The Association for Computing Machinery requested the study to try and collect available data on how the Internet dealt with the loss of key communications nodes in Lower Manhattan, said Craig Partridge, chair of the report committee and chief scientist at the pioneering Internet research and development company, BBN Technologies, in Cambridge, Mass.
"New York City is a 'super hub' of Internet links and services," Partridge said. "The collapse of the World Trade Center buildings damaged some of those, often in subtle and surprising ways."
Overall, the report concludes, the massive variety of interconnections throughout the Internet is strong enough to resist a localized physical attack. But damaging several locations -- especially in a repeating pattern -- could be more disruptive, the report said.
"Some parties far from the physical disaster site were affected," the report said. "(Service providers) in parts of Europe lost connectivity because they interconnected with the rest of the Internet in New York City, and South Africa was cut off as a result of losing connectivity with the (Internet's address database)."
There also were instances where local redundancy was more of a concept than hard reality. For example, some supposedly separate data links were found to be routed over the same fiber-optic cable, leaving both vulnerable to one case of damage. Many providers co-located similar or identical services to save cost, but in doing so increased their exposure to a single point of failure, the report said.
Users' lack of contingency plans also reduced the local robustness of the system, the report said. For example, one New York City hospital provided medical data to doctors via personal digital assistants, but the attack disrupted the hospital's single link to its external service provider, disabling the service briefly.
The report is correct in pointing out the inability of a single event to knock out the Internet, said Bob Cohen, senior vice president of communications for the Information Technology Association of America in Arlington, Va.
"It suggests the same things that we've testified to before Congress concerning the Internet's resilience," Cohen told United Press International. "The examples (of service loss) it presents go along with how we encourage people to ensure they have operational contingency plans in place."
The report pointed out the importance of users spontaneously coming up with solutions and deploying them, because no central coordination was available. In order to ensure future responses won't require such heroics, the report found service providers should analyze their reliance on other vulnerable systems, such as toll-free phone services.
The ability to operate facilities from remote locations could also be a key factor in responding to incidents in areas that turn out to be inaccessible for repair crews, the report said.