draft-ietf-avtcore-feedback-supression-rtp-17.txt   rfc6642.txt 
Network Working Group Q. Wu Internet Engineering Task Force (IETF) Q. Wu, Ed.
Internet-Draft F. Xia Request for Comments: 6642 F. Xia
Intended status: Standards Track R. Even Category: Standards Track R. Even
Expires: October 15, 2012 Huawei ISSN: 2070-1721 Huawei
April 13, 2012 June 2012
RTCP Extension for Third-party Loss Report RTP Control Protocol (RTCP) Extension for a Third-Party Loss Report
draft-ietf-avtcore-feedback-supression-rtp-17
Abstract Abstract
In a large RTP session using the RTP Control Protocol (RTCP) feedback In a large RTP session using the RTP Control Protocol (RTCP) feedback
mechanism defined in RFC 4585, a feedback target may experience mechanism defined in RFC 4585, a feedback target may experience
transient overload if some event causes a large number of receivers transient overload if some event causes a large number of receivers
to send feedback at once. This overload is usually avoided by to send feedback at once. This overload is usually avoided by
ensuring that feedback reports are forwarded to all receivers, ensuring that feedback reports are forwarded to all receivers,
allowing them to avoid sending duplicate feedback reports. However, allowing them to avoid sending duplicate feedback reports. However,
there are cases where it is not recommended to forward feedback there are cases where it is not recommended to forward feedback
reports, and this may allow feedback implosion. This memo discusses reports, and this may allow feedback implosion. This memo discusses
these cases and defines a new RTCP third-party loss report that can these cases and defines a new RTCP Third-Party Loss Report that can
be used to inform receivers that the feedback target is aware of some be used to inform receivers that the feedback target is aware of some
loss event, allowing them to suppress feedback. Associated SDP loss event, allowing them to suppress feedback. Associated Session
signaling is also defined. Description Protocol (SDP) signaling is also defined.
Status of this Memo
This Internet-Draft is submitted in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This is an Internet Standards Track document.
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on October 15, 2012. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6642.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction ....................................................3
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 2. Terminology .....................................................3
2.1. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Requirements Notation ......................................3
3. Example Use Cases . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Glossary ...................................................4
3.1. Source Specific Multicast (SSM) use case . . . . . . . . . 5 3. Example Use Cases ...............................................4
3.2. Unicast based Rapid Acquisition of Multicast Stream 3.1. Source-Specific Multicast (SSM) Use Case ...................4
(RAMS) use case . . . . . . . . . . . . . . . . . . . . . 6 3.2. Unicast-Based Rapid Acquisition of Multicast Stream
3.3. RTP Transport Translator use case . . . . . . . . . . . . 6 (RAMS) Use Case ............................................5
3.4. Multipoint Control Unit (MCU) use case . . . . . . . . . . 6 3.3. RTP Transport Translator Use Case ..........................5
3.5. Mixer use case . . . . . . . . . . . . . . . . . . . . . . 6 3.4. Multipoint Control Unit (MCU) Use Case .....................6
4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 3.5. Mixer Use Case .............................................6
5. Format of RTCP Feedback Messages . . . . . . . . . . . . . . . 8 4. Protocol Overview ...............................................6
5.1. Transport Layer Feedback: Third-Party Loss Report 5. Format of RTCP Feedback Messages ................................7
(TPLR) . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1. Transport-Layer Feedback: Third-Party Loss Report (TPLR) ...8
5.2. Payload Specific Feedback: Third-Party Loss Report 5.2. Payload-Specific Feedback: Third-Party Loss Report (TPLR) .8
(TPLR) . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. SDP Signaling ...................................................9
6. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations ........................................10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 8. IANA Considerations ............................................11
8. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 11 9. Acknowledgments ................................................11
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 10. References ....................................................12
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 10.1. Normative References .....................................12
10.1. Normative References . . . . . . . . . . . . . . . . . . . 13 10.2. Informative References ...................................12
10.2. Informative References . . . . . . . . . . . . . . . . . . 13
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 14
A.1. draft-ietf-avtcore-feedback-suppression-rtp-17 . . . . . . 14
A.2. draft-ietf-avtcore-feedback-suppression-rtp-16 . . . . . . 14
A.3. draft-ietf-avtcore-feedback-suppression-rtp-15 . . . . . . 14
A.4. draft-ietf-avtcore-feedback-suppression-rtp-14 . . . . . . 14
A.5. draft-ietf-avtcore-feedback-suppression-rtp-13 . . . . . . 15
A.6. draft-ietf-avtcore-feedback-suppression-rtp-12 . . . . . . 15
A.7. draft-ietf-avtcore-feedback-suppression-rtp-11 . . . . . . 15
A.8. draft-ietf-avtcore-feedback-suppression-rtp-10 . . . . . . 15
A.9. draft-ietf-avtcore-feedback-suppression-rtp-09 . . . . . . 15
A.10. draft-ietf-avtcore-feedback-suppression-rtp-08 . . . . . . 16
A.11. draft-ietf-avtcore-feedback-suppression-rtp-07 . . . . . . 16
A.12. draft-ietf-avtcore-feedback-suppression-rtp-06 . . . . . . 16
A.13. draft-ietf-avtcore-feedback-suppression-rtp-05 . . . . . . 16
A.14. draft-ietf-avtcore-feedback-suppression-rtp-04 . . . . . . 17
A.15. draft-ietf-avtcore-feedback-suppression-rtp-03 . . . . . . 17
A.16. draft-ietf-avtcore-feedback-suppression-rtp-02 . . . . . . 18
A.17. draft-ietf-avtcore-feedback-suppression-rtp-01 . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
The RTP Control Protocol (RTCP) feedback messages [RFC4585] allow the The RTP Control Protocol (RTCP) feedback messages [RFC4585] allow the
receivers in an RTP session to report events and ask for action from receivers in an RTP session to report events and ask for action from
the media source (or a delegated feedback target when using unicast the media source (or a delegated feedback target when using unicast
RTCP feedback with SSM [RFC5760]). There are cases where multiple RTCP feedback with Source-Specific Multicast (SSM) [RFC5760]). There
receivers may initiate the same, or an equivalent message towards the are cases where multiple receivers may initiate the same, or an
same media source or the same feedback target. When the receiver equivalent, message towards the same media source or the same
count is large, this behavior may cause transient overload of the feedback target. When the receiver count is large, this behavior may
media source, the network or both. This is known as a "feedback cause transient overload of the media source, the network, or both.
storm" or a "NACK storm". This is known as a "feedback storm" or a "NACK storm".
One scenario that can cause such feedback storms involves video Fast One scenario that can cause such feedback storms involves video Fast
Update requests. A storm of these feedback messages can occur in Update requests. A storm of these feedback messages can occur in
conversational multimedia scenarios like multipoint video switching conversational multimedia scenarios like multipoint video switching
conference [RFC4587], where many receivers may simultaneously lose conference [RFC4587], where many receivers may simultaneously lose
synchronization with the video stream when the speaker is changed in synchronization with the video stream when the speaker is changed in
the middle of a session. Receivers that issue fast update requests the middle of a session. Receivers that issue Fast Update requests
(i.e., Full Intra Request (FIR) described in RFC5104 [RFC5104]), can (i.e., Full Intra Request (FIR) described in RFC 5104 [RFC5104]), can
cause an implosion of FIR requests from receivers to the same media cause an implosion of FIR requests from receivers to the same media
source since these requests must currently be made blind, without source since these requests must currently be made blind, without
knowledge of requests made by other receivers. knowledge of requests made by other receivers.
RTCP feedback storms may cause short term overload, and in extreme RTCP feedback storms may cause short-term overload and, in extreme
cases to pose a possible risk of increasing network congestion on the cases, pose a possible risk of increasing network congestion on the
control channel (e.g., RTCP feedback), the data channel, or both. It control channel (e.g., RTCP feedback), the data channel, or both. It
is therefore desirable to provide a way of suppressing unneeded is therefore desirable to provide a way of suppressing unneeded
feedback. This document specifies a new third-party loss report for feedback. This document specifies a new Third-Party Loss Report for
this function. It supplements the existing the use of RTCP NACK this function. It supplements the existing use of RTCP NACK packets
packet and further is more precise in the uses where the network is and is also more precise in the uses where the network is active to
active to suppress feedback. It tells receivers explicitly that suppress feedback. It tells receivers explicitly that feedback for a
feedback for a particular packet or frame loss is not needed and can particular packet or frame loss is not needed and can provide an
provide an early indication before the receiver reacts to the loss early indication before the receiver reacts to the loss and invokes
and invokes its packet loss repair machinery. Section 3 provides its packet loss repair machinery. Section 3 provides some example
some example use cases of when to send the Third-Party Loss Report use cases of when to send the Third-Party Loss Report message.
message.
2. Requirements Notation 2. Terminology
2.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2.2. Glossary
2.1. Glossary
TPLR - Third-Party Loss Report TPLR - Third-Party Loss Report
TLLEI - Transport Layer Third-Party Loss Early Indication
PSLEI - Payload Specific Third-Party Loss Early Indication TLLEI - Transport-Layer Third-Party Loss Early Indication
PSLEI - Payload-Specific Third-Party Loss Early Indication
PT - Payload Type
FMT - Feedback Message Type
FCI - Feedback Control Information [RFC4585] FCI - Feedback Control Information [RFC4585]
AVPF - The Audio-Visual Profile with RTCP-based feedback [RFC4585]
AVPF - Audio-Visual Profile with RTCP-based feedback [RFC4585]
SSRC - Synchronization Source SSRC - Synchronization Source
BRS - Burst/Retransmission Sources [RFC6285]
BRS - Burst/Retransmission Source [RFC6285]
FIR - Full Intra Request [RFC5104] FIR - Full Intra Request [RFC5104]
PLI - Picture Loss Indication [RFC4585] PLI - Picture Loss Indication [RFC4585]
SSM - Source Specific Multicast [RFC5760]
RAMS - Unicast based Rapid Acquisition of Multicast Stream [RFC6285] SSM - Source-Specific Multicast [RFC5760]
RAMS - Unicast-based Rapid Acquisition of Multicast Stream [RFC6285]
MCU - Multipoint Control Unit [RFC5117] MCU - Multipoint Control Unit [RFC5117]
3. Example Use Cases 3. Example Use Cases
The operation of feedback suppression is similar for all types of RTP The operation of feedback suppression is similar for all types of RTP
sessions and topologies [RFC5117], however the exact messages used sessions and topologies [RFC5117]; however, the exact messages used
and the scenarios in which suppression is employed differ for various and the scenarios in which suppression is employed differ for various
use cases. The following sections outline some of the intended use use cases. The following sections outline some of the intended use
cases for using the Third-Party Loss Report for feedback suppression cases for using the Third-Party Loss Report for feedback suppression
and give an overview of the particular mechanisms. and give an overview of each.
3.1. Source Specific Multicast (SSM) use case 3.1. Source-Specific Multicast (SSM) Use Case
In SSM RTP sessions as described in "RTP Control Protocol (RTCP) In SSM RTP sessions as described in "RTP Control Protocol (RTCP)
Extensions for Single-Source Multicast Sessions with Unicast Extensions for Single-Source Multicast Sessions with Unicast
Feedback" [RFC5760], one or more Media Sources send RTP packets to a Feedback" [RFC5760], one or more media sources send RTP packets to a
Distribution Source. The Distribution Source relays the RTP packets distribution source. The distribution source relays the RTP packets
to the receivers using a source-specific multicast group. to the receivers using a source-specific multicast group.
As outlined in the RFC5760 [RFC5760], there are two Unicast Feedback As outlined in RFC 5760 [RFC5760], there are two Unicast Feedback
models that may be used for reporting, the Simple Feedback model and models that may be used for reporting: the Simple Feedback Model and
the Distribution Source Feedback Summary Model. In the simple the Distribution Source Feedback Summary Model. In the Simple
Feedback Model, there's no need for distribution source to create the Feedback Model, there's no need for the distribution source to create
RTCP TPLRs, instead, RTCP NACKs are reflected by the distribution the RTCP TPLRs; instead, RTCP NACKs are reflected by the distribution
source to the other Receivers. However in the Distribution Source source to the other receivers. However, in the Distribution Source
Feedback Summary model, the distribution source will not redistribute Feedback Summary Model, the distribution source will not redistribute
the NACK for some reason(e.g., to prevent revealing the identity or the NACK for some reason (e.g., to prevent revealing the identity or
existence of a system sending NACK)and may send an RTCP TPLR message existence of a system sending NACK) and may send an RTCP TPLR message
to the systems that were unable to receive the NACK, and won't to the systems that were unable to receive the NACK and won't receive
receive the NACK via other means. The RTCP TPLR can be generated at the NACK via other means. The RTCP TPLR can be generated at the
the distribution source when downstream loss is reported (e.g., distribution source when downstream loss is reported (e.g.,
downstream loss report is received), which indicates to the receivers downstream loss report is received), which indicates to the receivers
that they should not transmit feedback messages for the same loss that they should not transmit feedback messages for the same loss
event for a certain time. Therefore the distribution source in the event for a certain time. Therefore, the distribution source in the
feedback summary model can be reasonably certain that it will help Distribution Source Feedback Summary Model can be reasonably certain
the situation (i.e., unable receive the NACK) by sending this RTCP that it will help the situation (i.e., the distribution source is
TPLR message to all the relevant receivers impacted by the packet unable receive the NACK) by sending this RTCP TPLR message to all the
loss. relevant receivers impacted by the packet loss.
3.2. Unicast based Rapid Acquisition of Multicast Stream (RAMS) use 3.2. Unicast-Based Rapid Acquisition of Multicast Stream (RAMS) Use
case Case
The typical RAMS architecture [RFC6285] may have several Burst/ The typical RAMS architecture [RFC6285] may have several Burst/
Retransmission Sources(BRS) behind the multicast source (MS) placed Retransmission Sources (BRSs) behind the multicast source placed at
at the same level. These BRSes will receive the primary multicast the same level. These BRSs will receive the primary multicast RTP
RTP stream from the media source and cache most recent packets after stream from the media source and cache the most recent packets after
joining multicast session. If packet loss happens at the upstream of joining the multicast session. If packet loss happens at the
all the BRSs or the downstream of BRSes. One of the BRSes or all the upstream of all the BRSs or the downstream of BRSs, one or all of the
BRSes may send an RTCP NACK or RTCP TPLR message to the DS, where the BRSs may send an RTCP NACK or RTCP TPLR message to the distribution
SSRC in this RTCP NACK or RTCP TPLR message is the BRS that is source, where the SSRC in this RTCP NACK or RTCP TPLR message is the
sending the message. The DS forwards/reflects this message down on BRS that is sending the message. The distribution source forwards/
the primary SSM. The details on how DS deal with this message is reflects this message down on the primary SSM. The details on how
specified in [RETRANSMISSION-FOR-SSM]. the distribution source deals with this message are specified in
[RETRANS-FOR-SSM].
3.3. RTP Transport Translator use case 3.3. RTP Transport Translator Use Case
A Transport Translator (Topo-Trn-Translator), as defined in RFC5117 A Transport Translator (Topo-Trn-Translator), as defined in RFC 5117
[RFC5117] is typically forwarding the RTP and RTCP traffic between [RFC5117], is typically forwarding the RTP and RTCP traffic between
RTP clients, for example converting from multicast to unicast for RTP clients, for example, converting from multicast to unicast for
domains that do not support multicast. The translator may suffer a domains that do not support multicast. The translator may suffer a
loss of important video packets. In this case, the translator may loss of important video packets. In this case, the translator may
forward RTCP TPLR message received from upstream in the same way as forward an RTCP TPLR message received from upstream in the same way
forwarding other RTCP traffic. If the translator acting as the it forwards other RTCP traffic. If the translator acting as the
monitor [MONARCH] is aware of packet loss, it may use the SSRC of monitor [MONARCH] is aware of packet loss, it may use the SSRC of the
monitor as packet sender SSRC to create NACK message and send it to monitor as the SSRC of the packet sender to create a NACK message and
the receivers that are not aware of packet loss. send it to the receivers that are not aware of packet loss.
3.4. Multipoint Control Unit (MCU) use case 3.4. Multipoint Control Unit (MCU) Use Case
When the speaker is changed in a voice-activated multipoint video When the speaker is changed in a voice-activated multipoint video
switching conference [RFC4587], an RTP mixer can be used to select switching conference [RFC4587], an RTP mixer can be used to select
the available input streams and forward them to each participants. the available input streams and forward them to each participant. If
If the MCU is doing a blind switch without waiting for a the MCU is doing a blind switch without waiting for a synchronization
synchronization point on the new stream it can send a FIR to the new point on the new stream, it can send a FIR to the new video source.
video source. In this case the MCU should send a FIR suppression In this case, the MCU should send a FIR suppression message to the
message to the new receivers: e.g., when the RTP Mixer starts to new receivers. For example, when the RTP mixer starts to receive FIR
receive FIR from some participants it can suppress the remaining from some participants, it can suppress the remaining session
session participants from sending FIR by sending out an RTCP TPLR participants from sending FIR by sending out an RTCP TPLR message.
message.
3.5. Mixer use case 3.5. Mixer Use Case
A Mixer, in accordance with RFC5117 [RFC5117], aggregates multiple A mixer, in accordance with RFC 5117 [RFC5117], aggregates multiple
RTP streams from other session participants and generates a new RTP RTP streams from other session participants and generates a new RTP
stream sent to the session participants. In some cases, the video stream sent to the session participants. In some cases, the delivery
frames delivery may get damaged, for example due to packet loss or of video frames delivery may get damaged, for example, due to packet
delayed delivery, between media source and the mixer. In such case, loss or delayed delivery, between the media source and the mixer. In
the mixer need to check if the packet loss will result in PLI or FIR such cases, the mixer needs to check if the packet loss will result
transmissions from most of the group by analyzing the received video. in PLI or FIR transmissions from most of the group by analyzing the
If so the mixer may initiate FIR or PLI towards the media source on received video. If so, the mixer may initiate FIR or PLI towards the
behalf of all the session participants and send out an RTCP TPLR media source on behalf of all the session participants and send out
message to these session participants that may or are expected to an RTCP TPLR message to the session participants that may or are
send a PLI or FIR. Alternatively, when the mixer starts to receive expected to send a PLI or FIR. Alternatively, when the mixer starts
FIR or PLI from some participants and like to suppress the remaining to receive FIR or PLI from some participants and would like to
session participants from sending FIR or PLI by forwarding the FIR/ suppress the remaining session participants from sending FIR or PLI,
PLI from one session participant to others. it can just forward the FIR/PLI from one session participant to
others.
4. Protocol Overview 4. Protocol Overview
This document extends the RTCP feedback messages defined in the RTP/ This document extends the RTCP feedback messages defined in the RTP/
AVPF [RFC4585] defining an RTCP Third-Party Loss Report (TPLR) AVPF [RFC4585] by defining an RTCP Third-Party Loss Report (TPLR)
message. The RTCP TPLR message can be used by the intermediaries to message. The RTCP TPLR message can be used by the intermediaries to
inform the receiver that the sender of the RTCP TPLR has received inform the receiver that the sender of the RTCP TPLR has received
reports that the indicated packets were lost, and asks the receiver reports that the indicated packets were lost and ask the receiver not
not to send feedback to it regarding these packets. Intermediaries to send feedback to it regarding these packets. Intermediaries are
are variously referred to as Distribution source, Burst/ variously referred to as distribution sources, Burst/Retransmission
Retransmission Sources (BRS), MCUs, RTP translator, or RTP mixers, Sources, MCUs, RTP translators, or RTP mixers, depending on the
depending on the precise use case described Section 3. precise use case described Section 3.
RTCP TPLR follows the similar format of message type as RTCP NACK or RTCP TPLR follows a similar message type format as RTCP NACK or Full
Full Intra Request Command. However, the RTCP TPLR is defined as an Intra Request Command. However, RTCP TPLR is defined as an
indication that the sender of the feedback has received reports that indication that the sender of the feedback has received reports that
the indicated packets were lost, while NACK [RFC4585] just indicates the indicated packets were lost, while NACK [RFC4585] just indicates
that the sender of the NACK observed that these packets were lost. that the sender of the NACK observed that these packets were lost.
The RTCP TPLR message is generated by an intermediary that may not The RTCP TPLR message is generated by an intermediary that may not
have seen the actual packet loss. It is sent following the same have seen the actual packet loss. It is sent following the same
timing rule as sending NACK defined in RFC4585 [RFC4585]. The RTCP timing rule as sending NACK, defined in RFC 4585 [RFC4585]. The RTCP
TPLR message may be sent in a regular full compound RTCP packet or in TPLR message may be sent in a regular full compound RTCP packet or in
an early RTCP packet, as per the RTP/AVPF rules. Intermediaries in an early RTCP packet, as per the RTP/AVPF rules. Intermediaries in
the network that receive an RTCP TPLR MUST NOT send their own the network that receive an RTCP TPLR MUST NOT send their own
additional Third-Party Loss Report messages for the same packet additional Third-Party Loss Report messages for the same packet
sequence numbers. They SHOULD simply forward the RTCP TPLR message sequence numbers. They SHOULD simply forward the RTCP TPLR message
received from upstream direction to the receiver(s), additionally, received from upstream to the receiver(s). Additionally, they may
they may generate their own RTCP TPLR that reports a set of the generate their own RTCP TPLR that reports a set of the losses they
losses they see, which are different from ones reported in the RTCP see, which are different from ones reported in the RTCP TPLR they
TPLR they received. The RTCP TPLR does not have the retransmission received. The RTCP TPLR does not have retransmission request
request [RFC4588] semantics. [RFC4588] semantics.
When a receiver gets an RTCP TPLR message, it MUST follow the rules When a receiver gets an RTCP TPLR message, it MUST follow the rules
for NACK suppression in RFC4585 [RFC4585]and refrain from sending a for NACK suppression in RFC 4585 [RFC4585] and refrain from sending a
feedback request (e.g., NACK or FIR) for the missing packets reported feedback request (e.g., NACK or FIR) for the missing packets reported
in the message, which is dealt with in the same way as receiving in the message, which is dealt with in the same way as receiving a
NACK. NACK.
To increase the robustness to the loss of a TPLR, The RTCP TPLR may To increase the robustness to the loss of a TPLR, the RTCP TPLR may
be retransmitted. If the additional TPLR arrives at receiver, the be retransmitted. If the additional TPLR arrives at the receiver,
receiver SHOULD deal with the additional TPLR in the same way as the receiver SHOULD deal with the additional TPLR in the same way as
receiving the first TPLR for the same packet and no additional receiving the first TPLR for the same packet, and no additional
behavior for receiver is required. behavior for receiver is required.
A receiver may have sent a Feedback message according to the RTP/AVPF A receiver may have sent a feedback message according to the RTP/AVPF
scheduling algorithm of RFC4585 [RFC4585] before receiving an RTCP scheduling algorithm of RFC 4585 [RFC4585] before receiving an RTCP
TPLR message, but further feedback messages for those sequence TPLR message, but further feedback messages for those sequence
numbers SHOULD be suppressed after receiving the RTCP TPLR. Nodes numbers SHOULD be suppressed after receiving the RTCP TPLR. Nodes
that do not understand the RTCP TPLR message will ignore it, and that do not understand the RTCP TPLR message will ignore it and might
might therefore still send feedback according to the AVPF scheduling therefore still send feedback according to the AVPF scheduling
algorithm of RFC4585 [RFC4585]. The media source or intermediate algorithm of RFC 4585 [RFC4585]. The media source or intermediate
nodes cannot be certain that the use of an RTCP TPLR message actually nodes cannot be certain that the use of an RTCP TPLR message actually
reduces the amount of feedback it receives. reduces the amount of feedback they receive.
5. Format of RTCP Feedback Messages 5. Format of RTCP Feedback Messages
This document introduces two new RTCP Feedback messages for Third This document introduces two new RTCP feedback messages for Third-
Party Loss Report. Applications that are employing one or more loss- Party Loss Report. Applications that are employing one or more loss-
repair methods MAY use the RTCP TPLR together with their existing repair methods MAY use the RTCP TPLR together with their existing
loss-repair methods either for every packet they expect to receive, loss-repair methods either for every packet they expect to receive or
or for an application-specific subset of the RTP packets in a for an application-specific subset of the RTP packets in a session.
session.
The following two sections each define an RTCP TPLR message. Both The following two sections each define an RTCP TPLR message. Both
messages are feedback messages as defined in section 6.1 of RFC4585 messages are feedback messages as defined in Section 6.1 of RFC 4585
[RFC4585], and use the header format defined there. Each section [RFC4585] and use the header format defined there. Each section
defines how to populate the PT, FMT, length, SSRC of packet sender, defines how to populate the PT, FMT, length, SSRC of packet sender,
SSRC of media source, and FCI fields in that header. SSRC of media source, and FCI fields in that header.
5.1. Transport Layer Feedback: Third-Party Loss Report (TPLR) 5.1. Transport-Layer Feedback: Third-Party Loss Report (TPLR)
This TPLR message is identified by RTCP packet type value PT=RTPFB This TPLR message is identified by RTCP packet type values PT=RTPFB
and FMT=TBA1. and FMT=7.
Within the common packet header for feedback messages (as defined in Within the common packet header for feedback messages (as defined in
section 6.1 of RFC4585 [RFC4585]), the "SSRC of packet sender" field Section 6.1 of RFC 4585 [RFC4585]), the "SSRC of packet sender" field
indicates the source of the request, and the "SSRC of media source" indicates the source of the request, and the "SSRC of media source"
denotes the media sender of the flow for which the indicated losses field denotes the media sender of the flow for which the indicated
are being suppressed. losses are being suppressed.
The Feedback Control Information (FCI) field MUST contain one or more
entries of Transport Layer Third-Party loss Early Indication (TLLEI).
Each entry applies to the same media source identified by the SSRC The FCI field MUST contain one or more entries of Transport-Layer
contained in the SSRC of media source field of Feedback header. The Third-Party Loss Early Indication (TLLEI). Each entry applies to the
length field in the TLLEI feedback message MUST be set to N+2, where same media source identified by the SSRC contained in the "SSRC of
N is the number of FCI entries. media source" field of the Feedback header. The length field in the
TLLEI feedback message MUST be set to N+2, where N is the number of
FCI entries.
The FCI field for TLLEI uses the similar format of message Types The FCI field for TLLEI uses a similar message type format to that
defined in the section 6.2.1 of RFC4585 [RFC4585]. The format is defined in the Section 6.2.1 of RFC 4585 [RFC4585]. The format is
shown in Figure 1. shown in Figure 1.
0 1 2 3 0 1 2 3
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PID | BLP | | PID | BLP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Syntax of an FCI Entry in the TLLEI Feedback Message Figure 1: Syntax of an FCI Entry in the TLLEI Feedback Message
Packet ID (PID): 16 bits Packet ID (PID): 16 bits
The PID field is used to specify a lost packet. The PID field The PID field is used to specify a lost packet. The PID field
refers to the RTP sequence number of the lost packet. refers to the RTP sequence number of the lost packet.
bitmask of lost packets (BLP): 16 bits bitmask of lost packets (BLP): 16 bits
The BLP allows for reporting losses of any of the 16 RTP packets The BLP allows for reporting losses of any of the 16 RTP packets
immediately following the RTP packet indicated by the PID. The immediately following the RTP packet indicated by the PID. The
BLP's definition is identical to that given in the section 6.2.1 BLP's definition is identical to that given in Section 6.2.1 of
of [RFC4585]. [RFC4585].
5.2. Payload Specific Feedback: Third-Party Loss Report (TPLR) 5.2. Payload-Specific Feedback: Third-Party Loss Report (TPLR)
This TPLR message is identified by RTCP packet type value PT=PSFB and This TPLR message is identified by RTCP packet type values PT=PSFB
FMT=TBA2, which is used to suppress FIR [RFC5104] and PLI [RFC4585]. and FMT=8, which are used to suppress FIR [RFC5104] and PLI
[RFC4585].
Within the common packet header for feedback messages (as defined in Within the common packet header for feedback messages (as defined in
section 6.1 of RFC4585 [RFC4585]), the "SSRC of packet sender" field Section 6.1 of RFC 4585 [RFC4585]), the "SSRC of packet sender" field
indicates the source of the request, and the "SSRC of media source" indicates the source of the request, and the "SSRC of media source"
is not used and SHALL be set to 0. The SSRCs of the media senders to is not used and SHALL be set to 0. The SSRCs of the media senders to
which this message applies are in the corresponding FCI entries. which this message apply are in the corresponding FCI entries.
The FCI field for a Payload Specific Third-Party Loss Early The FCI field for a Payload-Specific Third-Party Loss Early
Indication (PSLEI) consists one or more FCI entries. Each entry Indication (PSLEI) consists one or more FCI entries. Each entry
applies to a different media source, identified by its SSRC. the applies to a different media source, identified by its SSRC, the
content of which is depicted in Figure 2. The length field in the content of which is depicted in Figure 2. The length field in the
PSLEI feedback message MUST be set to N+2, where N is the number of PSLEI feedback message MUST be set to N+2, where N is the number of
FCI entries. FCI entries.
The format is shown in Figure 2. The format is shown in Figure 2.
0 1 2 3 0 1 2 3
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC | | SSRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Syntax of an FCI Entry in the PSLEI Feedback Message Figure 2: Syntax of an FCI Entry in the PSLEI Feedback Message
Synchronization source (SSRC): 32 bits Synchronization source (SSRC): 32 bits
The SSRC value of the media source that is already aware, or in The SSRC value of the media source that is already aware, or in
the process of being made aware, that some receiver lost the process of being made aware, that some receiver lost
synchronization with the media stream and for which the PSLEI synchronization with the media stream and for which the PSLEI
receiver's own response to any such error is suppressed. receiver's own response to any such error is suppressed.
6. SDP Signaling 6. SDP Signaling
The Session Description Protocol (SDP) [RFC4566] attribute, rtcp-fb, The Session Description Protocol (SDP) [RFC4566] attribute, rtcp-fb,
is defined in the Section 4 of RFC4585 [RFC4585] and may be used to is defined in Section 4 of RFC 4585 [RFC4585] and may be used to
negotiate the capability to handle specific AVPF commands and negotiate the capability to handle specific AVPF commands and
indications. The ABNF for rtcp-fb is described in section 4.2 of indications. The ABNF for rtcp-fb is described in Section 4.2 of RFC
RFC4585 [RFC4585]. In this section, we extend the rtcp-fb attribute 4585 [RFC4585]. In this section, we extend the rtcp-fb attribute to
to include the commands and indications that are described for third- include the commands and indications that are described for Third-
party loss report in the present document. Party Loss Reports in the present document.
In the ABNF [RFC5234] for rtcp-fb-val defined in RFC4585 [RFC4585], In the ABNF [RFC5234] for rtcp-fb-val defined in RFC 4585 [RFC4585],
the feedback type "nack", without parameters, indicates use of the the feedback type "nack", without parameters, indicates use of the
Generic NACK feedback format as defined in Section 6.2.1of RFC4585 Generic NACK feedback format as defined in Section 6.2.1 of RFC 4585
[RFC4585]. In this document, we define two parameters that indicate [RFC4585]. In this document, we define two parameters that indicate
the third-party loss supported for use with "nack", namely: the third-party loss supported for use with "nack", namely:
o "tllei" denotes support of Transport Layer Third-Party Loss Early o "tllei" denotes support of Transport-Layer Third-Party Loss Early
Indication. Indication.
o "pslei" denotes support of Payload Specific Third-Party Loss Early o "pslei" denotes support of Payload-Specific Third-Party Loss Early
Indication. Indication.
The ABNF for these two parameters for "nack" is defined here (please The ABNF for these two parameters for use with "nack" is defined here
refer to section 4.2 of RFC4585 [RFC4585] for complete ABNF syntax). (please refer to Section 4.2 of RFC4585 [RFC4585] for complete ABNF
syntax).
rtcp-fb-val =/ "nack" rtcp-fb-nack-param rtcp-fb-val =/ "nack" rtcp-fb-nack-param
rtcp-fb-nack-param = SP "tllei" rtcp-fb-nack-param = SP "tllei"
;transport layer third party ;Transport-Layer Third-Party
; loss early indication ; Loss Early Indication
/ SP "pslei" / SP "pslei"
;payload specific third party ;Payload-Specific Third-Party
; loss early indication ; Loss Early Indication
/ SP token [SP byte-string] / SP token [SP byte-string]
; for future commands/indications ; for future commands/indications
token = <as defined in section 9 of [RFC4566]> token = <as defined in Section 9 of [RFC4566]>
byte-string = <as defined in section 4.2 of [RFC4585] > byte-string = <as defined in Section 9 of [RFC4566]>
Refer to Section 4.2 of RFC4585 [RFC4585] for a detailed description
and the full syntax of the "rtcp-fb" attribute.
7. Security Considerations 7. Security Considerations
The security considerations documented in [RFC4585] are also The security considerations documented in [RFC4585] are also
applicable for the TPLR messages defined in this document. applicable for the TPLR messages defined in this document.
More specifically, spoofed or maliciously created TPLR feedback More specifically, spoofed or maliciously created TPLR feedback
messages cause missing RTP packets to not be repaired in a timely messages cause missing RTP packets to not be repaired in a timely
fashion and add risk of (undesired) feedback suppression at RTCP fashion and add risk of (undesired) feedback suppression at RTCP
receivers that accept such TPLR messages. Any packet loss detected receivers that accept such TPLR messages. Any packet loss detected
by a receiver and where this RTP receiver also receives a TPLR by a receiver that also receives a TPLR message for the same missing
message for the same missing packet(s), will negatively impact the packet(s) will negatively impact the application that relies on the
application that relies on the (timely) RTP retransmission (timely) RTP retransmission capabilities.
capabilities.
A solution to prevent such attack with maliciously sent TPLR A solution to prevent such attack with maliciously sent TPLR messages
messages, is to apply an authentication and integrity protection is to apply an authentication and integrity protection framework for
framework for the feedback messages. This can be accomplished using the feedback messages. This can be accomplished using the RTP
the RTP profile that combines Secure RTP [RFC3711] and AVPF into profile that combines Secure RTP [RFC3711] and AVPF into SAVPF
SAVPF [RFC5124]. [RFC5124].
Note that intermediaries that are not visible at the RTP layer that Note that intermediaries that are not visible at the RTP layer that
wish to send the Third-Party Loss Reports on behalf of the media wish to send the Third-Party Loss Reports on behalf of the media
source can only do so if they spoof the SSRC of the media source. source can only do so if they spoof the SSRC of the media source.
This is difficult in case SRTP is in use. If the intermediary is This is difficult if SRTP is in use. If the intermediary is visible
visible at the RTP layer, this is not an issue, provided the at the RTP layer, this is not an issue, provided the intermediary is
intermediary is part of the security context for the session. part of the security context for the session.
8. IANA Consideration 8. IANA Considerations
This document instructs IANA to add two values to the '"ack" and Per this document, IANA has added two values to the '"ack" and "nack"
"nack" Attribute Values' sub-registry [RFC4585] of the 'Session Attribute Values' sub-registry [RFC4585] of the 'Session Description
Description Protocol (SDP) Parameters' registry. Protocol (SDP) Parameters' registry.
The value registration for the attribute value "nack": The value registration for the attribute value "nack":
Value name: tllei Value name: tllei
Long name: Transport Layer Third-Party Loss Early Indication Long name: Transport-Layer Third-Party Loss Early Indication
Usable with: nack Usable with: nack
Reference: RFC 4585. Reference: RFC 6642
Value name: pslei Value name: pslei
Long name: Payload Specific Third-Party Loss Early Indication Long name: Payload-Specific Third-Party Loss Early Indication
Usable with: nack Usable with: nack
Reference: RFC 4585. Reference: RFC 6642
The following value have been registered as one FMT value in the "FMT The following value has been registered as one FMT value in the "FMT
Values for RTPFB Payload Types" registry located at the time of Values for RTPFB Payload Types" registry
publication at: http://www.iana.org/assignments/rtp-parameters (http://www.iana.org/assignments/rtp-parameters).
RTPFB range RTPFB range
Name Long Name Value Reference Name Long Name Value Reference
-------------- --------------------------------- ----- --------- -------------- --------------------------------- ----- ---------
TLLEI Transport Layer Third-Party TBA1 [RFCXXXX] TLLEI Transport-Layer Third-Party 7 [RFC6642]
Loss Early Indication Loss Early Indication
The following value have been registered as one FMT value in the "FMT The following value has been registered as one FMT value in the "FMT
Values for PSFB Payload Types" registry located at the time of Values for PSFB Payload Types" registry
publication at: http://www.iana.org/assignments/rtp-parameters (http://www.iana.org/assignments/rtp-parameters).
PSFB range PSFB range
Name Long Name Value Reference Name Long Name Value Reference
-------------- --------------------------------- ----- -------- -------------- --------------------------------- ----- ---------
PSLEI Payload Specific Third-Party TBA2 [RFCXXXX] PSLEI Payload-Specific Third-Party 8 [RFC6642]
Loss Early Indication Loss Early Indication
9. Acknowledgments 9. Acknowledgments
The authors would like to thank David R Oran, Magnus Westerlund, The authors would like to thank David R. Oran, Magnus Westerlund,
Colin Perkins, Ali C. Begen, Tom van Caenegem, Francis Dupont, Colin Perkins, Ali C. Begen, Tom Van Caenegem, Francis Dupont,
Ingemar Johansson, Bill Ver Steeg, Jonathan Lennox, WeeSan Lee for Ingemar Johansson, Bill Ver Steeg, Jonathan Lennox, and WeeSan Lee
their valuable comments and suggestions on this document. for their valuable comments and suggestions on this document.
10. References 10. References
10.1. Normative References 10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
"Extended RTP Profile for Real-time Transport Control "Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
July 2006. July 2006.
[RFC4588] Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R. [RFC4588] Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R.
Hakenberg, "RTP Retransmission Payload Format", RFC 4588, Hakenberg, "RTP Retransmission Payload Format", RFC 4588,
July 2006. July 2006.
skipping to change at page 13, line 38 skipping to change at page 12, line 41
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)", Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004. RFC 3711, March 2004.
[RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for [RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for
Real-time Transport Control Protocol (RTCP)-Based Feedback Real-time Transport Control Protocol (RTCP)-Based Feedback
(RTP/SAVPF)", RFC 5124, February 2008. (RTP/SAVPF)", RFC 5124, February 2008.
10.2. Informative References 10.2. Informative References
[RFC6285] Steeg, B., Begen, A., Caenegem, T., and Z. Vax, "Unicast- [RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax,
Based Rapid Acquisition of Multicast RTP Sessions", "Unicast-Based Rapid Acquisition of Multicast RTP
June 2011. Sessions", RFC 6285, June 2011.
[MONARCH] Wu, Q., Hunt, G., and P. Arden, "Monitoring Architectures [MONARCH] Wu, Q., Hunt, G., and P. Arden, "Monitoring Architectures
for RTP", June 2011. for RTP", Work in Progress, May 2012.
[RETRANSMISSION-FOR-SSM] [RETRANS-FOR-SSM]
Caenegem, T., Steeg, B., and A. Begen, "Retransmission for Van Caenegem, T., Ver Steeg, B., and A. Begen,
Source-Specific Multicast (SSM) Sessions", May 2011. "Retransmission for Source-Specific Multicast (SSM)
Sessions", Work in Progress, May 2011.
[RFC5117] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117, [RFC5117] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117,
January 2008. January 2008.
[RFC4587] Even, R., "RTP Payload Format for H.261 Video Streams", [RFC4587] Even, R., "RTP Payload Format for H.261 Video Streams",
RFC 4587, August 2006. RFC 4587, August 2006.
[RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
Protocol (RTCP) Extensions for Single-Source Multicast Protocol (RTCP) Extensions for Single-Source Multicast
Sessions with Unicast Feedback", RFC 5760, February 2010. Sessions with Unicast Feedback", RFC 5760, February 2010.
Appendix A. Change Log
Note to the RFC-Editor: please remove this section prior to
publication as an RFC.
A.1. draft-ietf-avtcore-feedback-suppression-rtp-17
The following are the major changes compared to previous version:
o Editorial changes based on Gen-ART review.
o removes the discussion of improper dithering that is less of
motivation of the current version.
o change of the normative language from SHOULD NOT to MUST NOT in
the protocol overview section.
o Move Example use case section right after Introduction section.
A.2. draft-ietf-avtcore-feedback-suppression-rtp-16
The following are the major changes compared to previous version:
o Some Editorial changes.
A.3. draft-ietf-avtcore-feedback-suppression-rtp-15
The following are the major changes compared to previous version:
o Some Editorial changes.
A.4. draft-ietf-avtcore-feedback-suppression-rtp-14
The following are the major changes compared to previous version:
o Two References moving to normative references.
o Revise IANA section to clarify whether to create new registry or
add new value to the existing registry.
o Revise Security section to clarify ill effect of accepting
unauthenticated messages.
o Add a glossary to fix acronym issue.
o Other Editorial changes.
A.5. draft-ietf-avtcore-feedback-suppression-rtp-13
The following are the major changes compared to previous version:
o Additional Editorial changes.
A.6. draft-ietf-avtcore-feedback-suppression-rtp-12
The following are the major changes compared to previous version:
o Additional Editorial changes.
A.7. draft-ietf-avtcore-feedback-suppression-rtp-11
The following are the major changes compared to previous version:
o Additional Editorial changes.
A.8. draft-ietf-avtcore-feedback-suppression-rtp-10
The following are the major changes compared to previous version:
o Fix the definition of Synchronization source for TPLR in section
4.2.
o Associate SDP parameters tllei and pslei with "nack".
o Remove the packet loss recovery from TPLR loss handling part.
o Other typo fixed.
A.9. draft-ietf-avtcore-feedback-suppression-rtp-09
The following are the major changes compared to previous version:
o Clarify to suppression interval with regard to how long to receive
the
retransmitted packet. Treating TPLR in the same way as receiving
NACK.
o Replace timer based approach with timeless based approach.
A.10. draft-ietf-avtcore-feedback-suppression-rtp-08
The following are the major changes compared to previous version:
o Clarify which RTT is used and how timer is refreshed in the
section 3.
o Editorial changes to the Introduction, Protocol Overview, SDP
Signaling, Message Format, Use case, Security Consideration and
IANA sections.
o Remove Seq Nr field in the figure 2 for payload specific feedback.
o References reorganizing.
A.11. draft-ietf-avtcore-feedback-suppression-rtp-07
The following are the major changes compared to previous version:
o Restructuring the protocol overview section to clarify the round
trip
time calculation and receiver behavior to the additional TPLR.
o Restructuring the SSM use case section to focus on the use of
TPLR.
o Editorial changes to the abstract, introduction, message format,
use cases and IANA sections.
o References update
A.12. draft-ietf-avtcore-feedback-suppression-rtp-06
The following are the major changes compared to previous version:
o A few Editorial changes to the whole document.
A.13. draft-ietf-avtcore-feedback-suppression-rtp-05
The following are the major changes compared to previous version:
o Remove 3rd and 4th paragraphs of section 6.1 and replaced them
with 2nd and 3rd paragraphs of section 3.
o Remove section 6.1.1.1.
o Revise the last paragraph of section 1 to clarify the rationale of
using new message.
o Update RTP transport translator case in section 6.3 to correct the
use of the third-party loss report.
o Update MCU case in section 6.4 to correct the use of the third
party loss report.
o Revise SSM use case to address multiple DS issue.
o References Update.
o Move one rationale on preventing sending unicast NACK in
introduction section to SSM case section.
o Other Editorial changes to section 6.1, 6.1.1, 6.2.
A.14. draft-ietf-avtcore-feedback-suppression-rtp-04
The following are the major changes compared to previous version:
o Reference Update.
o Clarify the use of the third-party loss report in section 3 and
section 6.1.1.
A.15. draft-ietf-avtcore-feedback-suppression-rtp-03
The following are the major changes compared to previous version:
o In Appendix A, fix typo: Appendix A. Appendix A. -> Appendix A.
o Update abstract to clarify when third-party loss reports should be
sent instead of NACKs.
o Update section 3 Paragraph 2 to differentiate when a third-party
loss report should be used compared to a NACK.
o Update section 3 Paragraph 3 to explain when media source to send
a third-party loss.
o Move specific rules for section 6.1.1 and section 6.1.2 to section
6.1 as generic rules and delete section 6.1.1.
A.16. draft-ietf-avtcore-feedback-suppression-rtp-02
The following are the major changes compared to previous version:
o In Section 4.1, fix typo: change Section 4.3.1.1 of section
[RFC5104] to section 6.2.1 of [RFC4585].
o In Section 3: Clarify how to deal with downstream loss using
Third-party loss report and upstream loss using NACK.
o Update title and abstract to focus on third-party loss report.
o In Section 6.1: Update this section to explain how third party
loss report is used to deal with downstream loss.
o In section 6.1.2: Update this section to explain how third party
loss report is used to deal with downstream loss.
o In section 6.2: Rephrase the text to discuss how BRS deal with the
third-party loss report.
A.17. draft-ietf-avtcore-feedback-suppression-rtp-01
The following are the major changes compared to previous version:
o Remove the merge report from SSM use case and additional text to
address report merging issue.
o Revise section 3 and section 6 to address FEC packet dealing issue
and Leave how to repair packet loss beyond the scope.
o Modify the SSM use case and RAMS use case to focus on uses.
o Other Editorial changes.
Authors' Addresses Authors' Addresses
Qin Wu Qin Wu (editor)
Huawei Huawei
101 Software Avenue, Yuhua District 101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012 Nanjing, Jiangsu 210012
China China
Email: sunseawq@huawei.com EMail: sunseawq@huawei.com
Frank Xia Frank Xia
Huawei Huawei
1700 Alma Dr. Suite 500 1700 Alma Dr., Suite 500
Plano, TX 75075 Plano, TX 75075
USA USA
Phone: +1 972-509-5599 Phone: +1 972-509-5599
Email: xiayangsong@huawei.com EMail: xiayangsong@huawei.com
Roni Even Roni Even
Huawei Huawei
14 David Hamelech 14 David Hamelech
Tel Aviv 64953 Tel Aviv 64953
Israel Israel
Email: even.roni@huawei.com EMail: even.roni@huawei.com
 End of changes. 102 change blocks. 
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