i can see where SDN might be applied to build your own machinery for inter domain routing, but how does it help in the broader internet where bgp is applied? s

i can see where SDN might be applied to build your own machinery for inter domain routing, but how does it help in the broader internet where bgp is applied? sure, I guess if you developed a new mechanism for resolving transitive policy with baked in authentication, and got everyone to agree to use it, you wouldn't need to convince the router vendor. but it seems like the first two things are harder than the third.