Light on Linux requirements

Perhaps the most fundamental misconception about Asterisk is that it requires you to be a Linux shop. Not true. The open source PBX runs as a service on many platforms, including Windows, as there are projects available to enable Asterisk to run on 32-bit Windows.

Constructed much like your traditional PBX, Asterisk is based on a Unix-like OS hidden by a CLI or GUI management layer. You can deploy a standard Linux server and install the Asterisk package to create your own PBX or go with one of the several customized Linux distributions based around Asterisk.

Today's most popular distribution is Trixbox, which consolidates a CentOS Linux platform, Asterisk, a bevy of open source Asterisk management tools, and custom code to make rollouts easier. With Trixbox, you can go from bare metal to a fully functional Asterisk IP PBX in 20 minutes. The same can be said for Digium's recently released AsteriskONE, which takes a similar tack as Trixbox but offers different management tools.

In delineating differences between Trixbox and AsteriskONE, Spencer points out that, although Trixbox uses Asterisk, it is completely separate from Asterisk itself. "AsteriskONE is basically an HTML gateway between Asterisk and your Web browser," he says. "If you make a manual change, it's reflected in both Asterisk and the Web UI. Trixbox doesn't have that."

Trixbox does, however, offer significant features AsteriskONE lacks, such as easy implementation and configuration of the HUDLite user GUI, SugarCRM integration, and configuration tools for popular IP phone models. That said, AsteriskONE is still in beta.

As for managing an Asterisk deployment, a baseline grasp of Linux is advisable but not required. Open source tools such as FreePBX offer a full Web UI for managing Asterisk, from simple extension and trunk configuration to complex dial plans, IVR (interactive voice response) functions, voice mail, and more. In fact, you can build and deploy an Asterisk PBX without touching a command line, although familiarity with the Linux and Asterisk shells are necessary for large deployments. Smaller shops will likely never see what's behind the scenes, much as they don't worry about Linux running on security appliances.

The value of community

Support may be the most substantive knock against open source VOIP for the enterprise. Even then, Asterisk is an exception to the rule.

Whereas support for open source projects typically consists of online forums, mailing lists, and the occasional book, Asterisk has a company behind it. Digium offers support services in addition to hardware vetted for Asterisk use, such as analog and digital interface cards to connect Asterisk with the PSTN. Whether Digium's support scales to enterprise levels is yet to be seen, but it will at least lend Asterisk proposals legitimacy as they wend their way through the corporate food chain in quest of funding.

But the major boon for Asterisk adopters -- besides cost savings -- is that, with the right admins in place, the open source IP PBX can be modified to do just about anything. In fact, much of Asterisk is already modular, using the AGI (Asterisk Gateway Interface), which is patterned on the CGI intrinsic to Web servers.

AGI allows admins to write plug-ins for Asterisk in just about any language, including Python, PHP, Ruby, Java, C, and Perl. As such, customizing your PBX's feature set is relatively easy, and with the community of developers designing tools for Asterisk growing rapidly, ready-made features abound. Examples include a trouble-ticket management app that accepts ticket number input from a dial pad and another that performs an Amazon lookup of keyed-in 10-digit ISBN numbers and recites book prices back to the caller.

Open for experimentation

The phone system may very well remain the most commonly used and relied-on corporate app. Interaction with the phone system is constant, and the features, performance, and stability of the system are under constant subconscious scrutiny. Voice mail features and ease of use, voice mail/e-mail gateways, call quality, and follow-me features are all highly visible components of any PBX, to users on both sides of the dial tone, and IVR functions and reliability can make or break sales and business relationships. As such, commitment to an IP PBX should by no means be taken lightly -- especially when it comes to assessing how well a VOIP solution will adapt to future evolutions in your enterprise.

As with all open source solutions, the beauty of Asterisk is that it allows you to try before you buy. What's more, Asterisk is available in a dozen different forms, via packaged solutions such as Trixbox and AsteriskNOW or as raw source code. Trixbox and AsteriskNOW are also available as prepared VMware images -- simply download and boot them on a VMware workstation or server. It couldn't be easier to set aside your misgivings and investigate the viability of open source VOIP yourself.

Soon enough, as more and more companies become comfortable widening their search beyond commercial fare, they will find that open source dial tone is a worthwhile alternative, in it for the long haul. The cost savings are that compelling, as is the promise of greater customization and control. And as voice penetrates deeper into the enterprise in the years to come, the ability to quickly code customized features could give companies employing open source IP PBXes such as Asterisk a significant leg up in fulfilling the much-discussed promise of VOIP apps.