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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Audio/Video Transport Working Group G. Hunt 3 Internet-Draft Unaffiliated 4 Intended status: Standards Track A. Clark 5 Expires: July 22, 2012 Telchemy 6 S. Zhang, Ed. 7 J. Zhao 8 STTRI 9 Q. Wu 10 Huawei 11 January 19, 2012 13 RTCP XR Report Block for Burst/Gap Loss metric Reporting 14 draft-ietf-xrblock-rtcp-xr-burst-gap-loss-01.txt 16 Abstract 18 This document defines an RTCP XR Report Block that allows the 19 reporting of Burst and Gap Loss metrics for use in a range of RTP 20 applications. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on July 22, 2012. 39 Copyright Notice 41 Copyright (c) 2012 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 1.1. Burst and Gap Loss Report Block . . . . . . . . . . . . . 3 58 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 59 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 60 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 61 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 62 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5 63 3. Burst/Gap Loss Block . . . . . . . . . . . . . . . . . . . . . 6 64 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 65 3.2. Definition of Fields in Burst/Gap Loss Report Block . . . 6 66 3.3. Derived metrics based on reported metrics . . . . . . . . 8 67 4. Considerations for Voice-over-IP applications . . . . . . . . 10 68 5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 11 69 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 70 6.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 12 71 6.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 12 72 6.3. Contact information for registrations . . . . . . . . . . 12 73 7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 74 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14 75 9. Changes from previous version . . . . . . . . . . . . . . . . 15 76 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 77 10.1. Normative References . . . . . . . . . . . . . . . . . . . 16 78 10.2. Informative References . . . . . . . . . . . . . . . . . . 16 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 81 1. Introduction 83 1.1. Burst and Gap Loss Report Block 85 This draft defines a new block type to augment those defined in 86 [RFC3611] for use in a range of RTP applications. The new block type 87 supports the reporting of the proportion of packets lost by the 88 network. The losses during loss bursts are reported, together with 89 the number of bursts and additional data allowing the calculation of 90 statistical parameters (mean and variance) of the distribution of 91 burst lengths. Some uses of these metrics depend on the availability 92 of the metric "cumulative number of packets lost" from RTCP 93 [RFC3550]. 95 This block provides information on transient IP problems. Burst/Gap 96 metrics are typically used in Cumulative reports however MAY be used 97 in Interval reports. The burstiness of packet loss affects user 98 experience, may influence any sender strategies to mitigate the 99 problem, and may also have diagnostic value. 101 The metric belongs to the class of transport-related terminal metrics 102 defined in [MONARCH] (work in progress). 104 The definitions of Burst, Gap, Loss and Discard are consistent with 105 definitions in [RFC3611]. To accommodate the range of jitter buffer 106 algorithms and packet discard logic that may be used by implementors, 107 the method used to distinguish between bursts and gaps may be an 108 equivalent method to that defined in [RFC3611]. The method used 109 SHOULD produce the same result as that defined in [RFC3611] for 110 conditions of burst packet loss, but MAY produce different results 111 for conditions of time varying jitter. 113 1.2. RTCP and RTCP XR Reports 115 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 116 defined an extensible structure for reporting using an RTCP Extended 117 Report (XR). This draft defines a new Extended Report block that 118 MUST be used as defined in [RFC3550] and [RFC3611]. 120 1.3. Performance Metrics Framework 122 The Performance Metrics Framework [RFC6390] provides guidance on the 123 definition and specification of performance metrics. Metrics 124 described in this draft either reference external definitions or 125 define metrics generally in accordance with the guidelines in 126 [RFC6390]. 128 1.4. Applicability 130 These metrics are applicable to a range of RTP applications. 132 2. Terminology 134 2.1. Standards Language 136 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 137 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 138 document are to be interpreted as described in RFC 2119 [RFC2119]. 140 In addition, the following terms are defined: 142 Received, Lost and Discarded 144 A packet shall be regarded as lost if it fails to arrive within an 145 implementation-specific time window. A packet that arrives within 146 this time window but is too early or late to be played out shall 147 be regarded as discarded. A packet shall be classified as one of 148 received (or OK), discarded or lost. 150 Bursts and Gaps 152 The terms Burst and Gap are used in a manner consistent with that 153 of RTCP XR [RFC3611]. RTCP XR views a RTP stream as being divided 154 into bursts, which are periods during which the loss rate is high 155 enough to cause noticeable quality degradation (generally over 5 156 percent loss rate), and gaps, which are periods during which lost 157 packets are infrequent and hence quality is generally acceptable. 159 3. Burst/Gap Loss Block 161 Metrics in this block report on Burst/Gap Loss in the stream arriving 162 at the RTP system. 164 3.1. Report Block Structure 166 Burst/Gap Loss metrics block 168 0 1 2 3 169 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 | BT=NBGL |I|C| resv. | block length = 5 | 172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 173 | SSRC of Source | 174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 175 | Threshold | Sum of Burst Durations (ms) | 176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 | Packets Lost in Bursts | Total... | 178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 179 | ...Packets expected in bursts | Number of bursts | Sum of| 180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 | ...Squares of Burst Durations (ms-squared) | 182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 184 Figure 1: Report Block Structure 186 3.2. Definition of Fields in Burst/Gap Loss Report Block 188 Block type (BT): 8 bits 190 A Burst/Gap Loss Report Block is identified by the constant NBGL. 192 [Note to RFC Editor: please replace NBGL with the IANA provided 193 RTCP XR block type for this block.] 195 Interval Metric flag (I): 1 bit 197 This field is used to indicate whether the Packet Delay Variation 198 metrics block is an Interval or a Cumulative report, that is, 199 whether the reported values apply to the most recent measurement 200 interval duration between successive metrics reports (I=1) (the 201 Interval Duration) or to the accumulation period characteristic of 202 cumulative measurements (I=0) (the Cumulative Duration). 204 Loss and Discard Combination flag (C): 1 bit 206 The 'C' flag is used to indicate whether combining loss/discard 207 report is needed. This field MUST be set to '1' if the burst gap 208 loss report is present in conjunction with the burst gap discard 209 report in the same compound RTCP packet and MUST be set to '0' 210 otherwise. If the burst gap discard is not sent with burst gap 211 loss, then the receiver should discard burst gap loss with 'C' 212 flag set to 1. If the 'C' flag is set to 0, then receiver should 213 not discard burst gap loss metric block when burst gap discard is 214 not received. 216 Reserved (resv): 7 bits 218 These bits are reserved. They SHOULD be set to zero by senders 219 and MUST be ignored by receivers. 221 block length: 16 bits 223 The length of this report block in 32-bit words, minus one. For 224 the Delay block, the block length is equal to 5. 226 SSRC of source: 32 bits 228 As defined in Section 4.1 of [RFC3611]. 230 Threshold: 8 bits 232 The Threshold is equivalent to Gmin in [RFC3611], i.e. the number 233 of successive packets that must be received prior to and following 234 a lost frame in order for this lost frame to be regarded as part 235 of a gap. 237 Sum of Burst Durations (ms): 24 bits 239 The total duration of bursts of lost frames in the period of the 240 report (Interval or Cumulative). 242 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE SHOULD 243 be reported to indicate an over-range measurement. If the 244 measurement is unavailable, the value 0xFFFFFF SHOULD be reported. 246 Packets lost in bursts: 24 bits 248 The total number of packets lost during loss bursts. 250 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE SHOULD 251 be reported to indicate an over-range measurement. If the 252 measurement is unavailable, the value 0xFFFFFF SHOULD be reported. 254 Total packets expected in bursts: 24 bits 256 The total number of packets expected during loss bursts (that is, 257 the sum of received packets and lost packets). 259 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE SHOULD 260 be reported to indicate an over-range measurement. If the 261 measurement is unavailable, the value 0xFFFFFF SHOULD be reported. 263 Number of bursts: 16 bits 265 The number of bursts in the period of the report (Interval or 266 Cumulative). 268 If the measured value exceeds 0xFFFD, the value 0xFFFE SHOULD be 269 reported to indicate an over-range measurement. If the 270 measurement is unavailable, the value 0xFFFF SHOULD be reported. 272 Sum of Squares of Burst Durations (ms-squared): 36 bits 274 The sum of the squares of burst durations (where individual burst 275 durations are expressed in ms) over in the period of the report 276 (Interval or Cumulative). The units for this quantity are 277 milliseconds-squared. 279 If the measured value exceeds 0xFFFFFFFFD, the value 0xFFFFFFFFE 280 SHOULD be reported to indicate an over-range measurement. If the 281 measurement is unavailable, the value 0xFFFFFFFFF SHOULD be 282 reported. 284 3.3. Derived metrics based on reported metrics 286 The metrics described here are intended to be used as described in 287 this section, in conjunction with information from the Measurement 288 Information block [MEASID] (which MUST be present in the same RTCP 289 packet as the Burst/Gap Loss block) and also with the metric 290 "cumulative number of packets lost" provided in standard RTCP 291 [RFC3550]. 293 These metrics provides information relevant to statistical 294 parameters, including: 296 o The fraction of packets lost during bursts (i.e., Burst Loss Rate 297 in [SUMSTAT]) 299 o The fraction of packets lost during gaps (i.e., Gap Loss Rate in 300 [SUMSTAT]) 302 o burst duration mean [SUMSTAT] 304 o burst duration variance [SUMSTAT] 306 The details on calculation these parameters in the metrics are 307 described in [SUMSTAT]. 309 4. Considerations for Voice-over-IP applications 311 This metric block is applicable to a broad range of RTP applications. 312 Where the metric is used with a Voice-overIP (VoIP) application, the 313 following considerations apply. 315 RTCP XR views a call as being divided into bursts, which are periods 316 during which the loss rate is high enough to cause noticeable call 317 quality degradation (generally over 5 percent loss rate), and gaps, 318 which are periods during which lost packets are infrequent and hence 319 call quality is generally acceptable. 321 If Voice Activity Detection is used the Burst and Gap Duration shall 322 be determined as if silence frames had been sent, i.e. a period of 323 silence in excess of Gmin frames MUST terminate a burst condition. 325 The recommended value for the threshold Gmin in [RFC3611] results in 326 a Burst being a period of time during which the call quality is 327 degraded to a similar extent to a typical PCM Severely Errored Second 328 [PSES]. 330 5. SDP Signaling 332 [RFC3611] defines the use of SDP (Session Description Protocol) 333 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 334 without prior signaling. 336 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 337 in [RFC3611] by providing an additional value of "xr-format" to 338 signal the use of the report block defined in this document. 340 rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF 342 (defined in [RFC3611]) 344 xr-format =/ xr-bgl-block 346 xr-bgl-block = "brst-gap-loss" 348 6. IANA Considerations 350 New block types for RTCP XR are subject to IANA registration. For 351 general guidelines on IANA considerations for RTCP XR, refer to 352 [RFC3611]. 354 6.1. New RTCP XR Block Type value 356 This document assigns the block type value NDEL in the IANA "RTCP XR 357 Block Type Registry" to the "Burst/Gap Loss Metrics Block". 359 [Note to RFC Editor: please replace NBGL with the IANA provided RTCP 360 XR block type for this block.] 362 6.2. New RTCP XR SDP Parameter 364 This document also registers a new parameter "brst-gap-loss" in the 365 "RTCP XR SDP Parameters Registry". 367 6.3. Contact information for registrations 369 The contact information for the registrations is: 371 Geoff Hunt (r.geoff.hunt@gmail.com) 373 Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United 374 Kingdom 376 7. Security Considerations 378 It is believed that this proposed RTCP XR report block introduces no 379 new security considerations beyond those described in [RFC3611]. 380 This block does not provide per-packet statistics so the risk to 381 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 382 does not apply. 384 8. Contributors 386 The authors gratefully acknowledge the comments and contributions 387 made by Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin 388 Connor, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert 389 Higashi, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith 390 Lantz, Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, 391 Ravi Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada. 393 9. Changes from previous version 395 Changed BNF for SDP following Christian Groves' and Tom Taylor's 396 comments (4th and 5th May 2009), now aligned with RFC 5234 section 397 3.3 "Incremental Alternatives". 399 Updated references. 401 10. References 403 10.1. Normative References 405 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 406 Requirement Levels", March 1997. 408 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 409 Applications", RFC 3550, July 2003. 411 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 412 Protocol Extended Reports (RTCP XR)", November 2003. 414 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 415 Description Protocol", July 2006. 417 10.2. Informative References 419 [DISCARD] Hunt, G., "RTCP XR Report Block for Discard metric 420 Reporting", ID draft-ietf-rtcp-xr-discard-02, May 2009. 422 [MEASID] Wu, Q., "Measurement Identity and information Reporting 423 using SDES item and XR Block", 424 ID draft-ietf-xrblock-rtcp-xr-meas-identity-01, 425 October 2011. 427 [MONARCH] Hunt, G., "Monitoring Architectures for RTP", 428 ID draft-ietf-avtcore-monarch-04, August 2011. 430 [PSES] "URL", http://www.its.bldrdoc.gov/projects/devglossary/ 431 _severely_errored_second.html, October 2011. 433 [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric 434 Development", RFC 6390, July 2011. 436 [SUMSTAT] Zorn, G., "RTCP XR for Summary Statistics Metrics 437 Reporting", ID draft-zorn-xrblock-rtcp-xr-al-stat-03, 438 October 2011. 440 Authors' Addresses 442 Geoff Hunt 443 Unaffiliated 445 Email: r.geoff.hunt@gmail.com 447 Alan Clark 448 Telchemy Incorporated 449 2905 Premiere Parkway, Suite 280 450 Duluth, GA 30097 451 USA 453 Email: alan.d.clark@telchemy.com 455 Sunshine Zhang (editor) 456 Shanghai Research Institure of China Telecom Corporation Limited 457 No.1835,South Pudong Road 458 Shanghai 200122 459 China 461 Email: zhangyx@sttri.com.cn 463 Jing Zhao 464 Shanghai Research Institure of China Telecom Corporation Limited 465 No.1835,South Pudong Road 466 Shanghai 200122 467 China 469 Email: zhaojing@sttri.com.cn 471 Qin Wu 472 Huawei 473 101 Software Avenue, Yuhua District 474 Nanjing, Jiangsu 210012 475 China 477 Email: sunseawq@huawei.com