Rob Sherwood, one of the elders in software-defined networking (SDN), announced today that he's leaving Big Switch Networks to join Facebook.

"I’ve made the difficult decision to go back to my roots. I want to be in a lab. I want to look at a seemingly unsolvable problem and prove the naysayers wrong, yet again," Sherwood writes in a corporate blog entry posted today.

Today is Sherwood's last day at Big Switch. The Facebook assignment begins in early 2017, he writes.

In 2008, Sherwood was part of the Clean Slate lab at Stanford run by Nick McKeown. The lab was the germination point for the early drivers of SDN, including the OpenFlow protocol. McKeown and Martin Casado, then a student, would go on to found Nicira, which was acquired by VMware and is the basis for the NSX network virtualization product.

Sherwood, who was working at Deutsche Telekom while contributing to Clean Slate, went on to join Big Switch, another of the early SDN startups. Sherwood was named CTO in 2014, after a management shakeup that saw Doug Murray join as CEO.