AT&T, the long distance carrier that provides the best telephone service in the world, handles in excess of 100,000,000 calls daily. Yesterday, less than 25% got through. Why? There are two possible answers: AT&T's official response and another, equally plausible and certainly more sinister reason that many experts claim to be the real culprit. According to an AT&T spokesperson from its Basking Ridge, New Jersey office, "In my 20 years with AT&T, I have not seen a crisis so dramatic that it nearly shut down operations nation- wide." According to insiders, AT&T came close to declaring a national emergency and asking for Federal assistance. Airlines and hotel reservation services reported that phone traffic was down between 65-90%! Telemarketing organizations said that sales were off by over 80%. Perhaps an understanding of what goes on behind the scenes of a phone call is in order. When you pick up your phone, you hear a dial tone that is provid- ed by the Local Exchange Company, or as more commonly called, a Baby Bell. The LEC handles all local calls within certain dial- ing ranges. A long distance call is switched by the LEC to the 4ESS, a miracle of modern communications. There are 114 Number 4 and 5 Electronic Switching Systems used in all major AT&T switch- ing offices across the country. (A few rural areas still use relays and mechanical switches over 40 years old. When it rains, the relays get sticky and so does the call.) 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?