I was reading about DNS some days ago and learned how the requests are processed. If you surf to www.example.com, then a request will go to the Root Name Servers to see who owns that .com address, then another request will go to another, more local, DNS server to see who owns the example.com address and so on.
How is it technically possible that the 13 Root Name Servers can handle all requests done by earth's billions of Internet users simultaneously without being overloaded leading to a Denial-of-Service?