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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) == Unused Reference: 'RFC6709' is defined on line 494, but no explicit reference was found in the text ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) == Outdated reference: A later version (-15) exists of draft-ietf-xrblock-rtcp-xr-discard-11 == Outdated reference: A later version (-11) exists of draft-ietf-xrblock-rtcp-xr-summary-stat-05 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--).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: July 21, 2013 J. Zhao 6 STTRI 7 Q. Wu 8 Huawei 9 January 17, 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-08.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 July 21, 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-08 . . . . . . . 18 82 A.2. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-07 . . . . . . . 18 83 A.3. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-06 . . . . . . . 18 84 A.4. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-04 . . . . . . . 18 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 87 1. Introduction 89 1.1. Burst and Gap Loss Report Block 91 This draft defines a new block type to augment those defined in 92 [RFC3611] for use in a range of RTP applications. The new block type 93 supports the reporting of the proportion of packets lost by the 94 network. The losses during loss bursts are reported, together with 95 the number of bursts and additional data allowing the calculation of 96 statistical parameters (mean and variance) of the distribution of 97 burst lengths. Some uses of these metrics depend on the availability 98 of the metric "cumulative number of packets lost" from RTCP 99 [RFC3550]. 101 This block provides information on transient IP problems. Burst/Gap 102 metrics are typically used in Cumulative reports, however they also 103 MAY be used in Interval reports. The burstiness of packet loss 104 affects user experience, may influence any sender strategies to 105 mitigate the problem, and may also have diagnostic value. 107 The metric belongs to the class of transport-related end system 108 metrics defined in [RFC6792]. 110 The definitions of Burst, Gap, Loss and Discard are consistent with 111 definitions in [RFC3611]. To accommodate the range of jitter buffer 112 algorithms and packet discard logic that may be used by implementors, 113 the method used to distinguish between bursts and gaps may be an 114 equivalent method to that defined in [RFC3611]. The method used 115 SHOULD produce the same result as that defined in [RFC3611] for 116 conditions of burst packet loss, but MAY produce different results 117 for conditions of time varying jitter. 119 1.2. RTCP and RTCP XR Reports 121 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 122 defined an extensible structure for reporting using an RTCP Extended 123 Report (XR). This document defines a new Extended Report block for 124 use with [RFC3550] and [RFC3611]. 126 1.3. Performance Metrics Framework 128 The Performance Metrics Framework [RFC6390] provides guidance on the 129 definition and specification of performance metrics. The RTP 130 Monitoring Architectures [RFC6792] provides guideline for reporting 131 block format using RTCP XR. The Metrics Block described in this 132 document are in accordance with the guidelines in [RFC6390] and 133 [RFC6792]. 135 1.4. Applicability 137 These metrics are applicable to a range of RTP applications which 138 contain jitter buffers and don't use stream repair means,e.g., 139 Forward Error Correction (FEC) [RFC5109] and/or retransmission 140 [RFC4588]. 142 2. Terminology 144 2.1. Standards Language 146 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 147 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 148 document are to be interpreted as described in RFC 2119 [RFC2119]. 150 In addition, the following terms are defined: 152 Received, Lost and Discarded 154 A packet shall be regarded as lost if it fails to arrive within an 155 implementation-specific time window. A packet that arrives within 156 this time window but is too early or late to be played out or 157 thrown away before playout due to packet duplication or redundancy 158 shall be regarded as discarded. A packet shall be classified as 159 one of received (or OK), discarded or lost. The metric 160 "cumulative number of packets lost" defined in [RFC3550] reports a 161 count of packets lost from the media stream (single SSRC within 162 single RTP session). Similarly the metric "number of packets 163 discarded" defined in [DISCARD] reports a count of packets 164 discarded from the media stream (single SSRC within single RTP 165 session) arriving at the receiver. Another metric defined in 166 [RFC5725] is available to report on packets which are not 167 recovered by any repair techniques which may be in use. 169 Bursts and Gaps 171 The terms Burst and Gap are used in a manner consistent with that 172 of RTCP XR [RFC3611]. RTCP XR views a RTP stream as being divided 173 into bursts, which are periods during which the loss rate is high 174 enough to cause noticeable quality degradation (generally over 5 175 percent loss rate), and gaps, which are periods during which lost 176 packets are infrequent and hence quality is generally acceptable. 178 3. Burst/Gap Loss Block 180 Metrics in this block report on Burst/Gap Loss in the stream arriving 181 at the RTP system. The measurement of these metrics are made at the 182 receiving end of the RTP stream. Instances of this Metrics Block 183 refer by Synchronization source (SSRC) to the separate auxiliary 184 Measurement Information block [RFC6776] which describes measurement 185 periods in use(see RFC6776 section 4.2). This Metrics Block relies 186 on the measurement period in the Measurement Information block 187 indicating the span of the report and SHOULD be sent in the same 188 compound RTCP packet as the measurement information block. If the 189 measurement period is not received in the same compound RTCP packet 190 as this Metrics Block, this Metrics Block MUST be discarded. 192 3.1. Report Block Structure 194 Burst/Gap Loss metrics block 196 0 1 2 3 197 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 1 198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 199 | BT=NBGL | I |C| resv. | block length = 5 | 200 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 201 | SSRC of Source | 202 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 203 | Threshold | Sum of Burst Durations (ms) | 204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 205 | Packets Lost in Bursts | Total... | 206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 207 | ...Packets expected in bursts | Number of bursts | Sum of| 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 | ...Squares of Burst Durations (ms-squared) | 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 Figure 1: Report Block Structure 214 3.2. Definition of Fields in Burst/Gap Loss Report Block 216 Block type (BT): 8 bits 218 A Burst/Gap Loss Report Block is identified by the constant NBGL. 220 [Note to RFC Editor: please replace NBGL with the IANA provided 221 RTCP XR block type for this block.] 223 Interval Metric flag (I): 2 bits 225 This field is used to indicate whether the Burst/Gap Loss metrics 226 are Sampled, Interval or Cumulative metrics: 228 I=10: Interval Duration - the reported value applies to the 229 most recent measurement interval duration between successive 230 metrics reports. 232 I=11: Cumulative Duration - the reported value applies to the 233 accumulation period characteristic of cumulative measurements. 235 I=01: Sampled Value - the reported value is a sampled 236 instantaneous value. 238 In this document, Burst/Gap Loss Metrics can only be measured over 239 definite intervals, and cannot be sampled. Accordingly, the value 240 I=01, indicating a sampled value, MUST NOT be used. In addition, 241 the value I=00 is reserved and also MUST NOT be used. The block 242 MUST be discarded if the value I=01 or I=00 is received. 244 Loss and Discard Combination flag (C): 1 bit 246 The 'C' flag is used to indicate whether combining loss/discard 247 report is needed. This field MUST be set to '1' if the burst gap 248 loss report is present in conjunction with the burst gap discard 249 report in the same compound RTCP packet and MUST be set to '0' 250 otherwise. If the burst gap discard is not sent with the burst 251 gap loss, then the receiver MUST discard the burst gap loss with 252 'C' flag set to 1. If the 'C' flag is set to 0, then receiver 253 MUST NOT discard the burst gap loss Metrics Block when the burst 254 gap discard is not received. 256 Reserved (resv): 5 bits 258 These bits are reserved. They MUST be set to zero by senders and 259 ignored by receivers (See RFC6709 section 4.2). The block MUST be 260 discarded if the block length is set to a different value. 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. 280 Sum of Burst Durations (ms): 24 bits 282 The total duration of bursts of lost packets in the period of the 283 report (Interval or Cumulative). 285 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE MUST be 286 reported to indicate an over-range measurement. If the 287 measurement is unavailable, the value 0xFFFFFF MUST be reported. 289 Packets lost in bursts: 24 bits 291 The total number of packets lost during loss bursts. 293 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE MUST be 294 reported to indicate an over-range measurement. If the 295 measurement is unavailable, the value 0xFFFFFF MUST be reported. 297 Total packets expected in bursts: 24 bits 299 The total number of packets expected during loss bursts (that is, 300 the sum of received packets and lost packets). 302 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE MUST be 303 reported to indicate an over-range measurement. If the 304 measurement is unavailable, the value 0xFFFFFF MUST be reported. 306 Number of bursts: 16 bits 308 The number of bursts in the period of the report (Interval or 309 Cumulative). 311 If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be 312 reported to indicate an over-range measurement. If the 313 measurement is unavailable, the value 0xFFFF MUST be reported. 315 Sum of Squares of Burst Durations (ms-squared): 36 bits 317 The sum of the squares of burst durations (where individual burst 318 durations are expressed in ms) over in the period of the report 319 (Interval or Cumulative). The units for this quantity are 320 milliseconds-squared. 322 If the measured value exceeds 0xFFFFFFFFD, the value 0xFFFFFFFFE 323 MUST be reported to indicate an over-range measurement. If the 324 measurement is unavailable, the value 0xFFFFFFFFF MUST be 325 reported. 327 3.3. Derived metrics based on reported metrics 329 The metrics described here are intended to be used as described in 330 this section, in conjunction with information from the Measurement 331 Information block [RFC6776] (which MUST be present in the same RTCP 332 packet as the Burst/Gap Loss block) and also with the metric 333 "cumulative number of packets lost" provided in standard RTCP 334 [RFC3550]. 336 These metrics provide information relevant to statistical parameters, 337 including: 339 o The fraction of packets lost during bursts (i.e., Burst Loss Rate 340 in [SUMSTAT]), which can be calculated using the metric " Packets 341 Loss in Bursts " and the metric " Total Packets expected in Bursts 342 " provided in the Burst/Gap Loss metrics block. 344 o The fraction of packets lost during gaps (i.e., Gap Loss Rate in 345 [SUMSTAT]), which can be calculated using the metric " Packets 346 Loss in Bursts " and the metric " Total Packets expected in Bursts 347 " provided in the Burst/Gap Loss metrics block. 349 o burst duration mean [SUMSTAT], which can be calculated using the 350 metric " Packets Loss in Bursts " and the metric " Total Packets 351 expected in Bursts " provided in the Burst/Gap Loss metrics block. 353 o burst duration variance [SUMSTAT], which can be calculated using 354 the metric " Packets Loss in Bursts " and the metric " Total 355 Packets expected in Bursts " provided in the Burst/Gap Loss 356 metrics block. 358 The details on calculation these parameters in the metrics are 359 described in [SUMSTAT]. 361 4. Considerations for Voice-over-IP applications 363 This Metrics Block is applicable to a broad range of RTP 364 applications. Where the metric is used with a Voice-overIP (VoIP) 365 application and the stream repair means is not available, the 366 following considerations apply. 368 RTCP XR views a call as being divided into bursts, which are periods 369 during which the loss rate is high enough to cause noticeable call 370 quality degradation (generally over 5 percent loss rate), and gaps, 371 which are periods during which lost packets are infrequent and hence 372 call quality is generally acceptable. 374 If Voice Activity Detection is used the Burst and Gap Duration shall 375 be determined as if silence packets had been sent, i.e. a period of 376 silence in excess of Gmin packets MUST terminate a burst condition. 378 The recommended value for the threshold Gmin in [RFC3611] results in 379 a Burst being a period of time during which the call quality is 380 degraded to a similar extent to a typical Pulse-Code Modulation(PCM) 381 Severely Errored Second. 383 5. SDP Signaling 385 [RFC3611] defines the use of SDP (Session Description Protocol) 386 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 387 without prior signaling. 389 5.1. SDP rtcp-xr-attrib Attribute Extension 391 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 392 in [RFC3611] by providing an additional value of "xr-format" to 393 signal the use of the report block defined in this document. 395 xr-format =/ xr-bgl-block 397 xr-bgl-block = "brst-gap-loss" 399 5.2. Offer/Answer Usage 401 When SDP is used in offer-answer context, the SDP Offer/Answer usage 402 defined in [RFC3611] for unilateral "rtcp-xr" attribute parameters 403 applies. For detailed usage in Offer/Answer for unilateral 404 parameter, refer to section 5.2 of [RFC3611]. 406 6. IANA Considerations 408 New block types for RTCP XR are subject to IANA registration. For 409 general guidelines on IANA considerations for RTCP XR, refer to 410 [RFC3611]. 412 6.1. New RTCP XR Block Type value 414 This document assigns the block type value NBGL in the IANA " RTP 415 Control Protocol Extended Reports (RTCP XR) Block Type Registry " to 416 the "Burst/Gap Loss Metrics Block". 418 [Note to RFC Editor: please replace NBGL with the IANA provided RTCP 419 XR block type for this block.] 421 6.2. New RTCP XR SDP Parameter 423 This document also registers a new parameter "brst-gap-loss" in the " 424 RTP Control Protocol Extended Reports (RTCP XR) Session Description 425 Protocol (SDP) Parameters Registry". 427 6.3. Contact information for registrations 429 The contact information for the registrations is: 431 Qin Wu (sunseawq@huawei.com) 433 101 Software Avenue, Yuhua District 434 Nanjing, Jiangsu 210012 435 China 437 7. Security Considerations 439 It is believed that this proposed RTCP XR report block introduces no 440 new security considerations beyond those described in [RFC3611]. 441 This block does not provide per-packet statistics so the risk to 442 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 443 does not apply. 445 8. Contributors 447 Geoff Hunt wrote the initial draft of this document. 449 9. Acknowledgments 451 The authors gratefully acknowledge reviews and feedback provided by 452 Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, 453 Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, 454 Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, 455 Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi 456 Raviraj, Albrecht Schwarz, Tom Taylor, Hideaki Yamada, Adam Roach and 457 Dan Romascanu.. 459 10. References 461 10.1. Normative References 463 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 464 Requirement Levels", March 1997. 466 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 467 Applications", RFC 3550, July 2003. 469 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 470 Protocol Extended Reports (RTCP XR)", November 2003. 472 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 473 Description Protocol", July 2006. 475 [RFC5725] Begen, A., Hsu, D., and M. Lague, "Post-Repair Loss RLE 476 Report Block Type for RTP Control Protocol (RTCP) Extended 477 Reports (XRs)", RFC 5725, February 2020. 479 10.2. Informative References 481 [DISCARD] Wu, Q., "RTCP XR Report Block for Discard metric 482 Reporting", ID draft-ietf-xrblock-rtcp-xr-discard-11, 483 December 2012. 485 [RFC4588] Rey, J., Leon, D., , A., Varsa, V., and R. Hakenberg, "RTP 486 Retransmission Payload Format", RFC 4588, July 2006. 488 [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error 489 Correction", RFC 5109, December 2007. 491 [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric 492 Development", RFC 6390, July 2011. 494 [RFC6709] Carpenter, B., Aboba, B., and S. Cheshire, "Design 495 Considerations for Protocol Extensions", RFC 6709, 496 September 2012. 498 [RFC6776] Wu, Q., "Measurement Identity and information Reporting 499 using SDES item and XR Block", RFC 6776, October 2012. 501 [RFC6792] Hunt, G., "Monitoring Architectures for RTP", RFC 6792, 502 November 2012. 504 [SUMSTAT] Zorn, G., "RTCP XR for Summary Statistics Metrics 505 Reporting", ID draft-ietf-xrblock-rtcp-xr-summary-stat-05, 506 December 2012. 508 Appendix A. Change Log 510 Note to the RFC-Editor: please remove this section prior to 511 publication as an RFC. 513 A.1. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-08 515 The following are the major changes compared to previous version: 517 o Move RFC6709 as one informative reference. 519 A.2. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-07 521 The following are the major changes compared to previous version: 523 o Editorial changes based on comments in the WGLC. 525 A.3. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-06 527 The following are the major changes compared to previous version: 529 o SDP update based on SDP Directorate Review. 531 o Add some texts to get consistent with RFC6798 and Delay draft. 533 A.4. draft-ietf-xrblock-rtcp-xr-burst-gap-loss-04 535 The following are the major changes compared to previous version: 537 o Outdated reference update. 539 o Editorial changes based on comments that applied to PDV and Delay 540 drafts. 542 Authors' Addresses 544 Alan Clark 545 Telchemy Incorporated 546 2905 Premiere Parkway, Suite 280 547 Duluth, GA 30097 548 USA 550 Email: alan.d.clark@telchemy.com 552 Sunshine Zhang (editor) 553 Shanghai Research Institute of China Telecom Corporation Limited 554 No.1835,South Pudong Road 555 Shanghai 200122 556 China 558 Email: zhangyx@sttri.com.cn 560 Jing Zhao 561 Shanghai Research Institute of China Telecom Corporation Limited 562 No.1835,South Pudong Road 563 Shanghai 200122 564 China 566 Email: zhaojing@sttri.com.cn 568 Qin Wu 569 Huawei 570 101 Software Avenue, Yuhua District 571 Nanjing, Jiangsu 210012 572 China 574 Email: sunseawq@huawei.com