How Do You Get to SDN From Here?

The Open Networking Foundation is taking on one of the trickier aspects of the move to virtualization, publishing a document that details migration strategies for the move to software-defined networking (SDN) in campus, service provider edge, and wide-area networks. (See ONF Offers Guidance On SDN Migration.)

Developed by the Open Networking Foundation Migration Working Group and published Tuesday, the aptly titled "Migration Use Cases and Methods" draws heavily on the experience of three SDN pioneers: Google (Nasdaq: GOOG), NTT Group (NYSE: NTT), and Stanford University , to offer best-practices and lessons learned from real-world deployments.

Among its core recommendations are the need for gap analysis to determine the impact the move to SDN will have on current services, creation of pre- and post-migration checklists to guide assessments of connectivity and service continuity checks, and well-documented back-out procedures that can be used "in case of unexpected results."

"We set this up as a framework for SDN deployment," says Justin Dustzadeh, chief technology officer and vice president of technology strategy at Huawei Technologies Co. Ltd. , and chair of the ONF Migration Working Group. The idea was to look closely at what the three SDN deployments had done and to come back with a pragmatic approach that can be used across the industry.

That approach is laid out in stages, Dustzadeh says, beginning with defining the core requirements of a target OpenFlow-based network, continuing with preparation for the rollout, then moving on to laying out the steps of a phased migration and making sure that at each stage there is a rollback mechanism. In the final and fourth stage, the service provider needs to test and verify the SDN-based services, as well as the impact of the move to SDN on its original services.

Different networks, different views
The working group specifically chose three deployments in different parts of the network: Stanford linked two campus buildings, NTT used OpenFlow to connect edge routers to an external control plane, and Google created its much-ballyhooed B4 wide-area network based on SDN. (See NTT Advances SDN and Google: SDN Works for Us.)

The document is the first product of a working group that was launched in April 2013 in response to very real concerns by ONF members that moving to SDN might require the impossible: ditching billions of dollars of investment in current networks.

"A lot of people were saying they didn't want to throw money away, and they needed to know how they get there from here," says Dan Pitt, ONF executive director. Existing working groups weren't directly addressing the migration challenge in a practical way.

Next up for the Migration Working Group is exploration of the specific software tools and metrics needed to support the process of migrating to SDN, with the goal of bringing the IT world's level of automation for software upgrade to the carrier space, says Dustzadeh.

Along the way, his group isn't specifically addressing how carriers build the business case for SDN migration, but it is providing greater information and insight that can be used in that regard, he says.

"We have ongoing studies to also address the cost, performance, and other aspects that might be relevant in the bigger picture of SDN migration," Dustzadeh says. "Today, most operators and CEOs and business decision makers are trying to find out what does it take, what is it going to cost me, and what is the long-term return on investment, not only for simplifying my network but also enabling me to introduce new services more quickly and efficiently."

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