performance limitations of adsl users: a case study
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Performance Limitations of ADSL Users: A Case Study. Matti Siekkinen , University of Oslo Denis Collange, France T é l é com R&D Guillaume Urvoy-Keller, Ernst W. Biersack, Institut Eurecom PAM April 6, 2007. Outline. Introduction Motivation - PowerPoint PPT PresentationTRANSCRIPT
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Performance Limitations of ADSL Users:A Case Study
Matti Siekkinen, University of Oslo
Denis Collange, France Télécom R&D
Guillaume Urvoy-Keller, Ernst W. Biersack,Institut Eurecom
PAMApril 6, 2007
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April 21, 2023
Outline
Introduction Motivation Techniques for root cause analysis of TCP throughput
Measurement setup Analysis results Conclusions
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Introduction
What? Analyzed 24h packet trace from France Telecom’s ADSL access network Studied throughput limitations experienced by clients
Why? Knowing throughput limitations (=performance) is useful
o ISPs want satisfied clientso Need to know what’s going on before things can be improved
How? Root Cause Analysis of TCP Throughput
o Analysis and inference of the reasons that prevent a given TCP connection from achieving a higher throughput.
o Passive traffic analysis Why TCP?
o TCP typically over 90% of all traffic
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Background
“On the characteristics and origins of Internet flow rates” by Zhang et al. (SIGCOMM 2002) Pioneering research work Congestion is not always the cause for throughput limitations
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Limitation Causes for TCP Throughput
Application The application does not even attempt to use all network resources E.g. streaming applications and “bursty” applications (Web browsing)
Transport layer TCP receiver
o Receiver advertized window limits the rateo max amount of outstanding bytes = min(cwnd,rwnd)o Flow controlo Configuration issue
• default receiver advertized window is set too low• window scaling is not enabled
TCP protocolo Ramp-up period in slow start and congestion avoidance
Network layer Congestion at a bottleneck link
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Measurement Setup
24 hours of traffic on March 10, 2006 Passively capture all TCP/IP headers analyze offline
290 GB of TCP traffic 64% downstream, 36% upstream
Observed packets from ~3000 clients, analyze only 1335 Excluded clients did not generate enough traffic for RCA
Two pcap probes here
Internetcollectnetwork
accessnetwork
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Connections Size distribution highly skewed Use only 1% of the flows for RCA
o Represent > 85% of all traffic
Clients Heavy-hitters: 15% of clients generate 85-90% of traffic (up &
down) Low access link utilization
Warming up…
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Results of Limitation Analysis
Few active clients overall Application limitation dominates Network limitation by distant bottleneck also experienced
containsmost bytes
containssome bytes
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Application analysis:Application limited traffic
Quite stable and symmetric volumes Vast majority of all traffic
eDonkey and “other” dominateP2P
other
eDonkey
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Application analysis:Saturated access link
No recognized P2P Asymmetric port 80/8080 downstream
Real Web traffic?
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Impact of Limitation Causes
How far from optimal (access link saturation) are we? Main observations
Very low downlink utilization for application limited traffico Utilization < 20% during 65% of application limited periods of traffic
Uplink utilization < 50% during most of application and network limited uploads
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Connecting the evidence…
Most clients’ performance limited by applications Very low link utilizations for application limited traffic Most of application limited traffic seems to be P2P
Peers often have asymmetric uplink and downlink capacities P2P applications/users enforce upload rate limits
Poor aggregate download performance
Internet
Internet
Low downlinkutilization Low uplink capacity
+rate limiter
downloading client
uploadingclients
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Conclusions
Analyzed 24h packet trace from France Telecom’s ADSL access network Studied throughput limitations experienced by clients
Majority of clients mostly throughput limited by applications P2P clients throttle upload rate
o Too much? Asymmetric link capacities
Impact and implications ISP traffic is mostly application limited traffic Things can change dramatically with
o More intelligent P2P clientso Caches
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For the future…
Play with time scale Extended case study on ADSL clients
We saw a day, what about a week?
Could we do things on-line? Improving RCA techniques
Short connections Non FIFO traffic (e.g. wireless)
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Thank you for your attention