with similar effects but a different cause; here, the downward spikes on September 17, 1999, coincide near the peak of the physical damage inflicted by Hurricane Floyd. Again, the magnitude of the spikes are comparable with that of September 11, 2001.
On September 11, an important interconnection point (at 140 West Street in New York City) was severely damaged, some long-distance communications links (especially those under the World Trade Center complex) were severed, and there was a localized electrical power outage. Those experiences, together with discussions about them with several Internet service providers, give some indication of the Internet’s vulnerability to a direct and deliberate physical attack. As detailed in Chapter 2, the effects of the terrorist attacks were complex, but by simplifying somewhat, some broad patterns emerge:
Most of the attacks’ effects were local. The majority of the serious communications disruptions were suffered by networks and customers— such as the stock exchanges, Covad DSL customers, and the parts of NYSERNet in Lower Manhattan—physically close to 140 West Street. Effects of the attacks were substantially less notable in Upper Manhattan, and nationally they were hard to discern at all.
Nonlocal effects occurred in surprising places. Some Internet customers in western New England found that connectivity problems in New York affected their ability to dial in to their ISP. And one of the most seriously affected parts of the Internet turned out to be an ocean away—in South Africa.
Rich communications infrastructure and the flexibility of the Internet technology eased recovery. While a number of address ranges were briefly removed from the Internet by the attacks, most of them were back on the network in less than a day. The rich communications infrastructure of the United States made it feasible for most ISPs to reroute around the damage. In cases where rerouting was not an option (as at locations in Lower Manhattan), it was often possible to improvise new connectivity (e.g., a IEEE 802.11b wireless link extending out a window in New York City). Oversimplifying a little, it was only sites within a few blocks of the World Trade Center or sites with limited communications infrastructure (e.g., some of the non-U.S. areas affected by the collapse) that had difficulty recovering. And even in many of the difficult cases, recovery time was still measured in days (not weeks or months).