Uploaded October 2024 | Updated September 2026, 3 weeks ago
On January 15th, 1990, a single line of code triggered a cascading failure that crippled AT&T's long-distance network for nearly 9 hours, leaving millions of Americans unable to make calls. In today's episode of Dave’s Garage, we dive into the software bug that caused one of the largest telecommunications outages in history.
With AT&T controlling 70% of long-distance traffic, the outage impacted 50 million calls and cost the company $60 million in lost revenue. At the heart of the problem was a subtle race condition in the code running the SS7 signaling system—an error that passed unnoticed through code reviews and testing until the perfect storm of conditions exposed it.
We’ll walk through the technical details of the bug, how it spread through AT&T’s 114 switches, and the larger lessons it taught the telecom industry about software complexity and testing. Thanks to David Sobeski for the episode idea!
Free Sample of my Book on the Spectrum: amzn.to/3zBinWM
Dave's Attic - Friday 4PM Podcast - youtube.com/@UCtb6a_CnmGbSns9G8W2Ny0w
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Twitter: @davepl1968 davepl1968
Facebook: fb.com/davepl
On January 15th, 1990, a single line of code triggered a cascading failure that crippled AT&T's long-distance network for nearly 9 hours, leaving millions of Americans unable to make calls. In today's episode of Dave’s Garage, we dive into the software bug that caused one of the largest telecommunications outages in history.
With AT&T controlling 70% of long-distance traffic, the outage impacted 50 million calls and cost the company $60 million in lost revenue. At the heart of the problem was a subtle race condition in the code running the SS7 signaling system—an error that passed unnoticed through code reviews and testing until the perfect storm of conditions exposed it.
We’ll walk through the technical details of the bug, how it spread through AT&T’s 114 switches, and the larger lessons it taught the telecom industry about software complexity and testing. Thanks to David Sobeski for the episode idea!
Free Sample of my Book on the Spectrum: amzn.to/3zBinWM
Dave's Attic - Friday 4PM Podcast - youtube.com/@UCtb6a_CnmGbSns9G8W2Ny0w
Follow me for updates!
Twitter: @davepl1968 davepl1968
Facebook: fb.com/davepl
