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Topology Mapping

Topology Mapping. Bo Sheng Sept. 15. Outline. Overview Solutions LTM ACE Problems and discussion Conclusion. Introduction. Topology mapping Mismatch between overlay and physical infrastructure Topology optimization. Introduction. Traffic problem Facts

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Topology Mapping

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  1. Topology Mapping Bo Sheng Sept. 15

  2. Outline • Overview • Solutions • LTM • ACE • Problems and discussion • Conclusion

  3. Introduction • Topology mapping • Mismatch between overlay and physical infrastructure • Topology optimization

  4. Introduction • Traffic problem • Facts • 95% of any pairs of Gnutella nodes are within 7 hops • 50,000 nodes generate 1G/second, 330T/month • Reasons • Blind flooding • Cycles, merge of multiple paths, neighbors exchange • Topology problem • Multiple times over a physical link

  5. Introduction • Perfect match S S Network infrastructure Overlay network

  6. Introduction • Mismatch N3 N1 4 5 2 3 S S 2 5 4 N2 Network infrastructure Overlay network

  7. Topology Mismatch • Problems • Randomly choosing neighbors • Logically close, but physically far away S P N1 N2

  8. Topology Mismatch • Problems • Unnecessary traffic • Inefficient utilization of bandwidth • Only 2%~5% Gnutella connections link nodes within a single AS (autonomous system) • More than 40% Gnutella nodes are located within top 10 AS • Delayed response • Do we need long-distance neighbors?

  9. Topology Mismatch • Solutions to traffic problem • Selective flooding • Topology optimization • Avoid cycles • Mapping For each message, how many times it is delivered over a single physical link?

  10. Performance Metrics • Traffic cost • Search scope • Response time • Overhead

  11. Approaches • Location-aware Topology Matching (LTM), INFOCOM 2004 • Adaptive Connection Establishment (ACE), ICDCS 2004

  12. LTM • Three main operations • TTL-2-detector flooding • Message format • Short Source IP& timestamp • Long Source IP& timestamp, TTL1 IP& timestamp • d(i,S,v) • Link cost IP(S),T(S) S N1 N2 IP(S),T(S) IP(N1),T(N1) d(i,S,1) d(i,S,0)

  13. LTM • Three main operations • Low productive connection cutting • Case1: P receives d(i,S,1) and d(i,S,0) S N P will-cut list

  14. LTM • Three main operations • Low productive connection cutting • Case2: P receives multiple d(i,S,0) S N1 N2 P

  15. LTM • Three main operations • Low productive connection cutting • Case3: P receives one d(i,S,1) and multiple d(i,S,0) S N1 N2 P cut list

  16. LTM • Three main operations • Source peer probing S N1 P

  17. LTM Step2.case2 S S Step3 N1 N1 N2 P P

  18. LTM Step2.case3 Step2.case2 S S N1 N1 N2 N2 P P Step2.case3 Step2.case1

  19. LTM Step3 S S Step2.case1 N1 N1 P P

  20. LTM • States Case2 Case1 Case3 Step3

  21. LTM • Performance • Traffic • Search scope • Overhead

  22. ACE • Step1: • Probe link costs with neighbors • Build neighbor cost table • Exchange neighbors cost table with neighbors

  23. ACE • Step2: • Create a minimum spanning tree among each peer and its neighbors E E 14 14 4 4 15 G G S S 6 6 20 F F

  24. ACE • Step3: • Replace neighbors Case1: SH<SG E Case2: GH>SH>SG 14 4 Case3: SH>SG,SH>GH G S 6 H F

  25. ACE • Depth of optimization (h-neighbor closure) A 15 10 D 20 B 8 12 14 C E 7 A->B=10 A->D=15 E->C=7 E->D=14 B->E=8 D->E=14 Total:68

  26. ACE • 2-neighbor closure A A 15 10 D D 20 B B 8 12 14 C E C E 7 A->B=10 B->E=8 E->C=7 E->D=14 Total:39

  27. Discussion • Measurement • Link cost is not accurate • Link cutting and cycles • Heuristic to theoretical support • f (Pn,Tn)=?

  28. Conclusion • Importance • Effectiveness vs. cost • Future work

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