@GossiTheDog

The Optus outage was indeed iBGP, and it affected the underlying data routing across their network. That was visible in their Internet service. Have you seen any reports of AT&T fixed broadband having been affected? If it had anything to do with peering, that would also have been down. The fact that AT&T was urging affected customers to switch to "wi-fi calling" and that that was mostly working, would seem to indicate that there were not problems on the data network. That some "wi-fi calls" were not going through can be attributed, like the people complaining to T-Mobile and Verizon, to people trying to reach AT&T mobile customers.

Again, I don't yet have a theory that I believe holds water, I'm just trying to rule out things that appear to be contradicted by the facts as reported thus far.