While I can see not including routing and peering among AS's, DNS is pretty fundamental to the the Internet these days. I would consider any explanation that do

While I can see not including routing and peering among AS's, DNS is pretty fundamental to the the Internet these days. I would consider any explanation that doesn't mention it as pretty lacking. CDN use has exploded and, from a 30,000 ft view, the Web tends to look a lot like an overlay network on DNS.