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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is mentioned on line 448, but not defined ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) == Outdated reference: A later version (-09) exists of draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-06 == Outdated reference: A later version (-16) exists of draft-ietf-avt-srtp-not-mandatory-13 == Outdated reference: A later version (-10) exists of draft-ietf-avtcore-rtp-security-options-04 Summary: 1 error (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).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: February 02, 2014 I. Curcio 6 Nokia Research Center 7 August 01, 2013 9 RTP Control Protocol (RTCP) Extended Reports (XR) for Bytes Discarded 10 Metric 11 draft-singh-xrblock-rtcp-xr-bytes-discarded-metric-00 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 February 02, 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 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 79 1. Introduction 81 RTP [RFC3550] provides a transport for real-time media flows such as 82 audio and video together with the RTP control protocol (RTCP) which 83 provides periodic feedback about the media streams received in a 84 specific duration. In addition, RTCP can be used for timely feedback 85 about individual events to report (e.g., packet loss) [RFC4585]. 86 Both long-term and short-term feedback enable a media sender to adapt 87 its media transmission and/or encoding dynamically to the observed 88 path characteristics. 90 RFC3611 [RFC3611] defines RTCP Extended Reports as a detailed 91 reporting framework to provide more than just the coarse Receiver 92 Report (RR) statistics. The detailed reporting may enable a media 93 sender to react more appropriately to the observed networking 94 conditions as these can be characterized better, although at the 95 expense of extra overhead. 97 In addition to lost packets, RFC3611 defines the notion of 98 "discarded" packets: packets that were received but dropped from the 99 de-jitter buffer because they were either too early (for buffering) 100 or too late (for playout). The "discard rate" metric is part of the 101 VoIP metrics report block even though it is not just applicable to 102 audio: it is specified as the fraction of discarded packets since the 103 beginning of the session. See section 4.7.1 of RFC3611 [RFC3611]. 104 The discard metric is believed to be applicable to a large class of 105 RTP applications which use a de-jitter buffer RFC5481 [RFC5481]. 107 Recently proposed extensions to the Extended Reports (XR) reporting 108 suggest enhancing this discard metric: 110 o Reporting the number of discarded packets in a measurement 111 interval, i.e., during either the last reporting interval or since 112 the beginning of the session, as indicated by a flag in the 113 suggested XR report [I-D.ietf-xrblock-rtcp-xr-discard]. If an 114 endpoint needs to report packet discard due to other reasons than 115 early- and late-arrival (for example, discard due to duplication, 116 redundancy, etc.) then it should consider using the Discarded 117 Packets Report Block [I-D.ietf-xrblock-rtcp-xr-discard]. 119 o Reporting gaps and bursts of discarded packets during a 120 measurement interval, i.e., the last reporting interval or the 121 duration of the session 122 [I-D.ietf-xrblock-rtcp-xr-burst-gap-discard]. 124 o Reporting run-length encoding of discarded packet during a 125 measurement interval, i.e., between a set of sequence numbers 126 [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics]. 128 However, none of these metrics allow a receiver to report precisely 129 the number of bytes that were discarded. While this information 130 could in theory be derived from high-frequency reporting on the 131 number of discarded packets [I-D.ietf-xrblock-rtcp-xr-discard] or 132 from the Discard RLE report 133 [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics], these two mechanisms 134 do not appear feasible: The former would require an unduly high 135 amount of reporting which still might not be sufficient due to the 136 non-deterministic scheduling of RTCP packets. The latter incurs 137 significant complexity (by storing a map of sequence numbers and 138 packet sizes) and reporting overhead. 140 An XR block is defined in this document to indicate the number of 141 bytes discarded, per interval or for the duration of the session, 142 similar to other XR report blocks. 144 2. Terminology 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 BCP 14, RFC 2119 149 [RFC2119]. 151 The terminology defined in RTP [RFC3550] and in the extensions for XR 152 reporting [RFC3611] applies. 154 3. XR Bytes Discarded Report Block 156 The XR Bytes Discarded report block uses the following format which 157 follows the model of the framework for performance metric development 158 [RFC6390]. 160 0 1 2 3 161 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 7 162 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 163 | BT=BDR | I |E|reserved | block length=2 | 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | SSRC of source | 166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 167 | number of bytes discarded | 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 170 Figure 1: XR Bytes Discarded Report Block 172 Block Type (BT, 8 bits): A Bytes Discarded Packets Report Block is 173 identified by the constant BDR. 175 [Note to RFC Editor: please replace BDR with the IANA provided RTCP 176 XR block type for this block. Please remove this note prior to 177 publication as an RFC.] 179 The Interval Metric flag (I) (2 bits) is used to indicate whether the 180 discard metric is Interval, or a Cumulative metric, that is, whether 181 the reported value applies to the most recent measurement interval 182 duration between successive reports (I=10, the Interval Duration) or 183 to the accumulation period characteristic of cumulative measurements 184 (I=11, the Cumulative Duration). Since the bytes discarded are not 185 measured at a particular time instance but over one or several 186 reporting intervals, the metric MUST NOT be reported as a Sampled 187 Metric (I=01). In addition, the value I=00 is reserved and MUST NOT 188 be sent, and MUST be discarded when received. 190 The 'E' bit is introduced to distinguish between packets discarded 191 due to early arrival and those discarded due to late arrival. The 192 'E' bit is set to '1' if it reports bytes discarded due to early 193 arrival and is set to '0' if it reports bytes discarded due to late 194 arrival. If a duplicate packet is received and discarded, these 195 duplicate packets are ignored and not reported. In case both early 196 and late discarded packets shall be reported, two Bytes Discarded 197 report blocks MUST be included. 199 reserved (5 bits): This field is reserved for future definition. In 200 the absence of such definition, the bits in this field MUST be set to 201 zero and MUST be ignored by the receiver. 203 block length (16 bits) MUST be set to 2, in accordance with the 204 definition of this field in [RFC3611]. The block MUST be discarded 205 if the block length is set to a different value. 207 The 'number of bytes discarded' is a 32-bit unsigned integer value 208 indicating the total number of bytes discarded. Bytes discarded 209 corresponds to the RTP payload size of every RTP packet that is 210 discarded (due to early or late arrival). Hence, the bytes discarded 211 ignores the size of any RTP header extensions and the size of the 212 padding bits. Also the discarded packet is associated to the 213 interval in which it was discarded and not when it was expected. 215 If Interval Metric flag (I=11) is set, the value in the field 216 indicates the number of bytes discarded from the start of the 217 session, if Interval Metric flag (I=01) is set, it indicates the 218 number of bytes discarded since the last RTCP XR Byte Discarded Block 219 was received. 221 If the XR block follows a measurement identity block [RFC6776] in the 222 same RTCP compound packet then the cumulative (I=11) or the interval 223 (I=10) for this report block corresponds to the values of the 224 "measurement duration" in the measurement information block. 226 If the receiver sends the Bytes Discarded Report Block without the 227 measurement identity block then the discard block MUST be sent in 228 conjunction with an RTCP Receiver Report (RR) as a compound RTCP 229 packet. 231 4. Protocol Operation 233 This section describes the behavior of the reporting node (= media 234 receiver) and the media sender. 236 4.1. Reporting Node (Receiver) 238 Transmission of RTCP XR Bytes Discarded Report is up to the 239 discretion of the media receiver, as is the reporting granularity. 241 However, it is RECOMMENDED that the media receiver signals all 242 discarded packets using the method defined in this document. If all 243 packets over a reporting period were discarded, the media receiver 244 MAY use the Discard Report Block [I-D.ietf-xrblock-rtcp-xr-discard] 245 instead. 247 The media receiver MAY send the Bytes Discard Reports as part of the 248 regularly scheduled RTCP packets as per RFC3550. It MAY also include 249 Bytes Discard Reports in immediate or early feedback packets as per 250 RFC4585. 252 4.2. Media Sender 254 The media sender MUST be prepared to operate without receiving any 255 Bytes Discarded reports. If Bytes Discarded reports are generated by 256 the media receiver, the media sender cannot rely on all these reports 257 being received, nor can the media sender rely on a regular generation 258 pattern from the media receiver. 260 However, if the media sender receives any RTCP reports but no Bytes 261 Discard report blocks and is aware that the media receiver supports 262 Bytes Discard report blocks, it MAY assume that no packets were 263 discarded at the media receiver. 265 The media sender SHOULD accept the Bytes Discarded Report Block only 266 if it is received in a compound RTCP receiver report or if it is 267 preceded by a measurement identity block [RFC6776]. Under all other 268 circumstances it MUST ignore the block. 270 5. SDP signaling 272 A participant of a media session MAY use SDP to signal its support 273 for the report block specified in this document or use them without 274 any prior signaling (see section 5 of [RFC3611]). 276 For signaling in SDP, the RTCP XR attribute as defined in [RFC3611] 277 MUST be used. The SDP [RFC4566] attribute 'xr-format' defined in 278 RFC3611 is augmented as described in the following to indicate the 279 bytes discarded metric. 281 rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] 282 CRLF ; defined in [RFC3611] 284 xr-format =/ xr-discard-bytes 286 xr-discard-bytes = "discard-bytes" 288 The parameter 'discard-bytes' to indicate support for the Bytes 289 Discarded Report Block defined in Section 3. 291 When SDP is used in Offer/Answer context, the mechanism defined in 292 [RFC3611] for unilateral "rtcp-xr" attribute parameters applies (see 293 section 5.2 of [RFC3611]). 295 6. Security Considerations 297 The Bytes Discarded block does not provide per-packet statistics, 298 hence the risk to confidentiality documented in Section 7, paragraph 299 3 of [RFC3611] does not apply. In some situations, returning very 300 detailed error information (e.g., over-range measurement or 301 measurement unavailable) using this report block can provide an 302 attacker with insight into the security processing. Implementers 303 should consider the guidance in [I-D.ietf-avt-srtp-not-mandatory] for 304 using appropriate security mechanisms, i.e., where security is a 305 concern, the implementation should apply encryption and 306 authentication to the report block. For example this can be achieved 307 by using the AVPF profile together with the Secure RTP profile as 308 defined in [RFC3711]; an appropriate combination of the two profiles 309 (an "SAVPF") is specified in [RFC5124]. However, other mechanisms 310 also exist (documented in [I-D.ietf-avtcore-rtp-security-options]) 311 and might be more suitable. 313 Additionally, The security considerations of [RFC3550], [RFC3611], 314 and [RFC4585] apply. 316 7. IANA Considerations 318 New block types for RTCP XR are subject to IANA registration. For 319 general guidelines on IANA considerations for RTCP XR, refer to 320 [RFC3611]. 322 7.1. XR Report Block Registration 324 This document extends the IANA "RTP Control Protocol Extended Reports 325 (RTCP XR) Block Type Registry" by a new value: BDR (Bytes Discarded 326 Report). 328 [Note to RFC Editor: please replace BDR with the IANA provided RTCP 329 XR block type for this block here and in the diagrams above. Please 330 remove this note prior to publication as an RFC.] 332 7.2. SDP Parameter Registration 334 This document registers a new parameters for the Session Description 335 Protocol (SDP), "discard-bytes" in the "RTP Control Protocol Extended 336 Reports (RTCP XR) Session Description Protocol (SDP) Parameters 337 Registry". 339 7.3. Contact information for IANA registrations 341 Varun Singh (varun.singh@iki.fi) 343 Aalto University Comnet, Otakaari 5A, 02150 Espoo, Finland. 345 8. Acknowledgments 347 The authors would like to thank Alan Clark, Roni Even, Sam Hartman, 348 Colin Perkins, Dan Romascanu, Dan Wing, and Qin Wu for providing 349 valuable feedback on earlier versions of this draft. 351 9. References 353 9.1. Normative References 355 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 356 Requirement Levels", BCP 14, RFC 2119, March 1997. 358 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 359 Jacobson, "RTP: A Transport Protocol for Real-Time 360 Applications", STD 64, RFC 3550, July 2003. 362 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 363 Protocol Extended Reports (RTCP XR)", RFC 3611, November 364 2003. 366 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 367 "Extended RTP Profile for Real-time Transport Control 368 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July 369 2006. 371 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 372 Description Protocol", RFC 4566, July 2006. 374 [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New 375 Performance Metric Development", BCP 170, RFC 6390, 376 October 2011. 378 [RFC6776] Clark, A. and Q. Wu, "Measurement Identity and Information 379 Reporting Using a Source Description (SDES) Item and an 380 RTCP Extended Report (XR) Block", RFC 6776, October 2012. 382 [I-D.ietf-xrblock-rtcp-xr-discard] 383 Clark, A., Zorn, G., and W. Wu, "RTP Control Protocol 384 (RTCP) Extended Report (XR) Block for Discard Count metric 385 Reporting", draft-ietf-xrblock-rtcp-xr-discard-15 (work in 386 progress), June 2013. 388 9.2. Informative References 390 [I-D.ietf-xrblock-rtcp-xr-burst-gap-discard] 391 Clark, A., Huang, R., and W. Wu, "RTP Control 392 Protocol(RTCP) Extended Report (XR) Block for Burst/Gap 393 Discard metric Reporting", draft-ietf-xrblock-rtcp-xr- 394 burst-gap-discard-14 (work in progress), April 2013. 396 [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics] 397 Ott, J., Singh, V., and I. Curcio, "RTP Control Protocol 398 (RTCP) Extended Reports (XR) for Run Length Encoding (RLE) 399 of Discarded Packets", draft-ietf-xrblock-rtcp-xr-discard- 400 rle-metrics-06 (work in progress), July 2013. 402 [RFC5481] Morton, A. and B. Claise, "Packet Delay Variation 403 Applicability Statement", RFC 5481, March 2009. 405 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 406 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 407 RFC 3711, March 2004. 409 [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for 410 Real-time Transport Control Protocol (RTCP)-Based Feedback 411 (RTP/SAVPF)", RFC 5124, February 2008. 413 [I-D.ietf-avt-srtp-not-mandatory] 414 Perkins, C. and M. Westerlund, "Securing the RTP Protocol 415 Framework: Why RTP Does Not Mandate a Single Media 416 Security Solution", draft-ietf-avt-srtp-not-mandatory-13 417 (work in progress), May 2013. 419 [I-D.ietf-avtcore-rtp-security-options] 420 Westerlund, M. and C. Perkins, "Options for Securing RTP 421 Sessions", draft-ietf-avtcore-rtp-security-options-04 422 (work in progress), July 2013. 424 Appendix A. Metrics represented using RFC6390 Template 426 RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC 427 number, when assigned. 429 a. Bytes Discarded Metric 430 * Metric Name: Bytes Discarded Metric 432 * Metric Description: Total number of bytes discarded over the 433 period covered by this report. 435 * Method of Measurement or Calculation: See section 4, number of 436 bytes discarded definition [RFCXXXX]. 438 * Units of Measurement: See section 4, number of bytes discarded 439 definition [RFCXXXX]. 441 * Measurement Point(s) with Potential Measurement Domain: See 442 section 4, 1st paragraph [RFCXXXX]. 444 * Measurement Timing: See section 4, last three paragraphs of 445 [RFCXXXX] for measurement timing and for the Interval Metric 446 flag. 448 * Use and applications: See section 1, paragraph 1 of [RFCXXXX]. 450 * Reporting model: See RFC3611. 452 Appendix B. Change Log 454 Note to the RFC-Editor: please remove this section prior to 455 publication as an RFC. 457 B.1. changes in draft-singh-xrblock-rtcp-xr-bytes-discarded-metric-00 459 o Bytes discarded metric split from 460 [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics]. 462 Authors' Addresses 464 Varun Singh (editor) 465 Aalto University 466 School of Electrical Engineering 467 Otakaari 5 A 468 Espoo, FIN 02150 469 Finland 471 Email: varun@comnet.tkk.fi 472 URI: http://www.netlab.tkk.fi/~varun/ 473 Joerg Ott 474 Aalto University 475 School of Electrical Engineering 476 Otakaari 5 A 477 Espoo, FIN 02150 478 Finland 480 Email: jo@comnet.tkk.fi 482 Igor D.D. Curcio 483 Nokia Research Center 484 P.O. Box 1000 (Visiokatu 3) 485 Tampere, FIN 33721 486 Finland 488 Email: igor.curcio@nokia.com