idnits 2.17.1 draft-ietf-xrblock-rtcp-xr-bytes-discarded-metric-02.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (February 26, 2014) is 3706 days in the past. Is this intentional? 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 462, but not defined ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) Summary: 1 error (**), 0 flaws (~~), 2 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: August 30, 2014 I. Curcio 6 Nokia Research Center 7 February 26, 2014 9 RTP Control Protocol (RTCP) Extended Report (XR) for Bytes Discarded 10 Metric 11 draft-ietf-xrblock-rtcp-xr-bytes-discarded-metric-02 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 August 30, 2014. 40 Copyright Notice 42 Copyright (c) 2014 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 . . . . . . . . . . . . . . . . . . . . . 8 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-01 . . . . . . . . . . . . . . . . . . . 10 77 B.2. changes in draft-singh-xrblock-rtcp-xr-bytes- 78 discarded-metric-00 . . . . . . . . . . . . . . . . . . . 11 79 B.3. changes in draft-ietf-xrblock-rtcp-xr-bytes- 80 discarded-metric-00 . . . . . . . . . . . . . . . . . . . 11 81 B.4. changes in draft-ietf-xrblock-rtcp-xr-bytes- 82 discarded-metric-01 . . . . . . . . . . . . . . . . . . . 11 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 85 1. Introduction 87 RTP [RFC3550] provides a transport for real-time media flows such as 88 audio and video together with the RTP control protocol (RTCP), which 89 provides periodic feedback about the media streams received in a 90 specific duration. In addition, RTCP can be used for timely feedback 91 about individual events to report (e.g., packet loss) [RFC4585]. 92 Both long-term and short-term feedback enable a media sender to adapt 93 its media transmission and/or encoding dynamically to the observed 94 path characteristics. 96 [RFC3611] defines RTCP Extended Reports as a detailed reporting 97 framework to provide more than just the coarse Receiver Report (RR) 98 statistics. The detailed reporting may enable a media sender to 99 react more appropriately to the observed networking conditions as 100 these can be characterized better, although at the expense of extra 101 overhead. 103 In addition to lost packets, [RFC3611] defines the notion of 104 "discarded" packets: packets that were received but dropped from the 105 de-jitter buffer because they were either too early (for buffering) 106 or too late (for playout). The "discard rate" metric is part of the 107 VoIP metrics report block even though it is not just applicable to 108 audio: it is specified as the fraction of discarded packets since the 109 beginning of the session. See section 4.7.1 of [RFC3611]. The 110 discard metric is believed to be applicable to a large class of RTP 111 applications which use a de-jitter buffer [RFC5481]. 113 Recently proposed extensions to the Extended Reports (XR) reporting 114 suggest enhancing the discard metric: 116 o Reporting the number of discarded packets in a measurement 117 interval, i.e., during either the last reporting interval or since 118 the beginning of the session, as indicated by a flag in the 119 suggested XR report [RFC7002]. If an endpoint needs to report 120 packet discard due to other reasons than early- and late-arrival 121 (for example, discard due to duplication, redundancy, etc.) then 122 it should consider using the Discarded Packets Report Block 123 [RFC7002]. 125 o Reporting gaps and bursts of discarded packets during a 126 measurement interval, i.e., the last reporting interval or the 127 duration of the session [RFC7003]. 129 o Reporting run-length encoding of discarded packet during a 130 measurement interval, i.e., between a set of sequence numbers 131 [RFC7097]. 133 However, none of these metrics allow a receiver to report precisely 134 the number of RTP payload bytes that were discarded. While this 135 information could in theory be derived from high-frequency reporting 136 on the number of discarded packets [RFC7002] or from the Discard RLE 137 report [RFC7097], these two mechanisms do not appear feasible; the 138 former would require an unduly high amount of reporting which still 139 might not be sufficient due to the non-deterministic scheduling of 140 RTCP packets. The latter incurs significant complexity (by storing a 141 map of sequence numbers and packet sizes) and reporting overhead. 143 An XR block is defined in this document to indicate the number of RTP 144 payload bytes discarded, per interval or for the duration of the 145 session, similar to the other XR report blocks. 147 2. Terminology 149 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 150 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 151 document are to be interpreted as described in BCP 14, [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=10) is set, it indicates the 220 number of bytes discarded in the most recent reporting interval. 222 If the XR block follows a measurement identity block [RFC6776] in the 223 same RTCP compound packet then the cumulative (I=11) or the interval 224 (I=10) for this report block corresponds to the values of the 225 "measurement duration" in the measurement information block. 227 If the receiver sends the Bytes Discarded Report Block without the 228 measurement identity block then the discard block MUST be sent in 229 conjunction with an RTCP Receiver Report (RR) as a compound RTCP 230 packet. 232 4. Protocol Operation 234 This section describes the behavior of the reporting node (= media 235 receiver) and the media sender. 237 4.1. Reporting Node (Receiver) 238 The media receiver MAY send the Bytes Discard Reports as part of the 239 regularly scheduled RTCP packets as per RFC3550. It MAY also include 240 Bytes Discard Reports in immediate or early feedback packets as per 241 [RFC4585]. 243 Transmission of RTCP XR Bytes Discarded Report is up to the 244 discretion of the media receiver, as is the reporting granularity. 245 However, it is RECOMMENDED that the media receiver signals the bytes 246 discarded packets using the method defined in this document. When 247 reporting several metrics in a single RTCP packet, the reporting 248 intervals for the report blocks are synchronized, therefore the media 249 receiver may choose to additionally send the Discarded Packets 250 [RFC7002] or Discard RLE [RFC7097] Report Block to assist the media 251 sender in correlating the bytes discarded to the packets discarded in 252 that particular interval. 254 If all packets over a reporting period were discarded, the media 255 receiver MAY use the Discarded Packets Report Block [RFC7002] 256 instead. 258 4.2. Media Sender 260 The media sender MUST be prepared to operate without receiving any 261 Bytes Discarded reports. If Bytes Discarded reports are generated by 262 the media receiver, the media sender cannot rely on all these reports 263 being received, nor can the media sender rely on a regular generation 264 pattern from the media receiver. 266 However, if the media sender receives any RTCP reports but no Bytes 267 Discard report blocks and is aware that the media receiver supports 268 Bytes Discard report blocks, it MAY assume that no packets were 269 discarded by the media receiver. 271 The media sender SHOULD accept the Bytes Discarded Report Block only 272 if it is received in a compound RTCP receiver report or if it is 273 preceded by a measurement identity block [RFC6776]. Under all other 274 circumstances it MUST ignore the block. 276 5. SDP signaling 278 A participant of a media session MAY use SDP to signal its support 279 for the report block specified in this document or use them without 280 any prior signaling (see section 5 of [RFC3611]). 282 For signaling in SDP, the RTCP XR attribute as defined in [RFC3611] 283 MUST be used. The SDP [RFC4566] attribute 'xr-format' defined in 284 RFC3611 is augmented as described in the following to indicate the 285 bytes discarded metric. 287 rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] 288 CRLF ; defined in [RFC3611] 290 xr-format =/ xr-discard-bytes 292 xr-discard-bytes = "discard-bytes" 294 The parameter 'discard-bytes' to indicate support for the Bytes 295 Discarded Report Block defined in Section 3. 297 When SDP is used in Offer/Answer context, the mechanism defined in 298 [RFC3611] for unilateral "rtcp-xr" attribute parameters applies (see 299 section 5.2 of [RFC3611]). 301 6. Security Considerations 303 The Bytes Discarded block does not provide per-packet statistics, 304 hence the risk to confidentiality documented in Section 7, paragraph 305 3 of [RFC3611] does not apply. In some situations, returning very 306 detailed error information (e.g., over-range measurement or 307 measurement unavailable) using this report block can provide an 308 attacker with insight into the security processing. For example, 309 assume that the attacker sends a packet with a stale timestamp (i.e., 310 time in the past) to the receiver. If the receiver now sends a 311 discard report with the same number of bytes as the payload of the 312 injected packet, the attacker can infer that no security processing 313 was performed. If, on the other hand, the attacker does not receive 314 a discard report, it can equivalently assume that the security 315 procedures were performed on the packet. 317 Implementers should therefore consider the guidance in 318 [I-D.ietf-avt-srtp-not-mandatory] for using appropriate security 319 mechanisms, i.e., where security is a concern, the implementation 320 should apply encryption and authentication to the report block. For 321 example this can be achieved by using the AVPF profile together with 322 the Secure RTP profile as defined in [RFC3711]; an appropriate 323 combination of the two profiles (an "SAVPF") is specified in 324 [RFC5124]. However, other mechanisms also exist (documented in 325 [I-D.ietf-avtcore-rtp-security-options]) and might be more suitable. 327 The discarded bytes report is employed by the sender to perform 328 congestion control, typically, for calculating goodput. In these 329 cases an attacker MAY drive the endpoint to lower its sending rate 330 and under-utilised the link, therefore media senders should choose 331 appropriate security measures to mitigate such attacks. 333 Lastly, the security considerations of [RFC3550], [RFC3611], and 334 [RFC4585] apply. 336 7. IANA Considerations 338 New block types for RTCP XR are subject to IANA registration. For 339 general guidelines on IANA considerations for RTCP XR, refer to 340 [RFC3611]. 342 7.1. XR Report Block Registration 344 This document extends the IANA "RTP Control Protocol Extended Reports 345 (RTCP XR) Block Type Registry" by a new value: BDR (Bytes Discarded 346 Report). 348 [Note to RFC Editor: please replace BDR with the IANA provided RTCP 349 XR block type for this block here and in the diagrams above. Please 350 remove this note prior to publication as an RFC.] 352 7.2. SDP Parameter Registration 354 This document registers a new parameters for the Session Description 355 Protocol (SDP), "discard-bytes" in the "RTP Control Protocol Extended 356 Reports (RTCP XR) Session Description Protocol (SDP) Parameters 357 Registry". 359 7.3. Contact information for IANA registrations 361 RAI Area Directors: rai-ads@tools.ietf.org 363 8. Acknowledgments 365 The authors would like to thank Alan Clark, Benoit Claise, Roni Even, 366 Vijay Gurbani, Sam Hartman, Vinayak Hegde, Jeffrey Hutzelman, Barry 367 Leiba, Colin Perkins, Dan Romascanu, Dan Wing, and Qin Wu for 368 providing valuable feedback on earlier versions of this draft. 370 9. References 372 9.1. Normative References 374 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 375 Requirement Levels", BCP 14, RFC 2119, March 1997. 377 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 378 Jacobson, "RTP: A Transport Protocol for Real-Time 379 Applications", STD 64, RFC 3550, July 2003. 381 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 382 Protocol Extended Reports (RTCP XR)", RFC 3611, November 383 2003. 385 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 386 "Extended RTP Profile for Real-time Transport Control 387 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July 388 2006. 390 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 391 Description Protocol", RFC 4566, July 2006. 393 [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New 394 Performance Metric Development", BCP 170, RFC 6390, 395 October 2011. 397 [RFC6776] Clark, A. and Q. Wu, "Measurement Identity and Information 398 Reporting Using a Source Description (SDES) Item and an 399 RTCP Extended Report (XR) Block", RFC 6776, October 2012. 401 [RFC7002] Clark, A., Zorn, G., and Q. Wu, "RTP Control Protocol 402 (RTCP) Extended Report (XR) Block for Discard Count Metric 403 Reporting", RFC 7002, September 2013. 405 9.2. Informative References 407 [RFC7003] Clark, A., Huang, R., and Q. Wu, "RTP Control Protocol 408 (RTCP) Extended Report (XR) Block for Burst/Gap Discard 409 Metric Reporting", RFC 7003, September 2013. 411 [RFC7097] Ott, J., Singh, V., and I. Curcio, "RTP Control Protocol 412 (RTCP) Extended Report (XR) for RLE of Discarded Packets", 413 RFC 7097, January 2014. 415 [RFC5481] Morton, A. and B. Claise, "Packet Delay Variation 416 Applicability Statement", RFC 5481, March 2009. 418 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 419 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 420 RFC 3711, March 2004. 422 [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for 423 Real-time Transport Control Protocol (RTCP)-Based Feedback 424 (RTP/SAVPF)", RFC 5124, February 2008. 426 [I-D.ietf-avt-srtp-not-mandatory] 427 Perkins, C. and M. Westerlund, "Securing the RTP Protocol 428 Framework: Why RTP Does Not Mandate a Single Media 429 Security Solution", draft-ietf-avt-srtp-not-mandatory-16 430 (work in progress), January 2014. 432 [I-D.ietf-avtcore-rtp-security-options] 433 Westerlund, M. and C. Perkins, "Options for Securing RTP 434 Sessions", draft-ietf-avtcore-rtp-security-options-10 435 (work in progress), January 2014. 437 Appendix A. Metrics represented using RFC6390 Template 439 RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC 440 number, when assigned. 442 a. RTP Payload Bytes Discarded Metric 444 * Metric Name: RTP Payload Bytes Discarded Metric 446 * Metric Description: Total number of RTP Payload bytes 447 discarded over the period covered by this report. 449 * Method of Measurement or Calculation: See section 4, number of 450 bytes discarded definition in [RFCXXXX]. 452 * Units of Measurement: See section 4, number of RTP payload 453 bytes discarded definition in [RFCXXXX]. 455 * Measurement Point(s) with Potential Measurement Domain: See 456 section 4, 1st paragraph of [RFCXXXX]. 458 * Measurement Timing: See section 4, last three paragraphs of 459 [RFCXXXX] for measurement timing and for the Interval Metric 460 flag. 462 * Use and applications: See section 1, paragraph 1 of [RFCXXXX]. 464 * Reporting model: See RFC3611. 466 Appendix B. Change Log 468 Note to the RFC-Editor: please remove this section prior to 469 publication as an RFC. 471 B.1. changes in draft-singh-xrblock-rtcp-xr-bytes-discarded-metric-01 473 o Address SEC-DIR and Gen-art review. 475 o Incorporate IESG comments. 477 B.2. changes in draft-singh-xrblock-rtcp-xr-bytes-discarded-metric-00 479 o Bytes discarded metric split from [I-D.ietf-xrblock-rtcp-xr- 480 discard-rle-metrics] />. 482 B.3. changes in draft-ietf-xrblock-rtcp-xr-bytes-discarded-metric-00 484 o Submitted as a WG draft. 486 B.4. changes in draft-ietf-xrblock-rtcp-xr-bytes-discarded-metric-01 488 o Editorial fixes: Updated references from drafts to RFCs. 490 o Updated fields in the RFC6390 template. 492 o Changed 'number of bytes discarded' to 'number of RTP payload 493 bytes discarded'. 495 Authors' Addresses 497 Varun Singh (editor) 498 Aalto University 499 School of Electrical Engineering 500 Otakaari 5 A 501 Espoo, FIN 02150 502 Finland 504 Email: varun@comnet.tkk.fi 505 URI: http://www.netlab.tkk.fi/~varun/ 507 Joerg Ott 508 Aalto University 509 School of Electrical Engineering 510 Otakaari 5 A 511 Espoo, FIN 02150 512 Finland 514 Email: jo@comnet.tkk.fi 516 Igor D.D. Curcio 517 Nokia Research Center 518 P.O. Box 1000 (Visiokatu 3) 519 Tampere, FIN 33721 520 Finland 522 Email: igor.curcio@nokia.com