Topology Mapping

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# Topology Mapping - PowerPoint PPT Presentation

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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Presentation Transcript

### 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
• 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
Introduction
• Perfect match

S

S

Network infrastructure

Overlay network

Introduction
• Mismatch

N3

N1

4

5

2

3

S

S

2

5

4

N2

Network infrastructure

Overlay network

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?
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
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)

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)

S

N

P

will-cut list

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

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)

S

N1

N2

P

cut list

LTM
• Three main operations
• Source peer probing

S

N1

P

LTM

Step2.case2

S

S

Step3

N1

N1

N2

P

P

LTM

Step2.case3

Step2.case2

S

S

N1

N1

N2

N2

P

P

Step2.case3

Step2.case1

LTM

Step3

S

S

Step2.case1

N1

N1

P

P

LTM
• States

Case2

Case1

Case3

Step3

LTM
• Performance
• Traffic
• Search scope
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
• Step3:
• Replace neighbors

Case1: SH<SG

E

Case2: GH>SH>SG

14

4

Case3: SH>SG,SH>GH

G

S

6

H

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