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Product review: Asterisk brings open source VoIP to the enterprise

Asterisk, open source PBX software, is richly featured and benefits from fast development in the open source community. Better yet, it can save you money.

Product: Asterisk Business Edition
Product description: Open source PBX software
Class: Professional class, suitable for small and medium businesses
Company: Digium
Cost: $995 for the Business Edition

Yesterday at the IP.4.IT conference in Las Vegas, Nevada, Digium Inc. announced the release of Asterisk 1.2, the first major revision to Asterisk since its release in 2004. The update includes over 3,000 feature additions and improvements including code formatting, simplification and documentation. -- Editor

Did you know that there is completely open source, Linux-based VoIP software? Welcome to Asterisk. Written by Mark Spencer of Digium (A Huntsville, Alabama-based company), its code has been modified by the open source community, along with the usual testing and bug fixes, which have really helped the development of this software in terms of enhancing the stability and increasing its feature set.

Asterisk is open source PBX software that runs on Linux, BSD and MacOS X. It has pretty much all the features that one gets from mainstream PBX software and supports VoIP over many protocols. It can also give you the interoperability that one needs when using different types of telephony equipment. (Yes, it can work with Nortel.) Some features include voicemail service along with directory, voice response, call queuing and call conferencing, support for three-way calling, caller ID and SIP. From a hardware perspective, it needs no additional hardware to provide VoIP services. To connect to existing telephony equipment, it supports many different types of hardware devices, though it has a close partnership with Digium hardware, who is their sponsor.

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What makes this product particularly appealing to me is that it was developed on Linux for x/86, though it will also run on BSD and Mac OS X. The advantage here is that you can run Asterisk on commodity hardware, without having to spend big bucks. If you look on the Debian Website, you will find links to the Asterisk Web browser management utility, or Asterisk Management Portal (AMP), which will help you manage your environment.

The AMP project brings together applications to produce a standardized implementation of Asterisk, complete with a Web-based administrative interface. A company called Coalescent Systems has contributed the administration interface to this project. Features include the ability to quickly add or change extension and voicemail accounts in seconds, its support for SIP, IAX and ZAP clients, and its support for all Asterisk-supported trunk technologies. It also can help you reduce long distance costs with LCR, route incoming calls based on time of day, create interactive digital receptionist menus, design sophisticated call groups and upload custom on-hold music. For those of you who have been put on hold with funky elevator music, this might be a welcome change. It can also help back up and restore your system and save audio recordings of calls, though one needs to check on the legal ramifications of doing so.

Asterisk is definitely growing fast, with new features being added constantly. Digium's Website has more information on how to subscribe to the Asterisk mailing lists. Digium, which is a market leader in open source telephony, sells a professional-grade version of its open source PBX for the Linux operating system, called the Asterisk Business Edition. This version provides tested reliability of critical functions and features tailored for small- and medium-sized business applications. For $995, one also gets one year of technical support, which can be key for environments that really need availability. In addition to the support, you also get the following for the paid version of this software.

  • Technical manuals and start-up guides
  • Testing for over 240 calls per server
  • Free upgrades
  • Binaries installers and scripts
  • Commercial license with legal protection
If you are not sure if you want to buy the software, I would recommend first downloading the open source edition to see if it can work for you. If it can, and you are working in a corporate environment that really needs to be constantly available, (and where you might also need to convince the powers that be that the product is fully supported), then I would recommend purchasing this product, as the experienced professional support alone might come in handy in an emergency situation.

Ken Milberg is president of Unix Solutions, a consulting firm that has been working with Unix and Linux systems for more than a decade. He is also a board member of Unigroup of NY, the oldest Unix users group in NYC. Ken regularly answers user questions on Unix and Linux interoperability issues as a site expert on

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