So you cut over this new network but didn't take down the old one; what do you estimate the new network is accounting for in terms of your total inter-data center load?

Over a two-year period we have been shifting, incrementally, over to the new network, and it's fair to say that a substantial majority of the traffic is now on the new network.

Was OpenFlow fully baked as you were implementing it, or did you have to improvise a lot?

We had to improvise. OpenFlow is standardizing the interface, and I think this is very important for the community. So what OpenFlow and software-defined networking really enables us to do is separate the evolution path for hardware and software. In other words, you can get the hardware that meets your needs and separate that from the software that meets your needs for a particular deployment. Historically, those two things have been wedded together.

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