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

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3. Typically, the number of end systems is one order of magnitude greater than the number of switches. This has a multiplier e ect on the cost of an ATM network supporting ABR. The service can be made attractive only if: a) cheap ABR end-system implementations are available� b) there are mechanisms which carry the beni ts of ABR (cell loss control, thoughput, controlled delay, fairness) to the applications (an application would not choose ABR if its performance degrades due to cell loss at the ABR end-system� c) an application programming interface (API) is available for end-to-end ATM implementations which maps applications to ABR� d) a larger class of applications (like variable quality voice, audio, video) can be scalably supported using the ABR service (and allow higher/costlier classes of service for applications willing to pay the price for the higher quality of service). 373
CHAPTER 11 SUMMARY AND FUTURE WORK 11.1 Summary of Contributions This dissertation has examined the design of several tra c management mechanisms and methodologies for the ABR service in ATM networks. The ideas presented in this dissertation have signi cantly impacted the shape of the ATM Tra c Man- agement 4.0 standard. This section summarizes the contributions of this work. In Chapter 1 we gave a speci cation of the control problem in ABR tra c management. We presented an open-loop equation in this chapter and presented the requirements for the closed loop solution in Chapter 3. The goals we seek to address include: e ciency (high throughput and low delay), fairness, steady state and transient performance, bu er requirements, robustness, implementation complexity and scalability. Chapter 2 gives a tutorial introduction to the source, destination and switch rules as de ned by the ATM Tra c Management 4.0 standard. A large body of related work (ABR switch schemes) are surveyed in Chapter 4. Chapters 5 and 6 describe the OSU, ERICA and ERICA+ schemes and related performance analyses. 374
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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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Part b): When ABR load goes away, t
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All our simulations presented use t
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Averaging RTT(ms) Feedback Max Q Th
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a modi ed version of the ERICA algo
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ABR is better than UBR in these (en
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problems. During the ON time, the V
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hand, the frequency of the VBR is h
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like ERICA+ which uses the queueing
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minimum fairshare is low. This may
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8.17 E ect of Long-Range Dependent
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terminology) are called \Presentati
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The key point is that the MPEG-2 ra
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the MPEG-2 Transport Stream, and st
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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
Page 353 and 354: However, with modi cations to ERICA
Page 355 and 356: Video Sources ABR Metrics # Avg Src
Page 357 and 358: Video Sources ABR Metrics # Avg Src
Page 359 and 360: On the other hand, if the applicati
Page 361 and 362: of managing bu ers, queueing, sched
Page 363 and 364: hence control the total load on the
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
Page 369 and 370: which arises is where the rate calc
Page 371 and 372: 9.2 The ERICA Switch Scheme: Renota
Page 373 and 374: The unknowns in the above equations
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 385 and 386: sources in chapter 6. We expect the
Page 387 and 388: con guration mentioned in the table
Page 389 and 390: can be very di erent for di erent V
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
Page 399: section 9. Further, WAN switches wo
Page 403 and 404: good transient performance. Since r
Page 405 and 406: variant background tra c conditions
Page 407 and 408: APPENDIX A SOURCE, DESTINATION AND
Page 409 and 410: 7. After following behaviors #5 and
Page 411 and 412: set the QL and SN elds to zero, pre
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
Page 423 and 424: APPENDIX C ERICA SWITCH ALGORITHM:
Page 425 and 426: Number Active VCs In Last Interval
Page 427 and 428: IF (NOT(Averaging VCs Option)) THEN
Page 429 and 430: IF (Load Factor = In nity) THEN Loa
Page 431 and 432: ; (Contribution[VC] = Decay Factor)
Page 433 and 434: Name Explanation Flow Chart (FC) or
Page 435 and 436: Figure C.2: Flow Chart for Achievin
Page 437 and 438: Figure C.4: Flow Chart of averaging
Page 439 and 440: Figure C.6: Flow chart of averaging
Page 441 and 442: C.3 Pseudocode for VS/VD Design Opt
Page 443 and 444: (* | Bottleneck rate of next loop |
Page 445 and 446: Follow SESRules 1-4 (see appendix A
Page 447 and 448: CRM - Missing RM-cell Count DIR bit
Page 449 and 450: 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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