OpenFlow and software-defined networking (SDN) don't exist in a vacuum, and most customers won't have the luxury of building entirely new networks for them. Recognizing this, the Open Networking Foundation (ONF) created the Migration Working Group in April to create methods for migrating a traditional network into OpenFlow-based SDN.

Some results of the group's work so far are reflected in the paper, "Migration Use Cases and Methods." (Click that link to download the PDF.) The document was posted to the ONF site in December, but the ONF announced its public availability on Tuesday.

The document walks through a few high-profile examples of network migration:

• Google's B4 wide-area network — which has been discussed in many, many conference sessions but is presented here at a rather deep level of detail
• NTT's "BGP-free edge" project, where provider edge routers were connected to a new, external control plane via OpenFlow
• Stanford University's 2010 tryout of OpenFlow in the computer science department's Gates and Allen buildings.

It's a living document, which implies that more use cases could be on the way. The document's appendix lists the details — and there are a lot of them — that any given use case has to divulge.

The working group's ultimate goal is to produce the tools for migrating to an OpenFlow network. The prototype tool chain is due to the ONF in April.

(Photo by Flickr user Elsie esq., licensed under Creative Commons 2.0.)