application-level versus network-level proximity mohammad malli phd student planete project, inria -...
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Application-level versus Network-level Application-level versus Network-level Proximity Proximity
Mohammad Malli
PhD student Planete Project,
INRIA - Sophia Antipolis France
December 15, 2005 2
Introduction
• In P2P and CDN, the characterization of the proximity is very
important for identifying the best peer to contact or to take as
neighbor
• Our problem is to study how to characterize efficiently this
proximity
December 15, 2005 3
Motivation
• Most of existing protocols rely on the delay for characterizing
the proximity of peers
• Using the delay closest peer as the best peer hides the implicit
assumption that the path with the nearest peer has the largest
available bandwidth and the smallest loss rate
December 15, 2005 4
Questions
Q1. is the delay correlated with other network path parameters ?
Q2. does its use approximate the use of the others ?
Q3. How much is the performance degradation for applications
relying on the delay proximity ?
December 15, 2005 5
Measurement scenario
• We try to answer these questions using measurements runned
over the Planetlab plateform.
• 127 nodes, spread over the Internet covering America,
EU, and Asia, are used.
• The network characteristics is measured for more than 16k
paths.
December 15, 2005 6
Delay vs. available bandwidth
• 12 % of peers have the maximum available bandwidth on their path with the nearest peer
• Correlation coefficient between these two parameters is – 0.096
• Slow decrease of the available bw with the delay-based peer rank
December 15, 2005 7
Delay vs. loss rate
• 88 % of peers have the minimum loss rate on their path with the nearest peer
• When moving farer in the delay space, the loss rate increases rapidely
December 15, 2005 8
Impact of delay proximity on application performance
• The weak correlation obtained between the delay and the
other path parameters motivates us to evaluate the
performance degradation of applications when the proximity
is characterized based on the delay alone
• To this end, we consider two typical applications
• File transfer over TCP
• Interactive audio service
December 15, 2005 9
File transfer over TCPWe compute the degradation of the transfer time compared to the optimal ranking :
File size increases => degradation increases
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December 15, 2005 10
Interactive audio serviceWe compute the speech rating factor :
Delay proximity => medium audio quality for the 7 closest peers and low quality for the remaining 3 others
ed IIRR 0
December 15, 2005 11
Conclusions
• Delay is a poor predictor for quality for many applications
• This can be interpreted by the low correlation obtained
between the delay and the other network path parameters
• Now, we focus on how to deploy the application-level
proximity without loosing the scalability
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