In the current model of SDN, not much has really been tidied up or integrated. We still rely on all those things to some extent. After all, doing away with, say, VLAN would be like doing away with global brands like ketchup, and coke. Rather, network virtualization has been approached by emulating the old software stack, designed principally for LAN, based on tunnels that encapsulate the existing view of the world. The goal is to present and automate a familiar experience, rather than to simplify or create a new experience
Thoughtful stuff on rethinking the network stack in an SDN world.