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.