To David Duffett, thanks for the excellent chapter on internationalization, which would not have been served well by being written by us North Americans.

Next, we want to thank our fantastic editor, Michael Loukides, for your patience with this third edition, which took too long to get off the ground, and many long months to finally get written. Mike offered invaluable feedback and found incredibly tactful ways to tell us to rewrite a section (or chapter) when it was needed, and make us think it was our idea. Mike built us up when we were down, and brought us back to earth when we got uppity. You are a master, Mike, and seeing how many books have received your editorial oversight contributes to an understanding of why O’Reilly Media is the success that it is.

Thanks also to Rachel Head (nee Rachel Wheeler), our copyeditor, who fixes all our silly grammar, spelling, and style mistakes (and the many Canadianisms that Leif and Jim feel compelled to include), and somehow leaves the result reading as if it was what we wrote in the first place. Copyeditors are the unsung heroes of publishing, and Rachel is one of the very best.

Also thanks to Teresa Elsey, our production editor, and the rest of the unsung heroes in O’Reilly’s production department.

These are the folks that take our book and make it an O’Reilly book.

During the course of writing this book, we had the pleasure of being able to consult with many people with specific experience in various areas. Their generous contributions of time and expertise were instrumental in our research. Thanks to Randy Resnick, organizer of the VoIP User Group; Kevin Fleming of Digium; Lee Howard, author of iaxmodem and hylafax; Joshua Colp of Digium; Phillip Mullis of the Toronto Asterisk Users Group; Allison Smith, the Voice of Asterisk; Flavio E. Goncalves, author of books on Asterisk, OpenSER, and OpenSIPS; J. Oquendo, Security Guru; Tzafrir Cohen, font of knowledge about security and lots of other stuff; Jeff Gehlbach, for SNMP; Ovidiu Sas, for your encyclopedic knowlege of SIP; Tomo Takebe, for some SMDI help; Steve Underwood, for help with fax and spandsp; and Richard Genthner and John Covert, for helping with LDAP.

A special thanks should also go to John Todd for being one of the first to write comprehensive Asterisk how-tos, all those years ago, and for all the many other things you do (and have done) for the Asterisk community.

Thanks to Sean Bright, Ed Guy, Simon Ditner, and Paul Belanger for assisting us with clarifying best practices for user and group policies for Asterisk installation. In the past it was common to just install Asterisk with root permissions, but we have elected to describe an installation process that is more in keeping with Linux best practices,[2] and these fine gents contributed to our discussions on that.

Kudos to all the folks working on the FreeSWITCH, YATE, SER, Kamailio, OpenSIPS, SER, sipXecs, Woomera, and any other open source telecom projects, for stimulating new thoughts, and for pushing the envelope.

Everyone in the Asterisk community also needs to thank Jim Dixon for creating the first open source telephony hardware interfaces, starting the revolution, and giving his creations to the community at large.

Finally, and most importantly, thanks go to Mark Spencer, the original author of Asterisk and founder of Digium, for Asterisk, for Pidgin (, and for contributing his creations to the open source community. Asterisk is your legacy!

Leif Madsen

It sort of amazes me where I started with Asterisk, and where I’ve gone with Asterisk. In 2002, while attending school, a bunch of my friends and myself were experimenting with voice over the Internet using Microsoft’s MSN product. It worked quite well, and allowed us to play video games while conversing with each other—at least, until we wanted to add a third participant. So, I went out searching for some software that could handle multiple voices (the word was conferencing, but I didn’t even know that at the time, having had little exposure to PBX platforms). I searched the Internet but didn’t find anything in particular I liked (or that was free). I turned to IRC and explained what I was looking for. Someone (I wish I knew who) mentioned that I should check out some software called Asterisk (he presumably must have thought I was looking for MeetMe(), which I was).

Having the name, I grabbed the software and started looking at what it could do. Incredibly, the functionality I was looking for, which I thought would be the entirety of the software, was only one component in a sea of functionality. And having run a BBS for years prior to going to college, the fact that I could install a PCI card and connect it to the phone network was not lost on me. After a couple of hours of looking at the software and getting it compiled, I started telling one of my teachers about the PCI cards and how maybe we could get some for the classroom for labs and such (our classroom had 30 computers at 10 tables of 3). He liked the idea and started talking to the program coordinator, and within about 30 minutes an order had been placed for 20 cards. Pretty amazing considering they were TDM400Ps decked out with four daughter cards, and they had only heard about them an hour prior to that.

Then the obsession began. I spent every extra moment of that semester with a couple of computers dedicated to Asterisk use. In those two months, I learned a lot. Then we had a co-op break. I didn’t find any work immediately, so I moved home and continued working on Asterisk, spending time on IRC, reading through examples posted by John Todd, and just trying to wrap my head around how the software worked. Luckily I had a lot of help on IRC (for these were the days prior to any documentation on Asterisk), and I learned a lot more during that semester.

Seeing that the people who took a great interest in Asterisk at the time had a strong sense of community and wanted to contribute back, I wanted to do the same. Having no practical level of coding knowledge, I decided documentation would be something useful to start doing. Besides, I had been writing a lot of papers at school, so I was getting better at it. One night I put up a website called The Asterisk Documentation Assigned (TADA) and started writing down any documentation I could. A couple of weeks later Jared Smith and I started talking, and started the Asterisk Documentation Project (, with the goal of writing an Asterisk book for the community. That project became the basis of the first edition of this book, Asterisk: The Future of Telephony.

Nine years later, I’m still writing Asterisk documentation and have become the primary bug marshal and release manager for the Asterisk project, spoken at every single AstriCon since 2004 (at which Jared and I spoke about the Asterisk Documentation Project; I still have the AsteriskDocs magnet his wife made), and become a consultant specializing in database integration (thanks Tilghman for func_odbc) and clustering (thanks Mark Spencer for DUNDi). I really love Asterisk, and all that it’s allowed me to do.

First, thanks to my parents Rick and Carol, for the understanding and support in everything I’ve done in my life. From the first computer they purchased for far too much money when I was in grade 6 (I started taking an interest in computers in grade 2 using a Commodore 64, and they got me a computer after a parent-teacher interview a few years later) to letting me use the home phone line for my BBS endeavors (and eventually getting me my own phone line), and everything else they have ever done for me, I can never thank them enough. I love you both more than you’ll ever imagine.

Thanks to my Grandma T for letting me use her 286 during the years when I didn’t have a computer at home, and for taking me shopping every year on my birthday for 15 years. Love lots!

To my beautiful wife, Danielle, for setting the alarm every morning before she left for work, letting me sleep those extra 10 minutes before starting on this book, and understanding when I had to work late because I went past my 9 A.M. stop-writing time, thank you and I love you so much.

There are so many people who help me and teach me new things every day, but the most influential on my life in Asterisk are the following: Mark Spencer for writing software that has given me a fantastic career, John Todd for his early examples, Brian K. West for his early help and enthusiasm on IRC, Steve Sokol and Olle Johansson for flying me to my first AstriCon (and subsequent ones!) and letting me be part of the first Asterisk training classes, Jared Smith for helping start the documentation project and doing all the infrastructure that I could never have done, Jim Van Meggelen for joining in early on the project and teaching me new ways to look at life, and Russell Bryant for being an amazing project leader and easy to work with every day, and for not holding a grudge about the bush.

Jim Van Meggelen

When we set out to write the very first edition of this book over five years ago, we were confident that Asterisk was going to be a huge success. Now, a half-decade later, we’ve written this third edition of what the worldwide Asterisk community calls “The Asterisk Book,” and we’ve matured from revolutionaries into Asterisk professionals.

Asterisk has proven that open source telecom is a lasting idea, and the open source telecom landscape is nowadays complemented by more than just Asterisk. Projects like Freeswitch, sipXecs (from SipFoundry), OpenSER/Kamailio/OpenSIPS, and many, many more (and more to come) help to round out the ecosystem.

I want to take this opportunity to thank my very good friend Leif Madsen, who has been with me through all three editions. In our daily lives we don’t always have many opportunities to work with each other (or even grab a pint, these days!), and it’s always a delight to work with you. I also want to thank Russell Bryant, who joined us for this edition, and whose dedication to this project and the Asterisk project in general is an inspiration to me. You’re a Renaissance man, Russell. To Jared Smith, who helped found the Asterisk Documentation Project and coauthored the first two editions with Leif and me (but has since moved on to the Fedora project), I can only say: Asterisk’s loss is Fedora’s gain.

I would like to thank my business partners at Core Telecom Innovations and iConverged LLC, without whom I could not do all the cool things I get to do in my professional career.

I would like to thank all my friends in the improv community, for helping me to keep laughing at all the challenges that life presents.

Thanks to all my family, who bring love into my life.

Finally, thanks to you, the Asterisk community. This book is our gift to you. We hope you enjoy reading it as much as we’ve enjoyed writing it.

Russell Bryant

I started working on Asterisk in 2004. I was a student at Clemson University and was working as a co-op engineer at ADTRAN in Huntsville, Alabama. My first job at ADTRAN was working in the Product Qualification department. I remember working with Keith Morgan to use Asterisk as a VoIP traffic generator for testing QoS across a router test network. Meanwhile, a fellow co-op and friend, Adam Schreiber, introduced me to Mark Spencer. Over the next six months, I immersed myself in Asterisk. I learned as much as I could about Asterisk, telephony, and C programming. When Asterisk 1.0 was released in the fall of 2004, I was named the release maintainer.

At the beginning of 2005, I was hired by Digium to continue my work on Asterisk professionally. I have spent the past six amazing years working with Digium to improve Asterisk. I have worked as a software developer, a software team lead, and now as the engineering manager of the Asterisk development team. I am extremely grateful for the opportunity to contribute to so many areas of the Asterisk project. There are many people that deserve thanks for the support they have provided along the way.

To my wife, Julie, I cannot thank you enough for all the love and support you have given me. Thank you for keeping my life balanced and happy. You are the best. I love you!

To my parents, thank you for giving me so many great opportunities in my life to explore different things and find what I really enjoy. You taught me to work hard and never give up.

To Leif and Jim, thank you for your invitation to contribute to this book. It has been a fun project, largely due to the pleasure of working with the two of you. Thanks for the laughs and for your dedication to this book as a team effort.

I have learned a lot from many people at Digium. There are three people who stand out the most as my mentors: Mark Spencer, Kevin P. Fleming, and David Deaton. Thank you all for going the extra mile to teach me along the way. I am extremely grateful.

To the software development team at Digium, thank you for being such an amazing team to work with. Your dedication and brilliance play a huge part in the success of Asterisk and make Digium a great place to work.

To Travis Axtell, thank you for your help in my early days of learning about Linux and for being a good friend.

To my dogs, Chloe and Baxter, thanks for keeping me company while I worked on the book every morning.

To all of my friends and family, thank you for your love, support, and fun times.

To the entire Asterisk community, thank you for using, enjoying, and contributing to Asterisk. We hope you enjoy the book!

[1] We tried wherever possible to include the contributors’ names, but in some cases could not, and therefore included their handles instead.

[2] Without starting a holy war!