Tuesday, Nov 2
It looks like Facebook's outage was triggered by their withdrawing their routes to the AS containing all their DNS servers.
Cloudflare blog: blog.cloudflare.com/october-2021-facebook-outage
Geoff Huston blog: www.potaroo.net/ispcol/2021-10/nofacebook.html
Is a small DNS timeout actually a good idea?
Separation of control and traffic
TCP Reno