THE HAGUE, Netherlands — Nuage Networks has landed its biggest customer yet for software-defined wide-area networking (SD-WAN), as BT plans to offer the service to its enterprise customers globally.

More specifically, BT has selected Nuage's Virtualized Network Services (VNS), which the vendor considers a superset of SD-WAN. The deal hasn't been announced, but Neil McRae, BT's managing director and chief architect, discussed it openly during a Tuesday afternoon session at the SDN World Congress here.

BT had previously announced an SD-WAN service in January, using Cisco IWAN technology on the routers already in the network. What's different about the Nuage announcement is that the resulting service goes beyond the usual SD-WAN concept, focusing instead on letting users reach applications.

On Nuage's side, what makes BT different from other VNS customers, such as UK-based cloud provider Exponential-e, is its scope. BT offers services in more countries than are in the United Nations and has about 10,000 network nodes that SD-WAN could be applied to, McRae estimated.

Originally a subsidiary of Alcatel-Lucent, Nuage is now owned by Nokia. That was key to this deal, as BT liked that Nokia would be "able to match their global presence," said Houman Modarres, Nuage's head of marketing.

"They do global VPNs in a meaningful way," he said.

SD-WAN can automate the selection of a network path to connect two points. It's often described as a cost-saving measure, as it can be used in branch offices to shunt traffic to the Internet in cases where a more expensive MPLS line isn't necessary.

But that creates a story only about connecting one location to another, Nuage CEO Sunil Khandekar told SDxCentral. Nuage is emphasizing the broader goal of connecting users to applications, regardless of where either side is. That is, the users could be on wireless or wireline networks, and the applications could be in data centers or public clouds such as Amazon Web Services (AWS). (VNS makes use of Layer 3 network virtualization to do this across networks.)

That's one way BT intends to apply SD-WAN. The service would be handled by the same orchestration system that controls connections to BT's own data centers or to public clouds, McRae said.

"Our goal is to be the customer's networking department," he told SDxCentral after his talk. "We have connected hundreds of cloud providers to the network, and we know what works well for each cloud provider."

BT's SD-WAN rollout will be global, in the sense that all 10,000 BT nodes will be eligible to use the service. On a customer-by-customer basis, Nuage will "drop-ship" the necessary software, Khandekar said.

That's another place where Nokia's size comes in. "We have the infrastructure to do the fulfillment," Khandekar said.