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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) == Missing Reference: 'RFCXXXX' is mentioned on line 445, but not defined ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) == Outdated reference: A later version (-09) exists of draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-06 == Outdated reference: A later version (-16) exists of draft-ietf-avt-srtp-not-mandatory-13 == Outdated reference: A later version (-10) exists of draft-ietf-avtcore-rtp-security-options-04 Summary: 1 error (**), 0 flaws (~~), 5 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 XR Block Working Group V. Singh, Ed. 3 Internet-Draft J. Ott 4 Intended status: Standards Track Aalto University 5 Expires: May 08, 2014 I. Curcio 6 Nokia Research Center 7 November 04, 2013 9 RTP Control Protocol (RTCP) Extended Report (XR) for Bytes Discarded 10 Metric 11 draft-ietf-xrblock-rtcp-xr-bytes-discarded-metric-01 13 Abstract 15 The RTP Control Protocol (RTCP) is used in conjunction with the Real- 16 time Transport Protocol (RTP) in to provide a variety of short-term 17 and long-term reception statistics. The available reporting may 18 include aggregate information across longer periods of time as well 19 as individual packet reporting. This document specifies a report 20 computing the bytes discarded from the de-jitter buffer after 21 successful reception. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on May 08, 2014. 40 Copyright Notice 42 Copyright (c) 2013 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 58 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 3. XR Bytes Discarded Report Block . . . . . . . . . . . . . . . 4 60 4. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 5 61 4.1. Reporting Node (Receiver) . . . . . . . . . . . . . . . . 5 62 4.2. Media Sender . . . . . . . . . . . . . . . . . . . . . . 6 63 5. SDP signaling . . . . . . . . . . . . . . . . . . . . . . . . 6 64 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 65 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 66 7.1. XR Report Block Registration . . . . . . . . . . . . . . 7 67 7.2. SDP Parameter Registration . . . . . . . . . . . . . . . 7 68 7.3. Contact information for IANA registrations . . . . . . . 8 69 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 70 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 71 9.1. Normative References . . . . . . . . . . . . . . . . . . 8 72 9.2. Informative References . . . . . . . . . . . . . . . . . 9 73 Appendix A. Metrics represented using RFC6390 Template . . . . . 9 74 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 10 75 B.1. changes in draft-singh-xrblock-rtcp-xr-bytes- 76 discarded-metric-00 . . . . . . . . . . . . . . . . . . . 10 77 B.2. changes in draft-ietf-xrblock-rtcp-xr-bytes- 78 discarded-metric-00 . . . . . . . . . . . . . . . . . . . 10 79 B.3. changes in draft-ietf-xrblock-rtcp-xr-bytes- 80 discarded-metric-01 . . . . . . . . . . . . . . . . . . . 10 81 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 83 1. Introduction 85 RTP [RFC3550] provides a transport for real-time media flows such as 86 audio and video together with the RTP control protocol (RTCP) which 87 provides periodic feedback about the media streams received in a 88 specific duration. In addition, RTCP can be used for timely feedback 89 about individual events to report (e.g., packet loss) [RFC4585]. 90 Both long-term and short-term feedback enable a media sender to adapt 91 its media transmission and/or encoding dynamically to the observed 92 path characteristics. 94 RFC3611 [RFC3611] defines RTCP Extended Reports as a detailed 95 reporting framework to provide more than just the coarse Receiver 96 Report (RR) statistics. The detailed reporting may enable a media 97 sender to react more appropriately to the observed networking 98 conditions as these can be characterized better, although at the 99 expense of extra overhead. 101 In addition to lost packets, RFC3611 defines the notion of 102 "discarded" packets: packets that were received but dropped from the 103 de-jitter buffer because they were either too early (for buffering) 104 or too late (for playout). The "discard rate" metric is part of the 105 VoIP metrics report block even though it is not just applicable to 106 audio: it is specified as the fraction of discarded packets since the 107 beginning of the session. See section 4.7.1 of RFC3611 [RFC3611]. 108 The discard metric is believed to be applicable to a large class of 109 RTP applications which use a de-jitter buffer RFC5481 [RFC5481]. 111 Recently proposed extensions to the Extended Reports (XR) reporting 112 suggest enhancing this discard metric: 114 o Reporting the number of discarded packets in a measurement 115 interval, i.e., during either the last reporting interval or since 116 the beginning of the session, as indicated by a flag in the 117 suggested XR report [RFC7002]. If an endpoint needs to report 118 packet discard due to other reasons than early- and late-arrival 119 (for example, discard due to duplication, redundancy, etc.) then 120 it should consider using the Discarded Packets Report Block 121 [RFC7002]. 123 o Reporting gaps and bursts of discarded packets during a 124 measurement interval, i.e., the last reporting interval or the 125 duration of the session [RFC7003]. 127 o Reporting run-length encoding of discarded packet during a 128 measurement interval, i.e., between a set of sequence numbers 129 [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics]. 131 However, none of these metrics allow a receiver to report precisely 132 the number of RTP payload bytes that were discarded. While this 133 information could in theory be derived from high-frequency reporting 134 on the number of discarded packets [RFC7002] or from the Discard RLE 135 report [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics], these two 136 mechanisms do not appear feasible: The former would require an unduly 137 high amount of reporting which still might not be sufficient due to 138 the non-deterministic scheduling of RTCP packets. The latter incurs 139 significant complexity (by storing a map of sequence numbers and 140 packet sizes) and reporting overhead. 142 An XR block is defined in this document to indicate the number of RTP 143 payload bytes discarded, per interval or for the duration of the 144 session, similar to other XR report blocks. 146 2. Terminology 148 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 149 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 150 document are to be interpreted as described in BCP 14, RFC 2119 151 [RFC2119]. 153 The terminology defined in RTP [RFC3550] and in the extensions for XR 154 reporting [RFC3611] applies. 156 3. XR Bytes Discarded Report Block 158 The XR Bytes Discarded report block uses the following format which 159 follows the model of the framework for performance metric development 160 [RFC6390]. 162 0 1 2 3 163 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 7 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | BT=BDR | I |E|reserved | block length=2 | 166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 167 | SSRC of source | 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 | number of RTP payload bytes discarded | 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 172 Figure 1: XR Bytes Discarded Report Block 174 Block Type (BT, 8 bits): A Bytes Discarded Packets Report Block is 175 identified by the constant BDR. 177 [Note to RFC Editor: please replace BDR with the IANA provided RTCP 178 XR block type for this block. Please remove this note prior to 179 publication as an RFC.] 181 The Interval Metric flag (I) (2 bits) is used to indicate whether the 182 discard metric is Interval, or a Cumulative metric, that is, whether 183 the reported value applies to the most recent measurement interval 184 duration between successive reports (I=10, the Interval Duration) or 185 to the accumulation period characteristic of cumulative measurements 186 (I=11, the Cumulative Duration). Since the bytes discarded are not 187 measured at a particular time instance but over one or several 188 reporting intervals, the metric MUST NOT be reported as a Sampled 189 Metric (I=01). In addition, the value I=00 is reserved and MUST NOT 190 be sent, and MUST be discarded when received. 192 The 'E' bit is introduced to distinguish between packets discarded 193 due to early arrival and those discarded due to late arrival. The 194 'E' bit is set to '1' if it reports bytes discarded due to early 195 arrival and is set to '0' if it reports bytes discarded due to late 196 arrival. If a duplicate packet is received and discarded, these 197 duplicate packets are ignored and not reported. In case both early 198 and late discarded packets shall be reported, two Bytes Discarded 199 report blocks MUST be included. 201 reserved (5 bits): This field is reserved for future definition. In 202 the absence of such definition, the bits in this field MUST be set to 203 zero and MUST be ignored by the receiver. 205 block length (16 bits) MUST be set to 2, in accordance with the 206 definition of this field in [RFC3611]. The block MUST be discarded 207 if the block length is set to a different value. 209 The 'number of RTP payload bytes discarded' is a 32-bit unsigned 210 integer value indicating the total number of bytes discarded. Bytes 211 discarded corresponds to the RTP payload size of every RTP packet 212 that is discarded (due to early or late arrival). Hence, the bytes 213 discarded ignores the size of any RTP header extensions and the size 214 of the padding bits. Also the discarded packet is associated to the 215 interval in which it was discarded and not when it was expected. 217 If Interval Metric flag (I=11) is set, the value in the field 218 indicates the number of RTP payload bytes discarded from the start of 219 the session, if Interval Metric flag (I=01) is set, it indicates the 220 number of bytes discarded since the last RTCP XR Byte Discarded Block 221 was received. 223 If the XR block follows a measurement identity block [RFC6776] in the 224 same RTCP compound packet then the cumulative (I=11) or the interval 225 (I=10) for this report block corresponds to the values of the 226 "measurement duration" in the measurement information block. 228 If the receiver sends the Bytes Discarded Report Block without the 229 measurement identity block then the discard block MUST be sent in 230 conjunction with an RTCP Receiver Report (RR) as a compound RTCP 231 packet. 233 4. Protocol Operation 235 This section describes the behavior of the reporting node (= media 236 receiver) and the media sender. 238 4.1. Reporting Node (Receiver) 240 Transmission of RTCP XR Bytes Discarded Report is up to the 241 discretion of the media receiver, as is the reporting granularity. 243 However, it is RECOMMENDED that the media receiver signals all 244 discarded packets using the method defined in this document. If all 245 packets over a reporting period were discarded, the media receiver 246 MAY use the Discard Report Block [RFC7002] instead. 248 The media receiver MAY send the Bytes Discard Reports as part of the 249 regularly scheduled RTCP packets as per RFC3550. It MAY also include 250 Bytes Discard Reports in immediate or early feedback packets as per 251 RFC4585. 253 4.2. Media Sender 255 The media sender MUST be prepared to operate without receiving any 256 Bytes Discarded reports. If Bytes Discarded reports are generated by 257 the media receiver, the media sender cannot rely on all these reports 258 being received, nor can the media sender rely on a regular generation 259 pattern from the media receiver. 261 However, if the media sender receives any RTCP reports but no Bytes 262 Discard report blocks and is aware that the media receiver supports 263 Bytes Discard report blocks, it MAY assume that no packets were 264 discarded at the media receiver. 266 The media sender SHOULD accept the Bytes Discarded Report Block only 267 if it is received in a compound RTCP receiver report or if it is 268 preceded by a measurement identity block [RFC6776]. Under all other 269 circumstances it MUST ignore the block. 271 5. SDP signaling 273 A participant of a media session MAY use SDP to signal its support 274 for the report block specified in this document or use them without 275 any prior signaling (see section 5 of [RFC3611]). 277 For signaling in SDP, the RTCP XR attribute as defined in [RFC3611] 278 MUST be used. The SDP [RFC4566] attribute 'xr-format' defined in 279 RFC3611 is augmented as described in the following to indicate the 280 bytes discarded metric. 282 rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] 283 CRLF ; defined in [RFC3611] 285 xr-format =/ xr-discard-bytes 287 xr-discard-bytes = "discard-bytes" 289 The parameter 'discard-bytes' to indicate support for the Bytes 290 Discarded Report Block defined in Section 3. 292 When SDP is used in Offer/Answer context, the mechanism defined in 293 [RFC3611] for unilateral "rtcp-xr" attribute parameters applies (see 294 section 5.2 of [RFC3611]). 296 6. Security Considerations 298 The Bytes Discarded block does not provide per-packet statistics, 299 hence the risk to confidentiality documented in Section 7, paragraph 300 3 of [RFC3611] does not apply. In some situations, returning very 301 detailed error information (e.g., over-range measurement or 302 measurement unavailable) using this report block can provide an 303 attacker with insight into the security processing. Implementers 304 should consider the guidance in [I-D.ietf-avt-srtp-not-mandatory] for 305 using appropriate security mechanisms, i.e., where security is a 306 concern, the implementation should apply encryption and 307 authentication to the report block. For example this can be achieved 308 by using the AVPF profile together with the Secure RTP profile as 309 defined in [RFC3711]; an appropriate combination of the two profiles 310 (an "SAVPF") is specified in [RFC5124]. However, other mechanisms 311 also exist (documented in [I-D.ietf-avtcore-rtp-security-options]) 312 and might be more suitable. 314 Additionally, The security considerations of [RFC3550], [RFC3611], 315 and [RFC4585] apply. 317 7. IANA Considerations 319 New block types for RTCP XR are subject to IANA registration. For 320 general guidelines on IANA considerations for RTCP XR, refer to 321 [RFC3611]. 323 7.1. XR Report Block Registration 325 This document extends the IANA "RTP Control Protocol Extended Reports 326 (RTCP XR) Block Type Registry" by a new value: BDR (Bytes Discarded 327 Report). 329 [Note to RFC Editor: please replace BDR with the IANA provided RTCP 330 XR block type for this block here and in the diagrams above. Please 331 remove this note prior to publication as an RFC.] 333 7.2. SDP Parameter Registration 335 This document registers a new parameters for the Session Description 336 Protocol (SDP), "discard-bytes" in the "RTP Control Protocol Extended 337 Reports (RTCP XR) Session Description Protocol (SDP) Parameters 338 Registry". 340 7.3. Contact information for IANA registrations 342 Varun Singh (varun.singh@iki.fi) 344 Aalto University Comnet, Otakaari 5A, 02150 Espoo, Finland. 346 8. Acknowledgments 348 The authors would like to thank Alan Clark, Roni Even, Sam Hartman, 349 Colin Perkins, Dan Romascanu, Dan Wing, and Qin Wu for providing 350 valuable feedback on earlier versions of this draft. 352 9. References 354 9.1. Normative References 356 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 357 Requirement Levels", BCP 14, RFC 2119, March 1997. 359 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 360 Jacobson, "RTP: A Transport Protocol for Real-Time 361 Applications", STD 64, RFC 3550, July 2003. 363 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 364 Protocol Extended Reports (RTCP XR)", RFC 3611, November 365 2003. 367 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 368 "Extended RTP Profile for Real-time Transport Control 369 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July 370 2006. 372 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 373 Description Protocol", RFC 4566, July 2006. 375 [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New 376 Performance Metric Development", BCP 170, RFC 6390, 377 October 2011. 379 [RFC6776] Clark, A. and Q. Wu, "Measurement Identity and Information 380 Reporting Using a Source Description (SDES) Item and an 381 RTCP Extended Report (XR) Block", RFC 6776, October 2012. 383 [RFC7002] Clark, A., Zorn, G., and Q. Wu, "RTP Control Protocol 384 (RTCP) Extended Report (XR) Block for Discard Count Metric 385 Reporting", RFC 7002, September 2013. 387 9.2. Informative References 389 [RFC7003] Clark, A., Huang, R., and Q. Wu, "RTP Control Protocol 390 (RTCP) Extended Report (XR) Block for Burst/Gap Discard 391 Metric Reporting", RFC 7003, September 2013. 393 [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics] 394 Ott, J., Singh, V., and I. Curcio, "RTP Control Protocol 395 (RTCP) Extended Reports (XR) for Run Length Encoding (RLE) 396 of Discarded Packets", draft-ietf-xrblock-rtcp-xr-discard- 397 rle-metrics-06 (work in progress), July 2013. 399 [RFC5481] Morton, A. and B. Claise, "Packet Delay Variation 400 Applicability Statement", RFC 5481, March 2009. 402 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 403 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 404 RFC 3711, March 2004. 406 [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for 407 Real-time Transport Control Protocol (RTCP)-Based Feedback 408 (RTP/SAVPF)", RFC 5124, February 2008. 410 [I-D.ietf-avt-srtp-not-mandatory] 411 Perkins, C. and M. Westerlund, "Securing the RTP Protocol 412 Framework: Why RTP Does Not Mandate a Single Media 413 Security Solution", draft-ietf-avt-srtp-not-mandatory-13 414 (work in progress), May 2013. 416 [I-D.ietf-avtcore-rtp-security-options] 417 Westerlund, M. and C. Perkins, "Options for Securing RTP 418 Sessions", draft-ietf-avtcore-rtp-security-options-04 419 (work in progress), July 2013. 421 Appendix A. Metrics represented using RFC6390 Template 423 RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC 424 number, when assigned. 426 a. RTP Payload Bytes Discarded Metric 428 * Metric Name: RTP Payload Bytes Discarded Metric 429 * Metric Description: Total number of RTP Payload bytes 430 discarded over the period covered by this report. 432 * Method of Measurement or Calculation: See section 4, number of 433 bytes discarded definition in [RFCXXXX]. 435 * Units of Measurement: See section 4, number of RTP payload 436 bytes discarded definition in [RFCXXXX]. 438 * Measurement Point(s) with Potential Measurement Domain: See 439 section 4, 1st paragraph of [RFCXXXX]. 441 * Measurement Timing: See section 4, last three paragraphs of 442 [RFCXXXX] for measurement timing and for the Interval Metric 443 flag. 445 * Use and applications: See section 1, paragraph 1 of [RFCXXXX]. 447 * Reporting model: See RFC3611. 449 Appendix B. Change Log 451 Note to the RFC-Editor: please remove this section prior to 452 publication as an RFC. 454 B.1. changes in draft-singh-xrblock-rtcp-xr-bytes-discarded-metric-00 456 o Bytes discarded metric split from 457 [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics]. 459 B.2. changes in draft-ietf-xrblock-rtcp-xr-bytes-discarded-metric-00 461 o Submitted as a WG draft. 463 B.3. changes in draft-ietf-xrblock-rtcp-xr-bytes-discarded-metric-01 465 o Editorial fixes: Updated references from drafts to RFCs. 467 o Updated fields in the RFC6390 template. 469 o Changed 'number of bytes discarded' to 'number of RTP payload 470 bytes discarded'. 472 Authors' Addresses 474 Varun Singh (editor) 475 Aalto University 476 School of Electrical Engineering 477 Otakaari 5 A 478 Espoo, FIN 02150 479 Finland 481 Email: varun@comnet.tkk.fi 482 URI: http://www.netlab.tkk.fi/~varun/ 484 Joerg Ott 485 Aalto University 486 School of Electrical Engineering 487 Otakaari 5 A 488 Espoo, FIN 02150 489 Finland 491 Email: jo@comnet.tkk.fi 493 Igor D.D. Curcio 494 Nokia Research Center 495 P.O. Box 1000 (Visiokatu 3) 496 Tampere, FIN 33721 497 Finland 499 Email: igor.curcio@nokia.com