Asterisk - The Future Of Telephony

What is Asterisk?

Asterisk is an open source PBX, or "Private Branch eXchange", but such a simple description barely does it justice. Asterisk is, in fact, the leading telephony engine and tool kit in the world - released under GPL or "General Public License", and therefore available for download free of charge - allowing flexible communications solutions be created by developers and integrators alike. Not only is the Asterisk software itself, free, but it runs on Linux BSD ("Berkeley Software Distribution", a.k.a. "Berkeley Unix") emulated Microsoft Windows and Macintosh OS X such that it can offer interoperability with almost all standards-based telephony equipment at relatively low cost.

How and Where is Asterisk Deployed?

Asterisk can be deployed as a gateway, as a feature or media server, or in a call centre where it can provide the backbone of a complete ACD or "Automated Call Distribution" system for example. Asterisk can provide a bridge between the existing PSTN ("Public Switched Telephone Network") and IP or VoIP (Voice over Internet Protocol") telephony which is rapidly becoming a mainstream service. Asterisk supports a wide range of telecommunications standards and protocols - H.323, SIP ("Session Initiation Protocol"), MGCP ("Media Gateway Control Protocol"), etc. - and its modular design means that it can convert from one to another with relative ease. In fact, a total of four APIs ("Applications Programming Interfaces") are defined as loadable modules so the Asterisk core itself, does not deal with call connection, codec translation and other functions that can be performed elsewhere.

In terms of features and functionality, Asterisk is streets ahead of many proprietary systems including those at the high end of the market. Conference bridging, IVR ("Interactive Voice Response"), auto attendant and voicemail capabilities are all included, as is Unified Messaging which allows voice, fax, SMS and email messages to be accessed via a single mailbox.

How is Asterisk Used by Telecoms Service Providers?

Telephone service providers can take advantage of Asterisk for the provision of feature servers, voicemail systems, prepaid calling solutions, etc., all of which are more flexible and less expensive than those provided by alternative means. Asterisk is deployed on millions of servers worldwide to manage VoIP telephony for consumers and businesses, for example and requires no additional hardware. In fact many VoIP service providers nowadays, not only support Asterisk, but are explicitly designing their own services to work with Asterisk. Incoming and outgoing calls can be handled by different VoIP or telecoms service providers if need be, which can be useful if one telephone service provider allows only incoming VoIP calls to avoid the provision of directory services, etc.. It may be of course that a telephone service provider boycotts VoIP altogether, but this need not necessarily preclude the use of VoIP; Asterisk can convert calls between TDM ("Time Division Multiplexing") and VoIP, and back again, as they leave or enter the carrier network. Asterisk also supports a range of hardware for the connection of existing digital and analogue telephony equipment.