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  • VoIP Telephony with Asterisk

    BY Paul MahleISBN 09759992-0-6Mahler, P.S.

    Asterisk and IP Telephony / Paul MahleCopyright 2003, 2004 by Signate, LLC.All rights reserved. No part of this book may be reproduced in any form or by any means without permission in writing from the publisherPrinted in the United States of America20 19 18 17 16 15 14 13 12 11


    This book is a beginner's guide to Asterisk and VoIP. This book is a road map to your first successful installation of an Asterisk telephone system. The path you need to take is documented step-by-step The information you need is all here in a single place. This is not a beginner's guide to Linux in that assume you already are a skilled Linux and network administrator. However, you do not need grea expertise in telephony or IP telephony to benefit from this bookAsterisk software turns an inexpensive PC architecture server running Linux or Unix into a reliable, sophisticated, full-featured enterprise telephone system. Because Asterisk is free and runs on an industry standard PC platform, an Asterisk system will cost you far less than any traditional, proprietar PBX. With Asterisk, you can quickly and easily build a

    pkg://voip telephony with asterisk/apdxglossary_PBX

  • sophisticated business telephone system for any enterprise, no matter how large or small. Because it is reliable, free and effective, and because it i based on modernInternet protocols, Asterisk will replace many legacy telephone systems in the marketplace.Asterisk is far less expensive and much more effective that any competing telephone system. Asterisk provides all the functionality of a traditionalPBX, but it also provides new features and capabilities a legacyPBX can't offer. Because Asterisk is open you can change it and tune it as needed, unlike legacy systems which only provide closed black boxes with closed interfaces. With Asterisk you will neve again get locked into proprietary obsolete equipment from an unappealing single-source vendor.This book documents the first release of Asterisk. Asterisk is quickly evolving which makes it exceedingly difficult to completely and effectively document. Thus, this book is not a complete guide to all the functionality Asterisk provides. Not every Asterisk feature is covered, not every covered feature i covered completely. None-the-less, this book should help you more quickly come up to speed wit Asterisk. I have tried to write the book I wanted to have while I was learning AsteriskI have worked extremely hard to assure the accuracy of this text, and others have greatly contributed in their review of this book, but errors are unavoidable. If you find an error, please let me know with mai [email protected] or by going to our Web page at http://asterisk.signate.com so that we can fix it for the next edition. While this book is the result of the contribution of many people, the errors o omissions are my responsibility alone.Paul [email protected]



    There wouldn't be a book without the enormous help and support of Mark Spencer and Digium. James Lyons, Matthew Nicolson, Mat Fredrickson, John Bigelow and Mike Wood at Digium Technical support deserve special thanks for the many hours of patient help. They should get a medal. Gre Vance was always there to help.Thanks to David Edison and Daryl Jones for making it all possible. Thanks to Warren Woodford for creating an Asterisk ready distribution of Mepis. John Todd contributed very valuable technical material.The reviewers, Matt Florell, Mike Diehl, and Tom Scott, did an especially good job of finding, and fixing, many of my mistakes and adding new material. This book is much, much better because of thei hard work. I am especially grateful for their help.Thank you, so much, everyone! John Bigelow, Bill Boehlke

    pkg://voip telephony with asterisk/apdxglossary_Internetpkg://voip telephony with asterisk/apdxglossary_PBXpkg://voip telephony with asterisk/apdxglossary_PBXfile:///C|/Documents%20and%20Settings/Compaq_Owner/My%20Documents/eDonkey2000%20Downloads/VoIP%20telephony%20with%20Asterisk/[email protected]/http://asterisk.signate.com/file:///C|/Documents%20and%20Settings/Compaq_Owner/My%20Documents/eDonkey2000%20Downloads/VoIP%20telephony%20with%20Asterisk/[email protected]/http://www.signate.com/

  • Malcom Davenport, Mike Diehl

    David Edison, Matt Florell

    Mat Fredrickson, Chris Hariga

    Dr. Lewis Heniford, Amal Johnson

    Daryl Jones, James Lyons

    Matthew Nicholson, Mike Pechner

    Marcelo Rodriguez, Tom Scott,

    David Schlossman, Mark Spencer

    John Todd, Greg Vance,

    Mike Wood, Warren Woodford


    Telephony uses an old and inefficient model. Academics and researchers have shared their work for centuries. Scientists publish new discoveries in journals. Imagine where mankind would be if peopl had been unable to build on the knowledge of others. Yet this is the mentality on which proprietar telephone systems have dependedTraditional office telephones systems combine proprietary hardware and software. The resulting products have been either low cost and low function, or functional but expensive to purchase, maintain, and change. The developer of proprietary products has no interest in giving customers the ability t enhance or maintain them. Why should he? The proprietary model gives the traditional telephon supplier the ability to charge customers to use the products, charge to fix them, and charge again whe they need enhancement.The proprietary model gets even better for the telephone supplier and worse for the customers as customers become tied to the vendor's specific methods and capabilities. The cost of switching away from the supplier becomes very large, creating formidable barriers to change.That's why the open source model of software development is exploding. In the same way shared knowledge propels the whole of society forward, open technology development is showing that it ca drive innovation for an entire industry. Open source returns control to the user. Users can see the cod that makes the product work, change it, and learn from it. Shared problems are more easily found an fixed, without dependence on a single vendor's priorities. If customers don't like how one vendor i serving them, they can choose another without major switching costs.Now, open source development has come to telephony, in the form of Asterisk, the open

  • source telephony platform. A full-featured private branch exchange with capabilities for call distribution and interactive voice response, Asterisk runs on industry-standard hardware and shares your existing dat network rather than requiring separate lines and interconnection hardware. This combination ca reduce business customers' initial investment in telephony by as much as 90%, and provides the opportunity for equally dramatic reductions in calling costs.Even better, Asterisk lets customers integrate their telephone system with other applications as easily as they integrate their CRM application with their accounting software. Asterisk can be extende using its APIs, dynamic module loader, and AGI scripting interface, and customers can add their ow applications that run on the system in C or any scripting language of their choice. Asterisk means tha powerful capabilities like call recording and call retrieval will be affordable by the majority of businesses for the first time.Paul Mahler's book on Asterisk will help you learn how to install, configure and maintain Asterisk so you can begin realizing the benefits of open source telephony. I welcome you to the Asterisk communityWilliam Boehlke


    Signate, LL

    Chapter 1 - Introduction

    Asterisk is a PBX and a lot more. Asterisk is revolutionary, reliable, open source, free software that turns an ordinary inexpensive PC running Linux into a powerful enterprise telephone system. Asteris is an open source toolkit for telephony applications and a full-featured call-processing server. Asteris is an open architecture Computerized Telephony Integration platform. Many Asterisk systems are successfully installed around the world. Asterisk technology is working today for many businesses. Asterisk can be used for many things and has features includin

    Private Branch Exchange (PBX)

    Voicemail Services with Directory

    Conferencing Server

    Packet Voice Server

    Encryption of Telephone or Fax Calls

    Heterogeneous Voice over IP gateway (H.323, SIP, MGCP, IAX)

    pkg://voip telephony with asterisk/apdxglossary_PBXpkg://voip telephony with asterisk/apdxglossary_PBXpkg://voip telephony with asterisk/apdxglossary_Voicemailpkg://voip telephony with asterisk/apdxglossary_Telephonepkg://voip telephony with asterisk/apdxglossary_SIP

  • Custom Interactive Voice Response (IVR) system

    Soft switch

    Number Translation

    Calling Card Server

    Predictive Dialer

    Call Queueing with Remote Agents

    Gateway and Aggregation for Legacy PBX systems

    Remote Office or User Telephone Services

    PBX long distance Gateway

    Telemarketing Block

    Standalone Voicemail System

    Many of the world's largest telephone companies have committed to replacing their existing circuit switched systems with packet switched voice over IP systems. Many phone companies are alread transporting a significant portion of their traffic with IP. Many calls made over telephone compan equipment are already being transported with IP.Packet switched voice over IP systems are in principle as efficient as a synchronous circuit switched systems, but only recently have they had the potential to achieve the same level of reliability as the public switched telephone network or proprietaryPBX equipment. With the invention and implementation of RTP

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