Measuring ISP Toplogies
with Rocketfuel
Neil Spring, Ratul Mahajan, and David Wetherall
Presented By:
David Deschenes
March 25, 2003
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
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
Terminology
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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
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
Directed Probing
• Selects traceroute
measurements that
will transit the ISP in
question
• Measurement Types
– Dependent Prefix
– Insider
– Up/Down
Sample BGP Routing Table
Destination
1.2.3.0/24
Paths
13 4 2 5
6 9 10 5
11 7 5
4.5.0.0/16
378
78
Path Reductions
Ingress
Egress
Next-hop AS
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
Rocketfuel
BGP Table
Egress Discovery
Tasklist
Generation
Alias Resolution
Execution
Path Reductions
ISP Map
Impact of Reductions
• Direct probing reduced number of traces to 18% 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
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)
Questions?