Big Switch Networks is announcing Tuesday that it can create an overlay OpenFlow network on an arbitrary Layer 2 or 3 network.

The technology uses the tunneling capability that's standard with OpenFlow 1.3, the version approved about three weeks ago. The overlay network creates a subnetwork that can run on different switching or routing rules.

The overlay tunnels can be used for moving virtual machines around the cloud, which is what platforms such as VxLAN from VMware Inc. (NYSE: VMW) and NVGRE from Microsoft Corp. (Nasdaq: MSFT) do. But those are proprietary technologies that require a VMware or Microsoft controller. OpenFlow-based tunnels, on the other hand, could use anybody's OpenFlow controller (Big Switch's, in this case).

The capability is just now being released as part of Big Switch's Open SDN Controller. Big Switch expects to have at least 10 customer trials running by the end of June.

Why this matters
Like most of the software-defined networking (SDN) community, Big Switch is accepting that SDN will be adopted gradually -- and that's why it's important that these overlay networks can be built on top of the networks that are already running.

The ultimate goal is to create entire SDN-run networks, but "what we found last year was, every customer we worked with wanted a half-step towards this goal," says Kyle Forster, one of Big Switch's founders.

Equally important is the fact that OpenFlow-based overlays aren't counting on a specific type of network. That is, the controller would tell switches to create tunnels but wouldn't care which protocol they used to do it. Likewise, anybody's OpenFlow controller could issue the tunneling requests.

SDN proponents want this openness to remain a central tenet of the technology, and to that end, it's useful to them to emphasize the contrast between Big Switch's overlay networks and other, proprietary approaches.

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— Craig Matsumoto, Managing Editor, Light Reading