Asterisk

Asterisk™: The Definitive Guide

THIRD EDITION

Asterisk™: The Definitive Guide

Leif Madsen, Jim Van Meggelen, and Russell Bryant

Beijing • Cambridge • Farnham • Köln • Sebastopol • Tokyo

Asterisk™: The Definitive Guide, Third Edition
by Leif Madsen, Jim Van Meggelen, and Russell Bryant
Copyright © 2011 Leif Madsen, Jim Van Meggelen, and Russell Bryant. All rights reserved.Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (http://my.safaribooksonline.com). For more information, contact our corporate/institutional sales department: (800) 998-9938 orcorporate@oreilly.com.

Editor: Mike Loukides Production Editor: Teresa Elsey Copyeditor: Rachel Head Proofreader: Andrea Fox Production Services: Molly Sharp Printing History:
June 2005: August 2007: April 2011: First Edition. Second Edition. Third Edition.

Indexer: Fred Brown Cover Designer: Karen Montgomery Interior Designer: David Futato Illustrator: Robert Romano

Nutshell Handbook, theNutshell Handbook logo, and the O’Reilly logo are registered trademarks of O’Reilly Media, Inc. Asterisk: The Definitive Guide, the images of starfish, and related trade dress are trademarks of O’Reilly Media, Inc. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and O’Reilly Media, Inc.,was aware of a trademark claim, the designations have been printed in caps or initial caps.
While every precaution has been taken in the preparation of this book, the publisher and authors assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein.

ISBN: 978-0-596-51734-2 [LSI] 1302181785

Table of Contents

Foreword . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii 1. A Telephony Revolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1
Asterisk and VoIP: Bridging the Gap Between Traditional and Network Telephony The Zapata Telephony Project Massive Change Requires Flexible Technology Asterisk: The Hacker’s PBX Asterisk: The Professional’s PBX The Asterisk Community The Asterisk Mailing Lists Asterisk Wiki Sites The IRC Channels Asterisk User Groups The Asterisk Documentation Project The Business Case Conclusion 2 2 3 4 5 56 7 7 7 8 8 8

2. Asterisk Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Modules Applications Bridging Modules Call Detail Recording Modules Channel Event Logging Modules Channel Drivers Codec Translators Format Interpreters Dialplan Functions PBX Modules 10 12 15 15 16 17 18 18 19 21

v

Resource Modules AddonModules Test Modules File Structure Configuration Files Modules The Resource Library The Spool Logging The Dialplan Hardware Asterisk Versioning Previous Release Methodologies The New Release Methodology Conclusion

21 23 24 24 24 24 25 25 25 25 26 26 26 27 28

3. Installing Asterisk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Installation Cheat Sheet Distribution Installation CentOS Server Ubuntu Server Software Dependencies Downloading What You Need Getting the Source via Subversion Getting the Source via wget How to Install It LibPRI DAHDI Asterisk Setting File Permissions Base Configuration Disable SELinux Initial Configuration make menuselect Updating Asterisk Common Issues Upgrading Asterisk Conclusion 31 35 35 40 44...