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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: December 30, 2013 Network Zen 6 Q. Wu 7 Huawei 8 June 28, 2013 10 RTP Control Protocol (RTCP) Extended Report (XR) Block for Discard Count 11 metric Reporting 12 draft-ietf-xrblock-rtcp-xr-discard-15.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 December 30, 2013. 37 Copyright Notice 39 Copyright (c) 2013 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. Metrics represented using RFC6390 Template . . . . . 15 79 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 16 80 B.1. draft-ietf-xrblock-rtcp-xr-discard-14 . . . . . . . . . . 16 81 B.2. draft-ietf-xrblock-rtcp-xr-discard-13 . . . . . . . . . . 16 82 B.3. draft-ietf-xrblock-rtcp-xr-discard-12 . . . . . . . . . . 16 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 85 1. Introduction 87 1.1. Discard Count Report Block 89 This document defines a new block type to augment those defined in 90 [RFC3611] for use in a range of RTP applications. The new block type 91 supports the reporting of the number of packets which are received 92 correctly but are never played out, typically because they arrive too 93 late to be played out (buffer underflow) or too early (buffer 94 overflow). The metric is applicable both to systems which use packet 95 loss repair techniques (such as forward error correction [RFC5109] or 96 retransmission [RFC4588]) and to those which do not. 98 This metric is useful for identifying the existence, and 99 characterizing the severity, of a packet transport problem which may 100 affect users' perception of a service delivered over RTP. 102 This block may be used in conjunction with [BGDISCARD] which provides 103 additional information on the pattern of discarded packets. However 104 the metric in [BGDISCARD] may be used independently of the metrics in 105 this block. 107 When a Discard Count Metrics Block is sent together with a Burst Gap 108 Discard Metrics Block (defined in [BGDISCARD] ) to the media sender 109 or RTP based network management system, the information carried in 110 the Discard Count Metrics Block and the Burst Gap Discard Metrics 111 Block allows systems receiving the blocks to calculate burst gap 112 summary statistics (e.g., the gap discard rate). 114 The metric belongs to the class of transport-related end system 115 metrics defined in [RFC6792]. 117 1.2. RTCP and RTCP XR Reports 119 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 120 defined an extensible structure for reporting using an RTCP Extended 121 Report (XR). This document defines a new Extended Report block for 122 use with [RFC3550] and [RFC3611]. 124 1.3. Performance Metrics Framework 126 The Performance Metrics Framework [RFC6390] provides guidance on the 127 definition and specification of performance metrics. The RTP 128 Monitoring Architectures [RFC6792] provides guideline for reporting 129 block format using RTCP XR. The metrics block described in this 130 document are in accordance with the guidelines in [RFC6390] and 131 [RFC6792]. 133 1.4. Applicability 135 This metric is believed to be applicable to a large class of RTP 136 applications which use a de-jitter buffer [RFC5481]. 138 Discards due to late or early arriving packets affects user 139 experience. The reporting of discards alerts senders and other 140 receivers to the need to adjust their transmission or reception 141 strategies. The reports allow network managers to diagnose these 142 user experience problems. 144 The ability to detect duplicate packets can be used by managers to 145 detect network layer or sender behavior which may indicate network or 146 device issues. Based on the reports, these issues may be addressed 147 prior to any impact on user experience. 149 2. Terminology 151 2.1. Standards Language 153 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 154 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 155 document are to be interpreted as described in RFC 2119 [RFC2119]. 157 In addition, the following terms are defined: 159 Received, Lost and Discarded 161 A packet shall be regarded as lost if it fails to arrive within an 162 implementation-specific time window. A packet that arrives within 163 this time window but is either too early to be played out or too 164 late to be played out or thrown away before playout due to packet 165 duplication or redundancy shall be regarded as discarded. A 166 packet shall not be regarded as discarded if it arrives within 167 this time window but is dropped during decoding by some higher 168 layer decoder, e.g., due to a decoding error. A packet shall be 169 classified as one of received (or OK), discarded or lost. The 170 Discard Count Metric counts only discarded packets. The metric 171 "cumulative number of packets lost" defined in [RFC3550] reports a 172 count of packets lost from the media stream (single 173 Synchronization source (SSRC) within single RTP session). 174 Similarly the metric "number of packets discarded" reports a count 175 of packets discarded from the media stream (single SSRC within 176 single RTP session) arriving at the receiver. Another metric 177 defined in [RFC5725] is available to report on packets which are 178 not recovered by any repair techniques which may be in use. 180 3. Discard Count Metric Report Block 182 Metrics in this block report on the number of packets discarded in 183 the stream arriving at the RTP end system. The measurement of these 184 metrics is made at the receiving end of the RTP stream. Instances of 185 this metrics block refer by SSRC to the separate auxiliary 186 Measurement Information Block [RFC6776] which describes measurement 187 Intervals in use. This metrics block relies on the measurement 188 interval in the Measurement Information Block indicating the span of 189 the report and MUST be sent in the same compound RTCP packet as the 190 measurement information block. If the measurement interval is not 191 received in the same compound RTCP packet as this metrics block, this 192 metrics block MUST be discarded. 194 3.1. Report Block Structure 196 0 1 2 3 197 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 1 198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 199 | BT=PDC | I |DT | resv.| block length = 2 | 200 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 201 | SSRC of Source | 202 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 203 | discard count | 204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 206 Figure 1: Report Block Structure 208 3.2. Definition of Fields in Discard Count Metric Report Block 210 Block type (BT): 8 bits 212 A Discard Count Metric Report Block is identified by the constant 213 PDC. 215 [Note to RFC Editor: please replace PDC with the IANA provided 216 RTCP XR block type for this block.] 218 Interval Metric Flag (I): 2 bits 220 This field indicates whether the reported metric is an interval, 221 cumulative, or sampled metric [RFC6792]: 223 I=10: Interval Duration - the reported value applies to the 224 most recent measurement interval duration between successive 225 metrics reports. 227 I=11: Cumulative Duration - the reported value applies to the 228 accumulation period characteristic of cumulative measurements. 230 I=01: Sampled Value - the reported value is a sampled 231 instantaneous value. 233 In this document, the Discard Count Metric can only be measured 234 over definite intervals, and cannot be sampled. Accordingly, the 235 value I=01, indicating a sampled value, MUST NOT be sent, and MUST 236 be discarded when received. In addition, the value I=00 is 237 reserved and also MUST NOT be sent, and MUST be discarded when 238 received. 240 Discard Type (DT): 2bits 242 This field is used to identify the discard type used in this 243 report block. The discard type is defined as follows: 245 00: Report packet discarded or being thrown away before playout 246 due to packets duplication. 248 01: Report packet discarded due to too early to be played out. 250 10: Report packet discarded due to too late to be played out. 252 The value DT=11 is reserved for future definition and MUST NOT be 253 Sent,and MUST be discarded when received. 255 An endpoint MAY report any combination of discard types in each 256 reporting interval by including several Discard Count Metric 257 Report Blocks in a single RTCP XR packet. 259 Some systems send duplicate RTP packets for robustness or error 260 resilience. This is NOT RECOMMENDED since it breaks RTCP packet 261 statistics. If duplication is desired for error resilience, the 262 mechanism described in [RTPDUP] can be used, since this will not 263 cause breakage of RTP streams or RTCP statistics. 265 Reserved (resv): 4 bits 267 These bits are reserved. They MUST be set to zero by senders and 268 ignored by receivers (See RFC6709 section 4.2). 270 block length: 16 bits 272 The length of this report block in 32-bit words, minus one, in 273 accordance with the definition in [RFC3611]. This field MUST be 274 set to 2 to match the fixed length of the report block. The block 275 MUST be discarded if the block length is set to a different value. 277 SSRC of source: 32 bits 279 As defined in Section 4.1 of [RFC3611]. 281 discard count 283 Number of packets discarded over the period (Interval or 284 Cumulative) covered by this report. 286 The measured value is unsigned value. If the measured value 287 exceeds 0xFFFFFFFD, the value 0xFFFFFFFE MUST be reported to 288 indicate an over-range measurement. If the measurement is 289 unavailable, the value 0xFFFFFFFF MUST be reported. 291 Note that the number of packets expected in the period associated 292 with this metric (whether interval or cumulative) is available 293 from the difference between a pair of extended sequence numbers in 294 the Measurement Information block [RFC6776], so need not be 295 repeated in this block. 297 4. SDP Signaling 299 [RFC3611] defines the use of SDP (Session Description Protocol) 300 [RFC4566] for signaling the use of XR blocks. However XR blocks MAY 301 be used without prior signaling (see section 5 of RFC3611). 303 4.1. SDP rtcp-xr-attrib Attribute Extension 305 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 306 in [RFC3611] by providing an additional value of "xr-format" to 307 signal the use of the report block defined in this document. 309 xr-format =/ xr-pdc-block 310 xr-pdc-block = "pkt-discard-count" 312 4.2. Offer/Answer Usage 314 When SDP is used in offer-answer context, the SDP Offer/Answer usage 315 defined in [RFC3611] for unilateral "rtcp-xr" attribute parameters 316 applies. For detailed usage of Offer/Answer for unilateral 317 parameter, refer to section 5.2 of [RFC3611]. 319 5. IANA Considerations 321 New block types for RTCP XR are subject to IANA registration. For 322 general guidelines on IANA considerations for RTCP XR, refer to 323 [RFC3611]. 325 5.1. New RTCP XR Block Type value 327 This document assigns the block type value PDC in the IANA " RTP 328 Control Protocol Extended Reports (RTCP XR) Block Type Registry " to 329 the "Discard Count Metrics Block". 331 [Note to RFC Editor: please replace PDC with the IANA provided RTCP 332 XR block type for this block.] 334 5.2. New RTCP XR SDP Parameter 336 This document also registers a new parameter "pkt-discard-count" in 337 the " RTP Control Protocol Extended Reports (RTCP XR) Session 338 Description Protocol (SDP) Parameters Registry ". 340 5.3. Contact information for registrations 342 The following contact information is provided for all registrations 343 in this document: 345 Qin Wu (sunseawq@huawei.com) 347 101 Software Avenue, Yuhua District 348 Nanjing, Jiangsu 210012 349 China 351 6. Security Considerations 353 In some situations, returning very detailed error information 354 (e.g.,over-range measurement or measurement unavailable) using this 355 report block can provide an attacker with insight into the security 356 processing. Where this is a concern, the implementation should apply 357 authentication to this report block. This can be achieved by using 358 the AVPF profile together with the Secure RTP profile as defined in 359 [RFC3711]; as a prerequisite, an appropriate combination of those two 360 profiles (an "SAVPF") is being specified [RFC5124]. 362 Besides this, it is believed that this proposed RTCP XR report block 363 introduces no new security considerations beyond those described in 364 [RFC3611]. This block does not provide per-packet statistics so the 365 risk to confidentiality documented in Section 7, paragraph 3 of 366 [RFC3611] does not apply. 368 7. Contributors 370 Geoff Hunt wrote the initial draft of this document. 372 8. Acknowledgments 374 The authors gratefully acknowledge reviews and feedback provided by 375 Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, 376 Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, 377 Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, 378 Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi 379 Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada, Kevin 380 Gross, Varun Singh, Claire Bi, Roni Even, Dan Romascanu and Jonathan 381 Lennox. 383 9. References 385 9.1. Normative References 387 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 388 Requirement Levels", March 1997. 390 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 391 Applications", RFC 3550, July 2003. 393 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 394 Protocol Extended Reports (RTCP XR)", November 2003. 396 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 397 Description Protocol", July 2006. 399 [RFC6709] Carpenter, B., Aboba, B., and S. Cheshire, "Design 400 Considerations for Protocol Extensions", RFC 6709, 401 September 2012. 403 [RFC6776] Hunt, G., "Measurement Identity and information Reporting 404 using SDES item and XR Block", RFC 6776, October 2012. 406 9.2. Informative References 408 [BGDISCARD] 409 Hunt, G., "RTCP XR Report Block for Burst Gap Discard 410 metric Reporting", 411 ID draft-ietf-xrblock-rtcp-xr-burst-gap-discard-14, 412 April 2013. 414 [RFC4588] Rey, J., "RTP Retransmission Payload Format", RFC 4588, 415 July 2006. 417 [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error 418 Correction", RFC 5109, July 2006. 420 [RFC5725] Begen, A., "RTCP XR Report Block for Post-Repair Loss 421 metric Reporting", RFC 5725, February 2010. 423 [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric 424 Development", RFC 6390, October 2011. 426 [RFC6792] Wu, Q., "Monitoring Architectures for RTP", RFC 6792, 427 November 2012. 429 [RTPDUP] Begen, A. and C. Perkins, "Duplicating RTP Streams", 430 ID draft-ietf-avtext-rtp-duplication-02, March 2013. 432 Appendix A. Metrics represented using RFC6390 Template 434 RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC 435 number, when assigned. 437 a. Number of packets discarded Metric 439 * Metric Name: Number of RTP packets discarded Metric 441 * Metric Description: Number of RTP packets discarded over the 442 period covered by this report. 444 * Method of Measurement or Calculation: See section 3.2, number 445 of packets discarded definition [RFCXXXX]. 447 * Units of Measurement: See section 3.2, number of packets 448 discarded definition [RFCXXXX]. 450 * Measurement Point(s) with Potential Measurement Domain: See 451 section 3, 1st paragraph [RFCXXXX]. 453 * Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for 454 measurement timing and section 3.2 [RFCXXXX] for Interval 455 Metric flag. 457 * Use and applications: See section 1.4 [RFCXXXX]. 459 * Reporting model: See RFC3611. 461 Appendix B. Change Log 463 Note to the RFC-Editor: please remove this section prior to 464 publication as an RFC. 466 B.1. draft-ietf-xrblock-rtcp-xr-discard-14 468 The following are the major changes compared to previous version: 470 o Editorial changes to paragraph 4 of section 1.1. 472 B.2. draft-ietf-xrblock-rtcp-xr-discard-13 474 The following are the major changes compared to previous version: 476 o Some editorial changes to get in line with burst gap drafts. 478 B.3. draft-ietf-xrblock-rtcp-xr-discard-12 480 The following are the major changes compared to previous version: 482 o Incorporate some changes to burst gap draft that applies to this 483 document. 485 o Use RFC6390 template to the metrics in the appendix. 487 Authors' Addresses 489 Alan Clark 490 Telchemy Incorporated 491 2905 Premiere Parkway, Suite 280 492 Duluth, GA 30097 493 USA 495 Email: alan.d.clark@telchemy.com 497 Glen Zorn 498 Network Zen 499 77/440 Soi Phoomjit, Rama IV Road 500 Phra Khanong, Khlong Toie 501 Bangkok 10110 502 Thailand 504 Phone: +66 (0) 87 502 4274 505 Email: gwz@net-zen.net 507 Qin Wu 508 Huawei 509 101 Software Avenue, Yuhua District 510 Nanjing, Jiangsu 210012 511 China 513 Email: sunseawq@huawei.com