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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Audio/Video Transport Working Group A. Clark 3 Internet-Draft Telchemy 4 Intended status: Standards Track G. Zorn 5 Expires: April 15, 2013 Network Zen 6 Q. Wu 7 Huawei 8 October 12, 2012 10 RTP Control Protocol (RTCP) Extended Report (XR) Block for Discard Count 11 metric Reporting 12 draft-ietf-xrblock-rtcp-xr-discard-09.txt 14 Abstract 16 This document defines an RTP Control Protocol(RTCP) Extended Report 17 (XR) Block that allows the reporting of a simple discard count metric 18 for use in a range of RTP applications. 20 Status of this Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on April 15, 2013. 37 Copyright Notice 39 Copyright (c) 2012 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 1.1. Discard Count Report Block . . . . . . . . . . . . . . . . 3 56 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 57 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 58 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 60 2.1. Standards Language . . . . . . . . . . . . . . . . . . . . 5 61 3. Discard Count Metric Report Block . . . . . . . . . . . . . . 6 62 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 6 63 3.2. Definition of Fields in Discard Count Metric Report 64 Block . . . . . . . . . . . . . . . . . . . . . . . . . . 6 65 4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 9 66 4.1. SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 9 67 4.2. Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 9 68 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 69 5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 10 70 5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 10 71 5.3. Contact information for registrations . . . . . . . . . . 10 72 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 73 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12 74 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 75 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 76 9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 77 9.2. Informative References . . . . . . . . . . . . . . . . . . 14 78 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 15 79 A.1. draft-ietf-xrblock-rtcp-xr-discard-09 . . . . . . . . . . 15 80 A.2. draft-ietf-xrblock-rtcp-xr-discard-08 . . . . . . . . . . 15 81 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 83 1. Introduction 85 1.1. Discard Count Report Block 87 This document defines a new block type to augment those defined in 88 [RFC3611] for use in a range of RTP applications. The new block type 89 supports the reporting of the number of packets which are received 90 correctly but are never played out, typically because they arrive too 91 late to be played out (buffer underflow) or too early (buffer 92 overflow). The metric is applicable both to systems which use packet 93 loss repair techniques (such as forward error correction [RFC5109] or 94 retransmission [RFC4588]) and to those which do not. 96 This metric is useful for identifying the existence, and 97 characterizing the severity, of a packet transport problem which may 98 affect users' perception of a service delivered over RTP. 100 This block may be used in conjunction with [BGDISCARD] which provides 101 additional information on the pattern of discarded packets. However 102 the metric in [BGDISCARD] may be used independently of the metrics in 103 this block. 105 In case of Discard count metric block sent together with Burst gap 106 discard metric block defined in [BGDISCARD] to the media sender or 107 RTP based network management system, information carried in the 108 discard count metric block and Burst gap discard metric block allows 109 them calculate the some bust gap summary statistics, e.g., gap 110 discard rate. 112 The metric belongs to the class of transport-related end system 113 metrics defined in [MONARCH]. 115 1.2. RTCP and RTCP XR Reports 117 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 118 defined an extensible structure for reporting using an RTCP Extended 119 Report (XR). This document defines a new Extended Report block for 120 use with [RFC3550] and [RFC3611]. 122 1.3. Performance Metrics Framework 124 The Performance Metrics Framework [RFC6390] provides guidance on the 125 definition and specification of performance metrics. The RTP 126 Monitoring Architectures [MONARCH] provides guideline for reporting 127 block format using RTCP XR. The Metrics Block described in this 128 document are in accordance with the guidelines in [RFC6390] and 129 [MONARCH]. 131 1.4. Applicability 133 This metric is believed to be applicable to a large class of RTP 134 applications which use a jitter buffer. 136 Discards due to late or early arriving packets affects user 137 experience. The reporting of discards alerts senders and other 138 receivers to the need to adjust their transmission or reception 139 strategies. The reports allow network managers to diagnose these 140 user experience problems. 142 The ability to detect duplicate packets can be used by managers to 143 detect network layer or sender behavior which may indicate network or 144 device issues. Based on the reports, these issues may be addressed 145 prior to any impact on user experience. 147 2. Terminology 149 2.1. Standards Language 151 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 152 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 153 document are to be interpreted as described in RFC 2119 [RFC2119]. 155 In addition, the following terms are defined: 157 Received, Lost and Discarded 159 A packet shall be regarded as lost if it fails to arrive within an 160 implementation-specific time window. A packet that arrives within 161 this time window but is too early or late to be played out or 162 thrown away before playout due to packet duplication or redundancy 163 shall be regarded as discarded. A packet shall be classified as 164 one of received (or OK), discarded or lost. The Discard Count 165 Metric counts only discarded packets. The metric "cumulative 166 number of packets lost" defined in [RFC3550] reports a count of 167 packets lost from the media stream (single SSRC within single RTP 168 session). Similarly the metric "number of packets discarded" 169 reports a count of packets discarded from the media stream (single 170 SSRC within single RTP session) arriving at the receiver. Another 171 metric defined in [RFC5725] is available to report on packets 172 which are not recovered by any repair techniques which may be in 173 use. 175 3. Discard Count Metric Report Block 177 3.1. Report Block Structure 179 0 1 2 3 180 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 1 181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 182 | BT=PDC | I |DT | resv.| block length = 2 | 183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 184 | SSRC of Source | 185 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 186 | number of packets discarded | 187 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 189 Figure 1: Report Block Structure 191 3.2. Definition of Fields in Discard Count Metric Report Block 193 Block type (BT): 8 bits 195 A Discard Count Metric Report Block is identified by the constant 196 PDC. 198 [Note to RFC Editor: please replace PDC with the IANA provided 199 RTCP XR block type for this block.] 201 Interval Metric flag (I): 2 bits 203 This field indicates whether the reported metric is an interval, 204 cumulative, or sampled metric [MONARCH]. The Discard Count Metric 205 value can be reported as either an interval metric (I=10) or a 206 cumulative metric (I=11). It does not make sense to report the 207 Discard Count Metric as a sampled metric, so the value I=01 MUST 208 NOT be used. The value I=00 is reserved, and MUST NOT be used. 210 Discard Type (DT): 2bits 212 This field is used to identify the discard type used in this 213 report block. The discard type is defined as follows: 215 00: Report packet discarded or being thrown away before playout 216 due to packets duplication. 218 01: Report packet discarded due to too early to be played out. 220 10: Report packet discarded due to too late to be played out. 222 11: Report the total number of discarded packets due to both 223 early and late to be played out. 225 An endpoint MAY report only one of the above four discard types 226 blocks in an compound RTCP report in a reporting interval. It MAY 227 also report a combination of discard types in a compound RTCP 228 report but not all combinations are valid. The endpoint MAY 229 report duplicate packet discard (DT=0) block with any other 230 discard (DT=1, 2, or 3) block. Additionally, an endpoint MUST NOT 231 report combined discard (DT=3) block with early discard (DT=1) or 232 late discard (DT=2) report block. 234 Some systems send duplicate RTP packets for robustness or error 235 resilience. This is NOT RECOMMENDED since it breaks RTCP packet 236 statistics. If duplication is desired for error resilience, the 237 mechanism described in [RTPDUP] can be used, since this will not 238 cause breakage of RTP streams or RTCP statistics. 240 Reserved (resv): 4 bits 242 These bits are reserved. They MUST be set to zero by senders and 243 ignored by receivers. 245 block length: 16 bits 247 The length of this report block in 32-bit words, minus one. For 248 the Discard Count block, the block length is equal to 2. 250 SSRC of source: 32 bits 252 As defined in Section 4.1 of [RFC3611]. 254 number of packets discarded: 32 bits 256 Number of packets discarded over the period (Interval or 257 Cumulative) covered by this report. 259 If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE 260 MUST be reported to indicate an over-range measurement. If the 261 measurement is unavailable, the value 0xFFFFFFFF MUST be reported. 263 Note that the number of packets expected in the period associated 264 with this metric (whether interval or cumulative) is available 265 from the difference between a pair of extended sequence numbers in 266 the Measurement Information block [MEASI], so need not be repeated 267 in this block. 269 4. SDP Signaling 271 [RFC3611] defines the use of SDP (Session Description Protocol) 272 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 273 without prior signaling. 275 4.1. SDP rtcp-xr-attrib Attribute Extension 277 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 278 in [RFC3611] by providing an additional value of "xr-format" to 279 signal the use of the report block defined in this document. 281 xr-format =/ xr-pdc-block 283 xr-pdc-block = "pkt-dscrd-count" 285 4.2. Offer/Answer Usage 287 When SDP is used in offer-answer context, the SDP Offer/Answer usage 288 defined in [RFC3611] applies. 290 5. IANA Considerations 292 New block types for RTCP XR are subject to IANA registration. For 293 general guidelines on IANA considerations for RTCP XR, refer to 294 [RFC3611]. 296 5.1. New RTCP XR Block Type value 298 This document assigns the block type value PDC in the IANA "RTCP XR 299 Block Type Registry" to the "Discard Count Metrics Block". 301 [Note to RFC Editor: please replace PDC with the IANA provided RTCP 302 XR block type for this block.] 304 5.2. New RTCP XR SDP Parameter 306 This document also registers a new parameter "pkt-dscrd-count" in the 307 "RTCP XR SDP Parameters Registry". 309 5.3. Contact information for registrations 311 The following contact information is provided for all 312 registrations in this document: 314 Qin Wu (sunseawq@huawei.com) 316 101 Software Avenue, Yuhua District 317 Nanjing, Jiangsu 210012 318 China 320 6. Security Considerations 322 It is believed that this proposed RTCP XR report block introduces no 323 new security considerations beyond those described in [RFC3611]. 324 This block does not provide per-packet statistics so the risk to 325 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 326 does not apply. 328 7. Contributors 330 Geoff Hunt wrote the initial draft of this document. 332 8. Acknowledgments 334 The authors gratefully acknowledge reviews and feedback provided by 335 Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, 336 Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, 337 Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, 338 Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi 339 Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada,Kevin 340 Gross, Varun Singh, Claire Bi, Roni Even, Dan Romascanu. 342 9. References 344 9.1. Normative References 346 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 347 Requirement Levels", March 1997. 349 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 350 Applications", RFC 3550, July 2003. 352 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 353 Protocol Extended Reports (RTCP XR)", November 2003. 355 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 356 Description Protocol", July 2006. 358 9.2. Informative References 360 [BGDISCARD] 361 Hunt, G., "RTCP XR Report Block for Burst Gap Discard 362 metric Reporting", 363 ID draft-ietf-xrblock-rtcp-xr-burst-gap-discard-06, 364 October 2012. 366 [MEASI] Hunt, G., "Measurement Identity and information Reporting 367 using SDES item and XR Block", 368 ID draft-ietf-xrblock-rtcp-xr-meas-identity-10, 369 August 2012. 371 [MONARCH] Wu, Q., "Monitoring Architectures for RTP", 372 ID draft-ietf-avtcore-monarch-22, September 2012. 374 [RFC4588] Rey, J., "RTP Retransmission Payload Format", RFC 4588, 375 July 2006. 377 [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error 378 Correction", RFC 5109, July 2006. 380 [RFC5725] Begen, A., "RTCP XR Report Block for Post-Repair Loss 381 metric Reporting", RFC 5725, February 2010. 383 [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric 384 Development", RFC 6390, October 2011. 386 [RTPDUP] Begen, A. and C. Perkins, "Duplicating RTP Streams", 387 ID draft-ietf-avtext-rtp-duplication-00, July 2012. 389 Appendix A. Change Log 391 Note to the RFC-Editor: please remove this section prior to 392 publication as an RFC. 394 A.1. draft-ietf-xrblock-rtcp-xr-discard-09 396 The following are the major changes compared to previous version: 398 o SDP Duplicated Parameter Deleting. 400 A.2. draft-ietf-xrblock-rtcp-xr-discard-08 402 The following are the major changes compared to previous version: 404 o Outdated reference update. 406 o Editorial changes based on comments that applied to PDV and Delay 407 drafts. 409 Authors' Addresses 411 Alan Clark 412 Telchemy Incorporated 413 2905 Premiere Parkway, Suite 280 414 Duluth, GA 30097 415 USA 417 Email: alan.d.clark@telchemy.com 419 Glen Zorn 420 Network Zen 421 77/440 Soi Phoomjit, Rama IV Road 422 Phra Khanong, Khlong Toie 423 Bangkok 10110 424 Thailand 426 Phone: +66 (0) 87 502 4274 427 Email: gwz@net-zen.net 429 Qin Wu 430 Huawei 431 101 Software Avenue, Yuhua District 432 Nanjing, Jiangsu 210012 433 China 435 Email: sunseawq@huawei.com