Back in 2013, CenturyLink was a regional voice and internet provider. Not exactly the most likely candidate to be an early pioneer in NFV. But at that point, the company wanted to launch a network firewall system. And it turned out that the best business case for the new offering was a virtualized firewall. This paved the way for CenturyLink to adopt other network virtualization services, making the phone company a leader in SDN and NFV. Since then, CenturyLink has purchased Level 3, which also had network virtualization experience. And the combined company now offers global business services, such as SD-WAN.

Bill Walker, director of network architecture and innovation with CenturyLink, said there are three business cases for NFV. The worst business case is for new technology that is not directly revenue generating. The second is to replace some existing technology with NFV. “Until you get your money out of existing investments, you’re not going to replace anything that doesn’t need replacing,” said Walker.

The easiest business case is new revenue. And that turned out to be the business case for CenturyLink’s network firewall offering. Walker said launching the service the old-fashioned way would have required purchasing “these giant firewall machines” for the core and edge locations of the network. “I would have to buy 120 of those before I even signed up the first customer,” he said. “With NFV I run it with software on a couple of servers with a license. As I grow, I buy a $15,000 server every time I have new customers. If I have a 10 to 15 percent year-over-year growth, then that’s free money.”

The initial success with the virtualized firewall propelled CenturyLink into other virtualization services, as part of its Programmable Services Backbone (PSB) program, which the company announced in 2015.

Walker said the original NFV infrastructure from 2013 is still operating in CenturyLink’s network, running active customers and generating revenue. That infrastructure is VMware based. “We were probably bringing online one to two enterprise customers per day,” said Walker. “It was a pretty manual process at that point. An engineer brought on new customers.”

Later, the operator added a commercial OpenStack distribution to the mix. “While doing that, the whole network-based security product line paid for the infrastructure,” said Walker. “Once it was out there, it was easy to add capacity to the pool.”

Eventually, CenturyLink added more commercial versions of OpenStack as well as its own internal OpenStack infrastructure to its PSB. “Where the workloads go is really just a spreadsheet business case,” said Walker. We’re really happy with both OpenStack and VMware.”

In addition to NFV services such as firewall, CenturyLink added SD-WAN. In September the company said its SD-WAN service is now available in more than 30 countries.

CenturyLink also uses SDN to operate its own “plumbing” as Walker calls it.

“I hate SDN for SDN’s sake,” he said. “Really, it’s about software controlling the plumbing. It’s easiest to do NFV if you also use software to control that plumbing. SDN or NFV without the other is only a half-step. We’ve been doing SDN longer than NFV.”

Again, the company uses a variety of technologies including OpenDaylight (ODL) and ONOS controllers as well as some homegrown technology. “The upper level controllers that do end to end network plumbing is ours,” said Walker.  “It’s not a commercial product. If you go down it’s ONOS, ODL, and some are proprietary. They all integrate well with each other.”