Bufferbloat Detection In Network Paths · Bu erbloat Detection In Network Paths Danny Groenewegen1,...
Transcript of Bufferbloat Detection In Network Paths · Bu erbloat Detection In Network Paths Danny Groenewegen1,...
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Bufferbloat Detection In Network Paths
Danny Groenewegen1, Harald Kleppe1
1System and Network EngineeringUniversiteit van Amsterdam
Michiel Leenaars22NLnet Foundation
30th of June 2011RP2 presentations
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BufferbloatDark buffers in the Internet
Bufferbloat is the existence of excessively large (bloated) buffers insystems, particularly network communication systems.
I Every network protocol is affectedI Many of them rely on timely arrival of packets
I The problem was already discussed in RFC 970
I Cheaper memory, increasing buffers
I Increasing traffic
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Detecting bufferbloatResearch question
Is it possible to determine which device in a path causesbufferbloat?
I Is it possible to quantify the effects of bufferbloat?
I Can the same methods be applied on the Internet, where theyare influenced by other unpredictable traffic?
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Measuring link characteristics with pathcharProbing each hop in a path
I Vary TTL to probe each node in a path
I Difference between n − 1 and n gives link characteristics
1
1Allen Downey. Using pathchar to estimate Internet link characteristics;ACM SIGCOMM, pages 241-250, 1999
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Measuring link characteristics with pathcharEstimate bandwidth and latency
I Varying packet sizes givesbandwidth and latency
I Multiple repetitions givequeuing and loss information
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Estimating queue delaysFrom pathchar to measuring bufferbloat
I Improve the accuracy of queue delay estimatesI Probing each hop at (almost) the same timeI Only probing with one packet size
I Observing the minimum RTT in a congested pathI Bufferbloat effects are not always visible
I Measure with five minute intervals
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Quantifying bufferbloatBufferbloat scoring model
gr ad e = 0
f o r each measurement i n t e r v a l :median = median o f queue d e l a y sgr ad e += ( median / 0 . 0 1 0 ) / number o f i n t e r v a l s
i f g ra de > 1 0 :g r ad e = ”10+”
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Tests and results
I Simulated experiments in a lab setup
I Experiments on the Internet
I Validate the toolI Detect queue distribution in a pathI Compare bufferbloat scoring
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ResultsLab test #1
I 10 and 100 Mbit bottlenecksI Saturate bottlenecksI Identify second bottleneck behind an intermediate bottleneck
Router #1 Router #2 Router #3
Router #4Router #5
Host #1
Host #2Router #6
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ResultsLab test #1
I 10 and 100 Mbit bottlenecksI Saturate bottlenecksI Identify second bottleneck behind an intermediate bottleneck
Router #1 Router #2 Router #3
Router #4Router #5
Host #1
Host #2Router #6
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ResultsTest setup; Link 3: 10Mb/s; Link 6: 100Mb/s; Bufferbloat score: 10+
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Queue delay on top of minimum path RTT - bufferbloat-testsetup2
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ResultsConsumer ISP connection; Bufferbloat score: 5.0
I Probing from Diemen to Norway
I Saturating traffic from OS3 lab
I 25 / 1.5 Mbit consumer grade connection
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ResultsConsumer ISP connection
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ResultsChicago - Tokyo
I From a VPS in Chicago
I Towards a RIPE TTM host in Tokyo
I Eight hop path, trans-pacific
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ResultsChicago - Tokyo: Bufferbloat score: 8.6
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Results Summary
I Queue delay can be determined per link
I Possible to observe near zero queue delay
I Generally slightly less queue delay on IPv6 links than IPv4
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Conclusion
I Possible to detect bufferbloated linkI Determining which queueI Layer 2 components
I Methods seem to work on the InternetI Scoring model needs fine tuning
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Questions?
Thanks for listening!
Tool: https://github.com/hkleppe/Buffchar
More info: http://www.bufferbloat.net