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

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it is advantageous to \reschedule" the next cell, so that the source can take advantage of the high ACR allocation immediately [54] (also see chapter 7). Source Rule 10: Sources should initialize various elds of FRM cells as follows. For virtual path connections (VPCs), the virtual circuit id (VCI) is set to 6. For virtual channel connections (VCCs), the VCI of the connection is used. In either case, the protocol type id (PTI) in the ATM cell header is set to 6 (110). The protocol id eld in the payload of the RM cell is set to 1. The direction bit should be set to 0 (forward). The backward noti cation (BN) bits should be set to 0 (source generated). Explicit rate eld is initialized to the maximum rate below PCR that the source can support. Current cell rate is set to current ACR. Minimum cell rate is set to the value negotiated at connection setup. Queue length, sequence number, and request/acknowledge elds are set in accordance with ITU-T recommendation I.371 or to zero. All reserved octets are set to 6A (hex) or 01101010 (binary). This value is speci ed in ITU-T recommendation I.610 (whose number coincidently is also 6-A in hex). Other reserved bits are set to 0. Note that the sources are allowed to set ER and NI elds to indicate their own congestion. Source Rule 11: The out-of-rate FRM cells generated by sources are limited to to a rate below the \tagged cell rate (TCR)" parameter, which hasadefault value of 10 cells per second. Source Rule 12: The EFCI bit must be reset on every data cell sent. The alternative of congested sources being allowed to set EFCI bit was considered but rejected due to insu cient analysis. 31
Source Rule 13: Sources can optionally implement additional Use-It-or-Lose- It (UILI) policies (see discussion of source Rule 5 and also later in this disser- tation). 2.6 Destination End System Rules Destination Rule 1: Destinations should monitor the EFCI bits on the in- coming cells and store the value last seen on adatacell. Destination Rule 2: Destinations are required to turn around the forward RM cells with minimal modi cations as follows: the DIR bit is set to \backward" to indicate that the cell is a backward RM-cell� the BN bit is set to zero to indicate that the cell was not generated by aswitch� the CCR and MCR elds should not be changed. If the last cell has EFCI bit set, the CI bit in the next BRM is set and the stored EFCI state is cleared. If the destination has internal congestion, it may reduce the ER or set the CI or NI bits just like a switch. Observe that this rule is used in the VS/VD con guration where the virtual destination is bottlenecked by the allowed rate in the next segment. In any case, the ER is never increased. Destination Rules 3-4: The destination should turn around the RM cells as fast as possible. However, an RM cell may be delayed if the reverse ACR is low. In such cases destination rules 3 and 4 specify that old out-of-date information can be discarded. The destinations are allowed a number of options to do this. The implications of various options of destination Rule 3 are discussed in the 32
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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
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 and 44: feedback from nearby switches to re
Page 45 and 46: Note that in-rate and out-of-rate d
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: NI CI Action 0 0 ACR Min(ER, ACR +
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
Page 95 and 96: If the mean ACR is not a good estim
Page 97 and 98: is the ratio of the input rate to t
Page 99 and 100: which shares the link equally as al
Page 101 and 102: proportional to the the unused ABR
Page 103 and 104: The key technique in the scheme is
Page 105 and 106: the bandwidth allocations to satis
Page 107 and 108: 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
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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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