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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'RFCXXXX' is mentioned on line 564, but not defined == Unused Reference: 'RFC6390' is defined on line 504, but no explicit reference was found in the text ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group H. Asaeda 3 Internet-Draft NICT 4 Intended status: Standards Track Q. Wu 5 Expires: August 12, 2014 R. Huang 6 Huawei 7 February 8, 2014 9 RTP Control Protocol (RTCP) Extended Report (XR) Blocks for 10 Synchronization Delay and Offset Metrics Reporting 11 draft-ietf-xrblock-rtcp-xr-synchronization-08 13 Abstract 15 This document defines two RTP Control Protocol (RTCP) Extended Report 16 (XR) Blocks that allow the reporting of synchronization delay and 17 offset metrics for use in a range of RTP applications. 19 Status of this Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on August 12, 2014. 36 Copyright Notice 38 Copyright (c) 2014 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 1.1. Synchronization Delay and Offset Metrics Reporting 55 Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 57 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 58 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 4 61 3. RTP Flows Initial Synchronization Delay Report Block . . . . . 5 62 3.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 5 63 3.2. Definition of Fields in RTP Flow Initial 64 Synchronization Delay Metrics Block . . . . . . . . . . . 5 65 4. RTP Flows Synchronization Offset Metrics Block . . . . . . . . 6 66 4.1. Metric Block Structure . . . . . . . . . . . . . . . . . . 7 67 4.2. Definition of Fields in RTP Flow General 68 Synchronization Offset Metrics Block . . . . . . . . . . . 7 69 5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 9 70 5.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 9 71 5.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 10 72 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 73 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 74 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 75 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 76 9.1. Normative References . . . . . . . . . . . . . . . . . . . 11 77 9.2. Informative References . . . . . . . . . . . . . . . . . . 11 78 Appendix A. Metrics represented using RFC6390 Template . . . . . 12 79 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 13 80 B.1. draft-ietf-xrblock-rtcp-xr-syncronization-08 . . . . . . . 13 81 B.2. draft-ietf-xrblock-rtcp-xr-syncronization-07 . . . . . . . 13 82 B.3. draft-ietf-xrblock-rtcp-xr-syncronization-06 . . . . . . . 13 83 B.4. draft-ietf-xrblock-rtcp-xr-syncronization-05 . . . . . . . 13 84 B.5. draft-ietf-xrblock-rtcp-xr-syncronization-04 . . . . . . . 14 85 B.6. draft-ietf-xrblock-rtcp-xr-syncronization-03 . . . . . . . 14 86 B.7. draft-ietf-xrblock-rtcp-xr-syncronization-02 . . . . . . . 14 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 89 1. Introduction 91 1.1. Synchronization Delay and Offset Metrics Reporting Blocks 93 This document defines two new block types to augment those defined in 94 [RFC3611], for use in a range of RTP applications. 96 The first new block type supports reporting of Initial 97 Synchronization Delay to establish multimedia session. Information 98 is recorded about time difference between the start of RTP sessions 99 and the time the RTP receiver acquires all components of RTP sessions 100 in the multimedia session [RFC6051]. 102 The second new block type supports reporting of the relative 103 synchronization offset time of two arbitrary streams (e.g., between 104 audio and video streams), with the same RTCP CNAME included in RTCP 105 SDES packets [RFC3550]. 107 These metrics belong to the class of transport level metrics defined 108 in [RFC6792]. 110 1.2. RTCP and RTCP XR Reports 112 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 113 defined an extensible structure for reporting using an RTCP Extended 114 Report (XR). This document defines a new Extended Report block for 115 use with [RFC3550] and [RFC3611]. 117 1.3. Performance Metrics Framework 119 The RTP Monitoring Architectures [RFC6792] provides guideline for 120 reporting block format using RTCP XR. The new report block described 121 in this memo is in compliance with the monitoring architecture 122 specified in [RFC6792]. 124 1.4. Applicability 126 When joining each session in layered video sessions [RFC6190] or the 127 multimedia session, a receiver may not synchronize playout across the 128 multimedia session or layered video session until RTCP SR packets 129 have been received on all components of RTP sessions. The component 130 RTP session are referred to as each RTP session for each media type 131 in multimedia session or separate RTP session for each layer in the 132 layered video session. For multicast session, the initial 133 synchronization delay metric varies with the session bandwidth, the 134 number of members, and the number of senders in the session. The RTP 135 flow Initial synchronization delay block defined in this document can 136 be used to report such metric, i.e., the initial synchronization 137 delay to receive all the RTP streams belonging to the same multimedia 138 session or layered video session. In the absence of packet loss, the 139 initial synchronization delay equals to the average time taken to 140 receive the first RTCP packet in the RTP session with the longest 141 RTCP reporting interval. In the presence of packet loss, the media 142 synchronization should rely on the in-band mapping of RTP and NTP- 143 format timestamps [RFC6051] or wait until the reporting interval has 144 passed, and the next RTCP SR packet is sent. 146 Receivers of the RTP flow initial synchronization delay block could 147 use this metric to compare with targets (i.e., Service Level 148 Agreement or thresholds of the system) to help ensure the quality of 149 real-time application performance. 151 In an RTP multimedia session, there can be an arbitrary number of 152 streams carried in different RTP sessions, with the same RTCP CNAME. 153 These streams may be not synchronized with each other. For example, 154 one audio stream and one video stream belong to the same session, and 155 the audio stream is transmitted lagging behind video stream for 156 multiple tens of milliseconds [TR-126]. The RTP Flows 157 Synchronization Offset block can be used to report such 158 synchronization offset between video stream and audio stream. This 159 block is also applied to the case where an RTP session can contain 160 media streams with media from multiple media types. The metrics 161 defined in the RTP flows synchronization Offset block can be used by 162 the network manager for trouble shooting and dealing with user 163 experience issues. 165 2. Terminology 167 2.1. Standards Language 169 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 170 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 171 document are to be interpreted as described in RFC 2119 [RFC2119]. 173 In addition, the following terms are defined: 175 Initial Synchronization Delay: 177 A multimedia session comprises a set of concurrent RTP sessions 178 among a common group of participants, using one RTP session for 179 each media type. The initial synchronization Delay is the average 180 time for receiver to synchronize all components of a multimedia 181 session [RFC6051]. 183 Synchronization Offset: 185 Synchronization between two media streams must be maintained to 186 ensure satisfactory QoE. Two media streams can be of the same or 187 different media type belonging to one RTP session or in different 188 media types belonging to one multimedia session. The 189 Synchronization Offset is the relative time difference of the two 190 media streams that need to be synchronized. 192 3. RTP Flows Initial Synchronization Delay Report Block 194 This block is sent by RTP receivers and reports Initial 195 synchronization delay beyond the information carried in the standard 196 RTCP packet format. Information is recorded about time difference 197 between the start of multimedia session and the time when the RTP 198 receiver acquires all components of RTP sessions [RFC6051] measured 199 at the receiving end of RTP stream. 201 This block needs only be exchanged occasionally, for example sent 202 once at the start of RTP session. 204 3.1. Metric Block Structure 206 The RTP Flows Initial Synchronization Delay Report Block has the 207 following format: 209 0 1 2 3 210 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 1 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 | BT=RFISD | Reserved | Block length=2 | 213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 214 | SSRC of Source | 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 | Initial Synchronization Delay | 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 219 Figure 1: Report Block Structure 221 3.2. Definition of Fields in RTP Flow Initial Synchronization Delay 222 Metrics Block 224 Block type (BT): 8 bits 226 The RTP Flows Initial Synchronization Delay Report Block is 227 identified by the constant . 229 [Note to RFC Editor: please replace RFISD with the IANA provided 230 RTCP XR block type for this block.] 232 Reserved: 8 bits 234 This field is reserved for future definition. In the absence of 235 such a definition, the bits in this field MUST be set to zero and 236 ignored by the receiver. 238 Block length: 16 bits 240 The constant 2, in accordance with the definition of this field in 241 Section 3 of RFC 3611 [RFC3611]. 243 SSRC of source: 32 bits 245 The SSRC of the media source SHALL be set to the value of the SSRC 246 identifier carried in any arbitrary component of RTP sessions 247 belonging to the same multimedia session. 249 Initial Synchronization Delay: 32 bits 251 The average delay, expressed in units of 1/65536 seconds, from the 252 beginning of multimedia session [RFC6051] to the time when RTCP 253 packets are received on all of the components RTP sessions. It is 254 recommended that the beginning of multimedia session is chosen as 255 the time when the receiver has joined the first RTP session of the 256 multimedia session. The value of the initial synchronization 257 delay is calculated based on received RTCP SR packets or the RTP 258 header extension containing in-band mapping of RTP and NTP-format 259 timestamps [RFC6051]. If there is no packet loss, the initial 260 synchronization delay is expected to be equal to the average time 261 taken to receive the first RTCP packet in the RTP session with the 262 longest RTCP reporting interval or the average time taken to 263 receive the first RTP header extension containing in-band mapping 264 of RTP and NTP-format timestamps. 266 If the measurement is unavailable, the value of this field with 267 all bits set to 1 MUST be reported. 269 4. RTP Flows Synchronization Offset Metrics Block 271 In the RTP multimedia sessions or one RTP session, there can be an 272 arbitrary number of Media streams and each media stream (e.g., audio 273 stream or video stream) is sent in a separate RTP stream. In case of 274 one RTP session, each media stream or each medium uses different 275 SSRC. The receiver associates RTP streams to be synchronized by 276 means of RTCP CNAME contained in the RTCP Source Description (SDES) 277 packets [RFC3550]. 279 This block is sent by RTP receivers and reports synchronization 280 offset of two arbitrary RTP streams that needs to be synchronized in 281 the RTP multimedia session. Information is recorded about the 282 relative average time difference between two arbitrary RTP streams 283 (one is reporting stream, the other is reference stream) with the 284 same CNAME and measured at the receiving end of RTP stream. In order 285 to tell what the offset of reporting stream is relative to, the block 286 for reference stream with synchronization offset of zero should be 287 reported. 289 Instances of this Block refer by Synchronization source (SSRC) to the 290 separate auxiliary Measurement Information block [RFC6776] which 291 describes measurement periods in use (see [RFC6776] section 4.2). 292 This metrics block relies on the measurement period in the 293 Measurement Information block indicating the span of the report and 294 SHOULD be sent in the same compound RTCP packet as the measurement 295 information block. If the measurement period is not received in the 296 same compound RTCP packet as this Block, this Block MUST be 297 discarded. 299 4.1. Metric Block Structure 301 The RTP Flow General Synchronization Offset Report Block has the 302 following format: 304 0 1 2 3 305 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 1 306 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 307 | BT=RFSO | I | Reserved | Block length=3 | 308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 309 | SSRC of source | 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 311 | Synchronization Offset, most significant word | 312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 313 | Synchronization Offset, least significant word | 314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 316 Figure 2: Report Block Structure 318 4.2. Definition of Fields in RTP Flow General Synchronization Offset 319 Metrics Block 321 Block type (BT): 8 bits 323 The RTP Flow General Synchronization Offset Report Block is 324 identified by the constant . 326 [Note to RFC Editor: please replace RFSO with the IANA provided 327 RTCP XR block type for this block.] 329 Interval Metric Flag (I): 2 bits 331 This field is used to indicate whether the Burst/Gap Discard 332 Summary Statistics metrics are Sampled, Interval or Cumulative 333 metrics: 335 I=10: Interval Duration - the reported value applies to the 336 most recent measurement interval duration between successive 337 metrics reports. 338 I=11: Cumulative Duration - the reported value applies to the 339 accumulation period characteristic of cumulative measurements. 340 I=01: Sampled Value - the reported value is a sampled 341 instantaneous value. 343 In this document, the value I=00 is the reserved value and MUST 344 NOT be used. If the value I=00 is received, then the XR block 345 MUST be ignored by the receiver. 347 Reserved: 6 bits 349 This field is reserved for future definition. In the absence of 350 such a definition, the bits in this field MUST be set to zero and 351 MUST be ignored by the receiver. 353 Block length: 16 bits 355 The constant 3, in accordance with the definition of this field in 356 Section 3 of RFC 3611 [RFC3611]. 358 SSRC of Source: 32 bits 360 The SSRC of the media source SHALL be set to the value of the SSRC 361 identifier of the reporting RTP stream to which the XR relates. 363 Synchronization Offset: 64 bits 365 The synchronization offset of the reporting RTP stream relative to 366 the reference stream with the same CNAME. The calculation of 367 Synchronization Offset is similar to Difference D calculation in 368 the RFC3550. That is to say, if Si is the NTP timestamp from the 369 reporting RTP packet i, and Ri is the time of arrival in NTP 370 timestamp units for reporting RTP packet i, Sj is the NTP 371 timestamp from the reference RTP packet j, and Rj is the time of 372 arrival in NTP timestamp units for reference RTP packet j, then 373 the value of the synchronization offset D may be expressed as 375 D(i,j) = (Rj - Ri) - (Sj - Si) = (Rj - Sj) - (Ri - Si) 377 If in-band delivery of NTP-format timestamps is supported 378 [RFC6051], Si and Sj should be obtained directly from the RTP 379 packets where NTP timestamps are available. If not, Si and Sj 380 should be calculated from their corresponding RTP timestamps. The 381 value of the synchronization offset is represented using a 64-bit 382 signed NTP-format timestamp as defined in [RFC5905], which is 64- 383 bit signed fixed-point number with the integer part in the first 384 32 bits and the fractional part in the last 32 bits. A positive 385 value of the synchronization offset means that the reporting 386 stream leads before the reference stream, while a negative one 387 means the reporting stream lags behind the reference stream. The 388 synchronization offset of zero means the stream is the reference 389 stream. 391 If the measurement is unavailable, the value of this field with 392 all bits set to 1 MUST be reported. 394 5. SDP Signaling 396 [RFC3611] defines the use of SDP (Session Description Protocol) 397 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 398 without prior signaling. 400 5.1. SDP rtcp-xr-attrib Attribute Extension 402 Two new parameters are defined for the two report blocks defined in 403 this document to be used with Session Description Protocol (SDP) 404 [RFC4566] using the Augmented Backus-Naur Form (ABNF) [RFC5234]. 405 They have the following syntax within the "rtcp-xr" attribute 406 [RFC3611]: 408 xr-format = xr-rfisd-block 409 / xr-rfso-block 411 xr-rfisd-block = "rtp-flow-init-syn-delay" 412 xr-rfso-block = "rtp-flow-syn-offset" 414 Refer to Section 5.1 of RFC 3611 [RFC3611] for a detailed description 415 and the full syntax of the "rtcp-xr" attribute. 417 5.2. Offer/Answer Usage 419 When SDP is used in offer-answer context, the SDP Offer/Answer usage 420 defined in [RFC3611] applies. 422 6. IANA Considerations 424 New report block types for RTCP XR are subject to IANA registration. 425 For general guidelines on IANA allocations for RTCP XR, refer to 426 Section 6.2 of [RFC3611]. 428 This document assigns two new block type values in the RTCP XR Block 429 Type Registry: 431 Name: RFISD 432 Long Name: RTP Flows Initial Synchronization Delay 433 Value 434 Reference: Section 3 436 Name: RFSO 437 Long Name: RTP Flows Synchronization Offset Metrics Block 438 Value 439 Reference: Section 4 441 This document also registers two new SDP [RFC4566] parameters for the 442 "rtcp-xr" attribute in the RTCP XR SDP Parameters Registry: 444 * "rtp-flow-init-syn-delay " 445 * "rtp-flow-syn-offset" 447 The contact information for the registrations is: 449 Qin Wu 450 sunseawq@huawei.com 451 101 Software Avenue, Yuhua District 452 Nanjing, Jiangsu 210012, China 454 7. Security Considerations 456 The new RTCP XR report blocks proposed in this document introduces no 457 new security considerations beyond those described in [RFC3611]. 459 8. Acknowledgements 461 The authors would like to thank Bill Ver Steeg, David R Oran, Ali 462 Begen, Colin Perkins, Roni Even, Kevin Gross, Jing Zhao, Fernando 463 Boronat Segui, Mario Montagud Climent, Youqing Yang, Wenxiao Yu and 464 Yinliang Hu,Jonathan Lennox for their valuable comments and 465 suggestions on this document. 467 9. References 469 9.1. Normative References 471 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 472 Requirement Levels", BCP 14, RFC 2119, March 1997. 474 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 475 Jacobson, "RTP: A Transport Protocol for Real-Time 476 Applications", STD 64, RFC 3550, July 2003. 478 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 479 Protocol Extended Reports (RTCP XR)", RFC 3611, 480 November 2003. 482 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 483 Description Protocol", RFC 4566, July 2006. 485 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 486 Specifications: ABNF", STD 68, RFC 5234, January 2008. 488 [RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network 489 Time Protocol Version 4: Protocol and Algorithms 490 Specification", RFC 5905, June 2010. 492 [RFC6051] Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP 493 Flows", RFC 6051, November 2010. 495 [RFC6190] Wenger, S., Wang, Y., Schierl, T., and A. Eleftheriadis, 496 "RTP Payload Format for Scalable Video Coding", RFC 6190, 497 May 2011. 499 [RFC6776] Wu, Q., "Measurement Identity and information Reporting 500 using SDES item and XR Block", RFC 6776, August 2012. 502 9.2. Informative References 504 [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New 505 Performance Metric Development", RFC 6390, October 2011. 507 [RFC6792] Wu, Q., "Guidelines for Use of the RTP Monitoring 508 Framework", RFC 6792, November 2012. 510 [TR-126] BBF Forum, "Triple-play Services Quality of Experience 511 (QoE) Requirements", December 2006. 513 [Y.1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and 514 availability performance parameters", November 2007. 516 Appendix A. Metrics represented using RFC6390 Template 518 RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC 519 number, when assigned. 521 a. Initial Synchronization Delay Metric 523 * Metric Name: RTP Initial Synchronization Delay 525 * Metric Description: See Section 2.1,Initial Synchronization 526 Delay term [RFCXXXX]. 528 * Method of Measurement or Calculation: See section 3.2, Initial 529 Synchronization Delay definition [RFCXXXX]. 531 * Units of Measurement: See section 3.2, Initial Synchronization 532 Delay definition [RFCXXXX]. 534 * Measurement Point(s) with Potential Measurement Domain: See 535 section 3, 1st paragraph [RFCXXXX]. 537 * Measurement Timing: See section 3, 2nd paragraph [RFCXXXX] for 538 measurement timing. 540 * Use and applications: See section 1.4 [RFCXXXX]. 542 * Reporting model: See RFC3611. 544 b. Synchronization Offset Metric 546 * Metric Name: RTP Synchronization Offset Delay 548 * Metric Description: See Section 2.1, Synchronization Offset 549 term [RFCXXXX]. 551 * Method of Measurement or Calculation: See section 4.2, Initial 552 Synchronization Delay definition [RFCXXXX]. 554 * Units of Measurement: See section 4.2, Initial Synchronization 555 Delay definition [RFCXXXX]. 557 * Measurement Point(s) with Potential Measurement Domain: See 558 section 4, 2nd paragraph [RFCXXXX]. 560 * Measurement Timing: See section 4, 3rd paragraph [RFCXXXX] for 561 measurement timing and section 4.2 [RFCXXXX] for Interval 562 Metric flag. 564 * Use and applications: See section 1.4 [RFCXXXX]. 566 * Reporting model: See RFC3611. 568 Appendix B. Change Log 570 Note to the RFC-Editor: please remove this section prior to 571 publication as an RFC. 573 B.1. draft-ietf-xrblock-rtcp-xr-syncronization-08 575 The following are the major changes compared to previous version: 577 Some Editorial changes based on Gen-Art Reviewer comments. 579 B.2. draft-ietf-xrblock-rtcp-xr-syncronization-07 581 The following are the major changes compared to previous version: 583 Minor Editorial changes. 585 B.3. draft-ietf-xrblock-rtcp-xr-syncronization-06 587 The following are the major changes compared to previous version: 589 Some Editorial changes. 591 B.4. draft-ietf-xrblock-rtcp-xr-syncronization-05 593 The following are the major changes compared to previous version: 595 Editorial changes and typo fixed. 597 B.5. draft-ietf-xrblock-rtcp-xr-syncronization-04 599 The following are the major changes compared to previous version: 601 Additional text to clarify on how to distinguish report stream 602 from reference stream. 603 Other Editorial changes. 605 B.6. draft-ietf-xrblock-rtcp-xr-syncronization-03 607 The following are the major changes compared to previous version: 609 Remove the need to signal the reference source in the 610 synchronisation offset metrics RTCP XR report. 611 Apply RFC6390 template to metrics in the appendix. 612 Other editorial changes to get inline with other XRBLOCK drafts. 614 B.7. draft-ietf-xrblock-rtcp-xr-syncronization-02 616 The following are the major changes compared to previous version: 618 Editorial change based on comments raised on the list and in the 619 IETF85 meeting 621 Authors' Addresses 623 Hitoshi Asaeda 624 National Institute of Information and Communications Technology 625 4-2-1 Nukui-Kitamachi 626 Koganei, Tokyo 184-8795 627 Japan 629 Email: asaeda@nict.go.jp 631 Qin Wu 632 Huawei Technologies Co., Ltd. 633 101 Software Avenue, Yuhua District 634 Nanjing, Jiangsu 210012 635 China 637 Email: bill.wu@huawei.com 638 Rachel Huang 639 Huawei Technologies Co., Ltd. 640 101 Software Avenue, Yuhua District 641 Nanjing, Jiangsu 210012 642 China 644 Email: Rachel@huawei.com