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

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number of cells in the rst RTT depends upon the number of sources starting up together (one MSS for each source). Henceforth, the number of cells only double irrespective of the number of sources. Hence, the number of RTTs required to ll the pipe depends upon the number of sources as follows: After KRTTs, window W =2 K;1 MSS Note that MSS = 512 bytes + Overhead =12cells Or, E ective rate = MSS 2 K;1 N=RTT Here, N =number of sources The pipe is lled when the e ective input rate rst exceeds capacity (or overload becomes greater than 1, for ERICA) MSS 2 K;1 N=RTT L Here, L is the link rate in cells per second. or Link Bandwidth RT T K ; 1 = log2 ( ) (MSS N) This shows that the number of RTTs decreases as the log of N. Note that once the link (or path/pipe) becomes fully loaded, the TCP windows increase linearly and not exponentially (see section 8.3 earlier in this chapter). However, the sources may still not be rate-limited (the ACRs are still large, though the bottleneck load is greater than unity). The sources reach rate-limited steady 283
state only after the switch algorithm brings the bottleneck load down to unity again by reallocating the rates. 3. Switch algorithm issues: We have claimed that the switch algorithm cannot, in general, give correct feedback when the network load is bursty (i.e., has active and idle periods). Some of problems observed by common switch algorithms are discussed below: Figure 8.11: Out-of-phase E ect (TCP over ABR) a) Out-of-phase e ect: No load or sources are seen in the forward direction while sources and RM cells are seen in the reverse direction ( gure 8.11). Figure 8.12: Clustering E ect (TCP over ABR) b) Clustering e ect: The cells from TCP connections typically come in clus- ters [82] ( gure 8.12). Hence, the activityofmultiple connections is di cult to sense over small averaging intervals, though the corresponding load may be high. 284
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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
Page 259 and 260: Figure 7.2: Multiplicative vsAdditi
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Page 263 and 264: simulation results of bursty source
Page 265 and 266: 1. The time-based proposal also ind
Page 267 and 268: The switch maintains a local alloca
Page 269 and 270: PNI = f0, 1g : f1 ) No rule 5b, 0 )
Page 271 and 272: after reaching the goal. The time-b
Page 273 and 274: Figure 7.8: Closed-Loop Bursty Tra
Page 275 and 276: The algorithm measures the load and
Page 277 and 278: Medium Bursts Medium bursts are exp
Page 279 and 280: count-based technique may be insu c
Page 281 and 282: Figure 7.13: An event trace illustr
Page 283 and 284: CHAPTER 8 SUPPORTING INTERNET APPLI
Page 285 and 286: u ering which does not depend upon
Page 287 and 288: 4 make it to the destination are ar
Page 289 and 290: Figure 8.3: At the ATM layer, the T
Page 291 and 292: issues and e ect of bursty applicat
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Page 295 and 296: 8.8 Performance Metrics We measure
Page 297 and 298: the performance is fair. Also, the
Page 299 and 300: Figure 8.7(b) shows the rates (ACRs
Page 301 and 302: Window Size in bytes vfive-tcp/opti
Page 303 and 304: The e ect of large bu ers on CLR is
Page 305 and 306: 8.13 Summary of TCP/IP performance
Page 307 and 308: Feedback delay: Twice the delay fro
Page 309: on a link, two cells are expected a
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Page 315 and 316: to equalize rates for fairness, and
Page 317 and 318: QB = Link bandwidth (RT T ; T ) and
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Page 321 and 322: Part b): When ABR load goes away, t
Page 323 and 324: All our simulations presented use t
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Page 331 and 332: problems. During the ON time, the V
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Page 337 and 338: minimum fairshare is low. This may
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
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
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of managing bu ers, queueing, sched
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hence control the total load on the
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call such a switch a \VS/VD switch"
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Figure 9.2: Per-class queues in a n
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which arises is where the rate calc
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9.2 The ERICA Switch Scheme: Renota
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The unknowns in the above equations
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Figure 9.9: Two methods to measure
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9.4 VS/VD Switch Design Options 9.4
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# VC Rate VC Input Rate Input Rate
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8 uses source rate measurement, we
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The allocated rate update and the e
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sources in chapter 6. We expect the
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con guration mentioned in the table
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can be very di erent for di erent V
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CHAPTER 10 IMPLEMENTATION ISSUES At
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With an enhanced UBR service, appli
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2. Some switch schemes have a proce
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4. Large legacy switches have a pro
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section 9. Further, WAN switches wo
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CHAPTER 11 SUMMARY AND FUTURE WORK
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good transient performance. Since r
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variant background tra c conditions
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APPENDIX A SOURCE, DESTINATION AND
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7. After following behaviors #5 and
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set the QL and SN elds to zero, pre
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d) VS/VD Control: The switch may se
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5. Setting of other parameters at V
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4. The averaging interval timer exp
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1. Initialization: Target Cell Rate
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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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