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## PowerPoint Slideshow about ' Topology Mapping' - raina

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Presentation Transcript

Outline

- Overview
- Solutions
- LTM
- ACE

- Problems and discussion
- Conclusion

Introduction

- Topology mapping
- Mismatch between overlay and physical infrastructure
- Topology optimization

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

- Blind flooding

- Facts

Topology Mismatch

- Problems
- Randomly choosing neighbors
- Logically close, but physically far away

S

P

N1

N2

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?

- Unnecessary traffic

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?

Performance Metrics

- Traffic cost
- Search scope
- Response time
- Overhead

Approaches

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

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

- Message format

- TTL-2-detector flooding

IP(S),T(S)

S

N1

N2

IP(S),T(S)

IP(N1),T(N1)

d(i,S,1)

d(i,S,0)

LTM

- Three main operations
- Low productive connection cutting
- Case1: P receives d(i,S,1) and d(i,S,0)

- Low productive connection cutting

S

N

P

will-cut list

LTM

- Three main operations
- Low productive connection cutting
- Case2: P receives multiple d(i,S,0)

- Low productive connection cutting

S

N1

N2

P

LTM

- Three main operations
- Low productive connection cutting
- Case3: P receives one d(i,S,1) and multiple d(i,S,0)

- Low productive connection cutting

S

N1

N2

P

cut list

LTM

- Performance
- Traffic
- Search scope
- Overhead

ACE

- Step1:
- Probe link costs with neighbors
- Build neighbor cost table
- Exchange neighbors cost table with neighbors

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

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

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

Discussion

- Measurement
- Link cost is not accurate

- Link cutting and cycles
- Heuristic to theoretical support
- f (Pn,Tn)=?

Conclusion

- Importance
- Effectiveness vs. cost
- Future work

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