U Innsbruck Informatik U Innsbruck Informatik - - 1 1 Scalable Scalable Performance Performance Signalling Signalling and Congestion and Congestion Avoidance Avoidance PhD PhD presentation presentation Supervisor Supervisor : Max Mühlhäuser 2nd : Max Mühlhäuser 2nd supervisor supervisor : Jon : Jon Crowcroft Crowcroft Abteilung Telekooperation, TU Darmstadt, Nov. 18th 2002 Abteilung Telekooperation, TU Darmstadt, Nov. 18th 2002 Michael Michael Welzl Welzl [email protected][email protected]University of Linz University of Linz - - > University of Innsbruck > University of Innsbruck
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Scalable Performance Signalling and Congestion Avoidance · Scalable Performance . Signalling. and Congestion . ... congestion detected via packet loss in TCP RED ECN here: ... •
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U Innsbruck Informatik U Innsbruck Informatik -- 11
ScalableScalable Performance Performance SignallingSignallingand Congestion and Congestion AvoidanceAvoidance
PhDPhD presentationpresentationSupervisorSupervisor: Max Mühlhäuser 2nd : Max Mühlhäuser 2nd supervisorsupervisor: Jon : Jon CrowcroftCrowcroftAbteilung Telekooperation, TU Darmstadt, Nov. 18th 2002Abteilung Telekooperation, TU Darmstadt, Nov. 18th 2002
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CADPC vs. CADPC vs. TCPTCP--friendlyfriendly CC. CC. mechanismsmechanisms
Throughput
Avg. Queue Length
Loss
Fairness
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CADPC vs. 3 TCP(+ECN) CADPC vs. 3 TCP(+ECN) flavorsflavors
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FurtherFurther simulationssimulations (in (in thethe thesisthesis))
• Dynamic:– Dependence on smoothness parameter a and packet size– Robustness against fast routing changes– Effect of mixing converged flows– Performance across highly asymmetric connections + noisy links
• Long-term (throughput, loss, average queue length, fairness):– Check valid parameter space: bandwidth, no. of flows, packet size– Varying bottleneck bandwidth– Varying feedback delay– RED, REM and AVQ Active Queue Management– Behaviour with varying amount of web background traffic– Max-min fairness (scenario with 2 bottlenecks)
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OutlineOutline
• Problem identification / motivation
• Proposed solution
• Simulation results
• Conclusion
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...b...basedased on on drasticdrastic departuredeparture fromfromexistingexisting approachesapproaches
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Future Future workwork
• So far, ...– only max-min-fairness supported– only greedy sources simulated
• Gradual deployment ideas:
– CADPC / PTP within a DiffServ class (QoS “in the small“):“we offer QoS + provide router support,you use CADPC and obtain a good result[and we can calculate your rate, too]“
– If CADPC works with non-greedy senders:edge2edge PTP signalling
• PTP supported traffic engineering (TCP over CADPC)• CADPC <=> TCP translation at edge routers?
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TheThe End ...End ...
• Related publications
• PTP ns code
• PTP Linux code (router kernel patch + end system implementation)
• Future updates: thesis, CADPC code, ..
http://fullspeed.to/ptp
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Additional Additional informationinformation
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TheThe end2end end2end argumentargument
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ThisThis thesisthesis and and thethe end2end end2end argumentargument
• „Lower-level layers, which support many independent applications, should provide only resources of broad utility across applications, while providing to applications usable means for effective sharing of resources and resolution of resource conflicts. (networktransparency)“
[Active Networking and End-To-End Arguments, Comment by David P. Reed, Jerome H. Saltzer, and David D. Clark]
• Goals of this thesis:
– provide such means– use it!
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AIMD BackgroundAIMD Background
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User 1 Allocation x1
FairnessLine
EfficiencyLine
Use
r 2 A
lloca
tion
x2
StartingPoint
AIMD
Desirable
StartingPoint
AIAD
MIMD
Underload
Overload
AIMD in AIMD in TheoryTheory ((equalequal RTTsRTTs))
User 1 Allocation x1
FairnessLine
EfficiencyLine
Use
r 2 A
lloca
tion
x2
StartingPoint
AIMD
Desirable
StartingPoint
AIAD
MIMD
Underload
Overload
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x(t) ... normalised rate at time ta... smoothness factor(should be 0 < a <= 1)traffic (normalised) ... from PTP
• Converges to: n/(n+1)
• Continuous-time version of synchronous case (traffic=nx):logistic growth x‘(t) = x(t)a(1-x(t)/c) [c = 1/(1+n)]asymptotically stable equilibrium point: c