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

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Label Expansion Default Value PCR Peak Cell Rate - MCR Minimum Cell Rate 0 ACR Allowed Cell Rate - ICR Initial Cell Rate PCR TCR Tagged Cell Rate 10 cells/s Nrm Number of cells between FRM cells 32 Mrm Controls bandwidth allocation 2 between FRM, BRM and data cells Trm Upper Bound on Inter-FRM Time 100 ms RIF Rate Increase Factor 1/16 RDF Rate Decrease Factor 1/16 ADTF ACR Decrease Time Factor 0.5 ms TBE Transient Bu er Exposure 16,777,215 CRM Missing RM-cell Count d TBE/Nrm e CDF Cuto Decrease Factor 1/16 FRTT Fixed Round-Trip Time - Table 2.1: List of ABR Parameters exceed the ACR of the source. Such RM cells are called \in-rate" RM cells. Under exceptional circumstances, switches, destinations, or even sources can generate extra RM cells. These \out-of-rate" RM cells are not counted in the ACR of the source and are distinguished by having their cell loss priority (CLP) bit set, which means that the network will carry them only if there is plenty of bandwidth and can discard them if congested. The out-of-rate RM cells generated by the source and switch are limited to 10 RM cells per second per VC. One use of out-of-rate RM cells is for BECN from the switches. Another use is for a source, whose ACR has been set to zero by the network, to periodically sense the state of the network. Out-of-rate RM cells are also used by destinations of VCs whose reverse direction ACR is either zero or not su cient to return all RM cells received in the forward direction. 17
Note that in-rate and out-of-rate distinction applies only to RM cells. All data cells in ABR should have CLP set to 0 and must always be within the rate allowed by the network. 2.3 Forward and Backward RM cells Resource Management cells traveling from the source to the destination are called \forward RM" (FRM) cells. The destination turns around these RM cells and sends them back to the source on the same VC. Such RM cells traveling from the destination to the source are called Backward RM (BRM) cells. Forward and backward RM cells are illustrated in Figure 2.4. Note that when there is bi-directional tra c, there are FRMs and BRMs in both directions on the Virtual Channel (VC). A bit in the RM cell payload indicates whether it is an FRM or BRM. This direction bit (DIR) is changed from 0 to 1 by the destination. 2.4 RM Cell Format The complete format of the RM cells is shown in gure 2.5. Every RM cell has the regular ATM header of ve bytes. The payload type indicator (PTI) eld is set to 110 (binary) to indicate that the cell is an RM cell. The protocol id eld, which isone byte long, is set to one for ABR connections. The direction (DIR) bit distinguishes forward and backward RM cells. The backward noti cation (BN) bit is set only in switch generated BECN cells. The congestion indication (CI) bit is used by relative rate marking switches. It may also be used by explicit rate switches under extreme congestion as discussed later. The no increase (NI) bit is another bit available to explicit rate switches to indicate moderate congestion. The request/acknowledge, 18
Page 1 and 2: Tra c Management for the Available
Page 3 and 4: ABSTRACT With the merger of telecom
Page 5 and 6: Tra c Management for the Available
Page 7 and 8: To my family iv
Page 9 and 10: VITA April 30, 1971 :::::::::::::::
Page 11 and 12: 2.7 Switch Behavior . . . . . . . .
Page 13 and 14: 5.8 Proof: Fairness Algorithm Impro
Page 15 and 16: 8.15 Factors A ecting Bu ering Requ
Page 17 and 18: Bibliography . . . . . . . . . . .
Page 19 and 20: 8.12 Maximum Queues for Satellite N
Page 21 and 22: 5.1 Transmitted cell rate (instanta
Page 23 and 24: 6.13 Results foratwo sources con gu
Page 25 and 26: 7.11 E ect of UILI on Medium Bursts
Page 27 and 28: C.3 Flow Chart of Bi-Directional Co
Page 29 and 30: header information which limits the
Page 31 and 32: switches since a standard does not
Page 33 and 34: congestion control deals with the c
Page 35 and 36: hand side of the equation is the su
Page 37 and 38: analyses which are used to validate
Page 39 and 40: CHAPTER 2 THE ABR TRAFFIC MANAGEMEN
Page 41 and 42: time (RTT). As we explain later, AB
Page 43: feedback from nearby switches to re
Page 47 and 48: Data cells also have an Explicit Fo
Page 49 and 50: opportunity the source may nd that
Page 51 and 52: Figure 2.7: Scheduling of forward R
Page 53 and 54: as the timeout value) which reduces
Page 55 and 56: It has been incorrectly believed th
Page 57 and 58: NI CI Action 0 0 ACR Min(ER, ACR +
Page 59 and 60: Source Rule 13: Sources can optiona
Page 61 and 62: Switch Rule 1: This rule speci es t
Page 63 and 64: Observe that the ABR tra c manageme
Page 65 and 66: complex method like per-VC queuing
Page 67 and 68: graphs have a steady state with con
Page 69 and 70: Figure 3.2: Operating point between
Page 71 and 72: The following example illustrates t
Page 73 and 74: mention this concept of fairness fo
Page 75 and 76: control problem was also simpler. S
Page 77 and 78: of such an occurrence is expected t
Page 79 and 80: y giving only one feedback per meas
Page 81 and 82: CHAPTER 4 SURVEY OF ATM SWITCH CONG
Page 83 and 84: The adaptive FCVC algorithm [63] co
Page 85 and 86: np. Thus, long path VCs have fewer
Page 87 and 88: networks like ATM can have complete
Page 89 and 90: scheme followed by a discussion of
Page 91 and 92: exibility of decoupling the enforce
Page 93 and 94: 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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Page 243 and 244:
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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
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For the video sources, we choose me
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Video Sources ABR Metrics # Mean St
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However, with modi cations to ERICA
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Video Sources ABR Metrics # Avg Src
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Video Sources ABR Metrics # Avg Src
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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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