Internet Routing Fragility

The internet was designed in a different time at a different scale. It’s rare that a design continues to work at all when scaled multiple orders of magnitude so it remains impressive but there are issues. The blackholing of YouTube over the weekend showed one of them. Routing is fragile and open to administrative error and also certain forms of attack but this particular example was the more common one: human error.

Over the weekend, a decision was made in Pakistan took down Youtube for two hours. Here’s what happened. Pakistan Telecom received a government order to block Pakistani access to YouTube. They did this for their network (most of Pakistan) but also advertised this route incorrect route to their provider, PCCW, as well. PCCW shouldn’t have accepted iy but did. Since PCCW is big and hence fairly credible, the error propagated quickly throughout the world from there.

This issue was inconvenient but the same sort of attack can be constructed intentionally to disrupt access to a web sites or to direct users to a web site masquerading as another.

Perhaps the best detail is on the Renesys blog: Other sources:,


James Hamilton, Windows Live Platform Services
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