Ciminelli, whose firm provides metropolitan fiber systems, expects open-source technologies to make an increasingly bigger impact in the telecommunications portion of the market.

"As voice becomes more of an application, there is a lot less value associated with the name tags on the box," he contends.

Why Cisco may not need to worry

However, Ciminelli is in the minority, and open-source right now represents only a very small fraction of the market, according to Krithi Rao, an analyst at Frost & Sullivan in San Antonio.

"Most of the companies changing to open-source are in the small and middle-size business market," Rao says. "Most of the large companies, which is the market where Cisco concentrates, are going to stay with Cisco. Open-source is a niche market right now."