To your point with regards to multiple failures combined causing an outage, here's some basic reading on the Swiss cheese model: https://en.wikipedia.org/wiki/Swiss_cheese_model
>From over here it looks like the legacy filter was a latent failure, and the >BGP automation from the downstream peer of Telia was an active failure >(combined caused the outage). Now from the downstream peer's point of view, >perhaps the cause of their BGP automation failure was latent also, but we >wouldn't know without more details. Pretty interesting topic.
