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FreeSWITCH 1.2
FreeSWITCH 1.2

FreeSWITCH 1.2: Whether you're an IT pro or an enthusiast, setting up your own fully-featured telephony system is an exciting challenge, made all the more realistic for beginners by this brilliant book on FreeSWITCH. A 100% practical tutorial. , Second Edition

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FreeSWITCH 1.2

Chapter 1. Architecture of FreeSWITCH

Welcome to FreeSWITCH! If you are reading this, then undoubtedly you are interested in things like telecommunications and Voice over Internet Protocol (VoIP). FreeSWITCH is revolutionary software created during a telephony revolution. Before looking at the architecture of this powerful software, let's take a look at the colorful world of telecommunications. This will help to put FreeSWITCH into perspective.

In this chapter we will cover:

  • A telephony revolution

  • Advantages of FreeSWITCH

  • Endpoint and Dialplan modules

  • How FreeSWITCH simplifies complex applications like voicemail

A revolution has begun and secrets have been revealed


How and why the telephone works is a mystery to most people. It has been kept secret for years. We just plugged our phones into the wall and they worked, and most people do just that and expect it to work. The telephony revolution has begun, and we have begun to pry its secrets from the clutches of the legacy of the telephony industry. Now, everyday individuals like you and me are able to build phone systems that outperform traditional phone services and offer advanced features for relatively low cost. Some people even use FreeSWITCH to provide telephone services for making a profit. FreeSWITCH has been designed to make all of this easier, so we will go over the architecture to get a better understanding of how it works.

Do not be concerned if some of the concepts we introduce seem unnaturally abstract. Learning telephony takes time, especially VoIP. In fact, we recommend that you read this chapter more than once. Absorb as much as you can on the first pass, then come back after you complete Chapter 5, Understanding the XML Dialplan. You will be surprised at how much your understanding of VoIP and FreeSWITCH has improved. Then come back and skim it a third time after you have completed Chapter 10, Controlling FreeSWITCH Externally; at this point, you will have a firm grasp of VoIP and FreeSWITCH concepts. Give yourself plenty of time to digest all of these strange new concepts, and soon you will find that you are a skilled FreeSWITCH administrator. If you keep at it, you will be rewarded with a meaningful understanding of this strange and wonderful world we call telephony.

Telephones and telephony systems (such as telephone switches and PBXs) are very complicated and have evolved over the years into several varieties. The most popular type of phone in the U.K. and the U.S. is the traditional analog phone, which we affectionately refer to as POTS lines or Plain Old Telephone Service. From the traditional Ma Bell phone up to the long-range cordless phones that most of us have today, one thing has remained the same—the underlying technology. In the last 10-15 years, there has been a convergence of technology between computers and telephones that has produced a pair of affordable alternatives to POTS lines—Mobile phones and VoIP phones (also called Internet Phones).

FreeSWITCH fits into this big tangled mess of various telephone technologies by bridging them together, so that they can communicate despite being otherwise completely incompatible. FreeSWITCH also bridges telephone calls with computer programs that you can write yourself, and controls what happens in ways like never before. FreeSWITCH is software that runs on Windows and several UNIX varieties such as Mac OS X, Linux, Solaris, and BSD. This means you can install FreeSWITCH on your home PC or even a high-end server and use it to process phone calls. Installing FreeSWITCH is discussed in detail in Chapter 2, Building and Installation. We will be doing this as soon as we review the basic architecture.

The FreeSWITCH design – modular, scalable, and stable


The design goal of FreeSWITCH is to provide a modular, scalable system around a stable switching core, and to provide a robust interface for developers to add to and control the system. Various elements in FreeSWITCH are independent of each other and do not have much knowledge about how the other parts are working, other than what is provided in what are called exposed functions. The functionality of FreeSWITCH can also be extended with loadable modules, which tie a particular external technology into the core.

FreeSWITCH has many different module types that revolve around the central core, much like satellites orbiting a planet. The list includes:

Module type:

Purpose:

Endpoint

Telephone protocols like SIP/H.323 and POTS lines

Application

Performs a task such as playing audio or setting data

Application Programming Interface (API)

Exports a function that takes text input and returns text output, which could be used across modules or from an external connection

Automated Speech Recognition (ASR)

Interfaces with speech recognition systems

Chat

Bridges and exchanges various chat protocols

Codec

Translates between audio formats

Dialplan

Parses the call details and decides where to route the call

Directory

Connects directory information services, such as LDAP, to a common core lookup API

Event handlers

Allows external programs to control FreeSWITCH

File

Provides an interface to extract and play sound from various audio file formats

Formats

Plays audio files in various formats

Languages

Programming language interfaces used for call control

Loggers

Controls logging to the console, system log, or log files

Say

Strings together audio files in various languages to provide feedback to say things like phone numbers, time of day, spell words, and so on

Text-To-Speech (TTS)

Interfaces with text-to-speech engines

Timers

POSIX or Linux kernel timing in applications

XML Interfaces

Uses XML for Call Detail Records (CDRs), RADIUS, CURL, LDAP, RPC, and/or SCGI

The following image shows what the FreeSWITCH architecture looks like and how the modules orbit the core of FreeSWITCH:

By combining the functionality of the various module interfaces, FreeSWITCH can be configured to connect IP phones, POTS lines, and IP-based telephone services. It can also translate audio formats and interfaces with a custom menu system, which you can create by yourself. You can even control a running FreeSWITCH server from another machine. Let's start by taking a closer look at a pair of important module types.

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Key benefits

  • Learn how to install and configure a complete telephony system of your own, even if this is your first time using FreeSWITCHIn-depth discussions of important concepts like the dialplan, user directory, NAT handling, and the powerful FreeSWITCH event socketBest practices and expert tips from the FreeSWITCH experts, including the creator of FreeSWITCH, Anthony Minessale

Description

FreeSWITCH is an open source telephony platform designed to facilitate the creation of voice and chat-driven products, scaling from a soft-phone to a PBX and even up to an enterprise-class soft-switch. It is always exciting to design and build your own telephony system to suit your needs, but the task is time-consuming and involves a lot of technical skill."FreeSWITCH 1.2" comes to your rescue to help you set up a telephony system quickly and securely using FreeSWITCH. It is rich with practical examples and will give you all of the information and skills needed to implement your own PBX system.You will start with a detailed description of the FreeSWITCH system architecture. Thereafter you will receive step-by-step instructions on how to set up basic and advanced features for your telephony platform.The book begins by introducing the architecture and workings of FreeSWITCH before detailing how to plan a telephone system and then moves on to the installation, configuration, and management of a feature-packed PBX. You will learn about maintaining a user directory, XML dial plan, and advanced dial plan concepts, call routing, and the extremely powerful Event Socket. You will finally learn about the online community and history of FreeSWITCH."FreeSWITCH 1.2" is an indispensable tool for novice and expert alike.

Who is this book for?

This book is written for IT professionals and enthusiasts who are interested in quickly getting a powerful telephony system up and running using the free and open source application, FreeSWITCH. Telephony experience will be helpful, but not required.

What you will learn

  • Set up a basic system to make and receive phone calls, make calls between extensions, and utilize basic PBX functionalityDeploy different features of this telephony system with best practices and expert tipsUnderstand the inner workings and architecture of FreeSWITCHUse advanced features to create powerful dialplansOvercome frustrating NAT issuesControl FreeSWITCH remotely with the powerful event socketCreate web-controlled telephony apps with the new HTTAPI systemSecure your VoIP communications

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : May 24, 2013
Length: 428 pages
Edition : 2nd
Language : English
ISBN-13 : 9781782161004
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Product Details

Publication date : May 24, 2013
Length: 428 pages
Edition : 2nd
Language : English
ISBN-13 : 9781782161004
Concepts :
Tools :

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Table of Contents

14 Chapters
Architecture of FreeSWITCH Chevron down icon Chevron up icon
Building and Installation Chevron down icon Chevron up icon
Test Driving the Example Configuration Chevron down icon Chevron up icon
SIP and the User Directory Chevron down icon Chevron up icon
Understanding the XML Dialplan Chevron down icon Chevron up icon
Using XML IVRs and Phrase Macros Chevron down icon Chevron up icon
Dialplan Scripting with Lua Chevron down icon Chevron up icon
Advanced Dialplan Concepts Chevron down icon Chevron up icon
Moving Beyond the Static XML Configuration Chevron down icon Chevron up icon
Controlling FreeSWITCH Externally Chevron down icon Chevron up icon
Web-based Call Control with mod_httapi Chevron down icon Chevron up icon
Handling NAT Chevron down icon Chevron up icon
VoIP Security Chevron down icon Chevron up icon
Advanced Features and Further Reading Chevron down icon Chevron up icon

Customer reviews

Top Reviews
Rating distribution
Full star icon Full star icon Full star icon Full star icon Half star icon 4.5
(6 Ratings)
5 star 66.7%
4 star 16.7%
3 star 16.7%
2 star 0%
1 star 0%
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BHUPENDRA SINGH Jul 19, 2013
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This concise yet excellent book takes you step by step through most of the key areas from installation to configuration,and it does so in a manner that seems to strike the right balance between brevity and depth.A very good resource specially if you plan to move from Asterisk to FreeSwitch;it got full chapter on Asterisk migration.It also got separate chapters on understanding dialplan, mod_httapi for web based call control etc..
Amazon Verified review Amazon
CHARLES WALSH Sep 04, 2017
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Très bien
Amazon Verified review Amazon
Ali R. Jun 04, 2013
Full star icon Full star icon Full star icon Full star icon Full star icon 5
The authors of this FreeSWITCH book come through again. The layout and presentation are fantastic. After I bought this book, I saved it like a treat till I could sit down and enjoy it. I Would buy again the next edition and I highly recommend it to anyone interested in telephony platforms.
Amazon Verified review Amazon
FPYM Jun 17, 2013
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I recently finished FreeSWITCH 1.2 and also own the first two FreeSWITCH books. Bottom line: This is an excellent book.What is does well: - discuss how to do a variety of tasks - explain WHY things are done - discuss advanced tasks in a fantastic method (NAT, Encryption)Target Audience: - New to Advanced will use this bookWhat I would love more of: - Encryption (more of a cursory discussion). I feel this is going to be very hot in the years to come and more descriptive information would be appropriate.5 stars. Very well priced, excellent resource.
Amazon Verified review Amazon
Rafal Gwizdala Jun 20, 2013
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
This book covers very broad range of subjects and is really helpful when you want to learn FreeSWITCH and its capabilities or if you want to start developing FS-based applications. It contains tons of information and examples (in a reasonable proportion) so it gets you quickly on the right track. However, i think some subjects could be explained in more details, especially the API commands and events (but this probably would make the book twice as big). All in all, it's a great book and I recommend it to everyone who wants to learn how FS works.
Amazon Verified review Amazon
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