users had difficulty reading some popular news Web sites. Unprecedented levels of user demand immediately following the attack severely stressed the server computers for these sites. Web service providers quickly took a number of steps—such as reducing the complexity of Web pages, using alternative mechanisms for distributing content, and reallocating computing resources—to respond successfully to demand.
Despite these problems, the Internet, taken as a whole, was not significantly affected. For example, it did not suffer the kinds of overloads that are often associated with the telephone system in a time of crisis. The resilience of the network during the September 11 crisis was a credit to the ingenuity and perseverance of the people who worked to restore communication service near the attack sites; and fundamentally, it was testimony to the Internet’s inherently flexible and robust design.
However, the Internet’s performance on September 11 does not necessarily indicate how it might respond to being directly targeted. Furthermore, it is clear that the experience of individual Internet service providers (ISPs) and corporate networks on September 11 does not generalize: damage suffered, and ability to respond, varied widely from place to place. In particular, the modest effect on Internet communications overall does not indicate how well an individual ISP (and its customers) would fare in an attack targeted specifically to that ISP. Representatives of several ISPs told the committee that what made September 11 a relatively untroubled (albeit unnerving) day for them was simply the fact that their facilities were not concentrated at 140 West Street. But the experience did establish the Internet’s overall resilience in the face of significant infrastructural damage.
The workshop organized by the Committee on the Internet Under Crisis Conditions: Learning from the Impact of September 11 yielded a number of insights about what happened and did not happen to the Internet as a result of the attacks of September 11, 2001. It also provided a number of lessons learned that could reduce the impact of future crises, and it pointed to some ways in which the Internet itself could play a greater role in crisis response.
Finding 1. The events of September 11 had little effect on Internet services as a whole. The network displayed considerable flexibility that underscored its adaptability in the face of infrastructure damage and the demands imposed by a crisis.
In much of the data that the committee examined, an observer would be hard-pressed to find any unusual impact from the events of September