Omar Sultan about overlay networks:
Speaking of the long run, the other thing to bear in mind is scalability of design. Long, long ago, when I took my first programming class, my instructor showed me the GOTO command, had me do an assignment, then told me never to use it again—extolling the values of structured code the seductive evils of GOTO-spawned spaghetti code. The same it true with networking. Given a choice, the typical admin would create manageable broadcast domains, crisply defined failure domains and clear L2/L3 boundaries. In fact that is usually how they are designed and often implemented. So, how do we end up networks that look like spaghetti?
The big tip here is that sysadmins and netadmins should work together. Even better: if you let architects, engineers and operations from both disciplines work together you can enforce structure and discipline in your network. Key is to watch the overall architecture and that is just what DevOps is all about.