Now here's the invisible beauty. There are 14 direct connects between each of the 114 4ESS's and every other 4ESS, each capable of handling thousands of call at once. So, rarely do we ever get a long distance busy signal. The systems automatically reroute themselves.
The 4ESS then calls its own STP, Signal Transfer Point within an SS7 network. The SS7 network determines from which phone number the call originated and its destination. (More about that later!) It sends out an IAM, Initial Address Message, to the destination 4ESS switch and determines if a line is available to complete the call. The SS7 is so powerful it can actually create up to 7 additional virtual paths for the heaviest traffic. 800 numbers, Dial a Porn 900 numbers and other specially coded phone numbers are translated through the NCP( Network Control Point) and routed separately. Whew! Had enough? So have I.
The point is, massive computer switches all across our nations
automatically select the routing for each call. A call from
Miami to New York could be sent through 4ESS's in Dallas, Los
Angeles and Chicago before reaching its ultimate destination.
But what happened yesterday?
It seems that the switches got real stupid and slowed down. For those readers who recall the Internet Worm in November of 1988 and the phone system slowdown in early 1990 and then again in 1991, computers can be infected with errors, either accidentally or otherwise, and forced to misbehave.
AT&T's explanation is not satisfying for those who remember that
AT&T had said, "it can never happen again."
Today's official explanation is; "A minor hardware problem in one of our New York City 4ESS switches caused a cascading of similar hardware failures throughout the network. From all appearances, a faulty piece of software in the SS7 networks was the culprit. Our engineers are studying the problem and expect a solution shortly. We are sorry for any inconvenience to our valued cus- tomers."
I agree with AT&T on one aspect: it was a software problem.
According to well placed sources who asked to remain anonymous, the software problems were intentionally introduced into AT&T's long distance computers, by person or persons yet to be identi- fied. They went on to say that internal investigation teams have been assigned to find out who and how the "bug" was introduced. Regardless of the outcome of the investigation, AT&T is expected, they say, to maintain the cover of a hardware failure at the request of the public relations Vice President.
AT&T did, to their credit, get long distance services up and running at 11:30 P.M. last night, only 9 hours after the problem first showed up. They re-installed an older SS7 software ver- sion that is widely known to contain some "operational anomalies" according to the company; but they still feel that it is more reliable than what is currently in use.
If, in fact the biggest busy signal in history was caused by intruders into the world's largest communications systems, then we need to ask ourselves a few questions. Was yesterday a sym- bolic choice of dates for disaster or mere coincidence? Would the damage have been greater on a busier business day? Could it affect our defense systems and the government's ability to commu- nicate in case of emergency? How did someone, or some group, get into AT&T's computers and effect an entire nation's ability to do business? And then, was there a political motivation sufficient to justify am attack om AT&T and not on Sprint or MCI?