To some extent, the NSF Net's role has already been assumed in part by purely commercial networks that bypass the backbone. Transferring the remaining NSF Net functions to private industry is in keeping with the outline for the "national information infrastructure" that is at the center of the Clinton Administration's plan for a global information web.

Once freed from the responsibilities of supervising and supporting the backbone, the National Science Foundation plans to turn its attention to creating a separate high-speed network specifically for the original audience of scientific and academic researchers.

The plan to phase out the science agency's role was announced in 1992, but has encountered delays. The current timetable calls for the first phase of the private-sector handoff to be completed on Oct. 31, when an assortment of important regional Internet service providers are scheduled to be disconnected from the NSF Net backbone and connected to four new commercial network hubs, in San Francisco, Chicago, Washington and Pennsauken, N.J., a suburb of Philadelphia.

Although further delays now seem certain, most experts still expect the technical transition to be complete by the middle of next year.

"Quite frankly, this has taken longer than expected," said Don Mitchell, technical staff associate at the National Science Foundation in Arlington, Va. "Originally we thought we would have been transitioned by this point."

No one disputes that this increasing commercialization of the Internet will accelerate its transformation away from an esoteric communications system for American computer scientists and into an international system for the flow of data, text, graphics, sound and video among businesses, their customers and their suppliers.

"I see the commercial users of the Internet to be the big winners here," Mr. Becker said. "From an engineering standpoint, I don't think the new structure is any better than the old structure. But it will help to broaden the market, and that will bring in more customers and more new applications, and the industry will grow as a result of it."