But Robert Kahn, co-inventor of the Internet and chairman, CEO and president of the Corporation for National Research Initiatives, says security is a problem for intelligent endpoints that use the Internet, not for the network itself. "I don't know if [security is] a limitation. It's just an aspiration for something that could be better," he says.

In the meantime, many enterprises are redesigning their networks around private MPLS services. As carriers continue to consolidate their own networks around more-efficient IP-based architectures such as MPLS and the emerging IP Multimedia Subsystem (designed to transform the circuit-switched public telephone network), some cost savings are slowly trickling down to corporate customers.

"We saw that in the MPLS competitive-bid activity that we went through," Hill says. He says private services such as MPLS are vital to his company's use of videoconferencing and other high-bandwidth applications that require QoS and multicast capabilities.

Although using MPLS gets Hill out of the business of procuring individual circuits, even private MPLS network services don't deliver on QoS globally. The reason: No single vendor covers all locations, and the industry lacks a set of common QoS definitions and standards for network-to-network interfaces.

Carriers are working to remedy the problem. Verizon expects to start offering interoperable services late this year or early next. But Boeing's Hill remains skeptical that competing carriers will cooperate. "They want customers... getting locked into their services. They are singularly unmotivated to make those services interoperable," he says.