Reliability remains a key concern as the telecom industry implements SDN, as the drive to make networks more flexible and reconfiguration more automated can threaten the reputation telecom has for always-on networks, says Chris Emmons, Verizon's director of Network Planning, Corporate Network and Technology.

Emmons will be speaking next Tuesday at Light Reading's Carrier SDN Networks. In a pre-show interview with Light Reading, he called out reliability as a key challenge for companies such as Verizon Communications Inc. (NYSE: VZ), which wants to use SDN to offer greater customer control and to automate processes that today require human touch.

Verizon just last month laid out some basic strategies for its SDN deployment. (See Verizon Builds Key Vendors Into SDN Strategy.)

"We want to more efficiently use the network by directing traffic dynamically or semi-dynamically, based on load and demand," Emmons notes. "And we want to be able to optimize paths for performance, latency and things like that, through dynamic programmability. The challenge to doing that is really all about high reliability of a carrier network, especially a network like ours, where we built our reputation on being highly reliable."

Want to know more about SDN deployment plans? Hear keynotes and panels devoted to this topic at Light Reading's Big Telecom Event on June 9-10 in Chicago. Get yourself registered today or get left behind!

Implementing SDN will require fundamental changes in the underlying technology and with standards still evolving, reliability can seem like a moving target. For example, Emmons asks, once the control and data planes are separate and SDN-based controllers are being used for network control, what will the typical latency budget be between those controllers and the forwarding plane? And, will potential latency issues determine where those controllers sit in the network and how centralized control can be?

"Today, that control is with the forwarding plane in the same box," he notes. "When you try to extract that, depending on the dynamic nature of the underlying infrastructure, how many times do they have to talk to understand what to do with the data that is being processed?"

The nature of that "conversation" and the potential for latency to be introduced in the process of controlling the data plane could dictate how centralized network control can be, while maintaining service reliability, Emmons says.

These are some of the issues to be addressed when automating the process of network control. One of the goals of moving to virtualization is to eliminate human programming, since that not only slows things down but introduces errors, he says. Network operators still need to get more comfortable with how the automated process of letting a network optimize itself will maintain its core qualities such as being self-healing and self-provisioning.

"It can be a scary thing for people who have built a reputation for being highly reliable and predictable," Emmons says.

He does see some of the open-source work that is emerging in places such as OpenDaylight playing a role in how SDN evolves to be carrier-class in terms of reliability, while noting that open source plays much less of a role at the physical layer of the network than at higher levels.

"We see that more at higher layers -- at the lower layer, it's yet to be seen what the impact might be," he comments. "There is a lot of hype and swirl around this but there isn't a lot in the way of standards or open-source projects that we are able to leverage today for WAN-based SDNs. And a lot of what is out there so far is proprietary. That's one of the big challenges -- getting the industry pushing in a common direction and building an ecosystem around that common direction."

In that regard, Emmons seems to echo comments from a fellow Carrier SDN speaker, Level 3 Communications Inc. (NYSE: LVLT)'s Travis Ewert, vice president of network software development. (See Level 3 Stays Ahead in the On-Demand Race.)

You can still join us in Denver to hear more from Verizon's Emmons and more about his company's view of SDN. Information on registration can be found here. Telecom service providers can attend at no charge.

— Carol Wilson, Editor-at-Large, Light Reading