Post on 19-Jan-2016
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Canon in G Major: Designing DHTs with Hierarchical Structure
Prasanna Ganesan(Stanford University)Krishna Gummadi(University of Washington)
Hector Garcia-Molina(Stanford Universiy)
Motivating Scenario
• P-2-P Application– File sharing– Multi-media sharing– Collaborative computation– General purpose lookup directories
Motivating Scenario
Where is the paper “Canon in G Major”?
Hierarchy Design
EE CSCS BIO
KAIST Stanford
Engineering School
Single Point
Over Head
Isolating faultsAdapting growth
Flat Design(DHT)
No single point of failure
Flat & Hierarchical Design
• Flat Design– No single point of failure– P2P(DHT)
• Hierarchical Design– Isolating faults– Adapting growth– DNS
Canonical System
EE CSCS BIO
KAIST Stanford
Engineering School
Crescendo
Chord Chord
Merged Chord
EECS
KAIST
Chord
• Circular N-bit ID space
• Node x links to succ(x+2^i)
0
5
12
1
3
7
8
Crescendo
• Merge– Merging multiple rings– Multi-level hierarchies
• Incremental– New node joins bottom up
• Links per node– Log(n)
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
Merging
• Merging Rule– Closer than any other black node– Y=succ(x+2^i)
Routing Crescendo(intra-domain)
10
0
5
12
Greedy Clockwise routing
Path Locality-Fault isolation-Security-Efficiency
0 -> 12
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
Other DHTs
• Chord => Crescendo• CAN => Can-Can• Symphony => Cacophony• Kademlia => Kandy
Evaluation
• Links/node• Hops/query• latency
Number of Links vs. Number of Levels
9
10
11
12
13
14
15
16
17
1000 10000 100000
Number of Nodes
Nu
mb
er o
f L
inks
Chord
Levels=2
Levels=3
Levels=4
Levels=5
Levels vs. Routing Hops
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
1000 10000 100000
Number of Nodes
Nu
mb
er o
f H
op
s
Chord
Levels=2
Levels=3
Levels=4
Path Locality
0
100
200
300
400
500
600
700
800
900
1000
Top First Second Third Fourth
Query Locality
Lat
ency
(m
s)
Chord (Prox.)
Crescendo
Crescendo (Prox.)
Critique
• Strong point– Novel Idea– Good development of idea
• Weak point– Poor motivating scenario
New Idea
• Do you have any New Idea?