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Wu 6 Huawei 7 April 3, 2013 9 RTP Control Protocol (RTCP) Extended Report (XR) Blocks for 10 Synchronization Delay and Offset Metrics Reporting 11 draft-ietf-xrblock-rtcp-xr-synchronization-04 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 October 5, 2013. 36 Copyright Notice 38 Copyright (c) 2013 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 . . . . . . . . . . . . . . . . . . . . 9 72 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 73 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 74 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 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-04 . . . . . . . 13 81 B.2. draft-ietf-xrblock-rtcp-xr-syncronization-03 . . . . . . . 13 82 B.3. draft-ietf-xrblock-rtcp-xr-syncronization-02 . . . . . . . 13 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 85 1. Introduction 87 1.1. Synchronization Delay and Offset Metrics Reporting Blocks 89 This draft defines two new block types to augment those defined in 90 [RFC3611], for use in a range of RTP applications. 92 The first new block type supports reporting of Initial 93 Synchronization Delay to establish multimedia session. Information 94 is recorded about time difference between the start of RTP sessions 95 and the time the RTP receiver acquires all components of RTP sessions 96 in the multimedia session [RFC6051]. 98 The second new block type supports reporting of the relative 99 synchronization offset time of two arbitrary streams (e.g., between 100 audio and video streams), with the same RTCP CNAME included in RTCP 101 SDES packets [RFC3550]. 103 These metrics belong to the class of transport level metrics defined 104 in [RFC6792]. 106 1.2. RTCP and RTCP XR Reports 108 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 109 defined an extensible structure for reporting using an RTCP Extended 110 Report (XR). This document defines a new Extended Report block for 111 use with [RFC3550] and [RFC3611]. 113 1.3. Performance Metrics Framework 115 The RTP Monitoring Architectures [RFC6792] provides guideline for 116 reporting block format using RTCP XR. The new report block described 117 in this memo is in compliance with the monitoring architecture 118 specified in [RFC6792]. 120 1.4. Applicability 122 When joining each session in layered video sessions [RFC6190] or the 123 multimedia session, a receiver may not synchronize playout across the 124 multimedia session or layered video session until RTCP SR packets 125 have been received on all components of RTP sessions. The component 126 RTP session are referred to as each RTP session for each media type 127 in multimedia session or separate RTP session for each layer in the 128 layered video session. For multicast session, the initial 129 synchronization delay metric varies with the session bandwidth, the 130 number of members, and the number of senders in the session. The RTP 131 flow Initial synchronization delay block defined in this document can 132 be used to report such metric, i.e., the initial synchronization 133 delay to receive all the RTP streams belonging to the same multimedia 134 session or layered video session. In the absence of packet loss, the 135 initial synchronization delay equals to the average time taken to 136 receive the first RTCP packet in the RTP session with the longest 137 RTCP reporting interval. In the presence of packet loss, the media 138 synchronization should rely on the in-band mapping of RTP and NTP- 139 format timestamps [RFC6051] or wait until the reporting interval has 140 passed, and the next RTCP SR packet is sent. 142 Receivers of the RTP flow initial synchronization delay block could 143 use this metric to compare with targets (i.e., Service Level 144 Agreement or thresholds of the system) to help ensure the quality of 145 real-time application performance. 147 In an RTP multimedia session, there can be an arbitrary number of 148 streams carried in different RTP sessions, with the same RTCP CNAME. 149 These streams may be not synchronized with each other. For example, 150 one audio stream and one video stream belong to the same session, and 151 the audio stream is transmitted lagging behind video stream for 152 multiple tens of milliseconds [TR-126]. The RTP Flows 153 Synchronization Offset block can be used to report such 154 synchronization offset between video stream and audio stream. This 155 block is also applied to the case where an RTP session can contain 156 media streams with media from multiple media types. The metrics 157 defined in the RTP flows synchronization Offset block can be used by 158 network manager for trouble shooting and dealing with user experience 159 issues. 161 2. Terminology 163 2.1. Standards Language 165 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 166 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 167 document are to be interpreted as described in RFC 2119 [RFC2119]. 169 In addition, the following terms are defined: 171 Initial Synchronization Delay: 173 A multimedia session comprises a set of concurrent RTP sessions 174 among a common group of participants, using one RTP session for 175 each media type. The initial synchronization Delay is the average 176 time for receiver to synchronize all components of a multimedia 177 session [RFC6051]. 179 Synchronization Offset: 181 Synchronization between two media streams must be maintained to 182 ensure satisfactory QoE. Two media streams can be of the same or 183 different media type belonging to one RTP session or in different 184 media types belonging to one multimedia session. The 185 Synchronization Offset is the relative time difference of the two 186 media streams that need to be synchronized. 188 3. RTP Flows Initial Synchronization Delay Report Block 190 This block is sent by RTP receivers and reports Initial 191 synchronization delay beyond the information carried in the standard 192 RTCP packet format. Information is recorded about time difference 193 between the start of multimedia session and the time when the RTP 194 receiver acquires all components of RTP sessions [RFC6051] measured 195 at the receiving end of RTP stream. 197 This block needs only be exchanged occasionally, for example sent 198 once at the start of RTP session. 200 3.1. Metric Block Structure 202 The RTP Flows Initial Synchronization Delay Report Block has the 203 following format: 205 0 1 2 3 206 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 1 207 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 208 | BT=RFISD | Reserved | Block length=2 | 209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 210 | SSRC of Source | 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 | Initial Synchronization Delay | 213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 215 3.2. Definition of Fields in RTP Flow Initial Synchronization Delay 216 Metrics Block 218 Block type (BT): 8 bits 220 The RTP Flows Initial Synchronization Delay Report Block is 221 identified by the constant . 223 Reserved: 6 bits 225 This field is reserved for future definition. In the absence of 226 such a definition, the bits in this field MUST be set to zero and 227 MUST be ignored by the receiver. 229 Block length: 16 bits 231 The constant 2, in accordance with the definition of this field in 232 Section 3 of RFC 3611 [RFC3611]. 234 SSRC of source: 32 bits 236 The SSRC of the media source SHALL be set to the value of the SSRC 237 identifier carried in any arbitrary component of RTP sessions 238 belonging to the same multimedia session. 240 Initial Synchronization Delay: 32 bits 242 The average delay, expressed in units of 1/65536 seconds, from the 243 beginning of multimedia session [RFC6051] to the time when RTCP 244 packets are received on all of the components RTP sessions. It is 245 recommended that the beginning of multimedia session is chosen as 246 the time when the receiver has joined the first RTP session of the 247 multimedia session. The value of the initial synchronization 248 delay is calculated based on received RTCP SR packets or the RTP 249 header extension containing in-band mapping of RTP and NTP-format 250 timestamps [RFC6051]. If there is no packet loss, the initial 251 synchronization delay is expected to be equal to the average time 252 taken to receive the first RTCP packet in the RTP session with the 253 longest RTCP reporting interval or the average time taken to 254 receive the first RTP header extension containing in-band mapping 255 of RTP and NTP- format timestamps. 257 If the measurement is unavailable, the value of this field with 258 all bits set to 1 MUST be reported. 260 4. RTP Flows Synchronization Offset Metrics Block 262 In the RTP multimedia sessions or one RTP session, there can be an 263 arbitrary number of Media streams and each media stream (e.g., audio 264 stream or video stream) is sent in a separate RTP stream. In case of 265 one RTP session, each media stream or each medium uses different 266 SSRC. The receiver associates RTP streams to be synchronized by 267 means of RTCP CNAME contained in the RTCP Source Description (SDES) 268 packets [RFC3550]. 270 This block is sent by RTP receivers and reports synchronization 271 offset of two arbitrary RTP streams that needs to be synchronized in 272 the RTP multimedia session. Information is recorded about the 273 relative average time difference between two arbitrary RTP streams 274 (one is reporting stream, the other is reference stream) with the 275 same CNAME and measured at the receiving end of RTP stream. In order 276 to tell what the offset of reporting stream is relative to, the block 277 for reference stream with synchronization offset of zero should be 278 reported. 280 Instances of this Block refer by Synchronization source (SSRC) to the 281 separate auxiliary Measurement Information block [RFC6776] which 282 describes measurement periods in use (see [RFC6776] section 4.2). 283 This metrics block relies on the measurement period in the 284 Measurement Information block indicating the span of the report and 285 SHOULD be sent in the same compound RTCP packet as the measurement 286 information block. If the measurement period is not received in the 287 same compound RTCP packet as this Block, this Block MUST be 288 discarded. 290 4.1. Metric Block Structure 292 The RTP Flow General Synchronization Offset Report Block has the 293 following format: 295 0 1 2 3 296 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 1 297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 298 | BT=RFSO | I | Reserved | Block length=4 | 299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 300 | SSRC of source | 301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 302 | Synchronization Offset, most significant word | 303 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 304 | Synchronization Offset, least significant word | 305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 307 4.2. Definition of Fields in RTP Flow General Synchronization Offset 308 Metrics Block 310 Block type (BT): 8 bits 312 The RTP Flow General Synchronization Offset Report Block is 313 identified by the constant . 315 Interval Metric Flag (I): 2 bits 317 This field is used to indicate whether the Burst/Gap Discard 318 Summary Statistics metrics are Sampled, Interval or Cumulative 319 metrics: 321 I=10: Interval Duration - the reported value applies to the 322 most recent measurement interval duration between successive 323 metrics reports. 324 I=11: Cumulative Duration - the reported value applies to the 325 accumulation period characteristic of cumulative measurements. 326 I=01: Sampled Value - the reported value is a sampled 327 instantaneous value. 329 In this document, the value I=00 is the reserved value and MUST 330 NOT be used. 332 Reserved: 6 bits 334 This field is reserved for future definition. In the absence of 335 such a definition, the bits in this field MUST be set to zero and 336 MUST be ignored by the receiver. 338 Block length: 16 bits 340 The constant 3, in accordance with the definition of this field in 341 Section 3 of RFC 3611 [RFC3611]. 343 SSRC of Source: 32 bits 345 The SSRC of the media source SHALL be set to the value of the SSRC 346 identifier of the reporting RTP stream to which the XR relates. 348 Synchronization Offset: 64 bits 350 The synchronization offset of the reporting RTP stream relative to 351 the reference stream with the same CNAME. The calculation of 352 Synchronization Offset is similar to Difference D calculation in 353 the RFC3550. That is to say, if Si is the NTP timestamp from the 354 reporting RTP packet i, and Ri is the time of arrival in NTP 355 timestamp units for reporting RTP packet i, Sj is the NTP 356 timestamp from the reference RTP packet j, and Rj is the time of 357 arrival in NTP timestamp units for reference RTP packet j, then 358 the value of the synchronization offset D may be expressed as 359 D(i,j) = (Rj - Ri) - (Sj - Si) = (Rj - Sj) - (Ri - Si) 361 If in-band delivery of NTP-format timestamps is supported 362 [RFC6051], Si and Sj should be obtained directly from the RTP 363 packets where NTP timestamps are available. If not, Si and Sj 364 should be calculated from their corresponding RTP timestamps. The 365 value of the synchronization offset is represented using a 64-bit 366 signed NTP-format timestamp as defined in [RFC5905], which is 64- 367 bit signed fixed-point number with the integer part in the first 368 32 bits and the fractional part in the last 32 bits. . A positive 369 value of the synchronization offset means that the reporting 370 stream leads before the reference stream, while a negative one 371 means the reporting stream lags behind the reference stream. The 372 synchronization offset of zero means the stream is the reference 373 stream. 375 If the measurement is unavailable, the value of this field with 376 all bits set to 1 MUST be reported. 378 5. SDP Signaling 380 [RFC3611] defines the use of SDP (Session Description Protocol) 381 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 382 without prior signaling. 384 5.1. SDP rtcp-xr-attrib Attribute Extension 386 Two new parameters are defined for the two report blocks defined in 387 this document to be used with Session Description Protocol (SDP) 388 [RFC4566] using the Augmented Backus-Naur Form (ABNF) [RFC5234]. 389 They have the following syntax within the "rtcp-xr" attribute 390 [RFC3611]: 392 xr-format = xr-rfisd-block 393 / xr-rfso-block 395 xr-rfisd-block = " init-syn-delay" 396 xr-rfso-block = " syn-offset" 398 Refer to Section 5.1 of RFC 3611 [RFC3611] for a detailed description 399 and the full syntax of the "rtcp-xr" attribute. 401 5.2. Offer/Answer Usage 403 When SDP is used in offer-answer context, the SDP Offer/Answer usage 404 defined in [RFC3611] applies. 406 6. IANA Considerations 408 New report block types for RTCP XR are subject to IANA registration. 409 For general guidelines on IANA allocations for RTCP XR, refer to 410 Section 6.2 of [RFC3611]. 412 This document assigns two new block type values in the RTCP XR Block 413 Type Registry: 415 Name: RFISD 416 Long Name: RTP Flows Initial Synchronization Delay 417 Value 418 Reference: Section 3 420 Name: RFSO 421 Long Name: RTP Flows Synchronization Offset Metrics Block 422 Value 423 Reference: Section 4 425 This document also registers two new SDP [RFC4566] parameters for the 426 "rtcp-xr" attribute in the RTCP XR SDP Parameters Registry: 428 * "xr-rfisd " 429 * "xr-rfso" 431 The contact information for the registrations is: 433 Qin Wu 434 sunseawq@huawei.com 435 101 Software Avenue, Yuhua District 436 Nanjing, Jiangsu 210012, China 438 7. Security Considerations 440 The new RTCP XR report blocks proposed in this document introduces no 441 new security considerations beyond those described in [RFC3611]. 443 8. Acknowledgements 445 The authors would like to thank Bill Ver Steeg, David R Oran, Ali 446 Begen, Colin Perkins, Roni Even, Kevin Gross, Jing Zhao, Fernando 447 Boronat Segui, Mario Montagud Climent, Youqing Yang, Wenxiao Yu and 448 Yinliang Hu,Jonathan Lennox for their valuable comments and 449 suggestions on this document. 451 9. References 453 9.1. Normative References 455 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 456 Requirement Levels", BCP 14, RFC 2119, March 1997. 458 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 459 Jacobson, "RTP: A Transport Protocol for Real-Time 460 Applications", STD 64, RFC 3550, July 2003. 462 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 463 Protocol Extended Reports (RTCP XR)", RFC 3611, 464 November 2003. 466 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 467 Description Protocol", RFC 4566, July 2006. 469 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 470 Specifications: ABNF", STD 68, RFC 5234, January 2008. 472 [RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network 473 Time Protocol Version 4: Protocol and Algorithms 474 Specification", RFC 5905, June 2010. 476 [RFC6051] Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP 477 Flows", RFC 6051, November 2010. 479 [RFC6190] Wenger, S., Wang, Y., Schierl, T., and A. Eleftheriadis, 480 "RTP Payload Format for Scalable Video Coding", RFC 6190, 481 May 2011. 483 [RFC6776] Wu, Q., "Measurement Identity and information Reporting 484 using SDES item and XR Block", RFC 6776, August 2012. 486 9.2. Informative References 488 [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New 489 Performance Metric Development", RFC 6390, October 2011. 491 [RFC6792] Wu, Q., "Guidelines for Use of the RTP Monitoring 492 Framework", RFC 6792, November 2012. 494 [TR-126] BBF Forum, "Triple-play Services Quality of Experience 495 (QoE) Requirements", December 2006. 497 [Y.1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and 498 availability performance parameters", November 2007. 500 Appendix A. Metrics represented using RFC6390 Template 502 RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC 503 number, when assigned. 505 a. Initial Synchronization Delay Metric 507 * Metric Name: RTP Initial Synchronization Delay 509 * Metric Description: See Section 2.1,Initial Synchronization 510 Delay term [RFCXXXX]. 512 * Method of Measurement or Calculation: See section 3.2, Initial 513 Synchronization Delay definition [RFCXXXX]. 515 * Units of Measurement: See section 3.2, Initial Synchronization 516 Delay definition [RFCXXXX]. 518 * Measurement Point(s) with Potential Measurement Domain: See 519 section 3, 1st paragraph [RFCXXXX]. 521 * Measurement Timing: See section 3, 2nd paragraph [RFCXXXX] for 522 measurement timing. 524 * Use and applications: See section 1.4 [RFCXXXX]. 526 * Reporting model: See RFC3611. 528 b. Synchronization Offset Metric 530 * Metric Name: RTP Synchronization Offset Delay 532 * Metric Description: See Section 2.1, Synchronization Offset 533 term [RFCXXXX]. 535 * Method of Measurement or Calculation: See section 4.2, Initial 536 Synchronization Delay definition definition [RFCXXXX]. 538 * Units of Measurement: See section 4.2, Initial Synchronization 539 Delay definition definition [RFCXXXX]. 541 * Measurement Point(s) with Potential Measurement Domain: See 542 section 4, 2nd paragraph [RFCXXXX]. 544 * Measurement Timing: See section 4, 3rd paragraph [RFCXXXX] for 545 measurement timing and section 4.2 [RFCXXXX] for Interval 546 Metric flag. 548 * Use and applications: See section 1.4 [RFCXXXX]. 550 * Reporting model: See RFC3611. 552 Appendix B. Change Log 554 Note to the RFC-Editor: please remove this section prior to 555 publication as an RFC. 557 B.1. draft-ietf-xrblock-rtcp-xr-syncronization-04 559 The following are the major changes compared to previous version: 561 Additional text to clarify on how to distinguish report stream 562 from reference stream. 563 Other Editorial changes. 565 B.2. draft-ietf-xrblock-rtcp-xr-syncronization-03 567 The following are the major changes compared to previous version: 569 Remove the need to signal the reference source in the 570 synchronisation offset metrics RTCP XR report. 571 Apply RFC6390 template to metrics in the appendix. 572 Other editorial changes to get inline with other XRBLOCK drafts. 574 B.3. draft-ietf-xrblock-rtcp-xr-syncronization-02 576 The following are the major changes compared to previous version: 578 Editorial change based on comments raised on the list and in the 579 IETF85 meeting 581 Authors' Addresses 583 Hitoshi Asaeda 584 National Institute of Information and Communications Technology 585 4-2-1 Nukui-Kitamachi 586 Koganei, Tokyo 184-8795 587 Japan 589 Email: asaeda@nict.go.jp 590 Rachel Huang 591 Huawei Technologies Co., Ltd. 592 101 Software Avenue, Yuhua District 593 Nanjing, Jiangsu 210012 594 China 596 Email: Rachel@huawei.com 598 Qin Wu 599 Huawei Technologies Co., Ltd. 600 101 Software Avenue, Yuhua District 601 Nanjing, Jiangsu 210012 602 China 604 Email: sunseawq@huawei.com