FreeSWITCH

Original author(s)	Anthony Minessale
Developer(s)	Many contributors
Stable release	1.0.6 / April 6, 2010; 4 months ago (2010-04-06)
Development status	Active
Operating system	Cross-platform
Platform	Unix-like, Windows, Sun Solaris, Mac OS X
Available in	multi-lingual
Type	VoIP software, Softswitch
License	Mozilla Public License (MPL)
Website	FreeSWITCH

FreeSWITCH is a free/open source software communications platform for the creation of voice and chat driven products and is released under the MPL free software license. Its core library, libfreeswitch, is capable of being embedded into other projects, as well as being used as a stand-alone application.

Contents 1 History 2 Design 3 Platform support 4 Features 5 Codec Support 6 Issues 7 Comparison with other telephony engines 8 See also 9 References 10 External links

History

The FreeSWITCH project was first announced in January 2006 at O'Reilly's ETEL Conference¹. In June 2007, FreeSWITCH was selected by Truphone for carrier grade use,² and in August 2007, Gaboogie announced that it selected FreeSWITCH as its conferencing platform.³

FreeSWITCH's first official 1.0.0 (Phoenix) release was on May 26, 2008 ⁴. A minor 1.0.1 patch release came out on July 24, 2008.⁵ Current release is 1.0.6 which came out on 6 April 2010. ⁶

Design

According to the lead designer, Anthony Minessale⁷, FreeSWITCH is intended to be a softswitch that is built on top of a solid, state-machine driven core.⁸ The stated goals of the project include stability, scalability, and abstraction.

An older version of the FreeSWITCH website showed a caveman hammering on a stone wheel, with a caption that read, “There are a lot of wheels, we might as well use them.” It seems the FreeSWITCH developers are intent on not reinventing any wheels that can come from other sources. One means of eliminating unnecessary complexity is to use freely available software libraries that perform needed functions—though, of course, this can introduce its own problems (see dependency hell). FreeSWITCH lists these software packages among its primary dependencies:⁹

• Apache Portable Runtime (APR and APR-Util)
• SQLite – A lightweight implementation of a SQL engine
• PCRE – Perl Compatible Regular Expressions
• Sofia-SIP - An open-source SIP user agent library
• libspeex - Speex DSP library (replaced libresample as of version 1.0.3)
• Spandsp
• libSRTP – An open-source implementation of the Secure Real-time Transport Protocol

FreeSWITCH is a modular application, where modules can extend the functionality of FreeSWITCH but the abstraction layer prevents inter-module dependency. The goal is to ensure that one module is not required to load another.^{citation needed}

Platform support

• AuroraUX (LLVM+Clang/gmake)
• Sun Solaris 10 UNIX (Sun Studio)
• FreeBSD (gmake)
• Mac OS X (gmake)
• RHEL/CentOS Linux
• Debian/Ubuntu GNU/Linux
• Windows (Native)

Features

FreeSWITCH includes many modules which provide applications by default including conferencing, XML-RPC control of live calls, Interactive voice response (IVR), TTS/ASR (text to speech/automatic speech recognition), Public switched telephone network (PSTN) interconnection ability supporting both analogue and digital circuits, Voice over IP protocols including SIP, SCCP, H.323, XMPP, GoogleTalk and others.¹⁰

Applications using the FreeSWITCH library can be written in C/C++, Python, Perl, Lua, JavaScript using Mozilla's SpiderMonkey engine, Java and Microsoft .NET via Microsoft's CLR or via Mono. In each case, FreeSWITCH exposes primitives for call control and IVR functionality for the programmer to use.¹¹

Call control applications can use the Event Socket, which is a socket-based connection to the FreeSWITCH server. Any programming language or software that is capable of communicating via sockets can be used to control activity on the FreeSWITCH server. FreeSWITCH also comes with an Event Socket Library (ESL) and "ESL-wrappers" for Erlang, JavaScript, Lua, Perl, PHP, Python, and Ruby. The wrappers are libraries that abstract away some of the mundane aspects of socket-level programming.

Codec Support

FreeSWITCH supports a number of audio codecs:

• PCMU - G.711 mu-law
• PCMA - G.711 A-law
• G.722
• G.722.1
• G.722.1c
• G.726
• G.729
• GSM
• CELT
• iLBC
• DVI4 (IMA_ADPCM)
• BroadVoice
• SILK
• Speex

Issues

While there are some important features missing from FreeSWITCH, many issues deal with its unique configuration methods, or its significant differences from other popular PBX/Softswitch programs.

• BRI support is currently limited to Sangoma interface cards¹²
• XML configuration files may be confusing to new users, especially users that have traditionally used Asterisk^{citation needed}
• International EuroISDN is not fully supported¹³
• FreeSWITCH will support the T.38 fax in the next release¹⁴, but currently does not support acting as a fax gateway for T.38, although it allows T.38 passthrough¹⁵

Comparison with other telephony engines

FreeSWITCH occupies a space between pure switches which simply route calls, such as GnuGK and SER, and those which are primarily PABXes or IVRs, such as Asterisk and its derivatives. FreeSWITCH provides building blocks from which applications - such as a PABX, a voicemail system, a conferencing system or a calling card - can be built using any of the supported languages.

See also

• List of SIP software - other SIP related programs

References

External links

• FreeSWITCH Project Home Page - Contains general information and documentation for the project itself
• FreeSWITCH Wiki - Main source of documentation for FreeSWITCH
• #freeswitch on freenode
• FreeSWITCH book - by Anthony Minessale, Darren Schreiber, Michael S. Collins