Burning questions about Asterisk open-source PBX platform

The Asterisk PBX platform has been around for nine years and has drawn interest from a wide range of end users and businesses looking to expand on the basic software or add peripherals to make it more attractive to potential users.

Here are a few questions and answers to help get grounded in Asterisk.

What is Asterisk? Asterisk is an open-source PBX written by Mark Spencer that is available for free download. A free beta trial version of a simplified version called AsteriskNow is also available.

The software supports a stand-alone PBX or can function as a gateway between older TDM PBXs and IP networks. It includes features such as voice mail, conferencing, call distribution and voice phone menus, among many others.

Asterisk runs on Linux, Solaris, Mac OS and NetBSD, FreeBSD and OpenBSD servers.

The platform supports SIP, MGCP, H.323 and the Inter-Asterisk Exchange protocols.

How popular is Asterisk? Digium Inc., the company created by Spencer to capitalize on Asterisk, reported more than 1 million downloads in 2007 alone, and the company has been around since 1999. That doesn't mean all of those downloads are actually used to support phone networks, but it does show considerable interest.

Vendors that incorporate Asterisk into commercial PBX platforms don't report sales statistics, according to Infonetics Research, which tracks IP PBX sales. Anecdotally, in a 2007 survey of businesses about IP PBXs, just two out of 240 respondents said they used an Asterisk platform.

How many phones can Asterisk support?

The largest deployment Digium knows about is at the University of Pennsylvania, which has more than 10,000 phones.

Why would I want to use an unsupported PBX platform?

The main reason is price -- zero for the software. If you have the time and technical-savvy, you stand to save a lot of money initially deploying the system. Over time, you can save even more if you have the wherewithal to maintain the system, update it and modify it to your needs. Even with the hardware thrown in, the cost savings can be significant, as much as 90% off the price of a commercially available PBX.

That being said, there are potential downsides, the main one being support. For businesses the size that Asterisk can serve -- up to several hundred -- telecom staff may be lacking. It may be necessary to use professional help no matter what phone system they choose.

This can be addressed by using one of the many integrators that specialize in Asterisk deployments, opting for a simplified or preconfigured Asterisk package available from certain vendors and buckling down to Asterisk support groups with members on call to help each other out.

What does a commercial Asterisk appliance cost?

A basic appliance costs about $1,000 to $1,500. Various vendors sell additional support contracts and peripheral hardware, including phones.

These commercially upgraded platforms come with some advantages, such as custom hardware appliances as opposed to modified PCs. They also come with peripheral software that can add nonstandard features but also provide graphical interfaces to the PBX that make it simpler to configure and customize for individual use. Other software options include desktop software for configuring individual end-user preferences and tools for integrating voice-over-IP capabilities of Asterisk into business applications.

What is the minimum I need to set up Asterisk? You need a compatible server outfitted with custom WAN cards that support Asterisk, phone adapters for analog phones or Asterisk-compatible VoIP phones.

You have to set up a dialing plan for the network and configure the various call features you hope to use.

How can I add custom features to Asterisk? Asterisk has an open programming interface called Asterisk Gateway Interface that lets users write programs in C, Perl and PHP, and apply them to the Asterisk platform.

Are there free alternatives to Asterisk? Yes. They include sipX, OpenPBX, PBX4Linux, Yate, FreeSwitch.

Who is Mark Spencer and why did he create Asterisk? Mark Spencer is a computer engineer with authorship of the instant messaging client Pidgin to his credit. When he started up his own technical service and support business, he found that he didn't have enough money to buy a PBX for the business. Using his programming skills and knowledge of Linux, he wrote his own PBX software, which became Asterisk.

Where does the name come from? In Unix commands, the asterisk symbol (*) indicates "everything." So the command rm*.txt means delete everything or all files ending in .txt.

This story, "Burning questions about Asterisk open-source PBX platform" was originally published by Network World.

Copyright © 2008 IDG Communications, Inc.

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