The open-source movement, which has long made inroads into corporations via Linux and other enterprise-level software, now has a potentially bigger target in its cross hairs: the PBXs and network routers from companies such as Cisco Systems that form the basis of networking infrastructure.

For now, the movement is largely limited to small and midsize organizations and is focused around the Asterisk open-source private branch exchange and Vyatta open-source routers. Cisco and other old-time networking vendors certainly aren't yet shaking in their boots over it. But it's a growing movement that they ignore at their own peril; lower-cost, higher-function technologies have a way of replacing existing architecture far faster than vendors realize, open-source vendors say.

As you might expect, whether open-source PBXs and routers are superior to their proprietary cousins is a controversial issue. The small and midsize enterprises that have chucked their proprietary PBXs and routers for open-source systems say the new systems offer similar functionality with more flexibility and lower costs than proprietary systems. Proprietary providers, however, question whether open-source vendors offer adequate levels of support and whether those who buy them have the technical expertise needed to install and maintain the systems.

The threat to Cisco

Open-source "may not have a huge impact now, but we're starting to see some companies with 5,000 endpoints considering switching [to Asterisk]. The more that do, the more that it will have an impact," Chad Agate, co-founder and CEO of SIPBox says of Asterisk and open-source technologies. Prior to forming SIPBox, Agate had operated a company that sold Cisco systems, but he sold that firm to concentrate instead on selling Asterisk systems. SIPBox has replaced or is in the process of replacing Cisco, Nortel and Avaya systems -- some with hundreds of endpoints -- and expects more companies to follow suit.

"Open-source makes a lot of sense for nonprofits," which constitute a significant portion of SIPBox's customer base, Agate says. "They spend about 40 percent less than for the Cisco system and get the same feature set."

Asterisk runs on a wide variety of operating systems, including Windows, Linux, Mac OS X, OpenBSD, FreeBSD and Sun Solaris. It includes the high-end features of proprietary PBXs and operates on off-the-shelf software. New functions can be created by writing scripts in Asterisk's language, by writing modules in C and by writing scripts in Perl or other languages.

The trend to open-source technologies is somewhat limited now to companies that have relatively simple needs, have some technical expertise on staff or both, according to analysts. But the movement is clearly gaining momentum, with companies either replacing existing systems with open-source technologies or choosing open-source over proprietary products for new installations.

For example, Bill Ciminelli, vice president of network development and services at American Fiber Systems, is in the final stages of converting his company's PBX systems (one Nortel and a shared NEC system) to an open-source-based Asterisk system.

"If someone had presented the idea of an open-source system to me 18 months ago, I would have said no way," he says. "Now if someone comes to me with a [technology], I ask first if there's an open-source option."

What it came down to in the end was price for performance. Ciminelli figures that he would have to pay at least three times as much for the same number of connections on a Cisco system as he has on the Asterisk solution.