Asterisk is a software implementation of a telephone private branch exchange; it was
created in 1999 by Mark Spencer of Digium.
Like any PBX, it allows attached telephones to make calls to one another, and to connect
to other telephone services, such as the public switched telephone network and Voice over
Internet Protocol services.
Its name comes from the asterisk symbol, *. Asterisk is released under a dual license
model, using the GNU General Public License as a free software license and a proprietary
software license to permit licensees to distribute proprietary, unpublished system components.
Originally designed for Linux, Asterisk also runs on a variety of operating systems including
NetBSD, OpenBSD, FreeBSD, Mac OS X, and Solaris.
Asterisk is small enough to run in an embedded environment like Customer-premises equipment-hardware
running OpenWrt.
Features The Asterisk software includes many features
available in proprietary PBX systems: voice mail, conference calling, interactive voice
response, and automatic call distribution.
Users can create new functionality by writing dial plan scripts in several of Asterisk's
own extensions languages, by adding custom loadable modules written in C, or by implementing
Asterisk Gateway Interface programs using any programming language capable of communicating
via the standard streams system or by network TCP sockets.
Asterisk supports a wide range of Voice over IP protocols, including the Session Initiation
Protocol, the Media Gateway Control Protocol, and H.323.
Asterisk can interoperate with most SIP telephones, acting both as registrar and as a gateway
between IP phones and the PSTN.
The Inter-Asterisk eXchange protocol, RFC 5456, native to Asterisk, provides efficient
trunking of calls among Asterisk PBXes, in addition to distributed configuration logic,
and call completion to VoIP service providers who support it.
Some telephones support the IAX2 protocol directly.
By supporting a mix of traditional and VoIP telephony services, Asterisk allows deployers
to build new telephone systems, or gradually migrate existing systems to new technologies.
Some sites are using Asterisk servers to replace proprietary PBXes; others to provide additional
features or to reduce costs by carrying long-distance calls over the Internet.
Asterisk was one of the first open source PBX software packages.
In addition to VoIP protocols, Asterisk supports many traditional circuit-switching protocols
such as ISDN and SS7.
This requires appropriate hardware interface cards supporting such protocols, marketed
by third-party vendors.
Each protocol requires the installation of software modules.
With these features, Asterisk provides a wide spectrum of communications options.
Internationalization While initially developed in the United States,
Asterisk has become a popular VoIP PBX worldwide because it is freely available under open
source licensing, and has a modular, extensible design.
The American English, French, Persian and Mexican Spanish female voices along with other
new prompts like Australian English for the Interactive voice response and voice mail
features of Asterisk are frequently updated with submissions from developers in many languages
and dialects.
Additionally, voice sets are offered for commercial sale in different languages, dialects and
genders.
Derived products Asterisk is a core component in many PABX
in a box commercial products and open-source projects.
Some of the commercial products are hardware and software bundles, for which the manufacturer
supports and releases the software as open source.
Open-source examples include FreePBX and Elastix.
Asterisk is also included in the LinuxMCE home entertainment/automation system.
See also
2600hz IPBX Comparison of VoIP software
DUNDi libamc
FreeSWITCH IPBX GateKeeper H.323
GNU SIP Witch List of SIP software
OpenBTS SIP Express Router
Sippy B2BUA References
External links Official website
Asterisk Wiki Asterisk Documentation Project
Forbes article about Mark Spencer and Asterisk #asterisk on freenode
Interview with Mark Spencer on Leo Laporte's TWIT.TV FLOSS Weekly podcast
Selector Free MeetMe GUI AppKonference High-performance Asterisk conferencing
module, is a fork of