WASHINGTON, D.C. - People use the telephone network for voice and some IP data; they use the Internet for data and some voice. There will be one network someday. But today, there's considerable debate on what that next-generation network will be - an outgrowth of the public switched telephone network or the Internet.

That debate took center stage in Washington last week at the Next Generation Networks 2005 conference, an annual gathering of industry players and pundits.

"There's considerable uncertainty right now on what the next-generation network will look like," said Dave Passmore, conference chair and research director of Burton Group.

That uncertainty creates standoffs between standards organizations such as the International Telecommunication Union (ITU) and the IETF. It tries to take into account the effect of wireless, video, message-based routing and peer-to-peer applications on foundational IP routing structures that were developed when those technologies could scarcely be imagined. The uncertainty prompts questions about whether the Internet should be rebuilt using a "clean slate."

But most critical of all is that the uncertainty could potentially reach in to the pockets of carriers and their customers. The direction of next-generation networks could determine how tightly customers are tied to carriers, and who will be forced to reinvent their business models to stay alive.

"We need to acknowledge the fact that something is wrong with the business model of the public network," says Tom Nolle, president of consultancy CIMI Corp.

Passmore added, "Providers want to take back control of the Internet. They feel it's out of control."

Some consider the IP Multimedia Subsystem(IMS) architecture, endorsed by the telecom-heavy ITU for next-generation networks, as the key for operators to regain that control. Conceived by the Third Generation (3G) Partnership Project - a collaboration of telecom standards bodies initially chartered to define specifications for 3G mobile wireless systems - IMS essentially replaces the control infrastructure in the traditional circuit-switched telephone network, separating services from the underlying networks that carry them.

IMS enables services, such as text messaging, voice mail and file sharing, to reside on application servers anywhere and be delivered by multiple wired and wireless service providers.