T-Mobile explains what went wrong this week

Good explanation: Update on T-Mobile Network Issues | T-Mobile Newsroom

For reasons unknown, utilities, communications and airlines are always incredibly vague when problems occur and mostly say “We had problems. Top people are working on it.”

T-Mobile initially took that approach too with this week’s nationwide network outage, cutting off phone service for up to 86 million people. But they appear to have listened to customers who sought a more complete explanation.

Their explanation (see link) concurs with a network manager who said a cut fiber line in the south had caused a rerouting of data on to other links, overwhelming them and ultimately crashing the system. Basically, it led to an IP data traffic storm that took down the network.