1. Chapter 1 A Telephony Revolution

   1. VoIP: Bridging the Gap Between Traditional Telephony and Network Telephony

   2. Massive Change Requires Flexible Technology

   3. Asterisk: The Hacker's PBX

   4. Asterisk: The Professional's PBX

   5. The Asterisk Community

   6. The Business Case

   7. This Book

2. Chapter 2 Preparing a System for Asterisk

   1. Server Hardware Selection

   2. Environment

   3. Telephony Hardware

   4. Types of Phone

   5. Linux Considerations

   6. Conclusion

3. Chapter 3 Installing Asterisk

   1. What Packages Do I Need?

   2. Obtaining the Source Code

   3. Compiling Zaptel

   4. Compiling libpri

   5. Compiling Asterisk

   6. Installing Additional Prompts

   7. Updating Your Source Code

   8. Common Compiling Issues

   9. Loading Zaptel Modules

   10. Loading libpri

   11. Loading Asterisk

   12. Directories Used by Asterisk

   13. Conclusion

4. Chapter 4 Initial Configuration of Asterisk

   1. What Do I Really Need?

   2. Working with Interface Configuration Files

   3. FXO and FXS Channels

   4. Configuring an FXO Channel

   5. Configuring an FXS Channel

   6. Configuring SIP

   7. Configuring Inbound IAX Connections

   8. Configuring Outbound IAX Connections

   9. Debugging

   10. Conclusion

5. Chapter 5 Dialplan Basics

   1. Dialplan Syntax

   2. A Simple Dialplan

   3. Adding Logic to the Dialplan

   4. Conclusion

6. Chapter 6 More Dialplan Concepts

   1. Expressions and Variable Manipulation

   2. Dialplan Functions

   3. Conditional Branching

   4. Voicemail

   5. Macros

   6. Using the Asterisk Database (AstDB)

   7. Handy Asterisk Features

   8. Conclusion

7. Chapter 7 Understanding Telephony

   1. Analog Telephony

   2. Digital Telephony

   3. The Digital Circuit-Switched Telephone Network

   4. Packet-Switched Networks

   5. Conclusion

8. Chapter 8 Protocols for VoIP

   1. The Need for VoIP Protocols

   2. VoIP Protocols

   3. Codecs

   4. Quality of Service

   5. Echo

   6. Asterisk and VoIP

   7. Conclusion

9. Chapter 9 The Asterisk Gateway Interface (AGI)

   1. Fundamentals of AGI Communication

   2. Writing AGI Scripts in Perl

   3. Creating AGI Scripts in PHP

   4. Writing AGI Scripts in Python

   5. Debugging in AGI

   6. Conclusion

10. Chapter 10 Asterisk for the Über-Geek

    1. Festival

    2. Call Detail Recording

    3. Customizing System Prompts

    4. Manager

    5. Call Files

    6. DUNDi

    7. Conclusion

11. Chapter 11 Asterisk: The Future of Telephony

    1. The Problems with Traditional Telephony

    2. Paradigm Shift

    3. The Promise of Open Source Telephony

    4. The Future of Asterisk

1. Appendix A VoIP Channels

   1. IAX

   2. SIP

2. Appendix B Application Reference

3. Appendix C AGI Reference

4. Appendix D Configuration Files

   1. modules.conf

   2. adsi.conf

   3. adtranvofr.conf

   4. agents.conf

   5. alarmreceiver.conf

   6. alsa.conf

   7. asterisk.conf

   8. cdr.conf

   9. cdr_manager.conf

   10. cdr_odbc.conf

   11. cdr_pgsql.conf

   12. cdr_tds.conf

   13. codecs.conf

   14. dnsmgr.conf

   15. dundi.conf

   16. enum.conf

   17. extconfig.conf

   18. extensions.conf

   19. features.conf

   20. festival.conf

   21. iax.conf

   22. iaxprov.conf

   23. indications.conf

   24. logger.conf

   25. manager.conf

   26. meetme.conf

   27. mgcp.conf

   28. modem.conf

   29. musiconhold.conf

   30. osp.conf

   31. oss.conf

   32. phone.conf

   33. privacy.conf

   34. queues.conf

   35. res_odbc.conf

   36. rpt.conf

   37. rtp.conf

   38. sip.conf

   39. sip_notify.conf

   40. skinny.conf

   41. voicemail.conf

   42. vpb.conf

   43. zapata.conf

   44. zaptel.conf

5. Appendix E Asterisk Command-Line Interface Reference

   1. !

   2. abort halt

   3. add

   4. agi

   5. database

   6. iax2

   7. indication

   8. logger

   9. meetme

   10. pri

   11. remove

   12. restart

   13. set

   14. show

   15. sip

   16. stop

   17. zap

6. Colophon

About the Authors

Jim Van Meggelen is President and CTO of Core Telecom Innovations, a Canadian-based provider of open source telephony solutions. He has over 15 years of enterprise telecom experience, for such companies as Nortel, Williams, and Telus, and has extensive knowledge of both legacy and VoIP equipment from manufacturers such as Nortel, Cisco, and Avaya.

Jim was the architect of two of the world's largest managed enterprise voice networks, each solution serving roughly 20,000 users in more than 1,000 communities across Canada and providing telecommunications in 5 different languages through 6 time zones, administered completely from a central location. These networks pioneered the use of extensive automation and database control in a branch voice network-functionalities not generally available in proprietary telecommunications systems. Jim has now moved on from the world of proprietary telecom, and is commited to open source telephony.

Jim is one of the principal contributors to the Asterisk Documentation Project. He enjoys teaching, public speaking, improvisational acting, and writing.

Jared Smith is one of those rare individuals whose beloved hobby is the same as his profession. The son of a computer store owner, Jared wrote his first computer program at the age of 7 on his Commodore 64. The obvious choice of major for this geek-in-embryo was Computer Engineering, and Jared received his Bachelor of Science degree with a minor in Computer Science from Utah State University. He now has over a decade of professional systems administration and programming experience in the simulation, market research, and web analytics industries. As a key architect of one of the world's largest Asterisk installations, Jared has a wealth of hands-on telephony and VoIP knowledge, which he shares through users groups and various public speaking engagements. He is an active member of the Asterisk community and a co-founder of the Asterisk Documentation Project.

Jared is active in his community, donating Asterisk services to local schools and serving in his church. The greatest joy in Jared's life comes from spending time with his children, Caleb and Sydney Jo, and his wife, Jenny.

Leif Madsen is a graduate of the Telecommuncations Technology program from the Sheridan Institute of Technology and CEO of LeifMadsen Enterprise, Incorporated, a documentation and consulting firm specializing in Asterisk. He was one of the first Digium Certified Asterisk Professionals (dCAP), and assists with the Astricon conferences and trainings organized by IPsando, LLC.

Leif first took an interest in Asterisk while attempting to find a voice conferencing solution for himself and his friends. After someone suggested trying Asterisk, the obsession began. Wanting to contribute and be involved with the community, and noticing the lack of Asterisk documentation, he co-founded the Asterisk Documentation Project.

Colophon

Our look is the result of reader comments, our own experimentation, and feedback from distribution channels. Distinctive covers complement our distinctive approach to technical topics, breathing personality and life into potentially dry subjects.

The animals on the cover of Asterisk: The Future of Telephony are starfish. Starfish are classified as Asteroidea. They are a group of echinoderms, spiny-skinned invertebrates found only in the sea. Most starfish have five-fold symmetry (arms or rays in multiples of five), though some species can have four or nine arms. But all starfish are radially symmetrical: they have arms or rays branching out from a central body disc. There are over 1,500 species of starfish.

Starfish live on the floor of the sea and in tidal pools, clinging to rocks and moving (slowly) using a water-based vascular system to manipulate their hundreds of tiny, tube-like legs, called podia. A small bulb or ampulla at the top of the tube contracts, expelling water and expanding the starfish's leg. The ampulla relaxes, and the leg retracts. Starfish use muscles to bend their legs, but it is the flow of water pressure that keeps the feet moving. At the tip of each leg, starfish have suction cups that allow them to pry open clam, oyster, or mussel shells. Many starfish can push their stomachs out through their mouths in order to digest their prey in its shell. Starfish are carnivores; they eat coral, fish, and snails, as well as bivalves.

Starfish can flex and rearrange their arms to fit into small places as they move over the ocean floor. At the end of each arm, they have eyespots, primitive sensors that detect light and help the starfish determine direction. Starfish also have the ability to regenerate a missing limb. Some species can even regrow a complete, new starfish from a severed arm.

Colleen Gorman was the production editor, and Rachel Wheeler was the copyeditor for Asterisk: The Future of Telephony . Ann Schirmer proofread the book. Colleen Gorman and Marlowe Shaeffer provided quality control. Ellen Troutman wrote the index.

Ellie Volckhausen designed the cover of this book, based on a series design by Edie Freedman. The cover image is a 19th-century engraving from the Dover Pictorial Archive. Karen Montgomery produced the cover layout with Adobe InDesign CS using Adobe's ITC Garamond font.

David Futato designed the interior layout. This book was converted by Keith Fahlgren to FrameMaker 5.5.6 with a format conversion tool created by Erik Ray, Jason McIntosh, Neil Walls, and Mike Sierra that uses Perl and XML technologies. The text font is Linotype Birka; the heading font is Adobe Myriad Condensed; and the code font is LucasFont's TheSans Mono Condensed. The illustrations that appear in the book were produced by Robert Romano, Jessamyn Read, and Lesley Borash using Macromedia FreeHand MX and Adobe Photoshop CS. The tip and warning icons were drawn by Christopher Bing. This colophon was written by Colleen Gorman.