Has everyone forgotten the "Tier 1 depeerings" of several years ago? i.e. If you were pointing default at C&W, PSINet, Cogent, or Level3 when they each had or caused depeering issues, parts of the internet ceased to be reachable. In such cases, having full routes from multiple providers was the only way to be automatically protected from such games.
Not so. Anyone who had sufficient transit was also protected from the games. Lots of so-called regionals and tier-2 networks were shielded from this monkey-business. And, of course, they shielded their customers as well. A tier-1 network operator who operates such a fragile network becomes a single point of failure. And not just because of peering as the AT&T frame relay collapse shows. --Michael Dillon