Asterisk · The Definitive Guide by Meggelen, Jim -- Read -- Imperial Library of Trantor

Index

Asterisk™: The Definitive Guide

SPECIAL OFFER: Upgrade this ebook with O’Reilly Foreword Preface

Audience Organization Software Conventions Used in This Book Using Code Examples Safari Books Online How to Contact Us Acknowledgments

Leif Madsen Jim Van Meggelen Russell Bryant

1. A Telephony Revolution

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. Asterisk Architecture

Modules

Applications Bridging Modules Call Detail Recording Modules Channel Event Logging Modules Channel Drivers Codec Translators Format Interpreters Dialplan Functions PBX Modules Resource Modules Addon Modules 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

3. Installing Asterisk

Installation Cheat Sheet Distribution Installation

CentOS Server

Base system installation Base system update Enabling NTP for accurate system time Adding a system user

Ubuntu Server

Base system installation Base system update Enable NTP for accurate system time

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

indications.conf and asterisk.conf modules.conf musiconhold.conf

make menuselect

Uses for menuselect menuselect interfaces Using menuselect Scripting menuselect

Updating Asterisk Common Issues

-bash: wget: command not found configure: error: no acceptable C compiler found in $PATH make: gcc: command not found configure: error: C++ preprocessor “/lib/cpp” fails sanity check configure: error: *** Please install GNU make. It is required to build Asterisk! configure: *** XML documentation will not be available because the ‘libxml2’ development package is missing. configure: error: *** termcap support not found You do not appear to have the sources for the 2.6.18-164.6.1.el5 kernel installed. E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?

Upgrading Asterisk Conclusion

4. Initial Configuration Tasks

asterisk.conf

The [directories] Section The [options] Section The [files] Section The [compat] Section

modules.conf

The [modules] Section

indications.conf musiconhold.conf

Converting Music to a Format That Works Best with Asterisk

CentOS Ubuntu Completing file conversion

Conclusion

5. User Device Configuration

Telephone Naming Concepts Hardphones, Softphones, and ATAs Configuring Asterisk

How Channel Configuration Files Work with the Dialplan sip.conf iax.conf Modifying Your Channel Configuration Files for Your Environment

Loading Your New Channel Configurations

The Asterisk CLI

Testing to Ensure Your Devices Have Registered Analog Phones A Basic Dialplan to Test Your Devices Under the Hood: Your First Call Conclusion

6. Dialplan Basics

Dialplan Syntax

Contexts Extensions Priorities

Unnumbered priorities The 'same =>' operator Priority labels

Applications The Answer(), Playback(), and Hangup() Applications

A Simple Dialplan

Hello World

Building an Interactive Dialplan

The Goto(), Background(), and WaitExten() Applications Handling Invalid Entries and Timeouts Using the Dial() Application

Argument 1: Destination Argument 2: Timeout Argument 3: Option Argument 4: URI Updating the dialplan Blank arguments

Using Variables

Global variables Channel variables Environment variables Adding variables to our dialplan

Pattern Matching

Pattern-matching syntax Pattern-matching examples Using the ${EXTEN} channel variable

Includes

Conclusion

7. Outside Connectivity

The Basics of Trunking Fundamental Dialplan for Outside Connectivity PSTN Circuits

Traditional PSTN Trunks

Analog telephony Digital telephony

Installing PSTN Trunks

Downloading and installing DAHDI Configuring digital circuits

PRI ISDN BRI ISDN MFC/R2

Configuring analog circuits

The s extension

VoIP

PSTN Termination PSTN Origination VoIP to VoIP Configuring VoIP Trunks

Configuring SIP trunks between Asterisk systems

Connecting two Asterisk systems together with SIP Connecting an Asterisk system to a SIP provider Encrypting SIP calls

Configuring IAX trunks between Asterisk systems

IAX trunking IAX encryption

Emergency Dialing Conclusion

8. Voicemail

Comedian Mail

The [general] Section The [zonemessages] Section The Contexts Section An Initial voicemail.conf File

Dialplan Integration

The VoiceMail() Dialplan Application The VoiceMailMain() Dialplan Application Creating a Dial-by-Name Directory Using a Jitterbuffer

Storage Backends

Linux Filesystem ODBC IMAP

Using Asterisk As a Standalone Voicemail Server

Integrating Asterisk into a SIP Environment As a Standalone Voicemail Server

Dialplan requirements sip.conf requirements

SMDI (Simplified Message Desk Interface)

Conclusion

9. Internationalization

Devices External to the Asterisk Server PSTN Connectivity, DAHDI, Digium Cards, and Analog Phones

DAHDI Drivers

Asterisk

Caller ID Language and/or Accent of Prompts Time/Date Stamps and Pronunciation

Conclusion—Easy Reference Cheat Sheet

10. Deeper into the Dialplan

Expressions and Variable Manipulation

Basic Expressions Operators

Dialplan Functions

Syntax Examples of Dialplan Functions

Conditional Branching

The GotoIf() Application Time-Based Conditional Branching with GotoIfTime()

Macros

Defining Macros Calling Macros from the Dialplan Using Arguments in Macros

GoSub()

Defining Subroutines Calling Subroutines from the Dialplan Using Arguments in Subroutines Returning from a Subroutine

Local Channels Using the Asterisk Database (AstDB)

Storing Data in the AstDB Retrieving Data from the AstDB Deleting Data from the AstDB Using the AstDB in the Dialplan

Handy Asterisk Features

Zapateller() Call Parking Conferencing with MeetMe()

Conclusion

11. Parking and Paging

features.conf

The [general] section The [featuremap] Section The [applicationmap] Section Application Map Grouping Parking Lots

Overhead and “Underchin” Paging (a.k.a. Public Address)

Places to Send Your Pages

External paging Set paging Multicast paging via the MulticastRTP channel VoIP paging adaptors Combination paging Bringing it all together

Zone Paging

Conclusion

12. Internet Call Routing

DNS and SIP URIs

The SIP URI SRV Records Accepting Calls to Your System

Modifying sip.conf Standard dialplan File parsing Database lookup

Dialing SIP URIs from Asterisk

ENUM and E.164

E.164 and the ITU ENUM Asterisk and ENUM

ISN, ITAD, and freenum.org

Got ISN? ITAD Subscriber Numbers (ISNs) Management of Internet Numbering IP Telephony Administrative Domains (ITADs) Create a DNS Entry for Your ITAD Testing Your ITAD Using ISNs in Your Asterisk System

Receiving calls to your ITAD

Security and Identity

Toll Fraud Spam over Internet Telephony (SPIT) Distributed Denial of Service Attacks Phishing Security Is an Ongoing Process

Conclusion

13. Automatic Call Distribution (ACD) Queues

Creating a Simple ACD Queue Queue Members

Controlling Queue Members via the CLI Controlling Queue Members with Dialplan Logic Automatically Logging Into and Out of Multiple Queues An Introduction to Device State

The queues.conf File The agents.conf File Advanced Queues

Priority Queue (Queue Weighting) Queue Member Priority Changing Penalties Dynamically (queuerules.conf) Announcement Control Overflow

Controlling timeouts Controlling when to join and leave a queue

Using Local Channels

Queue Statistics: The queue_log File Conclusion

14. Device States

Device States

Checking Device States

Extension States

Hints Checking Extension States

SIP Presence

Asterisk Configuration

Using Custom Device States

An Example

Distributed Device States

Using OpenAIS

Installation OpenAIS configuration Asterisk configuration Testing device state changes

Using XMPP

Installation Creating XMPP accounts Asterisk configuration Testing

Shared Line Appearances

Installing the SLA Applications Configuration Overview Key System Example with Analog Trunks

sla.conf extensions.conf Additional phone configuration tasks

Key System Example with SIP Trunks

sla.conf extensions.conf

Shared Extension Example

sla.conf extensions.conf

Additional Configuration Limitations

Conclusion

15. The Automated Attendant

An Auto Attendant Is Not an IVR Designing Your Auto Attendant

The Greeting The Main Menu

Selection 1 Selection 2 Selection # Selection 3 Selection 9 Selection 0

Timeout Invalid Dial by Extension

Building Your Auto Attendant

Recording Prompts

Using the dialplan to create recordings

The Dialplan Delivering Incoming Calls to the Auto Attendant IVR

Conclusion

16. Relational Database Integration

Installing and Configuring PostgreSQL and MySQL

Installing PostgreSQL for CentOS Installing PostgreSQL for Ubuntu Installing MySQL for CentOS Installing MySQL for Ubuntu Configuring PostgreSQL Configuring MySQL

Installing and Configuring ODBC

Configuring ODBC for PostgreSQL Configuring ODBC for MySQL Configuring ODBC for Microsoft SQL Validating the ODBC Connector Configuring res_odbc to Allow Asterisk to Connect Through ODBC

Managing Databases

Troubleshooting Database Issues

A Gentle Introduction to func_odbc Getting Funky with func_odbc: Hot-Desking Using Realtime

Static Realtime Dynamic Realtime

Storing Call Detail Records (CDRs) ODBC Voicemail

Creating the Large Object Type for PostgreSQL ODBC Voicemail Storage Table Layout Configuring voicemail.conf for ODBC Storage Testing ODBC Voicemail

Verifying binary data stored in PostgreSQL Verifying binary data stored in MySQL

Conclusion

17. Interactive Voice Response

What Is IVR? Components of an IVR IVR Design Considerations

Do Don’t

Asterisk Modules for Building IVRs

CURL func_odbc AGI AMI

A Simple IVR Using CURL

Installing the cURL Module The Dialplan

A Prompt-Recording Application Speech Recognition and Text-to-Speech

Text-to-Speech Speech Recognition

Conclusion

18. External Services

Calendar Integration

Compiling Calendaring Support into Asterisk

CentOS dependencies Ubuntu dependencies

Configuring Calendar Support for Asterisk Triggering Calendar Reminders to Your Phone

Triggering a wakeup call Scheduling calls between two participants Calling meeting participants and placing them into a conference

Controlling Calls Based on Calendar Information Writing Call Information to a Calendar Conclusion

VoiceMail IMAP Integration

Compiling IMAP VoiceMail Support into Asterisk

CentOS dependencies Ubuntu dependencies Compiling the IMAP library Compiling Asterisk Configuring Asterisk

Enabling IMAP on your Gmail account Configuring voicemail.conf for IMAP

Using XMPP (Jabber) with Asterisk

Compiling Jabber Support into Asterisk

CentOS dependencies Ubuntu dependencies

Jabber Dialplan Commands

Connecting to an XMPP server Sending messages with JabberSend() Receiving messages with JABBER_RECEIVE()

chan_gtalk

Configuring gtalk.conf Accepting calls from Google Talk Accepting calls from Google Voice Outgoing calls via Google Talk Outgoing calls via Google Voice

Skype Integration

Installation of Skype for Asterisk Using Skype for Asterisk

Configuring chan_skype.conf Placing and receiving calls via Skype Sending and receiving messages via Skype Calling your Skype buddies without assigning extension numbers

LDAP Integration

Configuring OpenLDAP Compiling LDAP Support into Asterisk

Ubuntu dependencies CentOS dependencies

Configuring Asterisk for LDAP Support

Configuring res_ldap.conf Configuring extconfig.conf Configuring sip.conf for realtime

Text-to-Speech Utilities

Festival

Installing Festival on CentOS Installing Festival on Ubuntu Using Festival with Asterisk

Cepstral

Conclusion

19. Fax

What Is a Fax? Ways to Handle Faxes in Asterisk spandsp

Obtaining spandsp Compiling and Installing spandsp Adding the spandsp Library to Your libpath Recompiling Asterisk with spandsp Support Disabling spandsp (Should You Want to Test Digium Fax)

Digium Fax For Asterisk

Obtaining Digium FFA Disabling Digium FFA (Should You Want to Test spandsp)

Incoming Fax Handling

Fax to TIFF Fax to Email Fax Detection

Outgoing Fax Handling

Transmitting a Fax from Asterisk File Format for Faxing An Experiment in Email to Fax

Fax Pass-Through

Using Fax Buffers in chan_dahdi.conf

Conclusion

20. Asterisk Manager Interface (AMI)

Quick Start

AMI over TCP AMI over HTTP

Configuration

manager.conf http.conf

Protocol Overview

Message Encoding

Events Actions

AMI over HTTP

Authentication and session handling /rawman encoding /manager encoding /mxml encoding Manager events

Development Frameworks

CSTA

Interesting Applications

AsteriskGUI Flash Operator Panel

Conclusion

21. Asterisk Gateway Interface (AGI)

Quick Start AGI Variants

Process-Based AGI

EAGI

DeadAGI Is Dead FastAGI—AGI over TCP Async AGI—AMI-Controlled AGI

AGI Communication Overview

Setting Up an AGI Session

Process-based AGI/FastAGI Async AGI

Commands and Responses

Process-based AGI/FastAGI Async AGI

Ending an AGI Session

Process-based AGI/FastAGI Async AGI

Development Frameworks Conclusion

22. Clustering

Traditional Call Centers Hybrid Systems Pure Asterisk, Nondistributed Asterisk and Database Integration

Single Database Replicated Databases

Asterisk and Distributed Device States

Distributing Device States over a LAN Distributing Device States over a WAN

Multiple Queues, Multiple Sites Conclusion

23. Distributed Universal Number Discovery (DUNDi)

How Does DUNDi Work? The dundi.conf File Configuring Asterisk for Use with DUNDi

General Configuration Initial DUNDi Peer Definition Creating Mapping Contexts Using Mapping Contexts with Peers Allowing Remote Connections Controlling Responses

Manually adding responses Using pattern matches Dynamically adding extension numbers Using dialplan functions in mappings

Performing Lookups from the Dialplan

Conclusion

24. System Monitoring and Logging

logger.conf

Reviewing Asterisk Logs Logging to the Linux syslog Daemon Verifying Logging

Call Detail Records

CDR Contents Dialplan Applications cdr.conf Backends

cdr_adaptive_odbc cdr_csv cdr_custom cdr_manager cdr_mysql cdr_odbc cdr_pgsql cdr_radius cdr_sqlite cdr_sqlite3_custom cdr_syslog cdr_tds

Example Call Detail Records

Single-party call Two-party call

Caveats

CEL (Channel Event Logging)

Channel Event Types Channel Event Contents Dialplan Applications cel.conf Backends

cel_odbc cel_custom cel_manager cel_pgsql cel_radius cel_sqlite3_custom cel_tds

Example Channel Events

Single-party call Two-party call Blind transfer

SNMP

Installing the SNMP Module for Asterisk

CentOS dependency Ubuntu dependency Recompiling Asterisk with the res_snmp module

Configuring SNMP for Asterisk Using OpenNMS

Installing OpenNMS Editing /etc/asterisk/res_snmp.conf to work with your OpenNMS server Editing /etc/snmp/snmpd.conf to work with your OpenNMS server Enabling SNMPv3

Monitoring Asterisk with OpenNMS

Conclusion

25. Web Interfaces

Flash Operator Panel Queue Status and Reporting

Queue Status Display Queue Reporting

Call Detail Records A2Billing Conclusion

26. Security

Scanning for Valid Accounts Authentication Weaknesses Fail2ban

Installation

iptables Sending email

Configuration

Encrypted Media Dialplan Vulnerabilities Securing Asterisk Network APIs IAX2 Denial of Service Other Risk Mitigation Resources Conclusion—A Better Idiot

27. Asterisk: A Future for Telephony

The Problems with Traditional Telephony

Closed Thinking Limited Standards Compliancy Slow Release Cycles Refusing to Let Go of the Past and Embrace the Future

Paradigm Shift The Promise of Open Source Telephony

The Itch That Asterisk Scratches Open Architecture Standards Compliance Lightning-Fast Response to New Technologies Passionate Community Some Things That Are Now Possible

Legacy PBX migration gateway Low-barrier IVR Conference rooms Home automation

The Future of Asterisk

Speech Processing

Festival Speech recognition

High-Fidelity Voice Video

The challenge of videoconferencing Why we love videoconferencing Why videoconferencing may never totally replace voice

Wireless

WiFi WiMAX

Unified Messaging Peering

E.164 ENUM e164.org

Challenges

Too much change, too few standards Toll fraud VoIP spam Fear, uncertainty, and doubt Bottleneck engineering Regulatory wars Quality of service Complexity

Opportunities

Tailor-made private telecommunications networks Low barrier to entry Hosted solutions of similar complexity to corporate websites Proper integration of communications technologies

A. Understanding Telephony

Analog Telephony

Parts of an Analog Telephone

Ringer Dialpad Hybrid (or network)

Hook switch (or switch hook) Handset

Tip and Ring

Digital Telephony

Pulse-Code Modulation

Digitally encoding an analog waveform Increasing the sampling resolution and rate Nyquist’s Theorem Logarithmic companding Aliasing

The Digital Circuit-Switched Telephone Network

Circuit Types

The humble DS-0―The foundation of it all T-carrier circuits SONET and OC circuits

Digital Signaling Protocols

Channel Associated Signaling (CAS) ISDN

ISDN-BRI/BRA ISDN-PRI/PRA

Signaling System 7

Packet-Switched Networks Conclusion

B. Protocols for VoIP

The Need for VoIP Protocols VoIP Protocols

IAX (The “Inter-Asterisk eXchange” Protocol)

History Future Security considerations IAX and NAT

SIP

History Future Security considerations SIP and NAT

H.323

History Future Security considerations H.323 and NAT

MGCP Proprietary Protocols

Skinny/SCCP UNISTIM

Codecs

G.711 G.726 G.729A GSM iLBC Speex G.722 MP3

Quality of Service

TCP, UDP, and SCTP

Transmission Control Protocol User Datagram Protocol Stream Control Transmission Protocol

Differentiated Service Guaranteed Service

MPLS RSVP

Best Effort

Echo

Why Echo Occurs Managing Echo on DAHDI Channels Hardware Echo Cancellation

Asterisk and VoIP

Users and Peers and Friends—Oh My!

Users Peers Friends

VoIP Security

Spam over Internet Telephony (SPIT) Encrypting Audio with Secure RTP Spoofing What Can Be Done?

Basic network security

Segregating voice and data traffic DMZ Server hardening

Encryption Physical security

Conclusion

C. Preparing a System for Asterisk

Server Hardware Selection

Performance Issues Choosing a Processor

Small systems Medium systems Large systems

Choosing a Motherboard Power Supply Requirements

Computer power supplies Redundant power supplies

Environment

Power Conditioning and Uninterruptible Power Supplies

Power-conditioned UPSs

Grounding Electrical Circuits The Equipment Room

Humidity Temperature Dust Security

Telephony Hardware

Connecting to the PSTN

Analog interface cards Digital interface cards Channel banks Other types of PSTN interfaces

Connecting Exclusively to a Packet-Based Telephone Network Echo Cancellation

Types of Phones

Physical Telephones

Analog telephones Proprietary digital telephones ISDN telephones IP telephones

Softphones Telephony Adaptors Communications Terminals

Linux Considerations Conclusion

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