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 Reasons
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 3 2 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 Delayed response
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

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>SG14 4
Case3: SH>SG,SH>GH G S 6 H F

25. ACE Depth of optimization (h-neighbor closure) A B D C E A->B=1015 B 20 D 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 D D B B C E C E A->B=10 B->E=815 D D B 20 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 cutting and cycles
Link cost is not accurate
Link cutting and cycles
Heuristic to theoretical support
f (Pn,Tn)=?

28. Conclusion
Importance
Effectiveness vs. cost
Future work