Fundamentally, SDN is still mostly about network plumbing. While plumbing may be useful to tinker with, what you can do with your plumbing is far more intriguing. A rigid interpretation of SDN confines it to Layers 2 and 3, and that’s reasonable. But SDN opens opportunities for novel constructions in Layers 4 to 7 that solve real operational problems in data centers. “Data center,” in fact, might become anachronistic – data is everywhere, constantly on the move, seemingly always overflowing. Networks move data, but not all networks are suitable for all data.