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Understanding Alias Resolution in Internet Topology Measurement

Explore the importance of alias resolution in internet topology measurement, understanding existing approaches like DNS names and ICMP, and learning about unique router properties like IP-ID counter and buffer management. Discover the alias resolution process through traceroute-based techniques and improvements with ICMP, fragmentation, and UDP rate limiting.

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Understanding Alias Resolution in Internet Topology Measurement

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Presentation Transcript

  1. Alias Resolution Yao Zhao

  2. Why is Alias Resolution Important • Internet Topology Measurement • Traceroute based approaches [Mercator,Rocketfoul] • Traceroute discovers interfaces other than routers • If alias is not resolved • Virtual nodes • Virtual edges • Virtual topology

  3. Existing Alias Resolution Approaches • DNS names • Some IP addresses are associated with the same DNS name • Using ICMP Port Unreachable • Source address of ICMP Port Unreachable is the outgoing interface that sends back ICMP TTL-exceeded. • Monotonically Increasing IP-ID • The IP-ID of two IP addresses are correlated

  4. What Are Unique in A Router • IP-ID counter • Buffer • IP fragment buffer • Rate Limiting Property • Allowed number of packet in a certain time • Periodically Maintenance • “Coffee-break” and most likely occurs when routers push forwarding tables to the line cards. • Fragments purge period

  5. IP Fragments Buffer • Normal case A1B1C1D1A2B2 … A1 A2 B1 B2 C1 D1

  6. IP Fragments Buffer • Buffer full A1B1C1D1E1 A2B2 … E1 A1 B1 A2 C1 B2 D1 C2

  7. IP Fragments Buffer • Not alias A1E1B1F1C1G1D1H1A2E2 … A1 A2 B1 B2 C1 D1 E1 E2 F1 F2 G1 H1

  8. IP Fragments Buffer • Alias A1E1B1F1C1G1D1H1A2E2 … C1 A1 E1 G1 D1 B1 H1 F1

  9. Fragments purge period • If a router cannot assemble a fragment in a certain time, the router may send back “ICMP Reassemble Time Exceed” • Routers do this action periodically. A1 C1 D1 B1 A1 C1 -> IP1 B1 D1 -> IP2

  10. Overall Alias Resolution Process • Preparation • Run traceroute on Planetlab nodes to find routers • Using TTL to identify suspicious alias pairs • Alias resolution • Ally • UDP rate limiting • Fragmentation based approaches

  11. Improvements ICMP (85%) Frag Ally Rate Limit No response (15%) UDP (60%)

  12. Preliminary Results

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