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 ...
Figure 8.18: The \N Source + VBR" Con guration with satellite links and long feedback delays e ciency for three combinations of the mean and standard deviation. Table 8.14 is for TCP MSS = 512 bytes, while Table 8.15 is for TCP MSS = 9140 bytes. Observe that the queue lengths are quite large, while the total TCP throughput and e ciency are smaller (by 10-15%) compared to the values in Tables 8.12 and 8.13 (1000 km feedback delay cases) respectively. The total queue is still a small multiple of the feedback delay or RTT (a feedback delay of 550 ms corresponds to 201850 cells). This indicates that satellite switches need to provide at least so much bu ering to avoid loss on these high delay paths. A point to consider is that these large queues should not be seen in downstream workgroup or WAN switches, because they will not provide so much bu ering. Satellite switches can isolate downstream switches from such large queues by implementing the VSVD option as described in chapter 10. 329
Video Sources ABR Metrics # Avg Src STD Max Total VBR ABR E cy rate (Mbps) Switch Q TCP T'put T'put (% Max (Mbps) (cells) T'put T'put) 1. 5 5 255034 (1.3 f/b delay) 63.4 47.33 102.43 79.35% 2. 7.5 7 189276 (0.9 f/b delay) 59.8 57.23 92.53 82.86% 3. 10 5 148107 (0.7 f/b delay) 53.4 67.55 82.21 83.33% Table 8.14: Maximum Queues for Satellite Networks with Long Feedback Delay: MSS=512 bytes Video Sources ABR Metrics # Avg Src STD Max Total VBR ABR E cy rate (Mbps) Switch Q TCP T'put T'put (% Max (Mbps) (cells) T'put T'put) 1. 5 5 176007 (0.9 f/b delay) 71.92 47.33 102.43 80.70% 2. 7.5 7 252043 (1.3 f/b delay) 67.86 57.23 92.53 84.29% 3. 10 5 148646 (0.7 f/b delay) 59.33 67.55 82.21 82.95% Table 8.15: Maximum Queues for Satellite Networks with Long Feedback Delay: MSS=9140 bytes 8.18.5 Summary of the e ect of long-range dependent VBR In this section, we have described how to model several multiplexed MPEG-2 video sources over VBR. Compressed video sources exhibit long-range dependence in the tra c patterns they generate. The e ect of this long-range dependence is to introduce high variation in the ABR capacity. However a good switch scheme like ERICA+ is su cient to handle this variation in ABR capacity. This results in 330
- Page 305 and 306: 8.13 Summary of TCP/IP performance
- Page 307 and 308: Feedback delay: Twice the delay fro
- Page 309 and 310: on a link, two cells are expected a
- Page 311 and 312: state only after the switch algorit
- Page 313 and 314: queue length is less susceptible to
- Page 315 and 316: to equalize rates for fairness, and
- Page 317 and 318: QB = Link bandwidth (RT T ; T ) and
- Page 319 and 320: u ered at the end-system, and not i
- Page 321 and 322: Part b): When ABR load goes away, t
- Page 323 and 324: All our simulations presented use t
- Page 325 and 326: Averaging RTT(ms) Feedback Max Q Th
- Page 327 and 328: a modi ed version of the ERICA algo
- Page 329 and 330: ABR is better than UBR in these (en
- Page 331 and 332: problems. During the ON time, the V
- Page 333 and 334: hand, the frequency of the VBR is h
- Page 335 and 336: like ERICA+ which uses the queueing
- 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: 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 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 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
Video Sources <strong>ABR</strong> Metrics<br />
# Avg Src STD Max Total VBR <strong>ABR</strong> E cy<br />
rate (Mbps) Switch Q TCP T'put T'put (% Max<br />
(Mbps) (cells) T'put T'put)<br />
1. 5 5 255034 (1.3 f/b delay) 63.4 47.33 102.43 79.35%<br />
2. 7.5 7 189276 (0.9 f/b delay) 59.8 57.23 92.53 82.86%<br />
3. 10 5 148107 (0.7 f/b delay) 53.4 67.55 82.21 83.33%<br />
Table 8.14: Maximum Queues <strong>for</strong> Satellite Networks with Long Feedback Delay:<br />
MSS=512 bytes<br />
Video Sources <strong>ABR</strong> Metrics<br />
# Avg Src STD Max Total VBR <strong>ABR</strong> E cy<br />
rate (Mbps) Switch Q TCP T'put T'put (% Max<br />
(Mbps) (cells) T'put T'put)<br />
1. 5 5 176007 (0.9 f/b delay) 71.92 47.33 102.43 80.70%<br />
2. 7.5 7 252043 (1.3 f/b delay) 67.86 57.23 92.53 84.29%<br />
3. 10 5 148646 (0.7 f/b delay) 59.33 67.55 82.21 82.95%<br />
Table 8.15: Maximum Queues <strong>for</strong> Satellite Networks with Long Feedback Delay:<br />
MSS=9140 bytes<br />
8.18.5 Summary of <strong>the</strong> e ect of long-range dependent VBR<br />
In this section, we have described how to model several multiplexed MPEG-2<br />
video sources over VBR. Compressed video sources exhibit long-range dependence<br />
<strong>in</strong> <strong>the</strong> tra c patterns <strong>the</strong>y generate. The e ect of this long-range dependence is<br />
to <strong>in</strong>troduce high variation <strong>in</strong> <strong>the</strong> <strong>ABR</strong> capacity. However a good switch scheme<br />
like ERICA+ is su cient to handle this variation <strong>in</strong> <strong>ABR</strong> capacity. This results <strong>in</strong><br />
330
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