2006-05-19 1

Canon in G Major: Designing DHTs with Hierarchical Structure

Prasanna Ganesan, Krishna Gummadi, Hector Garcia-Molina

ICDCS2004

報告者 : 陳奕鈞

2006-05-19 2

Outline

• Motivation

• Canon

• Crescendo

• Routing Crescendo

• Evaluation

• Conclusion

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Motivation

• P-2-P Application– File sharing– Multi-media sharing– Collaborative computation– General purpose lookup directories

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Canon

Where is the paper “Canon in G Major”?

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Hierarchy Design

EE CSCS BIO

KAIST Stanford

Engineering School

Single Point

Over Head

Isolating faultsAdapting growth

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Flat Design(DHT)No single point of failure

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Flat & Hierarchical Design

• Flat Design– No single point of failure– P2P(DHT)

• Hierarchical Design– Isolating faults– Adapting growth– DNS

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Canon System

EE CSCS BIO

KAIST Stanford

Engineering School

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Crescendo

Chord Chord

Merged Chord

EECS

KAIST

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Chord

• Circular N-bit ID space

• Node x links to succ( )

0

5

12

1

3

7

8

i2x

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Crescendo• Merge

– Merging multiple rings– Multi-level hierarchies

• Incremental– New node joins bottom up

• Links per node– log(n)

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Merging

• Merging Rule– Each node m in one ring creates a link

to a node n in the other ring iff.a. n is the closest node that is at least distance

away for some b. n is closer to m than any node in m’s ring

N i 0 i2

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Merging

10

0

5

12

8

3

2

13

0

5

12

8

3

2

13

10

0

5

12

8

3

2

13

10

0

5

12

8

3

2

13

10

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Routing Crescendo(intra-domain)

10

0

5

12

Greedy Clockwise routing

Path Locality-Fault isolation--Efficiency

0 -> 12

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Routing Crescendo(inter-domain)

10

0

5

12

0

5

12

8

3

2

13

10

0

5

12

10

Path convergence:closest node to destination in the domain:same destination node same last node in the domain

0 -> 13

-Distributed Caching

-Bandwidth savings

0

5

12

8

3

2

13

10

5 -> 13

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Other DHTs

• Chord => Crescendo• CAN => Can-Can• Symphony => Cacophony• Kademlia => Kandy

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Evaluation

• Links/node• Hops/query• latency

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Number of Links vs. Number of Levels

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Levels vs. Routing Hops

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Path Locality

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Conclusion

– Novel Idea– Poor motivation