The Internet Under Crisis Conditions Learning from September 11 (2003) / Chapter Skim
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Summary and Findings
Summary and Findings
Pages 1-10
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Electrical power in Lower Manhattan was disrupted, and local telecommunications facilities there suffered a variety of problems with their backup power systems. Serious effects on communications networks, however, were confined to New York City and a few other regions highly dependent on it for their connectivity.
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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.
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A number of examples of how the Internet was used in the hours and days immediately following the September 11 attacks highlight the flexibility afforded by that design. NYSERNet, a nonprofit networking consortium, was able to reroute connectivity to bypass physical damage in Lower Manhattan.
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, the precision with which analysts can measure the impact of such events is limited by a lack of relevant data. The data available to the committee to gauge the impact of September 11 included active measurements of packet delay and loss over a small fraction of the Internet's paths, selected passive monitoring of application-level behavior and global-routing activity, and data from a survey of Internet users.
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Also, while many of the effects of September 11 were highly localized (like the attacks themselves) , some parties far from the physical disaster sites were affected ISPs in parts of Europe lost connectivity because they interconnected with the rest of the Internet in New York City, and South Africa experienced disruptions associated with the Domain Name System (DNS)
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The attacks of September 11 were not directed at the Internet. Nonetheless, because New York City is a major worldwide data-communications hub and a number of key communications links and facilities were concentrated in a handful of sites near the World Trade Center complex, the attack caused significant damage to Internet elements.
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, on which doctors rely to access medical information, were connected through an external ISP network. Thus when the hospital's sole link to the Internet was briefly broken by the collapse of the Twin Towers, doctors had trouble accessing hospital records.
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Reports also suggest that ISPs, unlike some other utilities, were not granted access to the restricted zone in Lower Manhattan, which further complicated their recovery efforts. Specific problems included these: Poor operating procedure resulted in a facility's backup generator being shut off to conserve fuel, which in turn led to service interruptions when grid electrical power was lost.
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On the other hand, it is also clear that if the television or telephone was unavailable or failed to provide the information people needed, they turned to the Internet even if they normally were not heavy Internet users. For instance, it appears that much of the surge in demand at online news sites on the morning of September 11 came from people who did not have access to television sets at their workplace.
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In contrast, the Internet makes use of mechanisms that continue to accept new messages but reduce transmission rates when the network is congested. Also, by virtue of their flexible design, Internet-style communications lend themselves to human actions that reduce the load whether by substituting a brief text message for a data-intensive voice call or removing data-intensive graphics from a Web page (as CNN did in the face of high loads)
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