madsen
Published: 2005 by O'Reilly
I've been playing with Asterisk for about a year, and I've been interested in it for twice that, pretty much since I started working with proprietary PBX systems. First was a Nortel, and now a Vodavi and an NEC. I can't understate the symplicity of having a computer-controlled (especially a Linux-based one) phone system.
Jim, Jared and Leif have done an excellent job of summarizing Asterisk in 380 pages. Of course, there's no way to completely cover everything that can be done with Asterisk in such a (relatively) tiny volume, but what they wrote was quality. The dialplan examples will give firm foundations upon which readers can build much more complicated system. The coverage of protocols was thorough. I think my favorite part, though, was the extensive background of traditional telephony. Even though Asterisk is poised to eliminate a lot of it, implementers of Asterisk will certainly be required to interface with it. And with the vast array of voice protocols, it must have been quite the effort to pull it all together.
The other portion of the book that piqued my interest was the Application Gateway Interface, AGI. Basically it's a way to write your dialplan in an external program which could be C, Perl, etc.. I've been meaning for some time to try my hand at an AGI script but never gotten around to it. This book has excellent examples and opens the door to programs which really can do anything.
I have the feeling that sometime within the next two years I will be replacing our NEC phone system with Asterisk, and I'm excited about it. Nervous too, a little. One of my main hold ups is phones, which this book didn't cover much. We also will need to implement call queues and conferences, both of which were only lightly written about. I suppose the conferences are pretty simple so that's no big deal.
Excellent book. Well worth the cost, and certainly worth reading the PDF.