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Raj JainThe Ohio State University
Raj Jain, Shiv Kalyanraman, Ram ViswanathanDepartment of Computer and Information Sci.
The Ohio State UniversityColumbus, OH 43210
Raj JainThe Ohio State University
Features
Scheme
Simulation results
Overview
Raj JainThe Ohio State University
Design FeaturesCongestion Avoidance
High throughputLow delayOperation independent of buffers
LinkUtilization
Time
QueueLength
Time
5
Raj JainThe Ohio State University
Design FeaturesWorks for bursty trafficFairness: Analytically provenMeasured overload/load at switch/sourceBounded oscillations ⇒ Good for VBRParameters: Few, insensitive, easyBipolar feedbackSeveral options: BECN
Precise fairness computation
Raj JainThe Ohio State University
Transmission Rate
The OSU Scheme
The sources periodically send a control cellThe switches measure load over a periodThe switches specify reduction factor in cellThe destination returns the cell to the sourceThe source adjusts the transmission rate
Offered average Rate Adjustment Factor
Raj JainThe Ohio State University
Control Cell FormatTransmitted Cell Rate (TCR)=1/Inter-cell timeOffered average cell rate (OCR)
Load adjustment factor: TCR New = TCR/LAFAveraging intervalFor BECN option: FECN/BECN bitTimestamp (when sent by the source)
1 ms
10 µs
TCR OCR
Raj JainThe Ohio State University
Source AlgorithmArbitrarily select: Initial TCR
Averaging interval TSend sells at inter-cell time = 1/TCRSend control cells every TOn receiving a control cell:
T ← Averaging interval from cellExecute LAF algorithm
Raj JainThe Ohio State University
Load Adjustment Factor in Cell<1Yes No
Current TCR = New TCR
YesNo
Ignore
Yes No
Ignore
New TCR = TCR in Control Cell
Load Adjustment Factor in Cell
New TCR <Current TCR
New TCR >Current TCR
Source LAF Algorithm
Raj JainThe Ohio State University
Switch LAF AlgorithmParameters:
Averaging interval TTarget utilization band (TUB): U(1± ∆)
Compute Target # of cells per T at UCount cells received over TLoad = Received/TargetTcell ← Max{Tcell, T}LAFcell ← Max{LAFcell, Load}
LoadLevel
Time
1
Raj JainThe Ohio State University
The TUB Algorithm
In-TUB?
OCR<Fair share?
LAFcell ← Max{LAFcell, Load/(1-∆)}
LAFcell ← Max{LAFcell, Load/(1+∆)}
LAFcell ← Max{LAFcell, Load}
Fair share = Target rate/# of active VCsAnalytically proven:Fair and Closed (remain in TUB)
Raj JainThe Ohio State University
SecondSource’s
Ratey
First Source’s Rate x
23
4
56
(x, y)
(x’, y’)
1
Proof
Fairness Line
x + y = U(1+∆)x + y = Ux + y = U(1-∆)
Efficiency Line
Raj JainThe Ohio State University
Raj JainThe Ohio State University
Single-Source Configuration
All links 150 Mbps, 1 kmMax-min optimal: 150 MbpsTUB = 0.90 (1 ± 0.1)Averaging interval = 150 µs
Sw 1 D1S1 Sw 1
Raj JainThe Ohio State University
Two-Source Configuration
All links 150 Mbps, 1 kmMax-min optimal: 75 MbpsTUB=0.90(1 ± 0.1)Averaging interval = 150 µs
Sw 1S1
Sw 2S2
D1
D2
Raj JainThe Ohio State University
Three-Source Configuration
All links 150 Mbps, 1 kmMax-min optimal: 50 MbpsTUB=0.90(1 ± 0.1)Averaging interval = 150 µs
S1
Sw 1 Sw 2S2
S3
D1
D2
D3
Raj JainThe Ohio State University
Transient Configuration
All links 150 Mbps, 1 kmTUB=0.90(1 ± 0.1)Averaging interval = 150 µs
Sw 1S1
Sw 2S2
D1
D2
OptimalRate
Time
S1
S2
Raj JainThe Ohio State University
Parking Lot Configuration
All links 150 Mbps, 1 kmMax-min optimal: 50, 50, 50 MbpsTUB=0.90(1 ± 0.1)Averaging interval 150 µs
S1
S2Sw 1 Sw 2 Sw 3
S3
D1
D2
D3
Raj JainThe Ohio State University
Upstream Configuration
All links 150 Mbps, 1 kmMax-min optimal: 50, 50, 50, 100 MbpsTUB=0.90(1 ± 0.1)Averaging interval = 150 µs
Sw 1 Sw 2 Sw 3
S4
D3
D4
S2
S1 D1
D2S3
Raj JainThe Ohio State University
VC Cell Rates
Raj JainThe Ohio State University
Link Utilization
Raj JainThe Ohio State University
Queue Length
Raj JainThe Ohio State University
Queue Size with Startup at PCR/10
Raj JainThe Ohio State University
VC Cell Rates in WAN Configuration
Raj JainThe Ohio State University
Queue Size with WAN Configuration
Raj JainThe Ohio State University
VC rates with Train Traffic
Raj JainThe Ohio State University
BECN Option
TUB Algorithm
AggressiveFairnessOption
PreciseFair share
ComputationOption
Switch LAF Algorithm
Load Measurement at Switches
Load Measurement at Sources
Family Portrait
Source LAF Algorithm
1 2 3 4 65
Raj JainThe Ohio State University
Summary
Design Principles: Input rate overload, Feedback-control relationship, TCR/OCR specification, TUB fairness
Features: High throughput, Low delay, Avoidance,Bipolar
Basic Scheme: Source/switch LAF algorithm
Options: Thoroughly tested all variations