The ability to report comprehensive details of the Internet’s response during September 11, or during any crisis for that matter, is further constrained by a number of factors. One of the consequences of the Internet’s fragmented and often proprietary measurement infrastructure is that data are taken piecemeal in diverse ways and stored in various formats. As a result, information that was available to the committee generally permitted only rough comparison with a normal or typical day in the context of a particular set of data. Measurement difficulties also arise from the size, complexity, and diversity of the Internet and from the fact that a great deal of the data that do exist are considered proprietary by the companies that collect them.

In the course of the committee’s work, it became clear that a number of questions could not be answered with the available information. These included:

  • How did Internet traffic vary from normal activity during and after the attacks? Some traffic data were available from individual ISPs, but it was not always clear how to extrapolate from these localized observations to a more generalized view.

  • What was the mix of applications used before, during, and after the attacks? Again, some local data were available from some ISPs, but it was unclear, as above, if they constituted a collective picture.

  • How much demand was there on news services before, during, and after the attacks? Some news services were so overwhelmed by demand that their monitoring systems shut down.

  • How much connectivity was lost as a result of the attacks? How many users were affected, and for how long? How quickly was connectivity restored? Answering these questions would require data from a large number of ISPs or from a carefully targeted sample of ISPs.

These unanswered questions suggest that a more robust assessment of crisis events in the future will require new approaches to gathering network measurement data. In addressing how measurement of the Internet may be improved, this chapter discusses methods and tools for measurement; the data available from September 11; types of measurements required to fully assess the Internet under crisis; challenges to be faced in gathering and analyzing these measurements; and suggestions for the future.

NETWORK MEASUREMENT METHODS AND TOOLS

Since the Internet’s inception, measurement has been a significant element of networking research, starting with the Network Measurement



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