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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 G. Zorn 5 Expires: October 13, 2013 Network Zen 6 Q. Wu 7 Huawei 8 April 11, 2013 10 RTP Control Protocol (RTCP) Extended Report (XR) Block for Discard Count 11 metric Reporting 12 draft-ietf-xrblock-rtcp-xr-discard-12.txt 14 Abstract 16 This document defines an RTP Control Protocol(RTCP) Extended Report 17 (XR) Block that allows the reporting of a simple discard count metric 18 for use in a range of RTP 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 October 13, 2013. 37 Copyright Notice 39 Copyright (c) 2013 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. Discard Count 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. Discard Count Metric Report Block . . . . . . . . . . . . . . 6 62 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 63 3.2. Definition of Fields in Discard Count Metric Report 64 Block . . . . . . . . . . . . . . . . . . . . . . . . . . 6 65 4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 9 66 4.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 9 67 4.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 9 68 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 69 5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 10 70 5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 10 71 5.3. Contact information for registrations . . . . . . . . . . 10 72 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 73 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12 74 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 75 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 76 9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 77 9.2. Informative References . . . . . . . . . . . . . . . . . . 14 78 Appendix A. Metrics represented using RFC6390 Template . . . . . 15 79 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 16 80 B.1. draft-ietf-xrblock-rtcp-xr-discard-12 . . . . . . . . . . 16 81 B.2. draft-ietf-xrblock-rtcp-xr-discard-11 . . . . . . . . . . 16 82 B.3. draft-ietf-xrblock-rtcp-xr-discard-10 . . . . . . . . . . 16 83 B.4. draft-ietf-xrblock-rtcp-xr-discard-09 . . . . . . . . . . 16 84 B.5. draft-ietf-xrblock-rtcp-xr-discard-08 . . . . . . . . . . 16 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 87 1. Introduction 89 1.1. Discard Count Report Block 91 This document 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 number of packets which are received 94 correctly but are never played out, typically because they arrive too 95 late to be played out (buffer underflow) or too early (buffer 96 overflow). The metric is applicable both to systems which use packet 97 loss repair techniques (such as forward error correction [RFC5109] or 98 retransmission [RFC4588]) and to those which do not. 100 This metric is useful for identifying the existence, and 101 characterizing the severity, of a packet transport problem which may 102 affect users' perception of a service delivered over RTP. 104 This block may be used in conjunction with [BGDISCARD] which provides 105 additional information on the pattern of discarded packets. However 106 the metric in [BGDISCARD] may be used independently of the metrics in 107 this block. 109 In case of Discard count Metrics Block sent together with Burst gap 110 discard Metrics Block defined in [BGDISCARD] to the media sender or 111 RTP based network management system, information carried in the 112 discard count Metrics Block and Burst gap discard Metrics Block 113 allows them calculate the some bust gap summary statistics, e.g., gap 114 discard rate. 116 The metric belongs to the class of transport-related end system 117 metrics defined in [RFC6792]. 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 This metric is believed to be applicable to a large class of RTP 138 applications which use a jitter buffer. 140 Discards due to late or early arriving packets affects user 141 experience. The reporting of discards alerts senders and other 142 receivers to the need to adjust their transmission or reception 143 strategies. The reports allow network managers to diagnose these 144 user experience problems. 146 The ability to detect duplicate packets can be used by managers to 147 detect network layer or sender behavior which may indicate network or 148 device issues. Based on the reports, these issues may be addressed 149 prior to any impact on user experience. 151 2. Terminology 153 2.1. Standards Language 155 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 156 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 157 document are to be interpreted as described in RFC 2119 [RFC2119]. 159 In addition, the following terms are defined: 161 Received, Lost and Discarded 163 A packet shall be regarded as lost if it fails to arrive within an 164 implementation-specific time window. A packet that arrives within 165 this time window but is too early or late to be played out or 166 thrown away before playout due to packet duplication or redundancy 167 shall be regarded as discarded. A packet shall be classified as 168 one of received (or OK), discarded or lost. The Discard Count 169 Metric counts only discarded packets. The metric "cumulative 170 number of packets lost" defined in [RFC3550] reports a count of 171 packets lost from the media stream (single SSRC within single RTP 172 session). Similarly the metric "number of packets discarded" 173 reports a count of packets discarded from the media stream (single 174 SSRC within single RTP session) arriving at the receiver. Another 175 metric defined in [RFC5725] is available to report on packets 176 which are not recovered by any repair techniques which may be in 177 use. 179 3. Discard Count Metric Report Block 181 Metrics in this block report on the number of packets discarded in 182 the stream arriving at the RTP end system. The measurement of these 183 metrics is made at the receiving end of the RTP stream. Instances of 184 this Metrics Block refer by SSRC to the separate auxiliary 185 Measurement Information block [RFC6776] which describes measurement 186 Intervals in use. This Metrics Block relies on the measurement 187 interval in the Measurement Information block indicating the span of 188 the report and MUST be sent in the same compound RTCP packet as the 189 measurement information block. If the measurement interval is not 190 received in the same compound RTCP packet as this Metrics Block, this 191 Metrics Block MUST be discarded. 193 3.1. Report Block Structure 195 0 1 2 3 196 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 1 197 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 198 | BT=PDC | I |DT | resv.| block length = 2 | 199 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 200 | SSRC of Source | 201 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 202 | number of packets discarded | 203 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 205 Figure 1: Report Block Structure 207 3.2. Definition of Fields in Discard Count Metric Report Block 209 Block type (BT): 8 bits 211 A Discard Count Metric Report Block is identified by the constant 212 PDC. 214 [Note to RFC Editor: please replace PDC with the IANA provided 215 RTCP XR block type for this block.] 217 Interval Metric Flag (I): 2 bits 219 This field indicates whether the reported metric is an interval, 220 cumulative, or sampled metric [RFC6792]. The Discard Count Metric 221 can only be measured over definite intervals, and cannot be 222 sampled. Accordingly, the value I=01, indicating a sampled value, 223 MUST NOT be sent, and MUST be discarded when received. In 224 addition, the value I=00 is reserved and also MUST NOT be sent, 225 and MUST be discarded when received. 227 Discard Type (DT): 2bits 229 This field is used to identify the discard type used in this 230 report block. The discard type is defined as follows: 232 00: Report packet discarded or being thrown away before playout 233 due to packets duplication. 235 01: Report packet discarded due to too early to be played out. 237 10: Report packet discarded due to too late to be played out. 239 The value DT=11 is reserved for future definition and MUST NOT be 240 Sent,and MUST be discarded when received. 242 An endpoint MAY report any combination of discard types in each 243 reporting interval by including several Discard Count Metric 244 Report Blocks in a single RTCP XR packet. 246 Some systems send duplicate RTP packets for robustness or error 247 resilience. This is NOT RECOMMENDED since it breaks RTCP packet 248 statistics. If duplication is desired for error resilience, the 249 mechanism described in [RTPDUP] can be used, since this will not 250 cause breakage of RTP streams or RTCP statistics. 252 Reserved (resv): 4 bits 254 These bits are reserved. They MUST be set to zero by senders and 255 ignored by receivers (See RFC6709 section 4.2). 257 block length: 16 bits 259 The length of this report block in 32-bit words, minus one, in 260 accordance with the definition in[RFC3611] . This field MUST be 261 set to 2 to match the fixed length of the report block. The block 262 MUST be discarded if the block length is set to a different value. 264 SSRC of source: 32 bits 266 As defined in Section 4.1 of [RFC3611]. 268 number of packets discarded: 32 bits 270 Number of packets discarded over the period (Interval or 271 Cumulative) covered by this report. 273 The measured value is unsigned value. If the measured value 274 exceeds 0xFFFFFFFD, the value 0xFFFFFFFE MUST be reported to 275 indicate an over-range measurement. If the measurement is 276 unavailable, the value 0xFFFFFFFF MUST be reported. 278 Note that the number of packets expected in the period associated 279 with this metric (whether interval or cumulative) is available 280 from the difference between a pair of extended sequence numbers in 281 the Measurement Information block [RFC6776], so need not be 282 repeated in this block. 284 4. SDP Signaling 286 [RFC3611] defines the use of SDP (Session Description Protocol) 287 [RFC4566] for signaling the use of XR blocks. However XR blocks MAY 288 be used without prior signaling (see section 5 of RFC3611). 290 4.1. SDP rtcp-xr-attrib Attribute Extension 292 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 293 in [RFC3611] by providing an additional value of "xr-format" to 294 signal the use of the report block defined in this document. 296 xr-format =/ xr-pdc-block 298 xr-pdc-block = "pkt-discard-count" 300 4.2. Offer/Answer Usage 302 When SDP is used in offer-answer context, the SDP Offer/Answer usage 303 defined in [RFC3611] for unilateral "rtcp-xr" attribute parameters 304 applies. For detailed usage of Offer/Answer for unilateral 305 parameter, refer to section 5.2 of [RFC3611]. 307 5. IANA Considerations 309 New block types for RTCP XR are subject to IANA registration. For 310 general guidelines on IANA considerations for RTCP XR, refer to 311 [RFC3611]. 313 5.1. New RTCP XR Block Type value 315 This document assigns the block type value PDC in the IANA " RTP 316 Control Protocol Extended Reports (RTCP XR) Block Type Registry " to 317 the "Discard Count Metrics Block". 319 [Note to RFC Editor: please replace PDC with the IANA provided RTCP 320 XR block type for this block.] 322 5.2. New RTCP XR SDP Parameter 324 This document also registers a new parameter "pkt-discard-count" in 325 the " RTP Control Protocol Extended Reports (RTCP XR) Session 326 Description Protocol (SDP) Parameters Registry ". 328 5.3. Contact information for registrations 330 The following contact information is provided for all 331 registrations in this document: 333 Qin Wu (sunseawq@huawei.com) 335 101 Software Avenue, Yuhua District 336 Nanjing, Jiangsu 210012 337 China 339 6. Security Considerations 341 It is believed that this proposed RTCP XR report block introduces no 342 new security considerations beyond those described in [RFC3611]. 343 This block does not provide per-packet statistics so the risk to 344 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 345 does not apply. 347 7. Contributors 349 Geoff Hunt wrote the initial draft of this document. 351 8. Acknowledgments 353 The authors gratefully acknowledge reviews and feedback provided by 354 Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, 355 Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, 356 Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, 357 Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi 358 Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada, Kevin 359 Gross, Varun Singh, Claire Bi, Roni Even, Dan Romascanu and Jonathan 360 Lennox. 362 9. References 364 9.1. Normative References 366 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 367 Requirement Levels", March 1997. 369 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 370 Applications", RFC 3550, July 2003. 372 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 373 Protocol Extended Reports (RTCP XR)", November 2003. 375 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 376 Description Protocol", July 2006. 378 [RFC6709] Carpenter, B., Aboba, B., and S. Cheshire, "Design 379 Considerations for Protocol Extensions", RFC 6709, 380 September 2012. 382 [RFC6776] Hunt, G., "Measurement Identity and information Reporting 383 using SDES item and XR Block", RFC 6776, October 2012. 385 9.2. Informative References 387 [BGDISCARD] 388 Hunt, G., "RTCP XR Report Block for Burst Gap Discard 389 metric Reporting", 390 ID draft-ietf-xrblock-rtcp-xr-burst-gap-discard-11, 391 April 2013. 393 [RFC4588] Rey, J., "RTP Retransmission Payload Format", RFC 4588, 394 July 2006. 396 [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error 397 Correction", RFC 5109, July 2006. 399 [RFC5725] Begen, A., "RTCP XR Report Block for Post-Repair Loss 400 metric Reporting", RFC 5725, February 2010. 402 [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric 403 Development", RFC 6390, October 2011. 405 [RFC6792] Wu, Q., "Monitoring Architectures for RTP", RFC 6792, 406 November 2012. 408 [RTPDUP] Begen, A. and C. Perkins, "Duplicating RTP Streams", 409 ID draft-ietf-avtext-rtp-duplication-02, March 2013. 411 Appendix A. Metrics represented using RFC6390 Template 413 RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC 414 number, when assigned. 416 a. Number of packets discarded Metric 418 * Metric Name: Number of RTP packets discarded Metric 420 * Metric Description: Number of RTP packets discarded over the 421 period covered by this report. 423 * Method of Measurement or Calculation: See section 3.2, number 424 of packets discarded definition [RFCXXXX]. 426 * Units of Measurement: See section 3.2, number of packets 427 discarded definition [RFCXXXX]. 429 * Measurement Point(s) with Potential Measurement Domain: See 430 section 3, 1st paragraph [RFCXXXX]. 432 * Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for 433 measurement timing and section 3.2 [RFCXXXX] for Interval 434 Metric flag. 436 * Use and applications: See section 1.4 [RFCXXXX]. 438 * Reporting model: See RFC3611. 440 Appendix B. Change Log 442 Note to the RFC-Editor: please remove this section prior to 443 publication as an RFC. 445 B.1. draft-ietf-xrblock-rtcp-xr-discard-12 447 The following are the major changes compared to previous version: 449 o Incorporate some changes to burst gap draft that applies to this 450 document. 452 o Use RFC6390 template to the metrics in the appendix. 454 B.2. draft-ietf-xrblock-rtcp-xr-discard-11 456 The following are the major changes compared to previous version: 458 o Editorial change t based on SDP Directorate and Colin's Review. 460 B.3. draft-ietf-xrblock-rtcp-xr-discard-10 462 The following are the major changes compared to previous version: 464 o Editorial change to get in line with recently discussed drafts. 466 o Remove DT=3 based on the discussion to summary statistics draft. 468 B.4. draft-ietf-xrblock-rtcp-xr-discard-09 470 The following are the major changes compared to previous version: 472 o SDP Duplicated Parameter Deleting. 474 B.5. draft-ietf-xrblock-rtcp-xr-discard-08 476 The following are the major changes compared to previous version: 478 o Outdated reference update. 480 o Editorial changes based on comments that applied to PDV and Delay 481 drafts. 483 Authors' Addresses 485 Alan Clark 486 Telchemy Incorporated 487 2905 Premiere Parkway, Suite 280 488 Duluth, GA 30097 489 USA 491 Email: alan.d.clark@telchemy.com 493 Glen Zorn 494 Network Zen 495 77/440 Soi Phoomjit, Rama IV Road 496 Phra Khanong, Khlong Toie 497 Bangkok 10110 498 Thailand 500 Phone: +66 (0) 87 502 4274 501 Email: gwz@net-zen.net 503 Qin Wu 504 Huawei 505 101 Software Avenue, Yuhua District 506 Nanjing, Jiangsu 210012 507 China 509 Email: sunseawq@huawei.com