Traffic Management for the Available Bit Rate (ABR) Service in ...
Traffic Management for the Available Bit Rate (ABR) Service in ... Traffic Management for the Available Bit Rate (ABR) Service in ...
E ect of di erent switch algorithms in di erent control loops, and di erent control loop lengths. E ect of non-ABR clouds and standardization issues involved. 363
CHAPTER 10 IMPLEMENTATION ISSUES At the time of this writing, the Tra c Management 4.0 [32] which includes the ABR speci cation has been available for a year and a half. However, the rst products implementing ABR are just entering the market. The reason for this long delay isin part because of the complexity of ABR implementation. We explore some of the issues in this chapter and study the implementation and performance of one of the ABR options, namely, Virtual Source/Virtual Destination, in depth. We will also mention some of the e orts currently underway to make the ABR service more attractive. 10.1 ATM Service Categories Revisited ATM provides multiple classes of service to realize the goal of an integrated ser- vices network. The CBR and VBR services were designed primarily for voice and isochronous tra c like video. These services required the network to reserve re- sources. As a result, the method used to reserve resources limited the total number of CBR or VBR connections that could be setup. Data tra c did not require such resource reservations, and it could potentially use the bandwidth \left over" by CBR and VBR. Therefore, the ATM Forum decided to develop a \best-e ort" service cate- gory for data tra c which uses the \left over" capacity onaphysical channel. Initial 364
- 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
- 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
- Page 383 and 384: The allocated rate update and the e
- Page 385 and 386: sources in chapter 6. We expect the
- Page 387 and 388: con guration mentioned in the table
- Page 389: can be very di erent for di erent V
- 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 and 400: section 9. Further, WAN switches wo
- Page 401 and 402: CHAPTER 11 SUMMARY AND FUTURE WORK
- 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
CHAPTER 10<br />
IMPLEMENTATION ISSUES<br />
At <strong>the</strong> time of this writ<strong>in</strong>g, <strong>the</strong> Tra c <strong>Management</strong> 4.0 [32] which <strong>in</strong>cludes <strong>the</strong><br />
<strong>ABR</strong> speci cation has been available <strong>for</strong> a year and a half. However, <strong>the</strong> rst products<br />
implement<strong>in</strong>g <strong>ABR</strong> are just enter<strong>in</strong>g <strong>the</strong> market. The reason <strong>for</strong> this long delay is<strong>in</strong><br />
part because of <strong>the</strong> complexity of <strong>ABR</strong> implementation. We explore some of <strong>the</strong> issues<br />
<strong>in</strong> this chapter and study <strong>the</strong> implementation and per<strong>for</strong>mance of one of <strong>the</strong> <strong>ABR</strong><br />
options, namely, Virtual Source/Virtual Dest<strong>in</strong>ation, <strong>in</strong> depth. We will also mention<br />
some of <strong>the</strong> e orts currently underway to make <strong>the</strong> <strong>ABR</strong> service more attractive.<br />
10.1 ATM <strong>Service</strong> Categories Revisited<br />
ATM provides multiple classes of service to realize <strong>the</strong> goal of an <strong>in</strong>tegrated ser-<br />
vices network. The CBR and VBR services were designed primarily <strong>for</strong> voice and<br />
isochronous tra c like video. These services required <strong>the</strong> network to reserve re-<br />
sources. As a result, <strong>the</strong> method used to reserve resources limited <strong>the</strong> total number<br />
of CBR or VBR connections that could be setup. Data tra c did not require such<br />
resource reservations, and it could potentially use <strong>the</strong> bandwidth \left over" by CBR<br />
and VBR. There<strong>for</strong>e, <strong>the</strong> ATM Forum decided to develop a \best-e ort" service cate-<br />
gory <strong>for</strong> data tra c which uses <strong>the</strong> \left over" capacity onaphysical channel. Initial<br />
364
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