Post #4171129
2026-07-28 02:18 UTC
36 years ago, on January 15, 1990, a software bug in the 4ESS switch triggered a cascade of failures that took down most of the AT&T long distance telephone network for about nine hours.
It was treated as a national crisis. There were investigations and task forces, both internal and external, and detailed findings were published and scrutinized. The case is still studied today in networking and software engineering courses.
Today's national T-Mobile failure will be forgotten by next week.
Replies (1)
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@mattblaze@federate.social 2026-07-28 02:23
What's the difference between 1990 and today? AT&T in 1990 was no longer a monopoly; there was competition in long distance, so some calls got through, just as calls went through today on T-Mobile's competetors. The main difference was expectation. 1990 was still the era of "5 9's" of reliability (99.999% uptime). Telephone services were simply not expected to fail. We expect phone (and Internet) service today to be MOSTLY reliable, but we're conditioned to expect failure from time to time.