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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Audio/Video Transport Working Group G. Hunt 3 Internet-Draft Unaffiliated 4 Intended status: Standards Track A. Clark 5 Expires: June 9, 2012 Telchemy 6 Q. Wu 7 Huawei 8 December 7, 2011 10 RTCP XR Report Block for Packet Delay Variation Metric Reporting 11 draft-ietf-xrblock-rtcp-xr-pdv-02.txt 13 Abstract 15 This document defines an RTCP XR Report Block that allows the 16 reporting of Packet Delay Variation metrics for a range of RTP 17 applications. 19 Status of this Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on June 9, 2012. 36 Copyright Notice 38 Copyright (c) 2011 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 1.1. Packet Delay Variation Metrics Block . . . . . . . . . . . 3 55 1.2. RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . . 3 56 1.3. Performance Metrics Framework . . . . . . . . . . . . . . 3 57 1.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 3 58 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 3. Packet Delay Variation Metrics Block . . . . . . . . . . . . . 5 60 3.1. Report Block Structure . . . . . . . . . . . . . . . . . . 5 61 3.2. Definition of Fields in PDV Metrics Block . . . . . . . . 5 62 3.3. Guidance on use of PDV metrics . . . . . . . . . . . . . . 9 63 3.4. Examples of use . . . . . . . . . . . . . . . . . . . . . 9 64 4. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 11 65 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 66 5.1. New RTCP XR Block Type value . . . . . . . . . . . . . . . 12 67 5.2. New RTCP XR SDP Parameter . . . . . . . . . . . . . . . . 12 68 5.3. Contact information for registrations . . . . . . . . . . 12 69 5.4. New registry of PDV types . . . . . . . . . . . . . . . . 12 70 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 71 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 72 7.1. Normative References . . . . . . . . . . . . . . . . . . . 15 73 7.2. Informative References . . . . . . . . . . . . . . . . . . 15 74 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 16 75 A.1. draft-ietf-avt-rtcp-xr-pdv-03 . . . . . . . . . . . . . . 16 76 A.2. draft-ietf-xrblock-rtcp-xr-pdv-00 . . . . . . . . . . . . 16 77 A.3. draft-ietf-xrblock-rtcp-xr-pdv-01 . . . . . . . . . . . . 16 78 A.4. draft-ietf-xrblock-rtcp-xr-pdv-02 . . . . . . . . . . . . 16 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 81 1. Introduction 83 1.1. Packet Delay Variation Metrics Block 85 This draft defines a new block type to augment those defined in 86 [RFC3611], for use in a range of RTP applications. 88 The new block type provides information on Packet Delay Variation 89 using one of several standard metrics. 91 The metrics belong to the class of transport metrics defined in 92 [MONARCH] (work in progress). 94 1.2. RTCP and RTCP XR Reports 96 The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] 97 defined an extensible structure for reporting using an RTCP Extended 98 Report (XR). This draft defines a new Extended Report block that 99 MUST be used in accordance with [RFC3550] and [RFC3611]. 101 1.3. Performance Metrics Framework 103 The Performance Metrics Framework [RFC6390] provides guidance on the 104 definition and specification of performance metrics. Metrics 105 described in this draft either reference external definitions or 106 define metrics generally in accordance with the guidelines in 107 [RFC6390]. 109 1.4. Applicability 111 These metrics are applicable to a range of RTP applications. 113 2. Definitions 115 This report block makes use of binary fractions. The terminology 116 used is 118 Numeric formats S X:Y 120 where S indicates a two's complement signed representation, X 121 the number of bits prior to the decimal place and Y the number 122 of bits after the decimal place. 124 Hence 8:8 represents an unsigned number in the range 0.0 to 125 255.996 with a granularity of 0.0039. S7:8 would represent the 126 range -127.996 to +127.996. 0:16 represents a proper binary 127 fraction with range 129 0.0 to 1 - 1/65536 = 0.9999847 131 though note that use of flag values at the top of the numeric 132 range slightly reduces this upper limit. For example, if the 133 16- bit values 0xfffe and 0xffff are used as flags for "over- 134 range" and "unavailable" conditions, a 0:16 quantity has range 136 0.0 to 1 - 3/65536 = 0.9999542 138 3. Packet Delay Variation Metrics Block 140 Metrics in this block report on packet delay variation in the stream 141 arriving at the RTP system. Instances of this Metrics Block refer by 142 SSRC to the separate auxiliary Measurement Information block [MEASI] 143 which contains measurement intervals. This metric block relies on 144 the measurement interval in the Measurement Information block 145 indicating the span of the report. If the measurement interval is 146 not received for this metric block, this metric block should be 147 discarded. 149 3.1. Report Block Structure 151 PDV metrics block 153 0 1 2 3 154 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 7 155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 156 | BT=NPDV | I |pdvtyp |Rsv| block length=3 | 157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 158 | SSRC of Source | 159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 | Pos PDV Threshold/Peak | Pos PDV Percentile | 161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 162 | Neg PDV Threshold/Peak | Neg PDV Percentile | 163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 164 | Mean PDV | unused | 165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 167 Figure 1: Report Block Structure 169 3.2. Definition of Fields in PDV Metrics Block 171 Block type (BT): 8 bits 173 A Packet Delay Variation Metrics Report Block is identified by the 174 constant NPDV. 176 [Note to RFC Editor: please replace NPDV with the IANA provided 177 RTCP XR block type for this block.] 179 Interval Metric flag (I): 2 bit 181 This field is used to indicate whether the Basic Loss/Discard 182 metrics are Sampled, Interval or Cumulative metrics, that is, 183 whether the reported values applies to the most recent measurement 184 interval duration between successive metrics reports (I=10) (the 185 Interval Duration) or to the accumulation period characteristic of 186 cumulative measurements (I=11) (the Cumulative Duration) or to the 187 value of a continuously measured or calculated that has been 188 sampled at end of the interval (I=01) (Sampled Value). 190 Packet Delay Variation Metric Type (pdvtyp): 4 bits 192 This field is used to identify the Packet Delay Variation Metric 193 Type used in this report block, according to the following code: 195 bits 014-017 197 0: interarrival jitter, Section 6.4.1 of [RFC3550], 199 1: MAPDV2, Clause 6.2.3.2 of [G.1020], 201 2: 2-point PDV, Clause 6.2.4 of [Y.1540]. 203 Rsv.: 2 bits 205 This field is reserved for future definition. In the absence of 206 such a definition, the bits in this field MUST be set to zero and 207 MUST be ignored by the receiver. 209 Block Length: 16 bits 211 The length of this report block in 32-bit words, minus one. For 212 the Packet Delay Variation Metrics block, the block length is 213 equal to 3. 215 SSRC of source: 32 bits 217 As defined in Section 4.1 of [RFC3611]. 219 Positive PDV Threshold/Peak: 16 bits 221 This field is associated with the Positive PDV percentile and 222 expressed in Milliseconds with numeric format S11:4. The term 223 Positive represents that the packets are arriving later than the 224 expected time. 226 If the measured value is more negative than -2047.9375 (the value 227 which would be coded as 0x8001), the value 0x8000 SHOULD be 228 reported to indicate an over-range negative measurement. If the 229 measured value is more positive than +2047.8125 (the value which 230 would be coded as 0x7FFD), the value 0x7FFE SHOULD be reported to 231 indicate an over-range positive measurement. If the measurement 232 is unavailable, the value 0x7FFF SHOULD be reported. 234 Positive PDV Percentile: 16 bits 236 The percentages of packets in the RTP stream for which individual 237 packet delays were less than the Positive PDV Threshold. It is 238 expressed in numeric format 8:8 with values from 0 to 100th 239 percentile. 241 If the measurement is unavailable, the value 0xFFFF SHOULD be 242 reported. 244 Negative PDV Threshold/Peak: 16 bits 246 This field is associated with the Negative PDV percentile and 247 expressed in Milliseconds with numeric format S11:4. The term 248 Negative represents that the packets are arriving earlier than the 249 expected time. 251 If the measured value is more negative than -2047.9375 (the value 252 which would be coded as 0x8001), the value 0x8000 SHOULD be 253 reported to indicate an over-range negative measurement. If the 254 measured value is more positive than +2047.8125 (the value which 255 would be coded as 0x7FFD), the value 0x7FFE SHOULD be reported to 256 indicate an over-range positive measurement. If the measurement 257 is unavailable, the value 0x7FFF SHOULD be reported. 259 Negative PDV Percentile: 16 bits 261 The percentages of packets in the RTP stream for which individual 262 packet delays were more than the Negative PDV Threshold. It is 263 expressed in numeric format 8:8 with values from 0 to 100th 264 percentile. 266 If the measurement is unavailable, the value 0xFFFF SHOULD be 267 reported. 269 If the PDV Type indicated is 2-point PDV and the Positive and 270 Negative PDV Percentiles are set to 100.0 then the Positive and 271 Negative Threshold/Peak PDV values are the peak values measured 272 during the reporting interval (which may be from the start of the 273 call for cumulative reports). In this case, the difference 274 between the Positive and Negative Threshold/Peak values defines 275 the range of 2-point PDV. 277 Mean PDV: 16 bits 279 The mean PDV value of data packets is expressed in milliseconds 280 with Numeric format S11:4 format. 282 For MAPDV2 this value is generated according to Clause 6.2.3.2 of 283 [G.1020]. For interval reports the MAPDV2 value is reset at the 284 start of the interval. 286 For interarrival jitter, the value reported is the value of J(i) 287 calculated according to [RFC3550] at the time the report is 288 generated. 290 For 2-point PDV, the value reported is the mean of per-packet 291 2-point PDV values. This metric indicates the arrival time of the 292 first media packet of the session with respect to the mean of the 293 arrival times of every packet of the session. A single value of 294 the metric (for a single session) may not be useful by itself, but 295 its average over a number of sessions may be useful in diagnosing 296 media delay at session startup. For example, this might occur if 297 media packets are often delayed behind signalling packets due to 298 head-of-line blocking. 300 If the measured value is more negative than -2047.9375 (the value 301 which would be coded as 0x8001), the value 0x8000 SHOULD be 302 reported to indicate an over-range negative measurement. If the 303 measured value is more positive than +2047.8125 (the value which 304 would be coded as 0x7FFD), the value 0x7FFE SHOULD be reported to 305 indicate an over-range positive measurement. If the measurement 306 is unavailable, the value 0x7FFF SHOULD be reported. 308 Unused: 16 bits 310 These bits are unused. They SHOULD be set to zero by the sender 311 and MUST be ignored by the receiver. 313 3.3. Guidance on use of PDV metrics 315 This subsection provides informative guidance on when it might be 316 appropriate to use each of the PDV metric types. 318 Interarrival jitter (Section 6.4.1 of [RFC3550]) allows comparison of 319 results with those from RTP end systems which support only RTCP as 320 defined in [RFC3550]. 322 MAPDV2 (Clause 6.2.3.2 of [G.1020]) compares instantaneous (per- 323 packet) delay variation against a moving average delay variation. 324 This metric could be useful in determining residual impairment when 325 an RTP end system uses an adaptive de-jitter buffer which tracks the 326 average delay variation, provided the adaptive de-jitter buffer have 327 similar averaging behaviour as the MAPDV2 algorithm. 329 2-point PDV (Clause 6.2.4 of [Y.1540]) reports absolute packet delay 330 variation with respect to the time of arrival of the first packet of 331 the connection. In an RTP context, the two "points" are at the 332 sender (the synchronization source which applies RTP timestamps) and 333 at the receiver. The value of this metric for the packet with index 334 j is identical to the quantity D(i,j) defined in Section 6.4.1 of 335 [RFC3550] if the packet index i is set equal to 1, that is, the 336 reference packet for the metric is the first packet of the 337 connection. The metric includes the effect of the frequency offsets 338 of clocks in both the sender and receiver end systems, so it is 339 useful mainly in network where synchronisation is distributed. As 340 well as measuring packet delay variation in such networks, it may be 341 used to ensure that synchronisation is effective, for example where 342 the network carries ISDN data traffic over RTP [RFC4040]. The metric 343 is likely to be useful in networks which use fixed de-jitter 344 buffering, because it may be used to determine the length of the 345 required de-jitter buffer, or to determine if network performance has 346 deteriorated such that existing de-jitter buffers are too small to 347 accommodate the observed delay variation. 349 3.4. Examples of use 351 (a) To report interarrival jitter [RFC3550]: 353 PDV Threshold = FFFF (Undefined); PDV Percentile = FFFF 354 (Undefined); PDV type = 0 (interarrival jitter) 356 causes interarrival jitter to be reported in the Mean PDV 357 field. 359 (b) To report MAPDV2 [G.1020]: 361 Pos PDV Threshold = 50.0; Pos PDV Percentile = 95.3; Neg PDV 362 Threshold = 50.0 (note this implies -50ms); Neg PDV Percentile 363 = 98.4; PDV type = 1 (MAPDV2) 365 causes average MAPDV2 to be reported in the Mean PDV field. 367 Note that implementations may either fix the reported 368 percentile and calculate the associated PDV level or may fix a 369 threshold PDV level and calculate the associated percentile. 370 From a practical implementation perspective it is simpler to 371 use the second of these approaches (except of course in the 372 extreme case of a 100% percentile). 374 2-point PDV, according to [Y.1540] is the difference in delay 375 between the current packet and the first packet of the stream. 376 If the sending and receiving clocks are not synchronized, this 377 metric includes the effect of relative timing drift. 379 4. SDP Signaling 381 [RFC3611] defines the use of SDP (Session Description Protocol) 382 [RFC4566] for signaling the use of XR blocks. XR blocks MAY be used 383 without prior signaling. 385 This section augments the SDP [RFC4566] attribute "rtcp-xr" defined 386 in [RFC3611] by providing an additional value of "xr-format" to 387 signal the use of the report block defined in this document. 389 rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF 391 (defined in [RFC3611]) 393 xr-format =/ xr-pdv-block 395 xr-pdv-block = "pkt-dly-var" [ "," pdvtype ] [ "," nspec "," pspec ] 397 pdvtype = "pdv=" 0 ; interarrival jitter RFC 3550 398 / 1 ; MAPDV2 ITU-T G.1020 399 / 2 ; 2-point PDV ITU-T Y.1540 400 nspec = "nthr=" fixpoint ; negative PDV threshold (ms) 401 / "npc=" fixpoint ; negative PDV percentile 402 pspec = "pthr=" fixpoint ; positive PDV threshold (ms) 403 / "ppc=" fixpoint ; positive PDV percentile 405 fixpoint = 1*DIGIT "." 1*DIGIT ; fixed point decimal 406 DIGIT = %x30-39 408 When SDP is used in offer-answer, a system sending SDP may request a 409 specific type of PDV measurement. In addition, they may state a 410 specific percentile or threshold value, and expect to receive the 411 corresponding threshold or percentile metric, respectively. The 412 system receiving the SDP SHOULD send the PDV metrics requested, but 413 if the metric is not available, the system receiving the SDP SHOULD 414 send the metric block with the flag value indicating that the metric 415 is unavailable. 417 5. IANA Considerations 419 New block types for RTCP XR are subject to IANA registration. For 420 general guidelines on IANA considerations for RTCP XR, refer to 421 [RFC3611]. 423 5.1. New RTCP XR Block Type value 425 This document assigns the block type value NPDV in the IANA "RTCP XR 426 Block Type Registry" to the "Packet Delay Variation Metrics Block". 428 [Note to RFC Editor: please replace NPDV with the IANA provided RTCP 429 XR block type for this block.] 431 5.2. New RTCP XR SDP Parameter 433 This document also registers a new parameter "pkt-dly-var" in the 434 "RTCP XR SDP Parameters Registry". 436 5.3. Contact information for registrations 438 The contact information for the registrations is: 440 Qin Wu (sunseawq@huawei.com) 442 101 Software Avenue, Yuhua District 443 Nanjing, Jiangsu 210012 444 China 446 5.4. New registry of PDV types 448 This document creates a new registry to be called "RTCP XR PDV block 449 - PDV type" as a sub-registry of the "RTP Control Protocol Extended 450 Reports (RTCP XR) Block Type Registry". Policies for this new 451 registry are as follows: 453 o The information required to support an assignment is an 454 unambiguous definition of the new metric, covering the base 455 measurements and how they are processed to generate the reported 456 metric. This should include the units of measurement, how values 457 of the metric are reported in the three 16-bit fields "Pos PDV 458 Threshold/Peak", "Neg PDV Threshold/Peak" and "Mean PDV" within 459 the report block, and how the metric uses the two 16-bit fields 460 "Pos PDV Percentile" and "Neg PDV Percentile". 462 o The review process for the registry is "Specification Required" as 463 described in Section 4.1 of [RFC5226]. 465 o Entries in the registry are integers. The valid range is 0 to 15 466 corresponding to the 4-bit field "pdvtyp" in the block. Values 467 are to be recorded in decimal. 469 o Initial assignments are as follows: 471 1. interarrival jitter, Section 6.4.1 of [RFC3550], 473 2. MAPDV2, Clause 6.2.3.2 of [G.1020], 475 3. 2-point PDV, Clause 6.2.4 of [Y.1540] 477 6. Security Considerations 479 It is believed that this proposed RTCP XR report block introduces no 480 new security considerations beyond those described in [RFC3611]. 481 This block does not provide per-packet statistics so the risk to 482 confidentiality documented in Section 7, paragraph 3 of [RFC3611] 483 does not apply. 485 7. References 487 7.1. Normative References 489 [G.1020] ITU-T, "ITU-T Rec. G.1020, Performance parameter 490 definitions for quality of speech and other voiceband 491 applications utilizing IP networks", July 2006. 493 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 494 Requirement Levels", March 1997. 496 [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time 497 Applications", RFC 3550, July 2003. 499 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 500 Protocol Extended Reports (RTCP XR)", November 2003. 502 [RFC4040] Kreuter, R., "RTP Payload Format for a 64 kbit/s 503 Transparent Call", April 2005. 505 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 506 Description Protocol", July 2006. 508 [RFC5226] Narten, T., "Guidelines for Writing an IANA Considerations 509 Section in RFCs", May 2008. 511 BCP 26 513 [Y.1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and 514 availability performance parameters", November 2007. 516 7.2. Informative References 518 [MEASI] Hunt, G., "Measurement Identity and information Reporting 519 using SDES item and XR Block", 520 ID draft-ietf-xrblock-rtcp-xr-measu-identity-01, 521 October 2011. 523 [MONARCH] Hunt, G., "Monitoring Architectures for RTP", 524 ID draft-ietf-avtcore-monarch-04, August 2011. 526 [RFC6390] Clark, A. and B. Claise, "Framework for Performance Metric 527 Development", RFC 6390, October 2011. 529 Appendix A. Change Log 531 Note to the RFC-Editor: please remove this section prior to 532 publication as an RFC. 534 A.1. draft-ietf-avt-rtcp-xr-pdv-03 536 The following are the major changes to previous version : 538 o Changed BNF for SDP following Christian Groves' and Tom Taylor's 539 comments (4th and 5th May 2009). 541 o Updated references. 543 A.2. draft-ietf-xrblock-rtcp-xr-pdv-00 545 The following are the major changes to previous version 546 draft-ietf-avt-rtcp-xr-pdv-03 : 548 o Updated references. 550 A.3. draft-ietf-xrblock-rtcp-xr-pdv-01 552 The following are the major changes to previous version 553 draft-ietf-xrblock-rtcp-xr-pdv-00 : 555 o Fix typos or nits in the definition of Negative PDV Threshold/ 556 Peak. 558 o Fix nits in Numeric format S7:8. 560 o remove the text that is relevant to tag field. 562 o Add text in SDP signaling section to clarify indicationof metric 563 unavailable. 565 A.4. draft-ietf-xrblock-rtcp-xr-pdv-02 567 The following are the major changes to previous version 568 draft-ietf-xrblock-rtcp-xr-pdv-00 : 570 o Updated references. 572 o Allocate one more bit for Interval metric flag to indicate sampled 573 metric can be used. 575 o Add a few clarification text for failure mode. 577 Authors' Addresses 579 Geoff Hunt 580 Unaffiliated 582 Email: r.geoff.hunt@gmail.com 584 Alan Clark 585 Telchemy Incorporated 586 2905 Premiere Parkway, Suite 280 587 Duluth, GA 30097 588 USA 590 Email: alan.d.clark@telchemy.com 592 Qin Wu 593 Huawei 594 101 Software Avenue, Yuhua District 595 Nanjing, Jiangsu 210012 596 China 598 Email: sunseawq@huawei.com