![Page 1: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/1.jpg)
Mapping the Internet Topology Via Multiple Agents
![Page 2: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/2.jpg)
What does the internet look like?
![Page 3: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/3.jpg)
Why do we care?
• While communication protocols will work correctly on ANY topology
….they may not be efficient for some topologies
• Knowledge of the topology can aid in optimizing protocols
![Page 4: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/4.jpg)
Topics
• Power laws in the internet topology
• Sampling bias in existing topology measurements
• The DIMES project
• Potential applications
• Open issues
![Page 5: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/5.jpg)
Mapping the Internet
• Required characteristics:– connectivity– delays
• Metrics– In/Outdegree– Distance (delay – problematic definition)
![Page 6: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/6.jpg)
Problem definition
G – (un)directed graphN – number of nodesE – number of edgesdv – outdegree of a node v
fd – frequency of an outdegreeP(h) – number of pairs in the “h-hop
neighborhood”
![Page 7: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/7.jpg)
On Power-law Relationships of the Internet Topology
Oct. 1999, Faloutsos Bros.
Mapped the internet at the AS and router level using BGP route views
Data sets: – Nov. ’97: 3015 nodes, 5156 edges– Apr. ’98: 3530 nodes, 6432 edges– Dec. ’98: 4389 nodes, 8256 edges
![Page 8: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/8.jpg)
Outdegree Exponent Power Law
fd ~ d^σ
![Page 9: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/9.jpg)
Other places that people look for power laws…
![Page 10: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/10.jpg)
![Page 11: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/11.jpg)
SCIENCE CITATION INDEX
( = 3)
Nodes: papers Links: citations
(S. Redner, 1998)
P(k) ~k-
2212
25
1736 PRL papers (1988)
Witten-SanderPRL 1981
![Page 12: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/12.jpg)
Sex-web
Nodes: people (Females; Males)Links: sexual relationships
Liljeros et al. Nature 2001
4781 Swedes; 18-74; 59% response rate.
![Page 13: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/13.jpg)
Recall – the Faloutsos graph
![Page 14: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/14.jpg)
Is It Really Power Law?
• Sampling bias could exist
• Crovella article title
• Target – find out if bias exists in prevailing measurement methods, and identify the sources for this bias.
• Configuration – graph model, sampling method, distributions, why this is similar to currently used methods
![Page 15: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/15.jpg)
Results
• Erdos – Renyi + graphs
![Page 16: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/16.jpg)
Sources of sampling bias
• Disproportional sampling of nodes
• Disproportional sampling of edges
• Conclusion
• Identify problems in existing measurement methods (Faloutsos, Caida)
![Page 17: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/17.jpg)
Analysis of Bias Cause
• Explanation– Better coverage with more measurement
sources
![Page 18: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/18.jpg)
DIMES
• Targets
• How we try to solve the problem
![Page 19: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/19.jpg)
DIMES Platform
• Description
• Screenshot
![Page 20: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/20.jpg)
Internet according to DIMES
• maps
![Page 21: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/21.jpg)
Application
• Research– Simulations
• Developing new algs, protocols• Evolution (how will the internet look like in 2020?)• Testing new tools, manufacturing scenarios
– “pure” research• Studying the internet “behavior”, growth• Developing models to describe it
![Page 22: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/22.jpg)
More Application
• Potentially commercial– Improve existing algs’ using knowledge about
the characteristics of the internet.• Multicast alg’• Low – priority packet routing
– Identify (and work around?) network vulnerabilities
![Page 23: Mapping the Internet Topology Via Multiple Agents](https://reader036.vdocuments.us/reader036/viewer/2022062314/56813237550346895d989d6f/html5/thumbnails/23.jpg)
Open Issues
• Measuring delays– Asymmetry– round trip is problematic– triangle inequality doesn’t necessarily hold
• Mapping interfaces to server
• Identifying POPs
• Identifying motiffs