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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) == Outdated reference: A later version (-15) exists of draft-ietf-xrblock-rtcp-xr-discard-01 == Outdated reference: A later version (-10) exists of draft-ietf-xrblock-rtcp-xr-meas-identity-01 == Outdated reference: A later version (-22) exists of draft-ietf-avtcore-monarch-04 == Outdated reference: A later version (-06) exists of draft-zorn-xrblock-rtcp-xr-al-stat-03 Summary: 1 error (**), 0 flaws (~~), 5 warnings (==), 1 comment (--). 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 23, 2012 Telchemy 6 R. Huang 7 Q. Wu, Ed. 8 Huawei 9 January 20, 2012 11 RTCP XR Report Block for Burst/Gap Discard metric Reporting 12 draft-ietf-xrblock-rtcp-xr-burst-gap-discard-02.txt 14 Abstract 16 This document defines an RTCP XR Report Block that allows the 17 reporting of Burst and Gap Discard metrics for use in a range of RTP 18 applications. 20 Status of this Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on July 23, 2012. 37 Copyright Notice 39 Copyright (c) 2012 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 1.1. Burst and Gap Discard Report Block . . . . . . . . . . . . 3 56 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 57 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 58 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5 61 3. Burst/Gap Discard Block . . . . . . . . . . . . . . . . . . . 6 62 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 63 3.2. Definition of Fields in Burst/Gap Loss Report Block . . . 6 64 3.3. Derived metrics based on reported metrics . . . . . . . . 8 65 4. Considerations for Voice-over-IP applications . . . . . . . . 9 66 5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 10 67 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 68 6.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 11 69 6.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 11 70 6.3. Contact information for registrations . . . . . . . . . . 11 71 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 72 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13 73 9. Changes from previous version . . . . . . . . . . . . . . . . 14 74 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 75 10.1. Normative References . . . . . . . . . . . . . . . . . . . 15 76 10.2. Informative References . . . . . . . . . . . . . . . . . . 15 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 79 1. Introduction 81 1.1. Burst and Gap Discard Report Block 83 This draft defines a new block type to augment those defined in 84 [RFC3611] for use in a range of RTP applications. The new block type 85 supports the reporting of the proportion of packets discarded by the 86 receiver due to jitter. The discards during discard bursts are 87 reported, together with the number of bursts and additional data 88 allowing the calculation of statistical parameters (mean and 89 variance) of the distribution of burst lengths. This block is 90 intended to be used in conjunction with [DISCARD] which provides the 91 total packets discarded, and on which this block therefore depends. 92 However the metric in [DISCARD] may be used independently of the 93 metrics in this block. 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 discard 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] . 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 draft defines a new Extended Report block that 115 MUST be used as defined in [RFC3550] and [RFC3611]. 117 1.3. Performance Metrics Framework 119 The Performance Metrics Framework [RFC6390] provides guidance on the 120 definition and specification of performance metrics. Metrics 121 described in this draft either reference external definitions or 122 define metrics generally in accordance with the guidelines in 123 [RFC6390]. 125 1.4. Applicability 127 These metrics are applicable to a range of RTP applications. 129 2. Terminology 131 2.1. Standards Language 133 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 134 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 135 document are to be interpreted as described in RFC 2119 [RFC2119]. 137 In addition, the following terms are defined: 139 Received, Lost and Discarded 141 A packet shall be regarded as lost if it fails to arrive within an 142 implementation-specific time window. A packet that arrives within 143 this time window but is too early or late to be played out shall 144 be regarded as discarded. A packet shall be classified as one of 145 received (or OK), discarded or lost. 147 Bursts and Gaps 149 The terms Burst and Gap are used in a manner consistent with that 150 of RTCP XR [RFC3611]. RTCP XR views a RTP stream as being divided 151 into bursts, which are periods during which the loss rate is high 152 enough to cause noticeable quality degradation (generally over 5 153 percent loss rate), and gaps, which are periods during which lost 154 packets are infrequent and hence quality is generally acceptable. 156 3. Burst/Gap Discard Block 158 Metrics in this block report on Burst/Gap Discard in the stream 159 arriving at the RTP system. 161 3.1. Report Block Structure 163 Burst/Gap Discard metrics block 165 0 1 2 3 166 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 7 167 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 168 | BT=NBGD |I| resv. | block length = 3 | 169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 170 | SSRC of Source | 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 172 | Threshold | Packets Discarded in Bursts | 173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 | Total Packets expected in bursts | Reserved. | 175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 Figure 1: Report Block Structure 179 3.2. Definition of Fields in Burst/Gap Loss Report Block 181 Block type (BT): 8 bits 183 A Burst/Gap Discard Report Block is identified by the constant 184 NBGD. 186 [Note to RFC Editor: please replace NBGD with the IANA provided 187 RTCP XR block type for this block.] 189 Interval Metric flag (I): 1 bit 191 This field is used to indicate whether the Packet Delay Variation 192 metrics block is an Interval or a Cumulative report, that is, 193 whether the reported values apply to the most recent measurement 194 interval duration between successive metrics reports (I=1) (the 195 Interval Duration) or to the accumulation period characteristic of 196 cumulative measurements (I=0) (the Cumulative Duration). 198 Reserved (resv): 7 bits 200 These bits are reserved. They SHOULD be set to zero by senders 201 and MUST be ignored by receivers. 203 block length: 16 bits 205 The length of this report block in 32-bit words, minus one. For 206 the Delay block, the block length is equal to 3. 208 SSRC of source: 32 bits 210 As defined in Section 4.1 of [RFC3611]. 212 Threshold: 8 bits 214 The Threshold is equivalent to Gmin in [RFC3611], i.e. the number 215 of successive packets that must be received prior to and following 216 a lost packet in order for this lost packet to be regarded as part 217 of a gap. 219 Packets lost in bursts: 24 bits 221 The total number of packets lost during loss bursts. 223 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE SHOULD 224 be reported to indicate an over-range measurement. If the 225 measurement is unavailable, the value 0xFFFFFF SHOULD be reported. 227 Total packets expected in bursts: 24 bits 229 The total number of packets expected during loss bursts (that is, 230 the sum of received packets and lost packets). 232 If the measured value exceeds 0xFFFFFD, the value 0xFFFFFE SHOULD 233 be reported to indicate an over-range measurement. If the 234 measurement is unavailable, the value 0xFFFFFF SHOULD be reported. 236 Reserved (resv): 8 bits 238 These bits are reserved. They SHOULD be set to zero by senders 239 and MUST be ignored by receivers. 241 3.3. Derived metrics based on reported metrics 243 The metrics described here are intended to be used as described in 244 this section, in conjunction with information from the Measurement 245 Information block [MEASID], discard block [DISCARD] (which MUST be 246 present in the same RTCP packet as the Burst/Gap Discard block). 248 These metrics provides the following information relevant to 249 statistical parameters, including: 251 o The fraction of packets discarded during bursts (burst discard 252 rate in [SUMSTAT]) 254 o The fraction of packets discarded during gaps (gap discard rate in 255 [SUMSTAT]) 257 The details on calculation these parameters in the metrics are 258 described in [SUMSTAT]. 260 4. Considerations for Voice-over-IP applications 262 This metric block is applicable to a broad range of RTP applications. 263 Where the metric is used with a Voice-overIP (VoIP) application, the 264 following considerations apply. 266 RTCP XR views a call as being divided into bursts, which are periods 267 during which the loss rate is high enough to cause noticeable call 268 quality degradation (generally over 5 percent loss rate), and gaps, 269 which are periods during which lost packets are infrequent and hence 270 call quality is generally acceptable. 272 If Voice Activity Detection is used the Burst and Gap Duration shall 273 be determined as if silence frames had been sent, i.e. a period of 274 silence in excess of Gmin frames MUST terminate a burst condition. 276 The recommended value for the threshold Gmin in [RFC3611] results in 277 a Burst being a period of time during which the call quality is 278 degraded to a similar extent to a typical PCM Severely Errored Second 279 [PSES]. 281 5. SDP Signaling 283 [RFC3611] defines the use of SDP (Session Description Protocol) 284 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 285 without prior signaling. 287 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 288 in [RFC3611] by providing an additional value of "xr-format" to 289 signal the use of the report block defined in this document. 291 rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF 293 (defined in [RFC3611]) 295 xr-format =/ xr-bgd-block 297 xr-bgd-block = "brst-gap-dscrd" 299 6. IANA Considerations 301 New block types for RTCP XR are subject to IANA registration. For 302 general guidelines on IANA considerations for RTCP XR, refer to 303 [RFC3611]. 305 6.1. New RTCP XR Block Type value 307 This document assigns the block type value NDEL in the IANA "RTCP XR 308 Block Type Registry" to the "Burst/Gap Discard Metrics Block". 310 [Note to RFC Editor: please replace NBGD with the IANA provided RTCP 311 XR block type for this block.] 313 6.2. New RTCP XR SDP Parameter 315 This document also registers a new parameter "brst-gap-dscrd" in the 316 "RTCP XR SDP Parameters Registry". 318 6.3. Contact information for registrations 320 The contact information for the registrations is: 322 Geoff Hunt (r.geoff.hunt@gmail.com) 324 Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United 325 Kingdom 327 7. Security Considerations 329 It is believed that this proposed RTCP XR report block introduces no 330 new security considerations beyond those described in [RFC3611]. 331 This block does not provide per-packet statistics so the risk to 332 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 333 does not apply. 335 8. Contributors 337 The authors gratefully acknowledge the comments and contributions 338 made by Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin 339 Connor, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert 340 Higashi, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith 341 Lantz, Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, 342 Ravi Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada. 344 9. Changes from previous version 346 Changed BNF for SDP following Christian Groves' and Tom Taylor's 347 comments (4th and 5th May 2009), now aligned with RFC 5234 section 348 3.3 "Incremental Alternatives". 350 Updated references. 352 10. References 354 10.1. Normative References 356 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 357 Requirement Levels", March 1997. 359 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 360 Applications", RFC 3550, July 2003. 362 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 363 Protocol Extended Reports (RTCP XR)", November 2003. 365 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 366 Description Protocol", July 2006. 368 10.2. Informative References 370 [DISCARD] Hunt, G., "RTCP XR Report Block for Discard metric 371 Reporting", ID draft-ietf-xrblock-rtcp-xr-discard-01, 372 December 2011. 374 [MEASID] Wu, Q., "Measurement Identity and information Reporting 375 using SDES item and XR Block", 376 ID draft-ietf-xrblock-rtcp-xr-meas-identity-01, 377 October 2011. 379 [MONARCH] Hunt, G., "Monitoring Architectures for RTP", 380 ID draft-ietf-avtcore-monarch-04, August 2011. 382 [PSES] "URL", http://www.its.bldrdoc.gov/projects/devglossary/ 383 _severely_errored_second.html, October 2011. 385 [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric 386 Development", RFC 6390, October 2011. 388 [SUMSTAT] Zorn, G., "RTCP XR for Summary Statistics Metrics 389 Reporting", ID draft-zorn-xrblock-rtcp-xr-al-stat-03, 390 October 2011. 392 Authors' Addresses 394 Geoff Hunt 395 Unaffiliated 397 Email: r.geoff.hunt@gmail.com 399 Alan Clark 400 Telchemy Incorporated 401 2905 Premiere Parkway, Suite 280 402 Duluth, GA 30097 403 USA 405 Email: alan.d.clark@telchemy.com 407 Rachel Huang 408 Huawei Technologies Co., Ltd. 409 101 Software Avenue, Yuhua District 410 Nanjing, Jiangsu 210012 411 China 413 Email: Rachel@huawei.com 415 Qin Wu (editor) 416 Huawei 417 101 Software Avenue, Yuhua District 418 Nanjing, Jiangsu 210012 419 China 421 Email: sunseawq@huawei.com