Efï¬cient Network Tomography for Internet Topology Discovery
Network tomography to enhance the performance of software defined network monitoring and management
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Transcript of Network tomography to enhance the performance of software defined network monitoring and management
NETWORK TOMOGRAPHY TO ENHANCE THE
PERFORMANCE OF SOFTWARE DEFINED
NETWORK MONITORING AND MANAGEMENT
K M Sabidur Rahman with Chaitrali Joshi and Tanjila Ahmed (ECS 273)
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Agenda
•Network Tomography and SDN
•MiniNet Data Collection
•EM algorithm
•Results from EM implementation in R
•Future work
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Network Tomography
“It is the study of a network’s internal characteristics using information
derived from end point data.” - Wikipedia
• Statistical theory and algorithms are used to estimate internal
characteristics of the network topology
• Flexibility of SDN can be used to make better results
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Shortcomings of current measurement methods
• Impractical to measure packet delays at every router
• Proprietary routers are inflexible
• Geographic separation of routers
• Storing packet information at every node is expensive
• Memory constraints
• Causes congestion in communication
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Experimental Setup
• Topology setup using Mininet
• Single source multiple
receiver
• Controller for SDN
• Python based POX
remote controller
S2
H2 S1
S3
H3 H4
H1
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EM Algorithm
•Iterative method for estimation of parameters in a statistical model
•It estimates the maximum likelihood of parameters
•Where the model depends on unobserved latent variable
•E step: Update the conditional expectation(log likelihood) of the parameter
by the given observation
•M step: Find the parameter that maximizes that quantity
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EM Algorithm y = observed end-to-end delay data z = unobserved link delay(latent variable) p=probability of delays on link i
Complete data likelihood can be factorized as :
where we have to estimate and z from end-to-end delay y
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EM Algorithm Complete data likelihood is dependent on likelihood of z as conditional pmf of y given z does not have p parameter.
Where ,number of packets that faces delay j on link i
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EM Algorithm
E Step :
M step:
This is our updated estimate of Pij.
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Results
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Data Link 1
EM
Nu
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f p
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Delay (ms)
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Results
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Data Link 2
EM Link 2
Nu
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Delay (ms)
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Results
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Data Link 3
EM
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mb
er o
f p
acke
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Delay (ms)
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Future
•Use more data 100,1000,2000
•Use more complex topology
•Use SDN control mechanism to find the minimum measurement needed for
a network
•Explore temporal effects on delays
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