Traffic Management for the Available Bit Rate (ABR) Service in ...

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At the source end system, the ACR is updated as: ACR = Functionf ER, VC's current ACR g 9.2.2 Rate Calculations in a VS/VD Switch Figure 9.7 shows the rate calculations in a VS/VD switch. Speci cally, the segment starting at Link2 (\next loop") returns an ER value, ER 2 in the BRM, and the FRM of the rst segment (\previous loop") is turned around with an ER value of ER 1. The ERICA algorithm for the port to Link2 calculates a rate (VAL 2) as: VAL 2 = Function f Input Rate, VC's Current Rate g. The rate calculations at the VS and VD are as follows: Figure 9.7: Rate calculations in VS/VD switches Destination algorithm for the previous loop: ER 1 = Min f ER 1�VAL 2�ACR 2 g Source Algorithm for the next loop: Optionally, ER 2 = Min f ER 2�VAL 2 g ACR 2 = Fn f ER 2�ACR 2 g 345
The unknowns in the above equations are the input rate and the VC's current rate. We shall see in the next section that there are several ways of measuring VC rates and input rates, combining the feedback from the next loop, and updating the ACR of the next loop. Note that though di erent switches may implement di erent algorithms, many measure quantities such as the VC's current rate and the ABR input rate. 9.3 VS/VD Switch Design Options In this section, we aim at answering the following questions: What is a VC's current rate? (4 options) What is the input rate? (2 options) Does the congestion control actions at a link a ect the next loop or the previous loop? (3 options) When is the VC's allocation at the link (VAL) calculated? (3 options) We willenumerate the 72 (= 4 2 3 3) option combinations and then study this state space for the best combination. 9.3.1 Measuring the VC's Current Rate There are four methods to measure the VC's current rate: 1. The rate of the VC is declared by the source end system of the previous loop in the Current Cell Rate (CCR) eld of the FRM cell (FRM1) received by the VD. This declared value can be used as the VC's rate. 346
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Tra c Management for the Available
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ABSTRACT With the merger of telecom
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Tra c Management for the Available
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To my family iv
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VITA April 30, 1971 :::::::::::::::
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2.7 Switch Behavior . . . . . . . .
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5.8 Proof: Fairness Algorithm Impro
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8.15 Factors A ecting Bu ering Requ
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Bibliography . . . . . . . . . . .
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8.12 Maximum Queues for Satellite N
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5.1 Transmitted cell rate (instanta
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6.13 Results foratwo sources con gu
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7.11 E ect of UILI on Medium Bursts
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C.3 Flow Chart of Bi-Directional Co
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header information which limits the
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switches since a standard does not
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congestion control deals with the c
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hand side of the equation is the su
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analyses which are used to validate
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CHAPTER 2 THE ABR TRAFFIC MANAGEMEN
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time (RTT). As we explain later, AB
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feedback from nearby switches to re
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Note that in-rate and out-of-rate d
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Data cells also have an Explicit Fo
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opportunity the source may nd that
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Figure 2.7: Scheduling of forward R
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as the timeout value) which reduces
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It has been incorrectly believed th
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NI CI Action 0 0 ACR Min(ER, ACR +
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Source Rule 13: Sources can optiona
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Switch Rule 1: This rule speci es t
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Observe that the ABR tra c manageme
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complex method like per-VC queuing
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graphs have a steady state with con
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Figure 3.2: Operating point between
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The following example illustrates t
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mention this concept of fairness fo
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control problem was also simpler. S
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of such an occurrence is expected t
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y giving only one feedback per meas
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CHAPTER 4 SURVEY OF ATM SWITCH CONG
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The adaptive FCVC algorithm [63] co
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np. Thus, long path VCs have fewer
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networks like ATM can have complete
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scheme followed by a discussion of
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exibility of decoupling the enforce
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4.6.1 Key Techniques In EPRCA, the
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If the mean ACR is not a good estim
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is the ratio of the input rate to t
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which shares the link equally as al
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proportional to the the unused ABR
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The key technique in the scheme is
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the bandwidth allocations to satis
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4.10 DMRCA scheme The Dynamic Max R
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on its CCR. Further MAX times out i
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other words, a di erent set of para
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A combination of several ideas in a
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4.13 SP-EPRCA scheme The SP-EPRCA s
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RTD and shuts o the source (for sta
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4.14.1 Common Drawbacks Though the
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The ATM Tra c Management standard a
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5.1.1 Control-Cell Format The contr
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The last two elds are used in the b
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Figure 5.3: Flow chart for updating
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LAF in cell Max(LAF in cell, z) The
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the time of departure (instant mark
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the steady state. The system operat
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5.2.3 Use Measured Rather Than Decl
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said about the maximum queue length
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The key problem with some unipolar
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Figure 5.6: Space time diagram show
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As noted, these heuristics do not g
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Transmitted Cell Rate ABR Queue Len
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4. The RM cell contains a timestamp
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1. The source o ered average cell r
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Transmitted Cell Rate Link Utilizat
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Figure 5.17: The parking lot fairne
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Figure 5.19: Network con guration w
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5.8 Proof: Fairness Algorithm Impro
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Region 2: y s and x s and U(1 + ) x
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eing divided into eight non-overlap
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Proof for Region 2 Triangular regio
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have: and y 0 = y(1 ; ) z x + y 0 =
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The OSU scheme is, therefore, incom
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workloads, where input load and cap
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(a) Regions used to prove Claim C1
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6.1 The Basic ERICA Algorithm The s
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A ow chart of the basic algorithm i
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efore competing sources can receive
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that the latest CCR information is
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the CCR value may not be an accurat
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(Target Utilization) (Link Bandwidt
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ABR Capacity Input Rate Overload Fa
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of arithmetic averaging used above.
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level of control. These parameters
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6.14 ERICA+: Queue Length as a Seco
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6.16 ERICA+: Maintain a \Pocket" of
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hence, introduces a new parameter,
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Figure 6.4: Linear functions for ER
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and Figure 6.6: The queue control f
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small averaging intervals. If the a
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The maximum value of T 0 also depen
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6.22 Performance Evaluation of the
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espectively. The target delay T 0 i
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6.22.4 Fairness Figure 6.9: Parking
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st link, VC 15 is limited to a thro
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From the gures, it is clear that ER
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counts the bursty source as active
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6.23 Summary of the ERICA and ERICA
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(a) Transmitted Cell Rate (c) Link
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(a) Transmitted Cell Rate (basic ER
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RM cells. In this chapter, we devot
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low. This tradeo was discovered and
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in the speci cation. b) ACR shall n
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7.1.6 December 1995 Proposals There
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Figure 7.2: Multiplicative vsAdditi
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is never triggered. However, the PR
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simulation results of bursty source
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1. The time-based proposal also ind
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The switch maintains a local alloca
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PNI = f0, 1g : f1 ) No rule 5b, 0 )
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after reaching the goal. The time-b
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Figure 7.8: Closed-Loop Bursty Tra
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The algorithm measures the load and
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Medium Bursts Medium bursts are exp
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count-based technique may be insu c
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Figure 7.13: An event trace illustr
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CHAPTER 8 SUPPORTING INTERNET APPLI
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u ering which does not depend upon
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4 make it to the destination are ar
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Figure 8.3: At the ATM layer, the T
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issues and e ect of bursty applicat
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from the loss and they trigger the
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8.8 Performance Metrics We measure
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the performance is fair. Also, the
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Figure 8.7(b) shows the rates (ACRs
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Window Size in bytes vfive-tcp/opti
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The e ect of large bu ers on CLR is
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8.13 Summary of TCP/IP performance
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Feedback delay: Twice the delay fro
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on a link, two cells are expected a
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state only after the switch algorit
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queue length is less susceptible to
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to equalize rates for fairness, and
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QB = Link bandwidth (RT T ; T ) and
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u ered at the end-system, and not i
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Page 339 and 340: 8.17 E ect of Long-Range Dependent
Page 341 and 342: terminology) are called \Presentati
Page 343 and 344: The key point is that the MPEG-2 ra
Page 345 and 346: the MPEG-2 Transport Stream, and st
Page 347 and 348: 8.17.4 Observations on the Long-Ran
Page 349 and 350: For the video sources, we choose me
Page 351 and 352: Video Sources ABR Metrics # Mean St
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Page 359 and 360: On the other hand, if the applicati
Page 361 and 362: of managing bu ers, queueing, sched
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Page 365 and 366: call such a switch a \VS/VD switch"
Page 367 and 368: Figure 9.2: Per-class queues in a n
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Page 371: 9.2 The ERICA Switch Scheme: Renota
Page 375 and 376: Figure 9.9: Two methods to measure
Page 377 and 378: 9.4 VS/VD Switch Design Options 9.4
Page 379 and 380: # VC Rate VC Input Rate Input Rate
Page 381 and 382: 8 uses source rate measurement, we
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Page 391 and 392: CHAPTER 10 IMPLEMENTATION ISSUES At
Page 393 and 394: With an enhanced UBR service, appli
Page 395 and 396: 2. Some switch schemes have a proce
Page 397 and 398: 4. Large legacy switches have a pro
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Page 401 and 402: CHAPTER 11 SUMMARY AND FUTURE WORK
Page 403 and 404: good transient performance. Since r
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Page 407 and 408: APPENDIX A SOURCE, DESTINATION AND
Page 409 and 410: 7. After following behaviors #5 and
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Page 413 and 414: d) VS/VD Control: The switch may se
Page 415 and 416: 5. Setting of other parameters at V
Page 417 and 418: 4. The averaging interval timer exp
Page 419 and 420: 1. Initialization: Target Cell Rate
Page 421 and 422: THEN IF (OCR In Cell Fair Share Rat
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APPENDIX C ERICA SWITCH ALGORITHM:
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Number Active VCs In Last Interval
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IF (NOT(Averaging VCs Option)) THEN
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IF (Load Factor = In nity) THEN Loa
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; (Contribution[VC] = Decay Factor)
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Name Explanation Flow Chart (FC) or
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Figure C.2: Flow Chart for Achievin
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Figure C.4: Flow Chart of averaging
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Figure C.6: Flow chart of averaging
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C.3 Pseudocode for VS/VD Design Opt
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(* | Bottleneck rate of next loop |
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Follow SESRules 1-4 (see appendix A
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CRM - Missing RM-cell Count DIR bit
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TUB -Target Utilization Band Trm -
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[12] J. Bennett and G. Tom Des Jard
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[38] M. Grossglauser, S.Keshav, and
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[64] H. T. Kung. Flow Controlled Vi
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