idnits 2.17.1 draft-ott-xrblock-rtcp-xt-discard-metrics-01.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 (September 13, 2011) is 4602 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) == Unused Reference: 'RFC3551' is defined on line 349, but no explicit reference was found in the text == Unused Reference: 'RFC5760' is defined on line 365, but no explicit reference was found in the text ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) == Outdated reference: A later version (-12) exists of draft-ietf-pmol-metrics-framework-08 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--).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 Aalto University 4 Intended status: Standards Track I. Curcio 5 Expires: March 16, 2012 Nokia Research Center 6 V. Singh 7 Aalto University 8 September 13, 2011 10 Real-time Transport Control Protocol Extension Report for Run Length 11 Encoding of Discarded Packets 12 draft-ott-xrblock-rtcp-xt-discard-metrics-01.txt 14 Abstract 16 The Real-time Transport Control Protocol (RTCP) is used in 17 conjunction with the Real-time Transport Protocol (RTP) in to provide 18 a variety of short-term and long-term reception statistics. The 19 available reporting may include aggregate information across longer 20 periods of time as well as individual packet reporting. This 21 document specifies a per-packet report metric capturing individual 22 packets discarded from the jitter buffer after successful reception. 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on March 16, 2012. 41 Copyright Notice 43 Copyright (c) 2011 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 3. XR Discard RLE Report Block . . . . . . . . . . . . . . . . . 4 61 4. XR Bytes Discarded Report Block . . . . . . . . . . . . . . . 5 62 5. Protocol Operation . . . . . . . . . . . . . . . . . . . . . . 6 63 5.1. Reporting Node (Receiver) . . . . . . . . . . . . . . . . 7 64 5.2. Media Sender . . . . . . . . . . . . . . . . . . . . . . . 7 65 6. SDP signaling . . . . . . . . . . . . . . . . . . . . . . . . 7 66 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8 67 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 68 8.1. XR Report Block Registration . . . . . . . . . . . . . . . 8 69 8.2. SDP Parameter Registration . . . . . . . . . . . . . . . . 9 70 8.3. Contact information for IANA registrations . . . . . . . . 9 71 9. Normative References . . . . . . . . . . . . . . . . . . . . . 9 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 74 1. Introduction 76 RTP [RFC3550] provides a transport for real-time media flows such as 77 audio and video together with the RTP control protocol which provides 78 periodic feedback about the media streams received in a specific 79 duration. In addition, RTCP can be used for timely feedback about 80 individual events to report (e.g., packet loss) [RFC4585]. Both 81 long-term and short-term feedback enable a sender to adapt its media 82 transmission and/or encoding dynamically to the observed path 83 characteristics. 85 RFC3611 [RFC3611] defines RTCP eXtension Reports as a detailed 86 reporting framework to provide more than just the coarse RR 87 statistics. The detailed reporting may enable a sender to react more 88 appropriately to the observed networking conditions as these can be 89 characterized better, albeit at the expense of extra overhead. 91 Among many other fields, RFC3611 specifies the Loss RLE block which 92 define runs of packets received and lost with the granularity of 93 individual packets. This can help both error recovery and path loss 94 characterization. In addition to lost packets, RFC 3611 defines the 95 notion of "discarded" packets: packets that were received but dropped 96 from the jitter buffer because they were either too early (for 97 buffering) or too late (for playout). This metric is part of the 98 VoIP metrics report block even though it is not just applicable to 99 audio: it is specified as the fraction of discarded packets since the 100 beginning of the session. See section 4.7.1 of RFC3611 [RFC3611]. 102 Recently proposed extensions to the XR reporting suggest enhancing 103 this discard metric: 104 o Reporting the number of discarded packets during either the last 105 reporting interval or since the beginning of the session, as 106 indicated by a flag in the suggested XR report 107 [I-D.ietf-avt-rtcp-xr-discard]. 108 o Reporting gaps and bursts of discarded packets during the last 109 reporting interval or cumulatively since the beginning of the 110 session [I-D.ietf-avt-rtcp-xr-burst-gap-discard]. 112 However, none of these metrics allow a receiver to report precisely 113 which packets were discarded. While this information could in theory 114 be derived from high-frequency reporting on the number of discarded 115 packets or from the gap/burst report, these two mechanisms do not 116 appear feasible: The former would require an unduly high amount of 117 reporting which still might not be sufficient due to the non- 118 deterministic scheduling of RTCP packets. The latter incur 119 significant complexity and reporting overhead and might still not 120 deliver the desired accuracy. 122 This document defines a discard report block following the idea of 123 the run-length encoding applied for lost and received packets in 124 RFC3611. 126 Complementary to or instead of the indication which packets were 127 lost, an XR block is defined to indicate the number of bytes lost, 128 per interval or for the duration of the session, similar to other XR 129 report blocks. 131 2. Terminology 133 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 134 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 135 document are to be interpreted as described in BCP 14, RFC 2119 136 [RFC2119] and indicate requirement levels for compliant 137 implementations. 139 The terminology defined in RTP [RFC3550] and in the extensions for XR 140 reporting [RFC3611] applies. 142 3. XR Discard RLE Report Block 144 The XR Discard RLE report block uses the same format as specified for 145 the loss and duplicate report blocks in RFC3611 [RFC3611]. Figure 146 Figure 1 recaps the packet format. The fields "BT", "T", "block 147 length", "SSRC of source", "begin_seq", and "end_seq" SHALL have the 148 same semantics and representation as defined in RFC3611. The 149 "chunks" encoding the run length SHALL have the same representation 150 as in RFC3611, but encode discarded packets. 152 0 1 2 3 153 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 155 | BT=DRLE |rsvd |E| T | block length | 156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 157 | SSRC of source | 158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 159 | begin_seq | end_seq | 160 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 161 | chunk 1 | chunk 2 | 162 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 163 : ... : 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | chunk n-1 | chunk n | 166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 168 Figure 1: XR Discard Report Block 170 The 'E' bit is introduced to distinguish between packets discarded 171 due to early arrival and those discarded due to late arrival. The 172 'E' bit MUST be set to '1' if the chunks represent packets discarded 173 due to too early arrival and MUST be set to '0' otherwise. 175 In case both early and late discarded packets shall be reported, two 176 Discard RLE report blocks MUST be included; their sequence number 177 range MAY overlap, but individual packets MUST only be reported as 178 either early or late. Packets reported in both MUST be considered as 179 discarded without further information available, packets reported in 180 neither are considered to be properly received and not discarded. 182 Discard RLE Report Blocks SHOULD be sent in conjunction with an RTCP 183 RR as a compound RTCP packet. 185 Editor's node: is it acceptable to use one of the 'reserved' bits for 186 this purpose or should two block types be used? 188 4. XR Bytes Discarded Report Block 190 The XR Bytes Discarded report block uses the following format which 191 follows the model of the framework for performance metric development 192 [I-D.ietf-pmol-metrics-framework]. 194 0 1 2 3 195 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 7 196 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 197 | BT=BDR |I|E| resv | block length=2 | 198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 199 | SSRC of source | 200 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 201 | number of bytes discarded | 202 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 204 Figure 2: XR Bytes Discarded Report Block 206 The Interval Metric flag (I) (1 bit) is used to indicate whether the 207 Post-Repair Loss metric is an Interval or a Cumulative metric, that 208 is, whether the reported value applies to the most recent measurement 209 interval duration between successive metrics reports (I=1) (the 210 Interval Duration) or to the accumulation period characteristic of 211 cumulative measurements (I=0) (the Cumulative Duration). Numerical 212 values for both these intervals are provided in the Measurement 213 Identifier block referenced by the tag field below. 215 The 'E' bit is introduced to distinguish between packets discarded 216 due to early arrival and those discarded due to late arrival. The 217 'E' bit MUST be set to '1' if the chunks represent packets discarded 218 due to too early arrival and MUST be set to '0' otherwise. In case 219 both early and late discarded packets shall be reported, two Bytes 220 Discarded report blocks MUST be included. 222 The 'number of bytes discarded' is a 32-bit unsigned integer value 223 indicating the total number of bytes discarded (I=0) or the number of 224 bytes discarded since the last RTCP XR Bytes Discarded block was 225 sent. 227 Bytes Discarded Report Blocks SHOULD be sent in conjunction with an 228 RTCP RR as a compound RTCP packet. 230 Editor's note: is it acceptable to use one of the 'reserved' bits for 231 this purpose or should two block types be used? 233 5. Protocol Operation 235 This section describes the behavior of the reporting (= receiver) RTP 236 node and the sender RTP node. 238 5.1. Reporting Node (Receiver) 240 Transmission of RTCP XR Discard RLE Reports is up to the discretion 241 of the receiver, as is the reporting granularity. However, it is 242 RECOMMENDED that the receiver signals all discarded packets using the 243 method defined in this document. If all packets over a reporting 244 period were lost, the receiver MAY use the Discard Report Block 245 [I-D.ietf-avt-rtcp-xr-discard] instead. In case of limited available 246 reporting bandwidth, it is up to the receiver whether or not to 247 include RTCP XR Discard RLE reports or not. 249 The receiver MAY send the Discard RLE Reports as part of the 250 regularly scheduled RTCP packets as per RFC3550. It MAY also include 251 Discard RLE Reports in immediate or early feedback packets as per 252 RFC4585. 254 5.2. Media Sender 256 The media sender MUST be prepared to operate without receiving any 257 Discard RLE reports. If Discard RLE reports are generated by the 258 receiver, the sender cannot rely on all these reports being received, 259 nor can the sender rely on a regular generation pattern from the 260 receiver side. 262 However, if the sender receives any RTCP reports but no Discard RLE 263 report blocks and is aware that the receiver supports Discard RLE 264 report blocks, it MAY assume that no packets were discarded at the 265 receiver. 267 6. SDP signaling 269 The report blocks specified in this document define extensions to 270 RTCP XR reporting. Whether or not this specific extended report is 271 sent is left to the discretion of the receiver. Its presence may 272 enable better operation of the sender since more detailed information 273 is available. Not providing this information will make the sender 274 rely on other RTCP report metrics. 276 A participant of a media session MAY use SDP to signal its support 277 for this attribute. In this case, the RTCP XR attribute as defined 278 in RFC3611 [RFC3611] MUST be used. The SDP RFC4566 [RFC4566] 279 attribute 'xr-format' defined in RFC3611 is augmented as described in 280 the following to indicate the discard metric. 282 rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] 283 CRLF ; defined in [RFC3611] 285 xr-format =/ xr-discard-rle 286 / xr-discard-bytes 288 xr-discard-rle = "discard-rle" 289 xr-discard-bytes = "discard-bytes" 291 The literal 'discard-rle' MUST be used to indicate support for the 292 Discard RLE Report Block defined in section Section 3, the literal 293 'discard-bytes' to indicate support for the Bytes Discarded Report 294 Block defined in section Section 4 296 For signaling support for the discard metric, the rules defined in 297 RFC3611 apply. Generally, senders and receivers SHOULD indicate this 298 capability if they support this metric and would like to use it in 299 the specific media session being signaled. The receiver MAY decide 300 not to send discard information unless it knows about the sender's 301 support to save on RTCP reporting bandwidth. 303 A participant in a media session MAY use the two report blocks 304 specified in this document without any explicit (SDP) signaling. 306 7. Security Considerations 308 The security considerations of RFC3550, RFC3611, and RFC4585 apply. 309 Since this document offers only a more precise reporting for an 310 already existing metric, no further security implications are 311 foreseen. 313 8. IANA Considerations 315 New block types for RTCP XR are subject to IANA registration. For 316 general guidelines on IANA considerations for RTCP XR, refer to 317 RFC3611 [RFC3611]. 319 8.1. XR Report Block Registration 321 This document extends the IANA "RTCP XR Block Type Registry" by two 322 new values: DRLE and BDR. 324 [Note to RFC Editor: please replace DRLE and BDR with the IANA 325 provided RTCP XR block type for this block here and in the diagrams 326 above.] 328 8.2. SDP Parameter Registration 330 This document registers two new parameters for the Session 331 Description Protocol (SDP), "discard-rle" and "discard-bytes", in the 332 "RTCP XR SDP Parameters Registry". 334 8.3. Contact information for IANA registrations 336 Joerg Ott (jo@comnet.tkk.fi) 338 Aalto University Comnet, Otakaari 5A, 02150 Espoo, Finland. 340 9. Normative References 342 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 343 Requirement Levels", BCP 14, RFC 2119, March 1997. 345 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 346 Jacobson, "RTP: A Transport Protocol for Real-Time 347 Applications", STD 64, RFC 3550, July 2003. 349 [RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and 350 Video Conferences with Minimal Control", STD 65, RFC 3551, 351 July 2003. 353 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 354 "Extended RTP Profile for Real-time Transport Control 355 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, 356 July 2006. 358 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 359 Description Protocol", RFC 4566, July 2006. 361 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 362 Protocol Extended Reports (RTCP XR)", RFC 3611, 363 November 2003. 365 [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control 366 Protocol (RTCP) Extensions for Single-Source Multicast 367 Sessions with Unicast Feedback", RFC 5760, February 2010. 369 [I-D.ietf-avt-rtcp-xr-discard] 370 Hunt, G. and A. Clark, "RTCP XR Report Block for Discard 371 metric Reporting", draft-ietf-avt-rtcp-xr-discard-02 (work 372 in progress), May 2009. 374 [I-D.ietf-avt-rtcp-xr-burst-gap-discard] 375 Hunt, G. and A. Clark, "RTCP XR Report Block for Burst/Gap 376 Discard metric Reporting", 377 draft-ietf-avt-rtcp-xr-burst-gap-discard-02 (work in 378 progress), May 2009. 380 [I-D.ietf-pmol-metrics-framework] 381 Clark, A. and B. Claise, "Guidelines for Considering New 382 Performance Metric Development", 383 draft-ietf-pmol-metrics-framework-08 (work in progress), 384 January 2011. 386 Authors' Addresses 388 Joerg Ott 389 Aalto University 390 Otakaari 5 A 391 Espoo, FIN 02150 392 Finland 394 Email: jo@comnet.tkk.fi 396 Igor D.D. Curcio 397 Nokia Research Center 398 P.O. Box 1000 (Visiokatu 1) 399 Tampere, FIN 33721 400 Finland 402 Email: igor.curcio@nokia.com 404 Varun Singh 405 Aalto University 406 School of Science and Technology 407 Otakaari 5 A 408 Espoo, FIN 02150 409 Finland 411 Email: varun@comnet.tkk.fi 412 URI: http://www.netlab.tkk.fi/~varun/