Looking at how Argo is presented (from the blog post), it seems like you've got a really strong use case for SDN, if you're not already using that already. As far as I can tell, dynamically updating routes across an internal network is one of the best non-internal-to-data-center uses of SDN - can you expand a little more on this, if you do use it, or on why you don't, if I'm completely off base?

Cheers, argo seems like an interesting project.