Using the MPLS cloud lets Hull avoid the hassle of ordering individual circuits, but now he's stuck managing the end-to-end QoS. That adds complexity and slows the implementation.

Boeing, which also has made a substantial investment in MPLS, is in the same boat. "If the market doesn't evolve over the next 24 to 36 months, we'll have to examine alternative services," says Cliff Naughton, director of network services.

"No service provider will build networks absolutely everywhere," says Matt Bross, CTO at BT Group PLC. So BT and other communications carriers are working through the IPsphere Forum , a consortium that could define those interfaces and make it easier for carriers to manage QoS from end to end. Kevin Dillon, chairman of IPsphere, says the consortium won't define those interfaces but will provide a mechanism that carriers can use to negotiate and set up bandwidth and latency guarantees. But Bross says the group's focus is on interoperability. "The ability to work across heterogeneous platforms and networks is the goal," he says.

Others have their doubts. The problem is that competing carriers may not trust one another enough to allow full interoperability, says David Passmore, an analyst at Burton Group.

The outcome remains uncertain. "Whether this ever will result in an end-to-end service that customers can buy remains to be seen," Passmore says. But Stu Elby, vice president of network architecture and enterprise technologies at Verizon Communications, says corporate customers can expect to see multidomain MPLS offerings by late 2006 or early 2007.