Measuring ISP Toplogies with Rocketfuel Neil Spring, Ratul Mahajan, and David Wetherall

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Measuring ISP Toplogieswith RocketfuelNeil
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

Sample BGP Routing Table
Destination Paths
1.2.3.0/24 13 4 2 5
1.2.3.0/24 6 9 10 5
1.2.3.0/24 11 7 5
4.5.0.0/16 3 7 8
4.5.0.0/16 7 8
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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 Table
Tasklist Generation
Egress Discovery
Path Reductions
Execution
Alias 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?