Under the moniker of Software Defined Network or SDN a flurry of new technical proposals are vying to become the next standards. The business case for them is very sound i.e service providers after failing in their first attempt in late 90s and early 2000s are now confident that there is a way to monetize services which run inside datacenters. The problem is of course the scale at which they need to operate requires that services run across traditional boundaries set up by networking. To cross these boundaries they are devicing clever ways of getting bits across a policy boundary using overlays (envelopes inside other envelopes). The debate is lately on which layer's envelope shall I use. Layer-2 or Layer-3. Ok, so at the end of day what is needed is a mechanism that abstracts the underlying network and presents it to the applications over sockets in a programmer friendly fashion .
What the networking guys need to do is to look at how this problem was solved in application world over a decade ago. Hint: Use HTTP for control plane, XML for management plane and whatever you want for data plane. The best overlay network in the world continues to be IM (instant messaging)