Open source PBXes: free flexibility

One great thing about the open source movement is that if there’s a feature of any kind that someone somewhere needs, it will be made available for everyone. As a result, the open source PBXes tested here are feature-filled Swiss Army knives of communications solutions.

Free IT resource TechNet: More ways to know it, share it, and keep it running. Sponsored by Microsoft Free IT resource Attend the SOA Executive Forum: Breaking SOA Bottlenecks SOAExecForum.com/may2007 Sponsored by InfoWorld

Like other open source products, these PBXes don’t necessarily cost anything to obtain. That doesn’t mean, however, there aren’t costs involved with getting these phone systems running. Phone hardware is still required, and the expertise to turn the software into something you can use in your enterprise doesn’t come cheap. Open source product support comes from the community itself, so you’ll need to know where to look and who to ask to get what you need.

If that doesn’t work for your company, both Pingtel and Digium will provide support and services for a reasonable cost. If you’re willing to invest some time and thought in picking the right product, getting the right plug-ins and options, and training someone on your staff to manage the PBX, you can save a lot of money and very likely get a solution that exactly fits your needs.

Asterisk V1.0.3

Digium calls Asterisk the first open source PBX. In reality, it’s a lot more than a PBX: It also takes on the functions of a media server, a protocol gateway, and a conference bridge. It goes beyond VoIP, too, supporting other types of digital communications and even POTS systems.

Asterisk can be installed on anything that will run Linux with kernel Version 2.4 or later. It will also run on FreeBSD Unix and on Mac OS X, and another version will run on coLinux under Microsoft Windows, although its functionality is limited.

As you’d expect for a product that supports such a wide variety of hardware, you can add a lot to the Asterisk system in terms of infrastructure and software. Because it’s open source, there’s also a wealth of applications that add functions to Asterisk, such as support for a variety of phone interfaces or concentrators and media gateway services such as outboard conferencing.

You’ll probably need to add at least some of those functions. Although Asterisk is fully functional when you download it, the base product doesn’t include many of the interfaces and capabilities — such as graphical management interfaces — available from third parties.

This observation is not to suggest that Asterisk is missing features — far from it. Most of the features are present in basic form, so you’ll be making management changes, adds, moves, and the like by editing a text file. As long as you can use a Linux text editor, follow some basic instructions, and deal with a set of configuration files that are reasonably intuitive, there’s little else you’ll need.

Although management via text-file editing is far from sexy, it is effective, fast, and reduces mouse-related carpal tunnel exposure. Dealing directly with configuration files, though, requires more admin expertise than using a GUI, and that may limit Asterisk’s usefulness at some companies.

For the test, the Digium engineers and I created a somewhat atypical phone network. It included a series of SIP-based phones, along with analog phones, MGCP (Media Gateway Control Protocol) and H.323 phones, SCCP (Signaling Connection Control Part) phones, and phones using several other digital protocols.

We installed the PBX software on a pair of mismatched, low-end Pentium desktop computers, each equipped with Ethernet adapters and a four-way T1 adapter. Two of the T1 lines linked the PBXes; two of the other T1 lines from one of the PBXes went to the analog phones.

The low-end desktop PCs were used to test Digium’s claim that you don’t need anything special to bring up its PBX. In reality, you’d be out of your mind to do this, because phone service is critical for most companies. Your phone system should be installed on some nicely redundant, server-quality platforms. The Asterisk installation proved its point, though — it requires no fancy hardware.

With this setup, I could call any phone on the network from any other phone. Call quality remained good, and all PBX features (including standards such as automatic call distribution, voice mail services, and call queuing) were available. Some features were phone-dependent — you won’t suddenly get advanced calling features on plain analog phones — but the basics were there for every phone.