The outages on Monday at Facebook, WhatsApp and Instagram occurred because of a problem in the company’s domain name system, a relatively unknown – at least to the masses – but crucial component of the internet.

That’s apparently what happened inside Facebook – but at a scale that’s temporarily crippled the entire Facebook ecosystem.

The problem at Facebook Inc. appears to have its origins in the Border Gateway Protocol, or BGP. If DNS is the internet’s phone book, BGP is its postal service.

[Via]