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 8.13: Overview of MPEG-2 Transport Streams The MPEG-2 standard speci es two kinds of streams to carry coded video: the \Transport Stream" and the \Program Stream". The latter is used for compatibility with MPEG-1 (used for stored compressed video/audio), while the former is used to carry compressed video over networks which may not provide an end-to-end constant delay and jitter-free abstraction. A Transport Stream can carry several programs multiplexed into one stream. Each program may consist of several \elementary streams," each containing MPEG-2 compressed video, audio, and other streams like close-captioned text, etc. Figure 8.13 shows one such program stream formed by multiplexing a compressed video and a compressed audio elementary stream. Speci cally, the gure shows the uncompressed video/audio stream going through the MPEG-2 elementary encoder to form the elementary stream. Typically, the uncompressed stream consists of frames generated at constant intervals (called \frame display times") of 33 ms (NTSC for- mat) or 40 ms (PAL format). These frames (or \Group of Pictures" in MPEG-2 313
terminology) are called \Presentation Units." MPEG-2 compression produces three di erent types of frames: I, P and B frames, called \Access Units," as illustrated in Figure 8.14. Figure 8.14: The I, P and B frames of MPEG-2 I (Intra-) frames are large. They contain the base picture, autonomously coded without need of a reference to another picture. They might take about 4-5 frame display times (approximately 160 ms) to be transmitted on the network depending upon the available rate. P (Predictive-) frames are medium-sized. They are coded with respect to previous I or P frame. Transmission times for P frames is typically about 0.5-1 frame display times. B (Birectionally predicted-) frames are very small. They are coded with respect to previous and later I or P frames and achieve maximum compression ratios (200:1). Transmission times for B frames is typically about 0.2 frame display times or even less. As shown in Figure 8.13, the access units are packetized to form the \Packetized Elementary Stream (PES)". PES packets may be variable in length. The packetiza- tion process is implementation speci c. PES packets may carry timestamps (called 314
- Page 289 and 290: Figure 8.3: At the ATM layer, the T
- Page 291 and 292: issues and e ect of bursty applicat
- Page 293 and 294: from the loss and they trigger the
- 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 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: 8.17 E ect of Long-Range Dependent
- 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 and 390: can be very di erent for di erent V
term<strong>in</strong>ology) are called \Presentation Units." MPEG-2 compression produces three<br />
di erent types of frames: I, P and B frames, called \Access Units," as illustrated <strong>in</strong><br />
Figure 8.14.<br />
Figure 8.14: The I, P and B frames of MPEG-2<br />
I (Intra-) frames are large. They conta<strong>in</strong> <strong>the</strong> base picture, autonomously coded<br />
without need of a reference to ano<strong>the</strong>r picture. They might take about 4-5 frame<br />
display times (approximately 160 ms) to be transmitted on <strong>the</strong> network depend<strong>in</strong>g<br />
upon <strong>the</strong> available rate.<br />
P (Predictive-) frames are medium-sized. They are coded with respect to previous<br />
I or P frame. Transmission times <strong>for</strong> P frames is typically about 0.5-1 frame display<br />
times.<br />
B (Birectionally predicted-) frames are very small. They are coded with respect<br />
to previous and later I or P frames and achieve maximum compression ratios (200:1).<br />
Transmission times <strong>for</strong> B frames is typically about 0.2 frame display times or even<br />
less.<br />
As shown <strong>in</strong> Figure 8.13, <strong>the</strong> access units are packetized to <strong>for</strong>m <strong>the</strong> \Packetized<br />
Elementary Stream (PES)". PES packets may be variable <strong>in</strong> length. The packetiza-<br />
tion process is implementation speci c. PES packets may carry timestamps (called<br />
314
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