ABSTRACT
Telephony met Information Age reality on January 16, 1990. It was AT&T’s misfortune to lose over 50% of its network capacity when a single-bit “soft-glitch” cascaded through 114 SS7 adjunct processors in its 4ESS network—in 20 min. AT&T’s SS6 traffic survived. (SS7 and SS6 are signaling protocols, i.e., rules governing network control information.) The impact software control of public-switched networks has had on network reliability became clear to all.
