The last major attack was in 2007, and only two servers were rendered unreachable: http://www.ripe.net/internet-coordination/news/industry-developments/global-

The last major attack was in 2007, and only two servers were rendered unreachable: http://www.ripe.net/internet-coordination/news/industry-developments/global-root-server-system-stands-firm-against-ddos-attack http://www.ripe.net/internet-coordination/news/industry-deve... For anyone to actually notice, you have to take down all 13 for 48 hours, and it will be another 48 hours after that before there is a complete outage for everyone.