idnits 2.17.1 draft-ietf-xrblock-rtcp-xr-burst-gap-loss-09.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (March 21, 2013) is 4026 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC6709' is defined on line 495, but no explicit reference was found in the text ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) == Outdated reference: A later version (-15) exists of draft-ietf-xrblock-rtcp-xr-discard-11 == Outdated reference: A later version (-11) exists of draft-ietf-xrblock-rtcp-xr-summary-stat-05 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Audio/Video Transport Working Group A. Clark 3 Internet-Draft Telchemy 4 Intended status: Standards Track S. Zhang, Ed. 5 Expires: September 22, 2013 J. Zhao 6 STTRI 7 Q. Wu 8 Huawei 9 March 21, 2013 11 RTP Control Protocol (RTCP) Extended Report (XR) Block for Burst/Gap 12 Loss metric Reporting 13 draft-ietf-xrblock-rtcp-xr-burst-gap-loss-09.txt 15 Abstract 17 This document defines an RTP Control Protocol (RTCP) Extended Report 18 (XR) Block that allows the reporting of Burst and Gap Loss metrics 19 for use in a range of RTP applications. 21 Status of this Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on September 22, 2013. 38 Copyright Notice 40 Copyright (c) 2013 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 1.1. Burst and Gap Loss Report Block . . . . . . . . . . . . . 3 57 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 58 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 59 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 60 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 61 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5 62 3. Burst/Gap Loss Block . . . . . . . . . . . . . . . . . . . . . 6 63 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 64 3.2. Definition of Fields in Burst/Gap Loss Report Block . . . 6 65 3.3. Derived metrics based on reported metrics . . . . . . . . 9 66 4. Considerations for Voice-over-IP applications . . . . . . . . 11 67 5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 12 68 5.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 12 69 5.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 12 70 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 71 6.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 13 72 6.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 13 73 6.3. Contact information for registrations . . . . . . . . . . 13 74 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 75 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15 76 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 77 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 78 10.1. Normative References . . . . . . . . . . . . . . . . . . . 17 79 10.2. Informative References . . . . . . . . . . . . . . . . . . 17 80 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 18 81 A.1. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-09 . . . . . . . 18 82 A.2. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-08 . . . . . . . 18 83 A.3. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-07 . . . . . . . 18 84 A.4. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-06 . . . . . . . 18 85 A.5. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-04 . . . . . . . 18 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 88 1. Introduction 90 1.1. Burst and Gap Loss Report Block 92 This draft defines a new block type to augment those defined in 93 [RFC3611] for use in a range of RTP applications. The new block type 94 supports the reporting of the proportion of packets lost by the 95 network. The losses during loss bursts are reported, together with 96 the number of bursts and additional data allowing the calculation of 97 statistical parameters (mean and variance) of the distribution of 98 burst lengths. Some uses of these metrics depend on the availability 99 of the metric "cumulative number of packets lost" from RTCP 100 [RFC3550]. 102 This block provides information on transient IP problems. Burst/Gap 103 metrics are typically used in Cumulative reports, however they also 104 MAY be used in Interval reports. The burstiness of packet loss 105 affects user experience, may influence any sender strategies to 106 mitigate the problem, and may also have diagnostic value. 108 The metric belongs to the class of transport-related end system 109 metrics defined in [RFC6792]. 111 The definitions of Burst, Gap, Loss and Discard are consistent with 112 definitions in [RFC3611]. To accommodate the range of jitter buffer 113 algorithms and packet discard logic that may be used by implementors, 114 the method used to distinguish between bursts and gaps may be an 115 equivalent method to that defined in [RFC3611]. The method used 116 should produce the same result as that defined in [RFC3611] for 117 conditions of burst packet loss, but may produce different results 118 for conditions of time varying jitter. 120 1.2. RTCP and RTCP XR Reports 122 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 123 defined an extensible structure for reporting using an RTCP Extended 124 Report (XR). This document defines a new Extended Report block for 125 use with [RFC3550] and [RFC3611]. 127 1.3. Performance Metrics Framework 129 The Performance Metrics Framework [RFC6390] provides guidance on the 130 definition and specification of performance metrics. The RTP 131 Monitoring Architectures [RFC6792] provides guideline for reporting 132 block format using RTCP XR. The Metrics Block described in this 133 document are in accordance with the guidelines in [RFC6390] and 134 [RFC6792]. 136 1.4. Applicability 138 These metrics are applicable to a range of RTP applications which 139 contain jitter buffers and don't use stream repair means,e.g., 140 Forward Error Correction (FEC) [RFC5109] and/or retransmission 141 [RFC4588]. 143 2. Terminology 145 2.1. Standards Language 147 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 148 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 149 document are to be interpreted as described in RFC 2119 [RFC2119]. 151 In addition, the following terms are defined: 153 Received, Lost and Discarded 155 A packet shall be regarded as lost if it fails to arrive within an 156 implementation-specific time window. A packet that arrives within 157 this time window but is too early or late to be played out or 158 thrown away before playout due to packet duplication or redundancy 159 shall be regarded as discarded. A packet shall be classified as 160 one of received (or OK), discarded or lost. The metric 161 "cumulative number of packets lost" defined in [RFC3550] reports a 162 count of packets lost from the media stream (single SSRC within 163 single RTP session). Similarly the metric "number of packets 164 discarded" defined in [DISCARD] reports a count of packets 165 discarded from the media stream (single SSRC within single RTP 166 session) arriving at the receiver. Another metric defined in 167 [RFC5725] is available to report on packets which are not 168 recovered by any repair techniques which may be in use. 170 Bursts and Gaps 172 The terms Burst and Gap are used in a manner consistent with that 173 of RTCP XR [RFC3611]. RTCP XR views a RTP stream as being divided 174 into bursts, which are periods during which the loss rate is high 175 enough to cause noticeable quality degradation (generally over 5 176 percent loss rate), and gaps, which are periods during which lost 177 packets are infrequent and hence quality is generally acceptable. 179 3. Burst/Gap Loss Block 181 Metrics in this block report on Burst/Gap Loss in the stream arriving 182 at the RTP system. The measurement of these metrics are made at the 183 receiving end of the RTP stream. Instances of this Metrics Block 184 refer by Synchronization source (SSRC) to the separate auxiliary 185 Measurement Information block [RFC6776] which describes measurement 186 periods in use(see RFC6776 section 4.2). This Metrics Block relies 187 on the measurement period in the Measurement Information block 188 indicating the span of the report and SHOULD be sent in the same 189 compound RTCP packet as the measurement information block. If the 190 measurement period is not received in the same compound RTCP packet 191 as this Metrics Block, this Metrics Block MUST be discarded. 193 3.1. Report Block Structure 195 Burst/Gap Loss metrics block 197 0 1 2 3 198 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 199 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 200 | BT=NBGL | I |C| resv. | block length = 5 | 201 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 202 | SSRC of Source | 203 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 204 | Threshold | Sum of Burst Durations (ms) | 205 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 206 | Packets Lost in Bursts | Total... | 207 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 208 | ...Packets expected in bursts | Number of bursts | Sum of| 209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 210 | ...Squares of Burst Durations (ms-squared) | 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 213 Figure 1: Report Block Structure 215 3.2. Definition of Fields in Burst/Gap Loss Report Block 217 Block type (BT): 8 bits 219 A Burst/Gap Loss Report Block is identified by the constant NBGL. 221 [Note to RFC Editor: please replace NBGL with the IANA provided 222 RTCP XR block type for this block.] 224 Interval Metric flag (I): 2 bits 226 This field is used to indicate whether the Burst/Gap Loss metrics 227 are Sampled, Interval or Cumulative metrics: 229 I=10: Interval Duration - the reported value applies to the 230 most recent measurement interval duration between successive 231 metrics reports. 233 I=11: Cumulative Duration - the reported value applies to the 234 accumulation period characteristic of cumulative measurements. 236 I=01: Sampled Value - the reported value is a sampled 237 instantaneous value. 239 In this document, Burst/Gap Loss Metrics can only be measured over 240 definite intervals, and cannot be sampled. Accordingly, the value 241 I=01, indicating a sampled value, MUST NOT be used. In addition, 242 the value I=00 is reserved and also MUST NOT be used. The block 243 MUST be discarded if the value I=01 or I=00 is received. 245 Loss and Discard Combination flag (C): 1 bit 247 The 'C' flag is used to indicate whether the loss/discard report 248 is combined with the burst gap loss report in the same compound 249 RTCP packet. The value MUST be set to '1' if the loss/discard 250 report and the burst gap loss report are combined. Otherwise, the 251 value MUST be set to '0'. If the burst gap discard is not sent 252 with the burst gap loss, then the receiver MUST discard the burst 253 gap loss with 'C' flag set to 1. If the 'C' flag is set to 0, 254 then receiver MUST NOT discard the burst gap loss Metrics Block 255 when the burst gap discard is not received. 257 Reserved (resv): 5 bits 259 These bits are reserved. They MUST be set to zero by senders and 260 ignored by receivers (See RFC6709 section 4.2). 262 block length: 16 bits 264 The length of this report block in 32-bit words, minus one. For 265 the Burst/Gap Loss block, the block length is equal to 5. The 266 block MUST be discarded if the block length is set to a different 267 value. 269 SSRC of source: 32 bits 271 As defined in Section 4.1 of [RFC3611]. 273 Threshold: 8 bits 275 The Threshold is equivalent to Gmin in [RFC3611], i.e. the number 276 of successive packets that must be received prior to and following 277 a lost packet in order for this lost packet to be regarded as part 278 of a gap. Note that the threshold is calculated in accordance 279 with Gmin Calculation defined in section 4.7.2 of RFC3611. 281 Sum of Burst Durations (ms): 24 bits 283 The total duration of bursts of lost packets in the period of the 284 report (Interval or Cumulative). 286 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE MUST be 287 reported to indicate an over-range measurement. If the 288 measurement is unavailable, the value 0xFFFFFF MUST be reported. 290 Packets lost in bursts: 24 bits 292 The total number of packets lost during loss bursts. 294 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE MUST be 295 reported to indicate an over-range measurement. If the 296 measurement is unavailable, the value 0xFFFFFF MUST be reported. 298 Total packets expected in bursts: 24 bits 300 The total number of packets expected during loss bursts (that is, 301 the sum of received packets and lost packets). 303 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE MUST be 304 reported to indicate an over-range measurement. If the 305 measurement is unavailable, the value 0xFFFFFF MUST be reported. 307 Number of bursts: 16 bits 309 The number of bursts in the period of the report (Interval or 310 Cumulative). 312 If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be 313 reported to indicate an over-range measurement. If the 314 measurement is unavailable, the value 0xFFFF MUST be reported. 316 Sum of Squares of Burst Durations (ms-squared): 36 bits 318 The sum of the squares of burst durations (where individual burst 319 durations are expressed in ms) over in the period of the report 320 (Interval or Cumulative). The units for this quantity are 321 milliseconds-squared. 323 If the measured value exceeds 0xFFFFFFFFD, the value 0xFFFFFFFFE 324 MUST be reported to indicate an over-range measurement. If the 325 measurement is unavailable, the value 0xFFFFFFFFF MUST be 326 reported. 328 3.3. Derived metrics based on reported metrics 330 The metrics described here are intended to be used as described in 331 this section, in conjunction with information from the Measurement 332 Information block [RFC6776] (which MUST be present in the same RTCP 333 packet as the Burst/Gap Loss block) and also with the metric 334 "cumulative number of packets lost" provided in standard RTCP 335 [RFC3550]. 337 These metrics provide information relevant to statistical parameters, 338 including: 340 o The fraction of packets lost during bursts (i.e., Burst Loss Rate 341 in [SUMSTAT]), which can be calculated using the metric " Packets 342 Loss in Bursts " and the metric " Total Packets expected in Bursts 343 " provided in the Burst/Gap Loss metrics block. 345 o The fraction of packets lost during gaps (i.e., Gap Loss Rate in 346 [SUMSTAT]), which can be calculated using the metric " Packets 347 Loss in Bursts " and the metric " Total Packets expected in Bursts 348 " provided in the Burst/Gap Loss metrics block. 350 o burst duration mean [SUMSTAT], which can be calculated using the 351 metric " Packets Loss in Bursts " and the metric " Total Packets 352 expected in Bursts " provided in the Burst/Gap Loss metrics block. 354 o burst duration variance [SUMSTAT], which can be calculated using 355 the metric " Packets Loss in Bursts " and the metric " Total 356 Packets expected in Bursts " provided in the Burst/Gap Loss 357 metrics block. 359 The details on calculation these parameters in the metrics are 360 described in [SUMSTAT]. 362 4. Considerations for Voice-over-IP applications 364 This Metrics Block is applicable to a broad range of RTP 365 applications. Where the metric is used with a Voice-overIP (VoIP) 366 application and the stream repair means is not available, the 367 following considerations apply. 369 RTCP XR views a call as being divided into bursts, which are periods 370 during which the loss rate is high enough to cause noticeable call 371 quality degradation (generally over 5 percent loss rate), and gaps, 372 which are periods during which lost packets are infrequent and hence 373 call quality is generally acceptable. 375 If Voice Activity Detection is used the Burst and Gap Duration shall 376 be determined as if silence packets had been sent, i.e. a period of 377 silence in excess of Gmin packets MUST terminate a burst condition. 379 The recommended value for the threshold Gmin in [RFC3611] results in 380 a Burst being a period of time during which the call quality is 381 degraded to a similar extent to a typical Pulse-Code Modulation(PCM) 382 Severely Errored Second. 384 5. SDP Signaling 386 [RFC3611] defines the use of SDP (Session Description Protocol) 387 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 388 without prior signaling. 390 5.1. SDP rtcp-xr-attrib Attribute Extension 392 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 393 in [RFC3611] by providing an additional value of "xr-format" to 394 signal the use of the report block defined in this document. 396 xr-format =/ xr-bgl-block 398 xr-bgl-block = "brst-gap-loss" 400 5.2. Offer/Answer Usage 402 When SDP is used in offer-answer context, the SDP Offer/Answer usage 403 defined in [RFC3611] for unilateral "rtcp-xr" attribute parameters 404 applies. For detailed usage in Offer/Answer for unilateral 405 parameter, refer to section 5.2 of [RFC3611]. 407 6. IANA Considerations 409 New block types for RTCP XR are subject to IANA registration. For 410 general guidelines on IANA considerations for RTCP XR, refer to 411 [RFC3611]. 413 6.1. New RTCP XR Block Type value 415 This document assigns the block type value NBGL in the IANA " RTP 416 Control Protocol Extended Reports (RTCP XR) Block Type Registry " to 417 the "Burst/Gap Loss Metrics Block". 419 [Note to RFC Editor: please replace NBGL with the IANA provided RTCP 420 XR block type for this block.] 422 6.2. New RTCP XR SDP Parameter 424 This document also registers a new parameter "brst-gap-loss" in the " 425 RTP Control Protocol Extended Reports (RTCP XR) Session Description 426 Protocol (SDP) Parameters Registry". 428 6.3. Contact information for registrations 430 The contact information for the registrations is: 432 Qin Wu (sunseawq@huawei.com) 434 101 Software Avenue, Yuhua District 435 Nanjing, Jiangsu 210012 436 China 438 7. Security Considerations 440 It is believed that this proposed RTCP XR report block introduces no 441 new security considerations beyond those described in [RFC3611]. 442 This block does not provide per-packet statistics so the risk to 443 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 444 does not apply. 446 8. Contributors 448 Geoff Hunt wrote the initial draft of this document. 450 9. Acknowledgments 452 The authors gratefully acknowledge reviews and feedback provided by 453 Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, 454 Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, 455 Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, 456 Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi 457 Raviraj, Albrecht Schwarz, Tom Taylor, Hideaki Yamada, Adam Roach, 458 Dan Romascanu,Chris Lonvick and Alfred C.,Morton Jr. 460 10. References 462 10.1. Normative References 464 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 465 Requirement Levels", March 1997. 467 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 468 Applications", RFC 3550, July 2003. 470 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 471 Protocol Extended Reports (RTCP XR)", November 2003. 473 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 474 Description Protocol", July 2006. 476 [RFC5725] Begen, A., Hsu, D., and M. Lague, "Post-Repair Loss RLE 477 Report Block Type for RTP Control Protocol (RTCP) Extended 478 Reports (XRs)", RFC 5725, February 2020. 480 10.2. Informative References 482 [DISCARD] Wu, Q., "RTCP XR Report Block for Discard metric 483 Reporting", ID draft-ietf-xrblock-rtcp-xr-discard-11, 484 December 2012. 486 [RFC4588] Rey, J., Leon, D., , A., Varsa, V., and R. Hakenberg, "RTP 487 Retransmission Payload Format", RFC 4588, July 2006. 489 [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error 490 Correction", RFC 5109, December 2007. 492 [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric 493 Development", RFC 6390, July 2011. 495 [RFC6709] Carpenter, B., Aboba, B., and S. Cheshire, "Design 496 Considerations for Protocol Extensions", RFC 6709, 497 September 2012. 499 [RFC6776] Wu, Q., "Measurement Identity and information Reporting 500 using SDES item and XR Block", RFC 6776, October 2012. 502 [RFC6792] Hunt, G., "Monitoring Architectures for RTP", RFC 6792, 503 November 2012. 505 [SUMSTAT] Zorn, G., "RTCP XR for Summary Statistics Metrics 506 Reporting", ID draft-ietf-xrblock-rtcp-xr-summary-stat-05, 507 December 2012. 509 Appendix A. Change Log 511 Note to the RFC-Editor: please remove this section prior to 512 publication as an RFC. 514 A.1. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-09 516 The following are the major changes compared to previous version: 518 o IETF LC comments are addressed together with AD's comment on 519 Normative language in this version. 521 A.2. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-08 523 The following are the major changes compared to previous version: 525 o Move RFC6709 as one informative reference. 527 A.3. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-07 529 The following are the major changes compared to previous version: 531 o Editorial changes based on comments in the WGLC. 533 A.4. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-06 535 The following are the major changes compared to previous version: 537 o SDP update based on SDP Directorate Review. 539 o Add some texts to get consistent with RFC6798 and Delay draft. 541 A.5. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-04 543 The following are the major changes compared to previous version: 545 o Outdated reference update. 547 o Editorial changes based on comments that applied to PDV and Delay 548 drafts. 550 Authors' Addresses 552 Alan Clark 553 Telchemy Incorporated 554 2905 Premiere Parkway, Suite 280 555 Duluth, GA 30097 556 USA 558 Email: alan.d.clark@telchemy.com 560 Sunshine Zhang (editor) 561 Shanghai Research Institute of China Telecom Corporation Limited 562 No.1835,South Pudong Road 563 Shanghai 200122 564 China 566 Email: zhangyx@sttri.com.cn 568 Jing Zhao 569 Shanghai Research Institute of China Telecom Corporation Limited 570 No.1835,South Pudong Road 571 Shanghai 200122 572 China 574 Email: zhaojing@sttri.com.cn 576 Qin Wu 577 Huawei 578 101 Software Avenue, Yuhua District 579 Nanjing, Jiangsu 210012 580 China 582 Email: sunseawq@huawei.com