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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

Topology Mapping

Bo Sheng

Sept. 15


Outline
Outline

  • Overview

  • Solutions

    • LTM

    • ACE

  • Problems and discussion

  • Conclusion


Introduction
Introduction

  • Topology mapping

    • Mismatch between overlay and physical infrastructure

    • Topology optimization


Introduction1
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


Introduction2
Introduction

  • Perfect match

S

S

Network infrastructure

Overlay network


Introduction3
Introduction

  • Mismatch

N3

N1

4

5

2

3

S

S

2

5

4

N2

Network infrastructure

Overlay network


Topology mismatch
Topology Mismatch

  • Problems

    • Randomly choosing neighbors

    • Logically close, but physically far away

S

P

N1

N2


Topology mismatch1
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 mismatch2
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
Performance Metrics

  • Traffic cost

  • Search scope

  • Response time

  • Overhead


Approaches
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

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

    • 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

  • 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
Discussion

  • Measurement

    • Link cost is not accurate

  • Link cutting and cycles

  • Heuristic to theoretical support

    • f (Pn,Tn)=?


Conclusion
Conclusion

  • Importance

  • Effectiveness vs. cost

  • Future work


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