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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is mentioned on line 448, but not defined ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) == Outdated reference: A later version (-09) exists of draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-06 == Outdated reference: A later version (-16) exists of draft-ietf-avt-srtp-not-mandatory-13 == Outdated reference: A later version (-10) exists of draft-ietf-avtcore-rtp-security-options-04 Summary: 1 error (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).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: April 04, 2014 I. Curcio 6 Nokia Research Center 7 October 01, 2013 9 RTP Control Protocol (RTCP) Extended Report (XR) for Bytes Discarded 10 Metric 11 draft-ietf-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 April 04, 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 . . . . . . . . . . . . . . . . . . . . . 6 61 4.1. Reporting Node (Receiver) . . . . . . . . . . . . . . . . 6 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 . . . . . . . . . . . . . . 8 67 7.2. SDP Parameter Registration . . . . . . . . . . . . . . . 8 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 . . . . . 10 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 . . . . . . . . . . . . . . . . . . . 11 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 81 1. Introduction 83 RTP [RFC3550] provides a transport for real-time media flows such as 84 audio and video together with the RTP control protocol (RTCP) which 85 provides periodic feedback about the media streams received in a 86 specific duration. In addition, RTCP can be used for timely feedback 87 about individual events to report (e.g., packet loss) [RFC4585]. 88 Both long-term and short-term feedback enable a media sender to adapt 89 its media transmission and/or encoding dynamically to the observed 90 path characteristics. 92 RFC3611 [RFC3611] defines RTCP Extended Reports as a detailed 93 reporting framework to provide more than just the coarse Receiver 94 Report (RR) statistics. The detailed reporting may enable a media 95 sender to react more appropriately to the observed networking 96 conditions as these can be characterized better, although at the 97 expense of extra overhead. 99 In addition to lost packets, RFC3611 defines the notion of 100 "discarded" packets: packets that were received but dropped from the 101 de-jitter buffer because they were either too early (for buffering) 102 or too late (for playout). The "discard rate" metric is part of the 103 VoIP metrics report block even though it is not just applicable to 104 audio: it is specified as the fraction of discarded packets since the 105 beginning of the session. See section 4.7.1 of RFC3611 [RFC3611]. 106 The discard metric is believed to be applicable to a large class of 107 RTP applications which use a de-jitter buffer RFC5481 [RFC5481]. 109 Recently proposed extensions to the Extended Reports (XR) reporting 110 suggest enhancing this discard metric: 112 o Reporting the number of discarded packets in a measurement 113 interval, i.e., during either the last reporting interval or since 114 the beginning of the session, as indicated by a flag in the 115 suggested XR report [I-D.ietf-xrblock-rtcp-xr-discard]. If an 116 endpoint needs to report packet discard due to other reasons than 117 early- and late-arrival (for example, discard due to duplication, 118 redundancy, etc.) then it should consider using the Discarded 119 Packets Report Block [I-D.ietf-xrblock-rtcp-xr-discard]. 121 o Reporting gaps and bursts of discarded packets during a 122 measurement interval, i.e., the last reporting interval or the 123 duration of the session 124 [I-D.ietf-xrblock-rtcp-xr-burst-gap-discard]. 126 o Reporting run-length encoding of discarded packet during a 127 measurement interval, i.e., between a set of sequence numbers 128 [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics]. 130 However, none of these metrics allow a receiver to report precisely 131 the number of bytes that were discarded. While this information 132 could in theory be derived from high-frequency reporting on the 133 number of discarded packets [I-D.ietf-xrblock-rtcp-xr-discard] or 134 from the Discard RLE report 135 [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics], these two mechanisms 136 do not appear feasible: The former would require an unduly high 137 amount of reporting which still might not be sufficient due to the 138 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 143 bytes discarded, per interval or for the duration of the session, 144 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 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 bytes discarded' is a 32-bit unsigned integer value 210 indicating the total number of bytes discarded. Bytes discarded 211 corresponds to the RTP payload size of every RTP packet that is 212 discarded (due to early or late arrival). Hence, the bytes discarded 213 ignores the size of any RTP header extensions and the size of the 214 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 bytes discarded from the start of the 219 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. 242 However, it is RECOMMENDED that the media receiver signals all 243 discarded packets using the method defined in this document. If all 244 packets over a reporting period were discarded, the media receiver 245 MAY use the Discard Report Block [I-D.ietf-xrblock-rtcp-xr-discard] 246 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 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 317 New block types for RTCP XR are subject to IANA registration. For 318 general guidelines on IANA considerations for RTCP XR, refer to 319 [RFC3611]. 321 7.1. XR Report Block Registration 323 This document extends the IANA "RTP Control Protocol Extended Reports 324 (RTCP XR) Block Type Registry" by a new value: BDR (Bytes Discarded 325 Report). 327 [Note to RFC Editor: please replace BDR with the IANA provided RTCP 328 XR block type for this block here and in the diagrams above. Please 329 remove this note prior to publication as an RFC.] 331 7.2. SDP Parameter Registration 333 This document registers a new parameters for the Session Description 334 Protocol (SDP), "discard-bytes" in the "RTP Control Protocol Extended 335 Reports (RTCP XR) Session Description Protocol (SDP) Parameters 336 Registry". 338 7.3. Contact information for IANA registrations 340 Varun Singh (varun.singh@iki.fi) 342 Aalto University Comnet, Otakaari 5A, 02150 Espoo, Finland. 344 8. Acknowledgments 346 The authors would like to thank Alan Clark, Roni Even, Sam Hartman, 347 Colin Perkins, Dan Romascanu, Dan Wing, and Qin Wu for providing 348 valuable feedback on earlier versions of this draft. 350 9. References 352 9.1. Normative References 354 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 355 Requirement Levels", BCP 14, RFC 2119, March 1997. 357 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 358 Jacobson, "RTP: A Transport Protocol for Real-Time 359 Applications", STD 64, RFC 3550, July 2003. 361 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 362 Protocol Extended Reports (RTCP XR)", RFC 3611, November 363 2003. 365 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 366 "Extended RTP Profile for Real-time Transport Control 367 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July 368 2006. 370 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 371 Description Protocol", RFC 4566, July 2006. 373 [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New 374 Performance Metric Development", BCP 170, RFC 6390, 375 October 2011. 377 [RFC6776] Clark, A. and Q. Wu, "Measurement Identity and Information 378 Reporting Using a Source Description (SDES) Item and an 379 RTCP Extended Report (XR) Block", RFC 6776, October 2012. 381 [I-D.ietf-xrblock-rtcp-xr-discard] 382 Clark, A., Zorn, G., and W. Wu, "RTP Control Protocol 383 (RTCP) Extended Report (XR) Block for Discard Count metric 384 Reporting", draft-ietf-xrblock-rtcp-xr-discard-15 (work in 385 progress), June 2013. 387 9.2. Informative References 389 [I-D.ietf-xrblock-rtcp-xr-burst-gap-discard] 390 Clark, A., Huang, R., and W. Wu, "RTP Control 391 Protocol(RTCP) Extended Report (XR) Block for Burst/Gap 392 Discard metric Reporting", draft-ietf-xrblock-rtcp-xr- 393 burst-gap-discard-14 (work in progress), April 2013. 395 [I-D.ietf-xrblock-rtcp-xr-discard-rle-metrics] 396 Ott, J., Singh, V., and I. Curcio, "RTP Control Protocol 397 (RTCP) Extended Reports (XR) for Run Length Encoding (RLE) 398 of Discarded Packets", draft-ietf-xrblock-rtcp-xr-discard- 399 rle-metrics-06 (work in progress), July 2013. 401 [RFC5481] Morton, A. and B. Claise, "Packet Delay Variation 402 Applicability Statement", RFC 5481, March 2009. 404 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 405 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 406 RFC 3711, March 2004. 408 [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for 409 Real-time Transport Control Protocol (RTCP)-Based Feedback 410 (RTP/SAVPF)", RFC 5124, February 2008. 412 [I-D.ietf-avt-srtp-not-mandatory] 413 Perkins, C. and M. Westerlund, "Securing the RTP Protocol 414 Framework: Why RTP Does Not Mandate a Single Media 415 Security Solution", draft-ietf-avt-srtp-not-mandatory-13 416 (work in progress), May 2013. 418 [I-D.ietf-avtcore-rtp-security-options] 419 Westerlund, M. and C. Perkins, "Options for Securing RTP 420 Sessions", draft-ietf-avtcore-rtp-security-options-04 421 (work in progress), July 2013. 423 Appendix A. Metrics represented using RFC6390 Template 425 RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC 426 number, when assigned. 428 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 B.2. changes in draft-ietf-xrblock-rtcp-xr-bytes-discarded-metric-00 464 o Submitted as a WG draft. 466 Authors' Addresses 468 Varun Singh (editor) 469 Aalto University 470 School of Electrical Engineering 471 Otakaari 5 A 472 Espoo, FIN 02150 473 Finland 475 Email: varun@comnet.tkk.fi 476 URI: http://www.netlab.tkk.fi/~varun/ 478 Joerg Ott 479 Aalto University 480 School of Electrical Engineering 481 Otakaari 5 A 482 Espoo, FIN 02150 483 Finland 485 Email: jo@comnet.tkk.fi 487 Igor D.D. Curcio 488 Nokia Research Center 489 P.O. Box 1000 (Visiokatu 3) 490 Tampere, FIN 33721 491 Finland 493 Email: igor.curcio@nokia.com