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Measuring ISP Toplogieswith Rocketfuel
Neil Spring, Ratul Mahajan, and David Wetherall
Presented By:David Deschenes
March 25, 2003
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Contributions
• Presents novel techniques for generating high quality ISP maps while using as few network measurements as possible
• Examines several properties of generated maps that are likely to be of use in creating synthetic Internet maps
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Motivation
• Brute-force approaches to Internet mapping produce excessive loads and can take extraordinary amounts of time
• Synthetic Internet maps of high quality are useful to researchers, especially with respect to the execution of realistic simulations
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Terminology
• An ISP network consists of multiple POPs
• Each POP is a collection of routers
• POPs are connected by backbone links
• Backbone routers are attached to backbone links
• Access routers intermediate between the ISP backbone and routers on neighboring networks
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Approach
• Omit measurements likely to be redundant– Expected BGP routing paths facilitate selection– Trades accuracy for efficiency
• Improve alias resolution– Make use of IP identifier, rate-limiting and TTL values
• Annotate maps– Hints about geographical location and role may be
extracted from DNS names
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Directed Probing
• Selects traceroute measurements that will transit the ISP in question
• Measurement Types– Dependent Prefix– Insider– Up/Down
Destination Paths
1.2.3.0/24 13 4 2 5
6 9 10 5
11 7 5
4.5.0.0/16 3 7 8
7 8
Sample BGP Routing Table
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Path Reductions
Ingress Egress Next-hop AS
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Alias Resolution
• Send a series of probe packets to potential matches, and test the following data– Packet TTLs– ICMP Rate-limiting– IP Identifiers
• The use of IP Identifiers proved most valuable, while the other data provided greater levels of confidence in IP Identifier matches
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Rocketfuel
BGP TableTasklist
GenerationEgress Discovery
Path ReductionsExecutionAlias Resolution
ISP Map
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Impact of Reductions
• Direct probing reduced number of traces to 1-8% depending on the ISP to be mapped
• Ingress reduction kept only 12% of those traces selected by direct probing
• Egress reduction kept only 18% of those traces selected by direct probing
• Next-hop AS reduction kept only 5% of those selected by direct probing
• Overall, after reductions, less than 0.1% of the traces required by a brute-force technique were executed by Rocketfuel
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Accuracy of Generated Maps
• Found from 64% to 96% of backbone routers depending on the ISP to be mapped (See Table 2)
• BGP adjacencies somewhat consistent with those provided by RouteViews (See Figure 9)
• Significant disparity between Rocketfuel and Skitter with regard to adjacencies (See Figure 10)
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Questions?