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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Q. Wu 3 Internet-Draft F. Xia 4 Intended status: Standards Track R. Even 5 Expires: August 13, 2012 Huawei 6 February 10, 2012 8 RTCP Extension for Third-party Loss Report 9 draft-ietf-avtcore-feedback-supression-rtp-11 11 Abstract 13 In a large RTP session using the RTCP feedback mechanism defined in 14 RFC 4585, a feedback target may experience transient overload if some 15 event causes a large number of receivers to send feedback at once. 16 This overload is usually avoided by ensuring that feedback reports 17 are forwarded to all receivers, allowing them to avoid sending 18 duplicate feedback reports. However, there are cases where it is not 19 recommended to forward feedback reports, and this may allow feedback 20 implosion. This memo discusses these cases and defines a new RTCP 21 third-party loss report that can be used to inform receivers that the 22 feedback target is aware of some loss event, allowing them to 23 suppress feedback. Associated SDP signalling is also defined. 25 Status of this Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on August 13, 2012. 42 Copyright Notice 44 Copyright (c) 2012 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4 62 4. Format of RTCP Feedback Messages . . . . . . . . . . . . . . . 5 63 4.1. Transport Layer Feedback: Third-party Loss Report . . . . 5 64 4.2. Payload Specific Feedback: Third-party Loss Report . . . . 6 65 5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 7 66 6. Example Use Cases . . . . . . . . . . . . . . . . . . . . . . 8 67 6.1. Source Specific Multicast (SSM) use case . . . . . . . . . 8 68 6.2. Unicast based Rapid Acquisition of Multicast Stream 69 (RAMS) use case . . . . . . . . . . . . . . . . . . . . . 8 70 6.3. RTP Transport Translator use case . . . . . . . . . . . . 9 71 6.4. Multipoint Control Unit (MCU) use case . . . . . . . . . . 9 72 6.5. Mixer use case . . . . . . . . . . . . . . . . . . . . . . 9 73 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 74 8. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 10 75 9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 11 76 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 77 10.1. Normative References . . . . . . . . . . . . . . . . . . . 11 78 10.2. Informative References . . . . . . . . . . . . . . . . . . 12 79 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 13 80 A.1. draft-ietf-avtcore-feedback-suppression-rtp-01 . . . . . . 13 81 A.2. draft-ietf-avtcore-feedback-suppression-rtp-02 . . . . . . 13 82 A.3. draft-ietf-avtcore-feedback-suppression-rtp-03 . . . . . . 14 83 A.4. draft-ietf-avtcore-feedback-suppression-rtp-04 . . . . . . 14 84 A.5. draft-ietf-avtcore-feedback-suppression-rtp-05 . . . . . . 14 85 A.6. draft-ietf-avtcore-feedback-suppression-rtp-06 . . . . . . 15 86 A.7. draft-ietf-avtcore-feedback-suppression-rtp-07 . . . . . . 15 87 A.8. draft-ietf-avtcore-feedback-suppression-rtp-08 . . . . . . 15 88 A.9. draft-ietf-avtcore-feedback-suppression-rtp-09 . . . . . . 16 89 A.10. draft-ietf-avtcore-feedback-suppression-rtp-10 . . . . . . 16 90 A.11. draft-ietf-avtcore-feedback-suppression-rtp-11 . . . . . . 16 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 93 1. Introduction 95 RTCP feedback messages [RFC4585] allow the receivers in an RTP 96 session to report events and ask for action from the media source (or 97 a delegated feedback target when using unicast RTCP feedback with SSM 98 [RFC5760]). There are cases where multiple receivers may initiate 99 the same, or an equivalent message towards the same media source or 100 the same feedback target. When the receiver count is large, this 101 behavior may cause transient overload of the media source, the 102 network or both. This is known as a "feedback storm" or a "NACK 103 storm". One common cause of such a feedback storm is receivers 104 utilizing RTP retransmission [RFC4588] as a packet loss recovery 105 technique, sending feedback using RTCP NACK messages [RFC4585] 106 without proper dithering of the retransmission requests (e.g., not 107 implementing the RFC 4585 dithering rules or sending NACKs to a 108 feedback target that doesn't redistribute them to other receivers). 110 Another use case involves video Fast Update requests. A storm of 111 these feedback messages can occur in conversational multimedia 112 scenarios like multipoint video switching conference [RFC4587]. In 113 this scenario, the receiver may lose synchronization with the video 114 stream when speaker is changed in the middle of session. Poorly 115 designed receivers that blindly issue fast update requests (i.e., 116 Full Intra Request (FIR) described in [RFC5104]), can cause an 117 implosion of FIR requests from receivers to the same media source. 119 RTCP feedback storms may cause short term overload, and in extreme 120 cases to pose a possible risk of increasing network congestion on the 121 control channel (e.g. RTCP feedback), the data channel, or both. It 122 is therefore desirable to provide a way of suppressing unneeded 123 feedback. This document specifies a new third-party loss report for 124 this function. It supplements the existing the use of RTCP NACK 125 packet and further is more precise in the uses where the network is 126 active to suppress feedback. It tells receivers explicitly that 127 feedback for a particular packet or frame loss is not needed for a 128 period of time and can provide an early indication before the 129 receiver reacts to the loss and invokes its packet loss repair 130 machinery. Section 6 provides some examples of when to send the 131 Third Party Loss Report message. 133 2. Terminology 135 The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 136 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 137 document are to be interpreted as described in [RFC2119]. 139 3. Protocol Overview 141 This document extends the RTCP feedback messages defined in the 142 Audio-Visual Profile with feedback (RTP/AVPF) [RFC4585] defining a 143 Third Party Loss Report message. The Third Party Loss Report message 144 can be used by the intermediaries to inform the receiver that the 145 sender of the Third Party Loss Report has received reports that the 146 indicated packets were lost, and asks the receiver not to send 147 feedback to it regarding these packets. Intermediaries are variously 148 referred to as Distribution source, Burst/Retransmission Sources 149 (BRS), MCUs, RTP translator, or RTP mixers, depending on the precise 150 use case described in section 6. 152 RTCP Third Party Loss Report follows the similar format of message 153 type as RTCP NACK or Full Intra Request Command. However, the Third 154 Party Loss Report is defined as an indication that the sender of the 155 feedback has received reports that the indicated packets were lost, 156 while NACK [RFC4585] just indicates that the sender of the NACK 157 observed that these packets were lost. The Third Party Loss Report 158 (TPLR) message is generated by an intermediary that may not seen the 159 actual packet loss. It is sent following the same timing rule as 160 sending NACK defined in [RFC4585]. The TPLR feedback message may be 161 sent in a regular full compound RTCP packet or in an early RTCP 162 packet, as per the RTP/AVPF rules. Intermediaries in the network 163 that receive a Third Party Loss Report SHOULD NOT send their own 164 additional Third Party Loss Report messages for the same packet 165 sequence numbers. They should simply forward the Third Party Loss 166 Report message received from upstream direction to the receiver(s), 167 additionally, they may generate their own Third Party Loss Report 168 that reports a set of the losses they see, which are different from 169 ones reported in the Third Party Loss report they received. The 170 Third Party Loss Report does not have the retransmission request 171 [RFC4588] semantics. 173 When a receiver gets a Third Party Loss Report message, it should 174 follow the rules for NACK suppression in RFC 4585 and refrain from 175 sending a feedback request (e.g., NACK or FIR) for the missing 176 packets reported in the message,which is dealt with in the same way 177 as receiving NACK. 179 To increase the robustness to the loss of a TPLR, TPLR may be 180 retransmitted. If the additional TPLR arrives at receiver, the 181 receiver should deal with the additional TPLR in the same way as 182 receiving the first TPLR for the same packet and no additional 183 behavior for receiver is required. 185 A receiver may have sent a Feedback message according to the RTP/AVPF 186 scheduling algorithm of [RFC4585] before receiving a Third Party Loss 187 Report message, but further feedback messages for those sequence 188 numbers SHOULD be suppressed for a period of time after receiving the 189 TPLR. Nodes that do not understand the Third Party Loss Report 190 message will ignore it, and might therefore still send feedback 191 according to the AVPF scheduling algorithm of [RFC4585]. The media 192 source or intermediate nodes cannot be certain that the use of a 193 Third Party Loss Report message actually reduces the amount of 194 feedback it receives. 196 4. Format of RTCP Feedback Messages 198 This document registers two new RTCP Feedback messages for Third 199 Party Loss Report. Applications that are employing one or more loss- 200 repair methods MAY use the Third Party Loss Report together with 201 their existing loss-repair methods either for every packet they 202 expect to receive, or for an application-specific subset of the RTP 203 packets in a session. In other words, receivers MAY ignore Third 204 Party Loss Report messages, but SHOULD react to them unless they have 205 good reason to still send feedback messages despite having been 206 requested to suppress them. 208 4.1. Transport Layer Feedback: Third-party Loss Report 210 This Third Party Loss Report message is an extension to the RTCP 211 Transport Layer Feedback Report and identified by RTCP packet type 212 value PT=RTPFB and FMT=TBD. 214 Within the common packet header for feedback messages (as defined in 215 section 6.1 of [RFC4585]), the "SSRC of packet sender" field 216 indicates the source of the request, and the "SSRC of media source" 217 denotes the media sender of the flow for which the indicated losses 218 are being suppressed. 220 The FCI field MUST contain one or more entries of transport layer 221 third party loss Early Indication (TLLEI). Each entry applies to the 222 same media source identified by the SSRC contained in the SSRC of 223 media source field of Feedback header. The length of the TLLEI 224 feedback message MUST be set to 2+1*N, where N is the number of FCI 225 entries. 227 The Feedback Control Information (FCI) for TLLEI uses the similar 228 format of message Types defined in the section 6.2.1 of [RFC4585]. 229 The format is shown in Figure 1. 231 0 1 2 3 232 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 1 233 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 | PID | BLP | 235 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 237 Figure 1: Syntax of an FCI Entry in the TLLEI Feedback Message 239 Packet ID (PID): 16 bits 241 The PID field is used to specify a lost packet. The PID field 242 refers to the RTP sequence number of the lost packet. 244 bitmask of lost packets (BLP): 16 bits 246 The BLP allows for reporting losses of any of the 16 RTP packets 247 immediately following the RTP packet indicated by the PID. The 248 BLP's definition is identical to that given in the section 6.2.1 249 of [RFC4585]. 251 4.2. Payload Specific Feedback: Third-party Loss Report 253 This message is an extension to the RTCP Payload Specific Feedback 254 report and identified by RTCP packet type value PT=PSFB and FMT=TBD, 255 which is used to suppress FIR [RFC5104]and PLI [RFC4585]. 257 Within the common packet header for feedback messages (as defined in 258 section 6.1 of [RFC4585]), the "SSRC of packet sender" field 259 indicates the source of the request, and the "SSRC of media source" 260 is not used and SHALL be set to 0. The SSRCs of the media senders to 261 which this message applies are in the corresponding FCI entries. 263 The Feedback Control Information (FCI) for a Payload Specific Third 264 Party Loss Early Indication (PSLEI) consists one or more FCI entries. 265 Each entry applies to a different media Source, identified by its 266 SSRC. the content of which is depicted in Figure 2. The length of 267 the PSLEI feedback message MUST be set to 2+1*N, where N is the 268 number of FCI entries. 270 The format is shown in Figure 2. 272 0 1 2 3 273 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 1 274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 275 | SSRC | 276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 278 Figure 2: Syntax of an FCI Entry in the PSLEI Feedback Message 280 Synchronization source (SSRC):32 bits 282 The SSRC value of the media source that has already been aware the 283 receiver lost synchronization with the video stream and signal to 284 the receiver not sending a decoder refresh point. 286 5. SDP Signaling 288 The Session Description Protocol (SDP) [RFC4566] attribute, rtcp-fb, 289 is defined in the Section 4 of [RFC4585] and may be used to negotiate 290 the capability to handle specific AVPF commands and indications. The 291 ABNF for rtcp-fb is described in section 4.2 of [RFC4585]. In this 292 section, we extend the rtcp-fb attribute to include the commands and 293 indications that are described for third party loss report in the 294 present document. 296 In the ABNF [RFC5234] for rtcp-fb-val defined in [RFC4585], the 297 feedback type "nack", without parameters, indicates use of the 298 Generic NACK feedback format as defined in Section 6.2.1of [RFC4585]. 299 In this document, we define two parameters that indicate the third 300 party loss supported for use with "nack", namely: 302 o "tllei" denotes support of transport layer third party loss early 303 indication. 305 o "pslei" denotes support of payload specific third party loss early 306 indication. 308 The ABNF for these two parameters for "nack" is defined here (please 309 refer to section 4.2 of [RFC4585] for complete ABNF syntax). 311 rtcp-fb-val =/ "nack" rtcp-fb-nack-param 312 rtcp-fb-nack-param = SP "tllei" 313 ;transport layer third party 314 ; loss early indication 315 / SP "pslei" 316 ;payload specific third party 317 ; loss early indication 318 / SP token [SP byte-string] 319 ; for future commands/indications 320 token = 321 byte-string = 323 Refer to Section 4.2 of [RFC4585] for a detailed description and the 324 full syntax of the "rtcp-fb" attribute. 326 6. Example Use Cases 328 The operation of feedback suppression is similar for all types of RTP 329 sessions and topologies [RFC5117], however the exact messages used 330 and the scenarios in which suppression is employed differ for various 331 use cases. The following sections outline some of the intended use 332 cases for using the Third Party Loss Report for feedback suppression 333 and give an overview of the particular mechanisms. 335 6.1. Source Specific Multicast (SSM) use case 337 In SSM RTP sessions as described in "RTP Control Protocol (RTCP) 338 Extensions for Single-Source Multicast Sessions with Unicast 339 Feedback" [RFC5760], one or more Media Sources send RTP packets to a 340 Distribution Source. The Distribution Source relays the RTP packets 341 to the receivers using a source- specific multicast group. 343 As outlined in the [RFC5760], there are two Unicast Feedback models 344 that may be used for reporting, the Simple Feedback model and the 345 Distribution Source Feedback Summary Model. In the simple Feedback 346 Model, there's no need for distribution source to create the Third 347 Party Loss Report, instead, NACKs are reflected by the distribution 348 source to the other Receivers. However in the Distribution Source 349 Feedback Summary model, the distribution source will not redistribute 350 the NACK for some reason(e.g., to prevent revealing the identity or 351 existence of a system sending NACK)and may send a Third Party Loss 352 Report to the systems that were unable to receive the NACK, and won't 353 receive the NACK via other means. Since the summary feedback does 354 not mandate the forwarding of NACK downstream. The Third Party Loss 355 Report can be generated at the distribution source when downstream 356 loss is told (e.g., downstream loss report is received), which 357 indicates to the receivers that they should not transmit feedback 358 messages for the same loss event for a certain time. Therefore the 359 distribution source in the feedback summary model can be reasonably 360 certain that it will help the situation by sending this Third Party 361 Loss Report message to all the relevant receivers impacted by the 362 packet loss. 364 6.2. Unicast based Rapid Acquisition of Multicast Stream (RAMS) use 365 case 367 The typical RAMS architecture [RFC6285] may have several Burst/ 368 Retransmission Sources(BRS) behind the multicast source (MS) placed 369 at the same level. These BRSes will receive the primary multicast 370 RTP stream from the media source and cache most recent packets after 371 joining multicast session. If packet loss happens at the upstream of 372 all the BRSs or the downstream of BRSes. One of the BRSes or all the 373 BRSes may send a NACK or TPLR message to the DS, where the SSRC in 374 this NACK or TPLR message is the BRS that is sending the message. 375 The DS forwards/reflects this message down on the primary SSM. The 376 details on how DS deal with this message is specified in 377 [RETRANSMISSION-FOR-SSM]. 379 6.3. RTP Transport Translator use case 381 A Transport Translator (Topo-Trn-Translator), as defined in [RFC5117] 382 is typically forwarding the RTP and RTCP traffic between RTP clients, 383 for example converting from multicast to unicast for domains that do 384 not support multicast. The translator may suffer a loss of important 385 video packets. In this case, the translator may forward TPLR message 386 received from upstream in the same way as forwarding other RTCP 387 traffic. If the translator acting as the monitor [MONARCH]is aware 388 of packet loss, it may use the SSRC of monitor as packet sender SSRC 389 to create NACK message and send it to the receivers that is not aware 390 of packet loss. 392 6.4. Multipoint Control Unit (MCU) use case 394 When the speaker is changed in a voice-activated multipoint video 395 switching conference [RFC4587], an RTP mixer can be used to select 396 the available input streams and forward them to each participants. 397 If the MCU is doing a blind switch without waiting for a 398 synchronization point on the new stream it can send a FIR to the new 399 video source. In this case the MCU should send a FIR suppression 400 message to the new receivers. e.g., when the RTP Mixer starts to 401 receive FIR from some participants it can suppress the remaining 402 session participants from sending FIR by sending out a Third party 403 Loss report message. 405 6.5. Mixer use case 407 A Mixer, in accordance with [RFC5117], aggregates multiple RTP 408 streams from other session participants and generates a new RTP 409 stream sent to the session participants. In some cases, the video 410 frames may get badly screwed up between media source and the mixer. 411 In such case, the mixer need to check if the packet loss will result 412 in PLI or FIR transmissions from most of the group by analyzing the 413 received video. If so the mixer may initiate FIR or PLI towards the 414 media source on behalf of all the session participants and send out a 415 Third party Loss report message to these session participants that 416 may or are expected to send a PLI or FIR. Alternatively, when the 417 mixer starts to receive FIR or PLI from some participants and like to 418 suppress the remaining session participants from sending FIR or PLI 419 by forwarding the FIR/PLI from one session participant to others. 421 7. Security Considerations 423 The defined messages have certain properties that have security 424 implications. These must be addressed and taken into account by 425 users of this protocol. 427 Spoofed or maliciously created feedback messages of the type defined 428 in this specification can have the following implications: 430 Sending the spurious Third Party Loss Report (e.g., the Third Party 431 Loss Report with the wrong sequence number of lost packet) that 432 causes missing RTP packets to not be repaired in a timely fashion. 434 To prevent these attacks, there is a need to apply authentication and 435 integrity protection of the feedback messages. This can be 436 accomplished against threats external to the current RTP session 437 using the RTP profile that combines Secure RTP [RFC3711] and AVPF 438 into SAVPF [RFC5124]. 440 Note that intermediaries that are not visible at the RTP layer that 441 wish to send the Third Party Loss Reports on behalf of the media 442 source can only do so if they spoof the SSRC of the media source. 443 This is difficult in case SRTP is in use. If the intermediary is 444 visible at the RTP layer, this is not an issue, provided the 445 intermediary is part of the security context for the session. 447 Also note that endpoints that receive a Third Party Loss Report would 448 be well-advised to ignore it, unless the security is in place to 449 authenticate the sender of the Third Party Loss Report. Accepting 450 Third Party Loss Report from un-authenticated sender can lead to a 451 denial of service attack, where the endpoint accepts poor quality 452 media that could be repaired. 454 8. IANA Consideration 456 For use with "nack" [RFC4585], a joint sub-registry has been set up 457 that registers the following two values: 459 The value registration for the attribute value "nack": 461 Value name: tllei 462 Long name: Transport Layer Third Party Loss Early Indication 463 Usable with: nack 464 Reference: RFC 4585. 466 Value name: pslei 467 Long name: Payload Specific Third Party 468 Usable with: nack 469 Reference: RFC 4585. 471 The following value have been registered as one FMT value in the "FMT 472 Values for RTPFB Payload Types" registry located at the time of 473 publication at: http://www.iana.org/assignments/rtp-parameters 475 RTPFB range 476 Name Long Name Value Reference 477 -------------- --------------------------------- ----- --------- 478 TLLEI Transport Layer Third Party TBA1 [RFCXXXX] 479 Loss Early Indication 481 The following value have been registered as one FMT value in the "FMT 482 Values for PSFB Payload Types" registry located at the time of 483 publication at: http://www.iana.org/assignments/rtp-parameters 485 PSFB range 486 Name Long Name Value Reference 487 -------------- --------------------------------- ----- --------- 488 PSLEI Payload Specific Third Party TBA2 [RFCXXXX] 489 Loss Early Indication 491 9. Acknowledgement 493 The authors would like to thank David R Oran, Magnus Westerlund, 494 Colin Perkins, Ali C. Begen, Tom VAN CAENEGEM, Ingemar Johansson S, 495 Bill Ver Steeg, Jonathan Lennox, WeeSan Lee for their valuable 496 comments and suggestions on this document. 498 10. References 500 10.1. Normative References 502 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 503 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 504 May 2008. 506 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 507 Requirement Levels", BCP 14, RFC 2119, March 1997. 509 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 510 "Extended RTP Profile for Real-time Transport Control 511 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, 512 July 2006. 514 [RFC4588] Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R. 515 Hakenberg, "RTP Retransmission Payload Format", RFC 4588, 516 July 2006. 518 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 519 Description Protocol", RFC 4566, July 2006. 521 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 522 Specifications: ABNF", STD 68, RFC 5234, January 2008. 524 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, 525 "Codec Control Messages in the RTP Audio-Visual Profile 526 with Feedback (AVPF)", RFC 5104, February 2008. 528 10.2. Informative References 530 [RFC5740] Adamson, B., Bormann, C., Handley, M., and J. Macker, 531 "NACK-Oriented Reliable Multicast (NORM) Transport 532 Protocol", November 2009. 534 [RFC6285] Steeg, B., Begen, A., Caenegem, T., and Z. Vax, "Unicast- 535 Based Rapid Acquisition of Multicast RTP Sessions", 536 June 2011. 538 [MONARCH] Wu, Q., Hunt, G., and P. Arden, "Monitoring Architectures 539 for RTP", June 2011. 541 [RETRANSMISSION-FOR-SSM] 542 Caenegem, T., Steeg, B., and A. Begen, "Retransmission for 543 Source-Specific Multicast (SSM) Sessions", May 2011. 545 [RFC5117] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117, 546 January 2008. 548 [RFC4587] Even, R., "RTP Payload Format for H.261 Video Streams", 549 RFC 4587, August 2006. 551 [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control 552 Protocol (RTCP) Extensions for Single-Source Multicast 553 Sessions with Unicast Feedback", RFC 5760, February 2010. 555 [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for 556 Real-time Transport Control Protocol (RTCP)-Based Feedback 557 (RTP/SAVPF)", RFC 5124, February 2008. 559 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 560 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 561 RFC 3711, March 2004. 563 Appendix A. Change Log 565 Note to the RFC-Editor: please remove this section prior to 566 publication as an RFC. 568 A.1. draft-ietf-avtcore-feedback-suppression-rtp-01 570 The following are the major changes compared to previous version: 572 o Remove the merge report from SSM use case and additional text to 573 address report merging issue. 575 o Revise section 3 and section 6 to address FEC packet dealing issue 576 and Leave how to repair packet loss beyond the scope. 578 o Modify the SSM use case and RAMS use case to focus on uses. 580 o Other Editorial changes. 582 A.2. draft-ietf-avtcore-feedback-suppression-rtp-02 584 The following are the major changes compared to previous version: 586 o In Section 4.1, fix typo: Section 4.3.1.1 of section [RFC5104]-> 587 section 6.2.1 of [RFC4585]. 589 o In Section 3: Clarify how to deal with downstream loss using Third 590 party loss report and upstream loss using NACK. 592 o Update title and abstract to focus on third party loss report. 594 o In Section 6.1: Update this section to explain how third party 595 loss report is used to deal with downstream loss. 597 o In section 6.1.2: Update this section to explain how third party 598 loss report is used to deal with downstream loss. 600 o In section 6.2: Rephrase the text to discuss how BRS deal with the 601 third party loss report. 603 A.3. draft-ietf-avtcore-feedback-suppression-rtp-03 605 The following are the major changes compared to previous version: 607 o In Appendix A, fix typo: Appendix A. Appendix A. -> Appendix A. 609 o Update abstract to clarify when third-party loss reports should be 610 sent instead of NACKs. 612 o Update section 3 Paragraph 2 to differentiate when a third-party 613 loss report should be used compared to a NACK. 615 o Update section 3 Paragraph 3 to explain when media source to send 616 a third-party loss. 618 o Move specific rules for section 6.1.1 and section 6.1.2 to section 619 6.1 as generic rules and delete section 6.1.1. 621 A.4. draft-ietf-avtcore-feedback-suppression-rtp-04 623 The following are the major changes compared to previous version: 624 o Reference Update. 626 o Clarify the use of the third party loss report in section 3 and 627 section 6.1.1. 629 A.5. draft-ietf-avtcore-feedback-suppression-rtp-05 631 The following are the major changes compared to previous version: 632 o Remove 3rd and 4th paragraphs of section 6.1 and replaced them 633 with 2nd and 3rd paragraphs of section 3. 635 o Remove section 6.1.1.1. 637 o Revise the last paragraph of section 1 to clarify the rationale of 638 using new message. 640 o Update RTP transport translator case in section 6.3 to correct the 641 use of the third party loss report. 643 o Update MCU case in section 6.4 to correct the use of the third 644 party loss report. 646 o Revise SSM use case to address multiple DS issue. 648 o References Update. 650 o Move one rationale on preventing sending unicast NACK in 651 introduction section to SSM case section. 653 o Other Editorial changes to section 6.1, 6.1.1, 6.2. 655 A.6. draft-ietf-avtcore-feedback-suppression-rtp-06 657 The following are the major changes compared to previous version: 659 o A few Editorial changes to the whole document. 661 A.7. draft-ietf-avtcore-feedback-suppression-rtp-07 663 The following are the major changes compared to previous version: 665 o Restructuring the protocol overview section to clarify the round 666 trip time calculation and receiver behavior to the additional 667 TPLR. 669 o Restructuring the SSM use case section to focus on the use of 670 TPLR. 672 o Editorial changes to the abstract, introduction, message format, 673 use cases and IANA sections. 675 o References update 677 A.8. draft-ietf-avtcore-feedback-suppression-rtp-08 679 The following are the major changes compared to previous version: 681 o Clarify which RTT is used and how timer is refreshed in the 682 section 3. 684 o Editorial changes to the Introduction, Protocol Overview, SDP 685 Signaling, Message Format, Use case,Security Consideration and 686 IANA sections. 688 o Remove Seq Nr field in the figure 2 for payload specific feedback. 690 o References reorganizing. 692 A.9. draft-ietf-avtcore-feedback-suppression-rtp-09 694 The following are the major changes compared to previous version: 696 o Clarify to suppression interval with regard to how long to receive 697 the retransmitted packet. Treating TPLR in the same way as 698 receiving NACK .Replace timer based approach with timeless based 699 approach 701 A.10. draft-ietf-avtcore-feedback-suppression-rtp-10 703 The following are the major changes compared to previous version: 705 o Fix the definition of Synchronization source for TPLR in section 706 4.2. 707 o Associate SDP parameters tllei and pslei with "nack". 708 o Remove the packet loss recovery from TPLR loss handling part. 709 o Other typo fixed. 711 A.11. draft-ietf-avtcore-feedback-suppression-rtp-11 713 The following are the major changes compared to previous version: 715 o Additional Editorial changes. 717 Authors' Addresses 719 Qin Wu 720 Huawei 721 101 Software Avenue, Yuhua District 722 Nanjing, Jiangsu 210012 723 China 725 Email: sunseawq@huawei.com 727 Frank Xia 728 Huawei 729 1700 Alma Dr. Suite 500 730 Plano, TX 75075 731 USA 733 Phone: +1 972-509-5599 734 Email: xiayangsong@huawei.com 735 Roni Even 736 Huawei 737 14 David Hamelech 738 Tel Aviv 64953 739 Israel 741 Email: even.roni@huawei.com