Virtualization and Software Defined Networking (SDN) are taking over data-center networks, but many question whether the technology is ready to penetrate deeply into large, global service provider networks. An executive at at least one major service provider says we still may be many years away from that happening.

James Walker, the president of the Cloud Ethernet Forum (CEF) and Vice President, Managed Network Services at global service provider Tata Communications, says his current focus is on connecting large-scale Ethernet services and data centers using existing technology, because SDN is not quite ready for prime time.

"SDN becomes a way for my network to interface with other networks," said Walker in an interview with the Rayno Report earlier this week. "Generally we don't have customers coming to us saying, I have a fully fledge SDN environment and I want to connect it. They say they are going to deploy it. Our Etherhet environment is very well suited to it because it's deterministic. We have the flexibility to respond to their peaks and spikes."

Walker says that Tata, like many providers, is playing with SDN technology in the labs, but he still sees barriers to putting it in large networks that connect across oceans, for example. Two of the major problems are distance and time. Walker hasn't yet seen an SDN controller technology that can respond to meet a 50 millisecond (ms) failover requirement on large networks.

"Controllers don't scale to that kind of stuff. I have 20 Terabtis of capacity lit. You have to do [trillions] of megabits per second of packet inspection, that's way more than any controller we've seen. The other challenge is distance. You can be 100 millisecond (ms) apart in Tokyo and San Francisco. If the two controllers are more than 50 ms apart, its a problem if a customer expects 50 ms failover."

Tata is no slouch, so it's worth listening. Tata operates one of the world's largest submarine cable networks and claims as much as 20% of global IP traffic. In his role with the CEF, Walker is intersted in finding the most efficient ways for large cloud data-center operators to connect with each other.

The big problem with existing SDN technology, as Walker sees it, is that it requires a relatively stable and monolithic network, handling specific applications. This is why, for example, it works well in Google's network, says Walker, because Google can predict its search and application traffic quite well. But when you put it in a large service provider network with huge distances and many different kinds of traffic and services, it doesn't have the right characteristics.

"A service provider environment has different requirements than a search engine," says Walker. "If a service provider network goes down, somebody might die... that doesn't happen if a search engine goes down."

So what technology is Walker big on? Ethernet, for one. And more specifically, Walker likes an Ethernet technology called Provider Backbone Bridging (PBB), an IEEE standard. PBB allows virtual LANs (VLANs) to be interconnected among carriers, and it is standard in many Ethernet boxes.

Walker continues to favor Ethernet and believes it will gradually supplant IP technologies such as MPLS in many areas. "Our big data center customers want to be focused on Ethernet," says Walker.

Interesting thoughts from the tech world of the big boys. I'll publish an expanded version of this interview in the next week.