[nevergore]

Shutting down the Internet on a national basis isn’t that difficult.....

Shutting down Level 3, MCI and AT&T will completely disrupt if not halt almost all internet, kill the primary and secondary DNS servers and all but a few intranets with private international conections will be down.

[Noumenon]

Shutting down Level 3, MCI and AT&T will completely disrupt if not halt almost all internet,

Yep - look for the bottlenecks or focal points. That's where the kill switches will be. It's too easy.