Some ideas: - Facebook sends SMS 2FA. Users on T-mo would be unable to receive codes. What behavior does the 2FA-sending code have in this condition? Does the

Some ideas: - Facebook sends SMS 2FA. Users on T-mo would be unable to receive codes. What behavior does the 2FA-sending code have in this condition? Does the process just sit there and time out (possibly exhausting some finite server resource, like file descriptors)? Are there automated retries in a client? Are humans retrying aggressively because they are frustrated by being unable to log in? - SWEs and SREs on on-call rotations may have configured pages to go to a cell phone on T-mo. Usually the three fallbacks are "phone call", "sms", and "pubsub/push notification", but both voice and data were broken today. May have taken longer to notice/escalate/resolve an outage. - Messenger may have seen increased load because people were using it to replace voice and texts that they would have normally sent over T-mo.