Why the AT&T network crashed

Citation metadata

Author: Paul Travis
Date: Jan. 22, 1990
From: Telephony(Vol. 218, Issue 4)
Publisher: Penton Media, Inc., Penton Business Media, Inc. and their subsidiaries
Document Type: Article
Length: 724 words

Document controls

Main content

Abstract :

AT&T blames a fault in new software designed to restore switching service for the network crash Jan 15, 1990. Larry Seese, AT&T's director of technology development, explains what happened: first, a piece of trunk interface equipment developed internal problems, which the equipment reported to a 4ESS switch in New York; the 4ESS stopped accepting calls and ran a corrective initialization on the equipment; and then, the New York switch attempted to go back into service, at which time a fault in a new program initiated a chain reaction that spread throughout the network, causing all the network's 4ESS switches to stop accepting calls. Specifically, according to Seese, the problem occurred when switches were confused by call attempts while in process of resetting internal logic to indicate 'in service' status. AT&T reduced messaging loads, allowing switches to reset and stabilizing the system.

Source Citation

Source Citation   

Gale Document Number: GALE|A8087500