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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: April 27, 2012 Huawei 6 October 25, 2011 8 RTCP Extension for Third-party Loss Report 9 draft-ietf-avtcore-feedback-supression-rtp-08 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 April 27, 2012. 42 Copyright Notice 44 Copyright (c) 2011 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 61 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4 62 4. Format of RTCP Feedback Messages . . . . . . . . . . . . . . . 5 63 4.1. Transport Layer Feedback: Third-party Loss Report . . . . 6 64 4.2. Payload Specific Feedback: Third-party Loss Report . . . . 7 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 . . . . . . . . . . . . . . . . . . . . . 9 70 6.3. RTP Transport Translator use case . . . . . . . . . . . . 9 71 6.4. Multipoint Control Unit (MCU) use case . . . . . . . . . . 10 72 6.5. Mixer use case . . . . . . . . . . . . . . . . . . . . . . 10 73 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 74 8. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 11 75 9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 12 76 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 77 10.1. Normative References . . . . . . . . . . . . . . . . . . . 12 78 10.2. Informative References . . . . . . . . . . . . . . . . . . 13 79 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 13 80 A.1. draft-ietf-avtcore-feedback-suppression-rtp-01 . . . . . . 14 81 A.2. draft-ietf-avtcore-feedback-suppression-rtp-02 . . . . . . 14 82 A.3. draft-ietf-avtcore-feedback-suppression-rtp-03 . . . . . . 14 83 A.4. draft-ietf-avtcore-feedback-suppression-rtp-04 . . . . . . 15 84 A.5. draft-ietf-avtcore-feedback-suppression-rtp-05 . . . . . . 15 85 A.6. draft-ietf-avtcore-feedback-suppression-rtp-06 . . . . . . 15 86 A.7. draft-ietf-avtcore-feedback-suppression-rtp-07 . . . . . . 16 87 A.8. draft-ietf-avtcore-feedback-suppression-rtp-08 . . . . . . 16 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 90 1. Introduction 92 RTCP feedback messages [RFC4585] allow the receivers in an RTP 93 session to report events and ask for action from the media source (or 94 a delegated feedback target when using unicast RTCP feedback with SSM 95 [RFC5760]). There are cases where multiple receivers may initiate 96 the same, or an equivalent message towards the same media source. 97 When the receiver count is large, this behavior may cause transient 98 overload of the media source, the network or both. This is known as 99 a "feedback storm" or a "NACK storm". One common cause of such a 100 feedback storm is receivers utilizing RTP retransmission [RFC4588] as 101 a packet loss recovery technique, sending feedback using RTCP NACK 102 messages [RFC4585] without proper dithering of the retransmission 103 requests (e.g., not implementing the RFC 4585 dithering rules or 104 sending NACKs to a middlebox that doesn't redistribute them to other 105 receivers). 107 Another use case involves video Fast Update requests. A storm of 108 these feedback messages can occur in conversational multimedia 109 scenarios like multipoint video switching conference [RFC4587]. In 110 this scenario, the receiver may lose synchronization with the video 111 stream when speaker is changed in the middle of session. Poorly 112 designed receivers that blindly issue fast update requests (i.e., 113 Full Intra Request (FIR) described in [RFC5104]), can cause an 114 implosion of FIR requests from receivers to the same media source. 116 RTCP feedback storms may cause short term overload, and in extreme 117 cases to pose a possible risk of increasing network congestion on the 118 control channel (e.g. RTCP feedback), the data channel, or both. It 119 is therefore desirable to provide a way of suppressing unneeded 120 feedback. 122 One approach to this, suggested in [DVB-IPTV], involves sending a 123 NACK message to the other clients (or receiver) in the same group as 124 the sender of NACK. However NACK is defined as a receiver report 125 sent from a receiver observing a packet loss, therefore it only 126 inform others that sender of NACK detected loss while the case where 127 the sender of the feedback has received reports that the indicated 128 packets were lost is not covered. This document specifies a new 129 third-party loss report for this function. It supplements the 130 existing the use of RTCP NACK packet and further is more precise in 131 the uses where the network is active to suppress feedback. It tells 132 receivers explicitly that feedback for a particular packet or frame 133 loss is not needed for a period of time and can provide an early 134 indication before the receiver reacts to the loss and invokes its 135 packet loss repair machinery. Section 6 provides some examples of 136 when to send the Third Party Loss Report message. 138 2. Terminology 140 The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 141 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 142 document are to be interpreted as described in [RFC2119]. 144 3. Protocol Overview 146 This document extends the RTCP feedback messages defined in the 147 Audio-Visual Profile with feedback (RTP/AVPF) [RFC4585] defining a 148 Third Party Loss Report message. The Third Party Loss Report message 149 can be used by the intermediaries to inform the receiver that the 150 sender of the Third Party Loss Report has received reports that the 151 indicated packets were lost, and asks the receiver not to send 152 feedback to it regarding these packets. 154 RTCP Third Party Loss Report follows the similar format of message 155 type as RTCP NACK or Full Intra Request Command. However, the Third 156 Party Loss Report is defined as an indication that the sender of the 157 feedback has received reports that the indicated packets were lost, 158 while NACK [RFC4585] just indicates that the sender of the NACK 159 observed that these packets were lost. The Third Party Loss Report 160 (TPLR) message is generated by a RTP system that may not seen the 161 actual packet loss. It is sent following the same timing rule as 162 sending NACK defined in [RFC4585]. The TPLR feedback message may be 163 sent in a regular full compound RTCP packet or in an early RTCP 164 packet, as per the RTP/AVPF rules. RTP Systems in the network that 165 receive a Third Party Loss Report SHOULD NOT send their own 166 additional Third Party Loss Report messages for the same packet 167 sequence numbers. They should simply forward the Third Party Loss 168 Report message received from upstream direction, additionally, they 169 may generate their own Third Party Loss Report that reports a set of 170 the losses they see, which are different from ones reported in the 171 Third Party Loss report they received. The Third Party Loss Report 172 does not have the retransmission request [RFC4588] semantics. 174 When a receiver gets a Third Party Loss Report message, it should 175 start a timer for the retransmitted data packet and this message and 176 refrain from sending a feedback request (e.g., NACK or FIR) for the 177 missing packets reported in the message during the lifetime of the 178 timer. If the sender of retransmitted packet is the media source, 179 the timer value shall be based on the observed time difference 180 between the round-trip time from the receiver to the original media 181 source and the round-trip time from the receiver to the sender of the 182 TPLR. A receiver should compute an estimate of the round-trip time 183 (RTT) to the original media source or the sender of retransmitted 184 data packet from Sender Report (SR) packets for the original stream, 185 or any other means. The round-trip time from the receiver to the 186 sender of the TPLR can be calculated from RTCP report round-trip time 187 if available, or any other means. 189 To increase the robustness to the loss of a TPLR or of a transmission 190 RTP data packet, TPLR for the same Packet may be generated and sent 191 out. The receiver should view the TPLR as a retransmission if this 192 TPLR is received from the same media source after the timer set 193 previously expires. In the case where the first TPLR is lost and the 194 additional TPLR arrives at the receiver, the receiver should 195 immediately refresh the timer to the same value as the previous timer 196 it set for the the retransmitted data packet. When the timer expires 197 and there is no retransmitted packet or a new Third Party Loss Report 198 message, the receiver should take its normal behavior as if there is 199 no current feedback suppression. 201 A receiver may still have sent a Feedback message according to the 202 RTP/AVPF scheduling algorithm of [RFC4585] before receiving a Third 203 Party Loss Report message, but further feedback messages for those 204 sequence numbers SHOULD be suppressed for a period of time after 205 receiving the TPLR. Nodes that do not understand the Third Party 206 Loss Report message will ignore it, and might therefore still send 207 feedback according to the AVPF scheduling algorithm of [RFC4585]. 208 The media source or intermediate nodes cannot be certain that the use 209 of a Third Party Loss Report message actually reduces the amount of 210 feedback it receives. 212 Since Third Party Loss Report interacts strongly with repair timing, 213 it has to work together with feedback to not adversely impact the 214 repair of lost source packets. In order not to incur a lot of NACK 215 requests due to additional TPLR described above, it is recommended 216 that the RTP system sending TPLR should be implemented more closer to 217 the media source. When the loss was detected and repair initiated 218 much closer to the media source, the delay for the receiver to 219 recover from packet loss can be reduced through the combination of 220 intermediary feedback to the source and Third Party Loss Report 221 downstream. 223 4. Format of RTCP Feedback Messages 225 This document registers two new RTCP Feedback messages for Third 226 Party Loss Report. Applications that are employing one or more loss- 227 repair methods MAY use the Third Party Loss Report together with 228 their existing loss-repair methods either for every packet they 229 expect to receive, or for an application-specific subset of the RTP 230 packets in a session. In other words, receivers MAY ignore Third 231 Party Loss Report messages, but SHOULD react to them unless they have 232 good reason to still send feedback messages despite having been 233 requested to suppress them. 235 4.1. Transport Layer Feedback: Third-party Loss Report 237 This Third Party Loss Report message is an extension to the RTCP 238 Transport Layer Feedback Report and identified by RTCP packet type 239 value PT=RTPFB and FMT=TBD. 241 Within the common packet header for feedback messages (as defined in 242 section 6.1 of [RFC4585]), the "SSRC of packet sender" field 243 indicates the source of the request, and the "SSRC of media source" 244 denotes the media sender of the flow for which the indicated losses 245 are being suppressed . 247 The FCI field MUST contain one or more entries of transport layer 248 third party loss Early Indication (TLLEI). Each entry applies to the 249 same media source identified by the SSRC contained in the SSRC of 250 media source field of Feedback header. The length of the TLLEI 251 feedback message MUST be set to 2+1*N, where N is the number of FCI 252 entries. 254 The Feedback Control Information (FCI) for TLLEI uses the similar 255 format of message Types defined in the section 6.2.1 of [RFC4585]. 256 The format is shown in Figure 1. 258 0 1 2 3 259 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 1 260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 261 | PID | BLP | 262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 264 Figure 1: Syntax of an FCI Entry in the TLLEI Feedback Message 266 Packet ID (PID): 16 bits 268 The PID field is used to specify a lost packet. The PID field 269 refers to the RTP sequence number of the lost packet. 271 bitmask of proceeding lost packets (BLP): 16 bits 273 The BLP allows for reporting losses of any of the 16 RTP packets 274 immediately following the RTP packet indicated by the PID. The 275 BLP's definition is identical to that given in [RFC4585]. 277 4.2. Payload Specific Feedback: Third-party Loss Report 279 This message is an extension to the RTCP Payload Specific Feedback 280 report and identified by RTCP packet type value PT=PSFB and FMT=TBD, 281 which is used to suppress FIR [RFC5104]or PLI [RFC4585]. 283 Within the common packet header for feedback messages (as defined in 284 section 6.1 of [RFC4585]), the "SSRC of packet sender" field 285 indicates the source of the request, and the "SSRC of media source" 286 is not used and SHALL be set to 0. The SSRCs of the media senders to 287 which this message applies are in the corresponding FCI entries. 289 The Feedback Control Information (FCI) for a Payload Specific Third 290 Party Loss Early Indication (PSLEI) consists one or more FCI entries. 291 Each entry applies to a different media Source, identified by its 292 SSRC. the content of which is depicted in Figure 2. The length of 293 the PSLEI feedback message MUST be set to 2+1*N, where N is the 294 number of FCI entries. 296 The format is shown in Figure 2. 298 0 1 2 3 299 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 1 300 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 301 | SSRC | 302 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 304 Figure 2: Syntax of an FCI Entry in the PSLEI Feedback Message 306 Synchronization source (SSRC):32 bits 308 The SSRC value of the media source that is requested to send a 309 decoder refresh point or that is indicated that it lost 310 synchronization with the video stream. 312 5. SDP Signaling 314 A new feedback value "tplr" needs to be defined for the Third Party 315 Loss Report message to be used with Session Description Protocol 316 (SDP) [RFC4566] using the Augmented Backus-Naur Form (ABNF) 317 [RFC4585]. 319 The "tplr" feedback value SHOULD be used with parameters that 320 indicate the third party loss supported. In this document, we define 321 two such parameter, namely: 323 o "tllei" denotes support of transport layer third party loss early 324 indication. 326 o "pslei" denotes support of payload specific third party loss early 327 indication. 329 In the ABNF [RFC5234] for rtcp-fb-val defined in [RFC4585], there is 330 a placeholder called rtcp-fb-id to define new feedback types. "tplr" 331 is defined as a new feedback type in this document, and the ABNF for 332 the parameters for tplr is defined here (please refer to section 4.2 333 of [RFC4585] for complete ABNF syntax). 335 rtcp-fb-val =/ "tplr" rtcp-fb-tplr-param 336 rtcp-fb-tplr-param = SP "tllei" 337 ;transport layer third party 338 ; loss early indication 339 / SP "pslei" 340 ;payload specific third party 341 ; loss early indication 342 / SP token [SP byte-string] 343 ; for future commands/indications 344 token = 345 byte-string = 347 Refer to Section 4.2 of [RFC4585] for a detailed description and the 348 full syntax of the "rtcp-fb" attribute. 350 6. Example Use Cases 352 The operation of feedback suppression is similar for all types of RTP 353 sessions and topologies [RFC5117], however the exact messages used 354 and the scenarios in which suppression is employed differ for various 355 use cases. The following sections outline some of the intended use 356 cases for using the Third Party Loss Report for feedback suppression 357 and give an overview of the particular mechanisms. 359 6.1. Source Specific Multicast (SSM) use case 361 In SSM RTP sessions as described in [RFC5760], one or more Media 362 Sources send RTP packets to a Distribution Source. The Distribution 363 Source relays the RTP packets to the receivers using a source- 364 specific multicast group. 366 As outlined in the [RFC5760], there are two Unicast Feedback models 367 that may be used for reporting, the Simple Feedback model and the 368 Distribution Source Feedback Summary Model. In the simple Feedback 369 Model, there's no need for distribution source to create the Third 370 Party Loss Report, instead, NACKs are reflected by the distribution 371 source to the other Receivers. However in the Distribution Source 372 Feedback Summary model, the distribution source will not redistribute 373 the NACK for some reason(e.g., to prevent revealing the identity or 374 existence of a system sending NACK)and may send a Third Party Loss 375 Report to the systems that were unable to receive the NACK, and won't 376 receive the NACK via other means. since the summary feedback does not 377 mandate the forwarding of NACK downstream. The Third Party Loss 378 Report can be generated at the distribution source when downstream 379 loss is told (e.g., downstream loss report is received), which 380 indicates to the receivers that they should not transmit feedback 381 messages for the same loss event for a certain time. Therefore the 382 distribution source in the feedback summary model can be reasonably 383 certain that it will help the situation by sending this Third Party 384 Loss Report message to all the relevant receivers impacted by the 385 packet loss. 387 6.2. Unicast based Rapid Acquisition of Multicast Stream (RAMS) use 388 case 390 The typical RAMS architecture [RFC6285] may have several Burst/ 391 Retransmission Sources(BRS) behind the multicast source (MS) placed 392 at the same level. These BRSes will receive the primary multicast 393 RTP stream from the media source and cache most recent packets after 394 joining multicast session. If packet loss happens at the upstream of 395 all the BRSs or the downstream of BRSes. One of the BRSes or all the 396 BRSes may send a NACK or TPLR message to the DS, where the SSRC in 397 this NACK or TPLR message is the BRS that is sending the message. 398 The DS forwards/reflects this message down on the primary SSM. The 399 details on how DS deal with this message is specified in 400 [RETRANSMISSION-FOR-SSM]. 402 6.3. RTP Transport Translator use case 404 A Transport Translator (Topo-Trn-Translator), as defined in [RFC5117] 405 is typically forwarding the RTP and RTCP traffic between RTP clients, 406 for example converting from multicast to unicast for domains that do 407 not support multicast. The translator may suffer a loss of important 408 video packets. In this case, the translator may forward TPLR message 409 received from upstream in the same way as forwarding other RTCP 410 traffic. If the translator acting as quality monitor [Monarch]is 411 aware of packet loss, it may use the SSRC of monitor as packet sender 412 SSRC to create NACK message and send it to the receivers that is not 413 aware of packet loss. 415 6.4. Multipoint Control Unit (MCU) use case 417 When the speaker is changed in a voice-activated multipoint video 418 switching conference [RFC4587], an RTP mixer can be used to select 419 the available input streams and forward them to each participants. 420 If the MCU is doing a blind switch without waiting for a 421 synchronization point on the new stream it can send a FIR to the new 422 video source. In this case the MCU should send a FIR suppression 423 message to the new receivers. e.g.,when the RTP Mixer starts to 424 receive FIR from some participants it can suppress the remaining 425 session participants from sending FIR by sending out a Third party 426 Loss report message. 428 6.5. Mixer use case 430 A Mixer, in accordance with [RFC5117], aggregates multiple RTP 431 streams from other session participants and generates a new RTP 432 stream sent to the session participants. In some cases, the video 433 frames may get badly screwed up between media source and the mixer. 434 In such case, the mixer need to check if the packet loss will result 435 in PLI or FIR transmissions from most of the group by analyzing the 436 received video. If so the mixer may initiate FIR or PLI towards the 437 media source on behalf of all the session participants and send out a 438 Third party Loss report message to these session participants that 439 may or are expected to send a PLI or FIR. Alternatively, when the 440 mixer starts to receive FIR or PLI from some participants and like to 441 suppress the remaining session participants from sending FIR or PLI 442 by forwarding the FIR/PLI from one session participant to others. 444 7. Security Considerations 446 The defined messages have certain properties that have security 447 implications. These must be addressed and taken into account by 448 users of this protocol. 450 Spoofed or maliciously created feedback messages of the type defined 451 in this specification can have the following implications: 453 Sending the spurious Third Party Loss Report (e.g., the Third Party 454 Loss Report with the wrong sequence number of lost packet) that 455 causes missing RTP packets to not be repaired in a timely fashion. 457 To prevent these attacks, there is a need to apply authentication and 458 integrity protection of the feedback messages. This can be 459 accomplished against threats external to the current RTP session 460 using the RTP profile that combines Secure RTP [RFC3711] and AVPF 461 into SAVPF [RFC5124]. 463 Note that middleboxes that are not visible at the RTP layer that wish 464 to send the Third Party Loss Reports on behalf of the media source 465 can only do so if they spoof the SSRC of the media source. This is 466 difficult in case SRTP is in use. If the middlebox is visible at the 467 RTP layer, this is not an issue, provided the middlebox is part of 468 the security context for the session. 470 Also note that endpoints that receive a Third Party Loss Report would 471 be well-advised to ignore it, unless the security is in place to 472 authenticate the sender of the Third Party Loss Report. Accepting 473 Third Party Loss Report from un-authenticated sender can lead to a 474 denial of service attack, where the endpoint accepts poor quality 475 media that could be repaired. 477 8. IANA Consideration 479 The new value "TPLR" has been registered with IANA in the "rtcp-fb" 480 Attribute Values registry located at the time of publication at: 481 http://www.iana.org/assignments/sdp-parameters 483 Value name: tplr 484 Long Name: Third Party Loss Reports 485 Reference: This document 487 A new registry " Third Party Loss Report Messages" has been created 488 to hold "tplr" parameters located at time of publication at: 489 http://www.iana.org/assignments/sdp-parameters 491 New registration in this registry follows the "Specification 492 required" policy as defined by [RFC5226]. In addition, they are 493 required to indicate any additional RTCP feedback types, such as 494 "nack" and "ack". 496 The following value have been registered as one FMT value in the "FMT 497 Values for RTPFB Payload Types" registry located at the time of 498 publication at: http://www.iana.org/assignments/rtp-parameters 500 RTPFB range 501 Name Long Name Value Reference 502 -------------- --------------------------------- ----- --------- 503 TLLEI Transport Layer Third Party TBA1 [RFCXXXX] 504 Loss Early Indication 506 The following value have been registered as one FMT value in the "FMT 507 Values for PSFB Payload Types" registry located at the time of 508 publication at: http://www.iana.org/assignments/rtp-parameters 509 PSFB range 510 Name Long Name Value Reference 511 -------------- --------------------------------- ----- --------- 512 PSLEI Payload Specific Third Party TBA2 [RFCXXXX] 513 Loss Early Indication 515 9. Acknowledgement 517 The authors would like to thank David R Oran, Magnus Westerlund, 518 Colin Perkins, Ali C. Begen, Tom VAN CAENEGEM, Ingemar Johansson S, 519 Bill Ver Steeg, Jonathan Lennox, WeeSan Lee for their valuable 520 comments and suggestions on this document. 522 10. References 524 10.1. Normative References 526 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 527 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 528 May 2008. 530 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 531 Requirement Levels", BCP 14, RFC 2119, March 1997. 533 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 534 "Extended RTP Profile for Real-time Transport Control 535 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, 536 July 2006. 538 [RFC4588] Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R. 539 Hakenberg, "RTP Retransmission Payload Format", RFC 4588, 540 July 2006. 542 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 543 Description Protocol", RFC 4566, July 2006. 545 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 546 Specifications: ABNF", STD 68, RFC 5234, January 2008. 548 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, 549 "Codec Control Messages in the RTP Audio-Visual Profile 550 with Feedback (AVPF)", RFC 5104, February 2008. 552 10.2. Informative References 554 [RFC5740] Adamson, B., Bormann, C., Handley, M., and J. Macker, 555 "NACK-Oriented Reliable Multicast (NORM) Transport 556 Protocol", November 2009. 558 [DVB-IPTV] 559 ETSI Standard, "Digital Video Broadcasting(DVB); Transport 560 of MPEG-2 TS Based DVB Services over IP Based Networks", 561 ETSI TS 102 034, V1.4.1 , August 2009. 563 [RFC6285] Steeg, B., Begen, A., Caenegem, T., and Z. Vax, "Unicast- 564 Based Rapid Acquisition of Multicast RTP Sessions", 565 June 2011. 567 [Monarch] Wu, Q., Hunt, G., and P. Arden, "Monitoring Architectures 568 for RTP", June 2011. 570 [RETRANSMISSION-FOR-SSM] 571 Caenegem, T., Steeg, B., and A. Begen, "Retransmission for 572 Source-Specific Multicast (SSM) Sessions", May 2011. 574 [RFC5117] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117, 575 January 2008. 577 [RFC4587] Even, R., "RTP Payload Format for H.261 Video Streams", 578 RFC 4587, August 2006. 580 [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control 581 Protocol (RTCP) Extensions for Single-Source Multicast 582 Sessions with Unicast Feedback", RFC 5760, February 2010. 584 [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for 585 Real-time Transport Control Protocol (RTCP)-Based Feedback 586 (RTP/SAVPF)", RFC 5124, February 2008. 588 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 589 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 590 RFC 3711, March 2004. 592 Appendix A. Change Log 594 Note to the RFC-Editor: please remove this section prior to 595 publication as an RFC. 597 A.1. draft-ietf-avtcore-feedback-suppression-rtp-01 599 The following are the major changes compared to previous version: 601 o Remove the merge report from SSM use case and additional text to 602 address report merging issue. 604 o Revise section 3 and section 6 to address FEC packet dealing issue 605 and Leave how to repair packet loss beyond the scope. 607 o Modify the SSM use case and RAMS use case to focus on uses. 609 o Other Editorial changes. 611 A.2. draft-ietf-avtcore-feedback-suppression-rtp-02 613 The following are the major changes compared to previous version: 615 o In Section 4.1, fix typo: Section 4.3.1.1 of section [RFC5104]-> 616 section 6.2.1 of [RFC4585]. 618 o In Section 3: Clarify how to deal with downstream loss using Third 619 party loss report and upstream loss using NACK. 621 o Update title and abstract to focus on third party loss report. 623 o In Section 6.1: Update this section to explain how third party 624 loss report is used to deal with downstream loss. 626 o In section 6.1.2: Update this section to explain how third party 627 loss report is used to deal with downstream loss. 629 o In section 6.2: Rephrase the text to discuss how BRS deal with the 630 third party loss report. 632 A.3. draft-ietf-avtcore-feedback-suppression-rtp-03 634 The following are the major changes compared to previous version: 636 o In Appendix A, fix typo: Appendix A. Appendix A. -> Appendix A. 638 o Update abstract to clarify when third-party loss reports should be 639 sent instead of NACKs. 641 o Update section 3 Paragraph 2 to differentiate when a third-party 642 loss report should be used compared to a NACK. 644 o Update section 3 Paragraph 3 to explain when media source to send 645 a third-party loss. 647 o Move specific rules for section 6.1.1 and section 6.1.2 to section 648 6.1 as generic rules and delete section 6.1.1. 650 A.4. draft-ietf-avtcore-feedback-suppression-rtp-04 652 The following are the major changes compared to previous version: 653 o Reference Update. 655 o Clarify the use of the third party loss report in section 3 and 656 section 6.1.1. 658 A.5. draft-ietf-avtcore-feedback-suppression-rtp-05 660 The following are the major changes compared to previous version: 661 o Remove 3rd and 4th paragraphs of section 6.1 and replaced them 662 with 2nd and 3rd paragraphs of section 3. 664 o Remove section 6.1.1.1. 666 o Revise the last paragraph of section 1 to clarify the rationale of 667 using new message. 669 o Update RTP transport translator case in section 6.3 to correct the 670 use of the third party loss report. 672 o Update MCU case in section 6.4 to correct the use of the third 673 party loss report. 675 o Revise SSM use case to address multiple DS issue. 677 o References Update. 679 o Move one rationale on preventing sending unicast NACK in 680 introduction section to SSM case section. 682 o Other Editorial changes to section 6.1, 6.1.1, 6.2. 684 A.6. draft-ietf-avtcore-feedback-suppression-rtp-06 686 The following are the major changes compared to previous version: 688 o A few Editorial changes to the whole document. 690 A.7. draft-ietf-avtcore-feedback-suppression-rtp-07 692 The following are the major changes compared to previous version: 694 o Restructuring the protocol overview section to clarify the round 695 trip time calculation and receiver behavior to the additional 696 TPLR. 698 o Restructuring the SSM use case section to focus on the use of 699 TPLR. 701 o Editorial changes to the abstract, introduction, message format, 702 use cases and IANA sections. 704 o References update 706 A.8. draft-ietf-avtcore-feedback-suppression-rtp-08 708 The following are the major changes compared to previous version: 710 o Clarify which RTT is used and how timer is refreshed in the 711 section 3. 713 o Editorial changes to the Introduction, Protocol Overview, SDP 714 Signaling, Message Format, Use case,Security Consideration and 715 IANA sections. 717 o Remove Seq Nr field in the figure 2 for payload specific feedback. 719 o References reorganizing. 721 Authors' Addresses 723 Qin Wu 724 Huawei 725 101 Software Avenue, Yuhua District 726 Nanjing, Jiangsu 210012 727 China 729 Email: sunseawq@huawei.com 730 Frank Xia 731 Huawei 732 1700 Alma Dr. Suite 500 733 Plano, TX 75075 734 USA 736 Phone: +1 972-509-5599 737 Email: xiayangsong@huawei.com 739 Roni Even 740 Huawei 741 14 David Hamelech 742 Tel Aviv 64953 743 Israel 745 Email: even.roni@huawei.com