idnits 2.17.1 draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-05.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 (December 19, 2012) is 4146 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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) == Outdated reference: A later version (-15) exists of draft-ietf-xrblock-rtcp-xr-discard-11 == Outdated reference: A later version (-14) exists of draft-ietf-xrblock-rtcp-xr-burst-gap-discard-08 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 XR Block Working Group J. Ott 3 Internet-Draft V. Singh 4 Intended status: Standards Track Aalto University 5 Expires: June 22, 2013 I. Curcio 6 Nokia Research Center 7 December 19, 2012 9 RTP Control Protocol (RTCP) Extended Reports (XR) for Run Length 10 Encoding (RLE) of Discarded Packets 11 draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-05.txt 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 per-packet 20 report metric capturing individual packets discarded from the jitter 21 buffer after 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 June 22, 2013. 40 Copyright Notice 42 Copyright (c) 2012 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 3. XR Discard RLE Report Block . . . . . . . . . . . . . . . . . 4 60 4. XR Bytes Discarded Report Block . . . . . . . . . . . . . . . 5 61 5. Protocol Operation . . . . . . . . . . . . . . . . . . . . . . 7 62 5.1. Reporting Node (Receiver) . . . . . . . . . . . . . . . . 7 63 5.2. Media Sender . . . . . . . . . . . . . . . . . . . . . . . 7 64 6. SDP signaling . . . . . . . . . . . . . . . . . . . . . . . . 8 65 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8 66 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 67 8.1. XR Report Block Registration . . . . . . . . . . . . . . . 9 68 8.2. SDP Parameter Registration . . . . . . . . . . . . . . . . 9 69 8.3. Contact information for IANA registrations . . . . . . . . 9 70 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 71 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 72 10.1. Normative References . . . . . . . . . . . . . . . . . . . 9 73 10.2. Informative References . . . . . . . . . . . . . . . . . . 10 74 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 10 75 A.1. changes in 76 draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-00 . . . . 10 77 A.2. changes in 78 draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-01 . . . . 10 79 A.3. changes in 80 draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-02 . . . . 11 81 A.4. changes in 82 draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-03 . . . . 11 83 A.5. changes in 84 draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-04 . . . . 11 85 A.6. changes in 86 draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-05 . . . . 11 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 89 1. Introduction 91 RTP [RFC3550] provides a transport for real-time media flows such as 92 audio and video together with the RTP control protocol (RTCP) which 93 provides periodic feedback about the media streams received in a 94 specific duration. In addition, RTCP can be used for timely feedback 95 about individual events to report (e.g., packet loss) [RFC4585]. 96 Both long-term and short-term feedback enable a sender to adapt its 97 media transmission and/or encoding dynamically to the observed path 98 characteristics. 100 RFC3611 [RFC3611] defines RTCP Extended Reports as a detailed 101 reporting framework to provide more than just the coarse RR 102 statistics. The detailed reporting may enable a sender to react more 103 appropriately to the observed networking conditions as these can be 104 characterized better, although at the expense of extra overhead. 106 Among many other report blocks, RFC3611 specifies the Loss RLE block 107 which reports runs of packets received and lost with the granularity 108 of individual packets. This can help both error recovery and path 109 loss characterization. In addition to lost packets, RFC3611 defines 110 the notion of "discarded" packets: packets that were received but 111 dropped from the jitter buffer because they were either too early 112 (for buffering) or too late (for playout). The "discard rate" metric 113 is part of the VoIP metrics report block even though it is not just 114 applicable to audio: it is specified as the fraction of discarded 115 packets since the beginning of the session. See section 4.7.1 of 116 RFC3611 [RFC3611]. 118 Recently proposed extensions to the XR reporting suggest enhancing 119 this discard metric: 120 o Reporting the number of discarded packets in a measurement 121 interval, i.e., during either the last reporting interval or since 122 the beginning of the session, as indicated by a flag in the 123 suggested XR report [I-D.ietf-xrblock-rtcp-xr-discard]. If an 124 endpoint needs to report packet discard due to other reasons than 125 early- and late-arrival (for example, discard due to duplication, 126 redundancy, etc.) then it should consider using the Discarded 127 Packets Report Block [I-D.ietf-xrblock-rtcp-xr-discard]. 128 o Reporting gaps and bursts of discarded packets during a 129 measurement interval, i.e., the last reporting interval or the 130 duration of the session 131 [I-D.ietf-xrblock-rtcp-xr-burst-gap-discard]. 133 However, none of these metrics allow a receiver to report precisely 134 which packets were discarded. While this information could in theory 135 be derived from high-frequency reporting on the number of discarded 136 packets [I-D.ietf-xrblock-rtcp-xr-discard] or from the gap/burst 137 report [I-D.ietf-xrblock-rtcp-xr-burst-gap-discard], these two 138 mechanisms do not appear feasible: The former would require an unduly 139 high amount of reporting which still might not be sufficient due to 140 the non-deterministic scheduling of RTCP packets. The latter incur 141 significant complexity and reporting overhead and might still not 142 deliver the desired accuracy. 144 This document defines a discard report block following the idea of 145 the run-length encoding applied for lost and received packets in 146 [RFC3611]. 148 Complementary to or instead of the indication which packets were 149 discarded, an XR block is defined to indicate the number of bytes 150 discarded, per interval or for the duration of the session, similar 151 to other XR report blocks. 153 2. Terminology 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 BCP 14, RFC 2119 158 [RFC2119] and indicate requirement levels for compliant 159 implementations. 161 The terminology defined in RTP [RFC3550] and in the extensions for XR 162 reporting [RFC3611] applies. 164 3. XR Discard RLE Report Block 166 The XR Discard RLE report block uses the same format as specified for 167 the loss and duplicate report blocks in [RFC3611]. Figure 1 recaps 168 the packet format. The fields "BT", "T", "block length", "SSRC of 169 source", "begin_seq", and "end_seq" SHALL have the same semantics and 170 representation as defined in [RFC3611]. The "chunks" encoding the 171 run length SHALL have the same representation as in RFC3611, but 172 encode discarded packets. 174 0 1 2 3 175 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 7 176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 | BT=DRLE |rsvd |E| T | block length | 178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 179 | SSRC of source | 180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 | begin_seq | end_seq | 182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 183 | chunk 1 | chunk 2 | 184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 185 : ... : 186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 187 | chunk n-1 | chunk n | 188 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 190 Figure 1: XR Discard Report Block 192 Block Type (BT, 8 bits): A Run-length encoded Discarded Packets 193 Report Block is identified by the constant DRLE. 195 [Note to RFC Editor: please replace DRLE with the IANA provided RTCP 196 XR block type for this block. Please remove this note prior to 197 publication as an RFC.] 199 rsvd (3 bits): These reserved bits SHOULD be set to zero by receivers 200 and MUST be ignored by senders. 202 The 'E' bit is introduced to distinguish between packets discarded 203 due to early arrival and those discarded due to late arrival. The 204 'E' bit MUST be set to '1' if the chunks represent packets discarded 205 due to too early arrival and MUST be set to '0' otherwise. 207 In case both early and late discarded packets shall be reported, two 208 Discard RLE report blocks MUST be included; their sequence number 209 range MAY overlap, but individual packets MUST only be reported as 210 either early or late and not appear marked in both. Packets reported 211 in neither are considered to be properly received and not discarded. 213 Discard RLE Report Blocks SHOULD be sent in conjunction with an RTCP 214 RR as a compound RTCP packet. 216 4. XR Bytes Discarded Report Block 218 The XR Bytes Discarded report block uses the following format which 219 follows the model of the framework for performance metric development 220 [RFC6390]. 222 0 1 2 3 223 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 7 224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 225 | BT=BDR | I |E|reserved | block length=2 | 226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 227 | SSRC of source | 228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 229 | number of bytes discarded | 230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 232 Figure 2: XR Bytes Discarded Report Block 234 Block Type (BT, 8 bits): A Bytes Discarded Packets Report Block is 235 identified by the constant BDR. 237 [Note to RFC Editor: please replace BDR with the IANA provided RTCP 238 XR block type for this block. Please remove this note prior to 239 publication as an RFC.] 241 The Interval Metric flag (I) (2 bits) is used to indicate whether the 242 discard metric is Interval, or a Cumulative metric, that is, whether 243 the reported value applies to the most recent measurement interval 244 duration between successive reports (I=10, the Interval Duration) or 245 to the accumulation period characteristic of cumulative measurements 246 (I=11, the Cumulative Duration). Since the bytes discarded are not 247 measured at a particular time instance but over one or several 248 reporting intervals, the metric MUST NOT be reported as a Sampled 249 Metric (I=01). 251 The 'E' bit is introduced to distinguish between packets discarded 252 due to early arrival and those discarded due to late arrival. The 253 'E' bit MUST be set to '1' if it reports bytes discarded due to early 254 arrival and MUST be set to '0' if it reports bytes discarded due to 255 late arrival. In case both early and late discarded packets shall be 256 reported, two Bytes Discarded report blocks MUST be included. 258 These reserved bits (5 bits) SHOULD be set to zero by receivers and 259 MUST be ignored by senders. 261 block length (16 bits) MUST be set to 2, in accordance with the 262 definition of this field in [RFC3611]. The block MUST be discarded 263 if the block length is set to a different value. 265 The 'number of bytes discarded' is a 32-bit unsigned integer value 266 indicating the total number of bytes discarded. 268 If Interval Metric flag (I=11) is set, the value in the field 269 indicates the number of bytes discarded from the start of the 270 session, if Interval Metric flag (I=01) is set, it indicates the 271 number of bytes discarded since the last RTCP XR Byte Discarded Block 272 was received. 274 If the XR block follows a measurement identity block [RFC6776] in the 275 same RTCP compound packet then the cumulative (I=11) or the interval 276 (I=10) for this report block corresponds to the values of the 277 "measurement duration" in the measurement information block. 279 If the receiver sends the Bytes Discarded Report Block without the 280 measurement identity block then the discard block MUST be sent in 281 conjunction with an RTCP RR as a compound RTCP packet. 283 5. Protocol Operation 285 This section describes the behavior of the reporting (= receiver) 286 node and the media sender. 288 5.1. Reporting Node (Receiver) 290 Transmission of RTCP XR Discard RLE Reports is up to the discretion 291 of the receiver, as is the reporting granularity. However, it is 292 RECOMMENDED that the receiver signals all discarded packets using the 293 method defined in this document. If all packets over a reporting 294 period were lost, the receiver MAY use the Discard Report Block 295 [I-D.ietf-xrblock-rtcp-xr-discard] instead. In case of limited 296 available reporting bandwidth, it is up to the receiver whether or 297 not to include RTCP XR Discard RLE reports. 299 The receiver MAY send the Discard RLE Reports as part of the 300 regularly scheduled RTCP packets as per RFC3550. It MAY also include 301 Discard RLE Reports in immediate or early feedback packets as per 302 RFC4585. 304 5.2. Media Sender 306 The media sender MUST be prepared to operate without receiving any 307 Discard RLE reports. If Discard RLE reports are generated by the 308 receiver, the sender cannot rely on all these reports being received, 309 nor can the sender rely on a regular generation pattern from the 310 receiver side. 312 However, if the sender receives any RTCP reports but no Discard RLE 313 report blocks and is aware that the receiver supports Discard RLE 314 report blocks, it MAY assume that no packets were discarded at the 315 receiver. 317 The sender SHOULD accept the Bytes Discarded Report Block only if it 318 is received in a compound RTCP receiver report or if it is preceded 319 by a measurement identity block [RFC6776]. Under all other 320 circumstances it MUST ignore the block. 322 6. SDP signaling 324 A participant of a media session MAY use SDP to signal its support 325 for the two report blocks specified in this document or use them 326 without any prior signaling (see section 5 of [RFC3611]). 328 For signaling in SDP, the RTCP XR attribute as defined in [RFC3611] 329 MUST be used. The SDP [RFC4566] attribute 'xr-format' defined in 330 RFC3611 is augmented as described in the following to indicate the 331 RLE discard metric and bytes discarded metric. 333 rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] 334 CRLF ; defined in [RFC3611] 336 xr-format =/ xr-discard-rle 337 / xr-discard-bytes 339 xr-discard-rle = "discard-rle" 340 xr-discard-bytes = "discard-bytes" 342 The parameter 'discard-rle' MUST be used to indicate support for the 343 Discard RLE Report Block defined in Section 3, the parameter 344 'discard-bytes' to indicate support for the Bytes Discarded Report 345 Block defined in Section 4 347 When SDP is used in Offer/Answer context, the mechanism defined in 348 [RFC3611] for unilateral "rtcp-xr" attribute parameters applies (see 349 section 5.2 of [RFC3611]). 351 7. Security Considerations 353 The security considerations of [RFC3550], [RFC3611], and [RFC4585] 354 apply. Since this document offers only a more precise reporting for 355 an already existing metric, no further security implications are 356 foreseen. 358 8. IANA Considerations 360 New block types for RTCP XR are subject to IANA registration. For 361 general guidelines on IANA considerations for RTCP XR, refer to 362 [RFC3611]. 364 8.1. XR Report Block Registration 366 This document extends the IANA "RTP Control Protocol Extended Reports 367 (RTCP XR) Block Type Registry" by two new values: DRLE and BDR. 369 [Note to RFC Editor: please replace DRLE and BDR with the IANA 370 provided RTCP XR block type for this block here and in the diagrams 371 above. Please remove this note prior to publication as an RFC.] 373 8.2. SDP Parameter Registration 375 This document registers two new parameters for the Session 376 Description Protocol (SDP), "discard-rle" and "discard-bytes", in the 377 "RTP Control Protocol Extended Reports (RTCP XR) Session Description 378 Protocol (SDP) Parameters Registry". 380 8.3. Contact information for IANA registrations 382 Joerg Ott (jo@comnet.tkk.fi) 384 Aalto University Comnet, Otakaari 5A, 02150 Espoo, Finland. 386 9. Acknowledgements 388 Thanks to Qin Wu, Colin Perkins, Dan Romascanu, Roni Even and Dan 389 Wing for providing valuable feedback on earlier versions of this 390 draft 392 10. References 394 10.1. Normative References 396 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 397 Requirement Levels", BCP 14, RFC 2119, March 1997. 399 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 400 Jacobson, "RTP: A Transport Protocol for Real-Time 401 Applications", STD 64, RFC 3550, July 2003. 403 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 404 Protocol Extended Reports (RTCP XR)", RFC 3611, 405 November 2003. 407 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 408 "Extended RTP Profile for Real-time Transport Control 409 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, 410 July 2006. 412 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 413 Description Protocol", RFC 4566, July 2006. 415 [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New 416 Performance Metric Development", BCP 170, RFC 6390, 417 October 2011. 419 [RFC6776] Clark, A. and Q. Wu, "Measurement Identity and Information 420 Reporting Using a Source Description (SDES) Item and an 421 RTCP Extended Report (XR) Block", RFC 6776, October 2012. 423 10.2. Informative References 425 [I-D.ietf-xrblock-rtcp-xr-discard] 426 Clark, A., Zorn, G., and W. Wu, "RTP Control Protocol 427 (RTCP) Extended Report (XR) Block for Discard Count metric 428 Reporting", draft-ietf-xrblock-rtcp-xr-discard-11 (work in 429 progress), December 2012. 431 [I-D.ietf-xrblock-rtcp-xr-burst-gap-discard] 432 Clark, A., Huang, R., and W. Wu, "RTP Control 433 Protocol(RTCP) Extended Report (XR) Block for Burst/Gap 434 Discard metric Reporting", 435 draft-ietf-xrblock-rtcp-xr-burst-gap-discard-08 (work in 436 progress), December 2012. 438 Appendix A. Change Log 440 Note to the RFC-Editor: please remove this section prior to 441 publication as an RFC. 443 A.1. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-00 445 o Changed the interval flag from 1 to 2 bits in the discarded bytes 446 report. Also added the measurement identification tag to the 447 block. 448 o Added this section. 450 A.2. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-01 451 o Removed the measurement identification tag in the bytes discarded 452 block. 454 A.3. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-02 456 o Removed the extra Tag bits from the Discarded bytes XR block. 457 o Clarified use of measurement identity block in Section 4 and 5.2 459 A.4. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-03 461 o Added explanation for block length in bytes discarded block. 462 o Added an acknowledgement section. 464 A.5. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-04 466 o Added Block Type definition to each XRBlock. 467 o Made changes requested in WGLC. 469 A.6. changes in draft-ietf-xrblock-rtcp-xr-discard-rle-metrics-05 471 o Made changes requested by SDP directorate. 473 Authors' Addresses 475 Joerg Ott 476 Aalto University 477 School of Electrical Engineering 478 Otakaari 5 A 479 Espoo, FIN 02150 480 Finland 482 Email: jo@comnet.tkk.fi 484 Varun Singh 485 Aalto University 486 School of Electrical Engineering 487 Otakaari 5 A 488 Espoo, FIN 02150 489 Finland 491 Email: varun@comnet.tkk.fi 492 URI: http://www.netlab.tkk.fi/~varun/ 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