While Asterisk IP PBX software can be a boon for cash-strapped businesses that need phone upgrades, the free, open source platform has also spawned a host of for-profit vendors that charge for Asterisk professional services, peripherals and software extensions, and still manage to undercut the prices charged by more established IP PBX vendors.

Digium, the business founded by Asterisk creator Mark Spencer to capitalise on his PBX, says it plans later this year to release a new version that will support much larger deployments. New Jersey-based service provider VoicePulse plans a hosted PBX service based on Asterisk deployed on virtual servers.

With successful partnerships already under its belt, the company promises to broaden its influence this year as 3Com makes Asterisk available on a blade for its multifunction branch-office routers. This is in addition to the relabelled commercial Asterisk appliance made by Digium for 3Com small-business customers.

In Japan, NTT Software, a subsidiary of the country's biggest phone company, is preparing PBX appliances of its own that are based on Asterisk.

On a smaller scale, a growing group of start-ups lies at the heart of an Asterisk-based business community that has sprung up to exploit the basic platform. For instance, vendors Escaux and Fonality, to name two, sell full-blown custom Asterisk PBXs. Critical Links' Edgebox surrounds Asterisk with a router, Wi-Fi access point, NAC and other security to fashion a branch-office-in-a-box device.

Even an Asterisk online superstore called The VoIP Connection has sprung up to sell Asterisk appliances as well as phones, headsets, gateways and other add-ons needed to set up Asterisk networks.

It may not be right for every business, particularly the largest, but some vendors claim their Asterisk-based gear and services can cost one-tenth as much as equipment sold by major vendors such as Avaya, Cisco, Nortel, NEC and Siemens.

Despite its impressive array of partners, Asterisk is still a minor player in the PBX world, says Matthias Machowinski, an analyst for Infonetics Research.

In research his firm did a year ago in which 240 businesses were interviewed, just two said they used Asterisk-based gear, he says. "I would think it's a small part of the market," he says.

Since these companies are private, there are no numbers on how well Asterisk-based products sell, he says, but, "I'm sure it's pretty low at this point." IP PBX sales worldwide were estimated at $8.5 billion last year, $2.8 billion of that in North America, Machowinski says.

Still, there are signs that Asterisk is at least intriguing to a great number of people. Digium boasted at the end of last year that 1 million copies of Asterisk had been downloaded, indicating a very broad interest even if it is just from tyre-kickers.

Things to look for

For those who persevere and actually deploy Asterisk-based systems, the financial benefits can be huge. For instance, the City of Madera, in California, saved hundreds of thousand of dollars using free Asterisk IP PBX software to overhaul its phone system, but it had a knowledgeable network manager who could do all the work himself.

The city budgeted $400,000 that it fully expected to pay if it put out an RFP to major vendors. It wound up spending just $140,000 by using Asterisk, and that included a general network upgrade enabled by other open source software, says Paul Wheeler, the network manager who oversaw the project. The three redundant Asterisk PBXs in the network cost just the price of standard Intel servers, T-1 cards plus some of Wheeler's time.

"I'm the open source guy," Wheeler says, but businesses that don't have such a guy will likely want to consider professional support for the PBX, if not a commercially packaged Asterisk appliance.

This need was recognised first by Digium, which hopes to capitalise on the software using the same model Red Hat does with open source Linux: The software can be obtained for free, but businesses will pay for added features and reliable technical support.

Last year the company took $13.8 million in venture funding aimed at boosting sales by packaging Asterisk in a form easier for non-technical customers to deploy. To that end, it created AsteriskNow, a streamlined version of Asterisk with a user interface intended to get the PBX up and running in a small businesses in a half-hour.

It spent some of that money buying a competitor, Switchvox, which also sold Asterisk-based PBX appliances and that had a better user interface than Digium's, according to the company. And it bought Sokol & Associates, a provider of Asterisk customer training.

Other competitors are taking the same tack. Escaux, for example, makes net.PBX, an Asterisk-based product that adds features many businesses might find essential. These include call centre software for one of its models, a capability not included with free Asterisk. Businesses might also want Escaux's Web management software, a configuration platform that sets up call distribution.

Net.PBX also provides desktop software that configures personal preferences for handling calls, setting presence information and the like, as well as operator software to display incoming and outgoing calls in progress. The company also offers a tool to embed VoIP capabilities in business applications, allowing them to trigger phone calls directly.

Another Asterisk PBX vendor, Fonality, ships appliances called PBXtra. These are configured in the factory based on customers' answers to an online form. A purchase includes two hours of support time to help get the gear up and running. The company also sells supplemental support contracts scaled to how many phones customers have. The support includes remote monitoring of the system as well as maintenance and management consultation.

Because Asterisk supports SIP for call set-up and control, it also supports any brand of SIP phones that follow industry standards. For customers, this means they are not locked into expensive VoIP phones made by PBX vendors that use proprietary protocols, Machowinski says. This works to keep phone prices down and to enable customers to readily switch vendors if it makes sense.

Digium lists 32 companies on its website whose products are certified to interoperate with its PBXs. The certifications are designed to give customers confidence that if they buy the products, they will work readily with Asterisk, even if installed by the relatively non-technical user. These products range from phones to call-centre software to routing and billing software to paging platforms.

Open to custom code

Even with this wide range of professional options, Asterisk is open to custom code via the C programming language or Perl scripts written for the Asterisk application programming interface. This has enabled some users to massively alter Asterisk to their own purposes.

VoicePulse, the New Jersey residential VoIP provider, built its entire network around Asterisk in 2003. The company made extensive revisions and extensions so its final code was 60 percent Asterisk and 40 percent VoicePulse, says Ravi Sakaria, the company's founder, president and CEO.

These revisions turned Asterisk into a soft-switch that enabled VoicePulse to open for business without a massive infusion of borrowed capital, Sakaria says - something that was not an option.

While the company has since added an open source soft switch to its network, it still relies on Asterisk to provide customer phone features and interfaces to backbone carriers.

"If it wasn't for Asterisk, we wouldn't have been able to launch the company at all," Sakaria says.