simulator
DESCRIPTION
TRANSCRIPT
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The Query-Cycle Simulator for Simulating P2P Networks
Mario T. Schlosser
Tyson E. Condie
Sepandar D. Kamvar
Stanford University
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Problem: Accurately Simulate
Real-World P2P Networks.
Motivation: Testing P2P
Algorithms.
Problem
For each peer i {
-Repeat until convergence {
-Compute. . .
-Send . . .
}
}
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Goals P2P Simulator
Descriptive Simple Easily Extensible Make it available on the web so that people
can test and compare their algorithms on a standard platform.
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Query Cycle Model
Query Cycle 1
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Query Cycle Model
Query Cycle 2
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Query Cycle Model
Query Cycle 3
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Properties to Model Peer Content Network Parameters Peer Behavior
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Properties to Model Peer Content
How Much? What Type?
Network Parameters Peer Behavior
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Data Volume Observations
Model
Simulator assigns # of files owned by peer i according to
distribution.
Saroiu,Gummandi,and Gribble. A Measurement Study of Peer-to-Peer File Sharing Systems, 2002.
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Content Type: Observations Content Categories
Zipf distribution on file popularityCrespo and Garcia-Molina. Semantic Overlay Networks, 2002.
Korfhage, Information Storage and Retrieval, 1997.
Punk Rock Hip-
HopJazz
0
0.2
0.4
0.6
0.8
1
1.2
1 2 3 4 5
Files
Po
pu
lari
ty
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Content Type: Model Modeling Content Categories:
Assume n content categories. C={c1,c2,…,cn} A peer i is assigned content categories according to the Zipf
distribution:
It is then assigned an interest level p(c|i) to each of the assigned content categories by a uniform random distribution.
n
i
i
ccp
1
/1
/1)(
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Content Type: Model Modeling Files:
Each distinct file f may be uniquely identified by {c,r} A peer is assigned files by:
cF
i
rc
i
rcfp
1
,
/1
/1)|(
)|()|()|( ,, cfpicpifp rcrc
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Recap on Content Assignment
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Recap on Content Assignment
Assign Data Volume
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Recap on Content Assignment
{c1, c3, c4}
Assign Content Categories
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Recap on Content Assignment
{c1=.5, c3=.3, c4=.2}
Assign Interest Level to Content Categories
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Recap on Content Assignment
{c1=.5, c3=.3, c4=.2}
Assign Files
{c,r}={c1,f1} {c,r}={c1,f7} . . .
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Properties to Model Peer Content Network Parameters
Topology Bandwidth
Peer Behavior
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Network Parameters Topology:
Observation: Power Law Topology Model: probability of connecting to a peer is
proportional to the degree of that peer. Bandwidth
Simple Bandwidth Model Can be easily extended.
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Properties to Model Peer Content Network Parameters Peer Behavior
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Query-Cycle Model At each cycle, peer i may be:
active inactive or down
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At each cycle, peer i may be: active inactive or down
Query-Cycle Model
Issues a single query.
Waits for incoming responses.
Selects a source and downloads file.
Also:
Responds to queries.
Forwards query messages.
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At each cycle, peer i may be: active inactive or down
Query-Cycle Model
Responds to queries.
Forwards Query Messages.
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At each cycle, peer i may be: active inactive or down
Query-Cycle Model
Does nothing.
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Properties to Model Peer Content Network Parameters Peer Behavior
Uptime and Session Duration Query Activity Queries Query Responses Downloads
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Uptime Observations
ModelAt each query cycle, probability of being up is drawn from distribution in Saroiu et al.
Saroiu,Gummandi,and Gribble. A Measurement Study of Peer-to-Peer File Sharing Systems, 2002.
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Queries Observations
None
Model Based on the idea that peers query for files in
the same categories that they own.
)|()|()|( ,, cfpicpiqp rcrc
cF
i
rc
i
rcfp
1
,
/1
/1)|(
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Responses and Downloads Responses
If a peer receives a query for which it owns the file, it responds.
Source Selection Random
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Extensions Different Types of Peers
i.e., Malicious Peers Different Models for Different Situations
Reputation-based source selection. Edutella: model distribution over markups
rather than content categories. Web Services: Change models for content
distribution, query activity, etc. However, parameters are the same.
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Samples
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Future Work Test predictions against observations in
P2P networks “in the wild”. Observations, observations,
observations. Model other networks.
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The End Code, demos will be available at
http://www.stanford.edu/~sdkamvar/research.html next monday.
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Motivation
Network or peer property Affected algorithms
TopologyContent distribution
Bandwidth, uptime of peers
Structuring algorithmsWhatever
Stability of trust algorithms
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Query Activity Observations
ModelAt each query cycle, . . .
Saroiu,Gummandi,and Gribble. A Measurement Study of Peer-to-Peer File Sharing Systems, 2002.