September to December of 2000 is the most puzzling chunk of time for Cisco to explain. By September, a number of its component makers, such as Solectron, were backing off of their growth projections. Xilinx, a Silicon Valley-based company that makes specialised programmable semiconductors, told the world its growth would be 10 per cent, down from previous projections of 16 per cent to 20 per cent. Both Kris Chellam, CFO of Xilinx, and Shah say most of their strategising that autumn centred on whether the downturn would be a "V" shaped one - deep, short but right back up - or a longer, more serious "U" shaped recession.

But Cisco remained upbeat. Xilinx's Wall street warning came two months before Cisco Chief Strategy Officer Mike Volpi told the Wall Street Journal in November: "We haven't seen any sign of a slowdown." Volpi told The Journal that Cisco hadn't changed its internal plans since the beginning of its fiscal year in August. "We have guided [Wall Street] accurately, and we can execute to plan."

On December 4, CEO Chambers crowed to analysts: "I have never been more optimistic about the future of our industry as a whole or of Cisco."

Eleven days later, CIO Solvik says, the company saw the problem for the first time. It overlaid the virtual close and its forecast, and sales had crossed under its projections. Cisco decided to seriously curtail expenses. Three weeks later, revisiting the data would lead to a hiring freeze. Solvik says the near-real-time data prevented what eventually happened to Cisco from being worse, if that's even imaginable.

"I'm saying it could have been a lot worse," Solvik says. "We were able to react to trends day by day [using our infrastructure]."

But what was Cisco doing in September, October and November? Why wasn't the virtual close telling Cisco that demand was evaporating? Why wasn't the infrastructure that allowed Cisco to forecast Japan's economic slump so accurately able to even see a more severe swing here? If Cisco acted quickly when the sales line fell under the forecasts line, why didn't executives see those lines converging?

"We disclosed at the time what we thought," Solvik responds. "Other than what we publicly stated, I can't comment on the outlook [at the time]."

By year's end, the economy was foundering. It was neither a "U" nor a "V" but a "7". A cliff. The Fortune 100 halted capital spending. Alternative telecommunications carriers disappeared, along with many of the dotcoms that had been so feverishly buying Cisco gear. That equipment ended up on a grey market; barely used Cisco switches could be had for 15 cents on the dollar, and Cisco lost money every time one was snapped up. Traditional telecom companies stopped spending too. In short, demand vanished. Cisco finally threw on the brakes on December 15. The freight train spit sparks and burned up the steel track as it tried to stop short of the cliff. It jolted down the supply chain, derailing suppliers like Xilinx and manufacturers like Solectron and their distributors.

And Cisco, the networking industry's big engine, went over the edge.