draft-ietf-avtcore-feedback-supression-rtp-16.txt   draft-ietf-avtcore-feedback-supression-rtp-17.txt 
Network Working Group Q. Wu Network Working Group Q. Wu
Internet-Draft F. Xia Internet-Draft F. Xia
Intended status: Standards Track R. Even Intended status: Standards Track R. Even
Expires: October 1, 2012 Huawei Expires: October 15, 2012 Huawei
March 30, 2012 April 13, 2012
RTCP Extension for Third-party Loss Report RTCP Extension for Third-party Loss Report
draft-ietf-avtcore-feedback-supression-rtp-16 draft-ietf-avtcore-feedback-supression-rtp-17
Abstract Abstract
In a large RTP session using the RTCP feedback mechanism defined in In a large RTP session using the RTP Control Protocol (RTCP) feedback
RFC 4585, a feedback target may experience transient overload if some mechanism defined in RFC 4585, a feedback target may experience
event causes a large number of receivers to send feedback at once. transient overload if some event causes a large number of receivers
This overload is usually avoided by ensuring that feedback reports to send feedback at once. This overload is usually avoided by
are forwarded to all receivers, allowing them to avoid sending ensuring that feedback reports are forwarded to all receivers,
duplicate feedback reports. However, there are cases where it is not allowing them to avoid sending duplicate feedback reports. However,
recommended to forward feedback reports, and this may allow feedback there are cases where it is not recommended to forward feedback
implosion. This memo discusses these cases and defines a new RTCP reports, and this may allow feedback implosion. This memo discusses
third-party loss report that can be used to inform receivers that the these cases and defines a new RTCP third-party loss report that can
feedback target is aware of some loss event, allowing them to be used to inform receivers that the feedback target is aware of some
suppress feedback. Associated SDP signalling is also defined. loss event, allowing them to suppress feedback. Associated SDP
signaling is also defined.
Status of this Memo Status of this Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4
2.1. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 5 3. Example Use Cases . . . . . . . . . . . . . . . . . . . . . . 5
4. Format of RTCP Feedback Messages . . . . . . . . . . . . . . . 6 3.1. Source Specific Multicast (SSM) use case . . . . . . . . . 5
4.1. Transport Layer Feedback: Third-Party Loss Report 3.2. Unicast based Rapid Acquisition of Multicast Stream
(TPLR) . . . . . . . . . . . . . . . . . . . . . . . . . . 6 (RAMS) use case . . . . . . . . . . . . . . . . . . . . . 6
4.2. Payload Specific Feedback: Third-Party Loss Report 3.3. RTP Transport Translator use case . . . . . . . . . . . . 6
(TPLR) . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.4. Multipoint Control Unit (MCU) use case . . . . . . . . . . 6
5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 8 3.5. Mixer use case . . . . . . . . . . . . . . . . . . . . . . 6
6. Example Use Cases . . . . . . . . . . . . . . . . . . . . . . 9 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Source Specific Multicast (SSM) use case . . . . . . . . . 9 5. Format of RTCP Feedback Messages . . . . . . . . . . . . . . . 8
6.2. Unicast based Rapid Acquisition of Multicast Stream 5.1. Transport Layer Feedback: Third-Party Loss Report
(RAMS) use case . . . . . . . . . . . . . . . . . . . . . 10 (TPLR) . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.3. RTP Transport Translator use case . . . . . . . . . . . . 10 5.2. Payload Specific Feedback: Third-Party Loss Report
6.4. Multipoint Control Unit (MCU) use case . . . . . . . . . . 10 (TPLR) . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.5. Mixer use case . . . . . . . . . . . . . . . . . . . . . . 11 6. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 11 8. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 12 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1. Normative References . . . . . . . . . . . . . . . . . . . 13 10.1. Normative References . . . . . . . . . . . . . . . . . . . 13
10.2. Informative References . . . . . . . . . . . . . . . . . . 13 10.2. Informative References . . . . . . . . . . . . . . . . . . 13
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 14 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 14
A.1. draft-ietf-avtcore-feedback-suppression-rtp-01 . . . . . . 14 A.1. draft-ietf-avtcore-feedback-suppression-rtp-17 . . . . . . 14
A.2. draft-ietf-avtcore-feedback-suppression-rtp-02 . . . . . . 14 A.2. draft-ietf-avtcore-feedback-suppression-rtp-16 . . . . . . 14
A.3. draft-ietf-avtcore-feedback-suppression-rtp-03 . . . . . . 15 A.3. draft-ietf-avtcore-feedback-suppression-rtp-15 . . . . . . 14
A.4. draft-ietf-avtcore-feedback-suppression-rtp-04 . . . . . . 15 A.4. draft-ietf-avtcore-feedback-suppression-rtp-14 . . . . . . 14
A.5. draft-ietf-avtcore-feedback-suppression-rtp-05 . . . . . . 15 A.5. draft-ietf-avtcore-feedback-suppression-rtp-13 . . . . . . 15
A.6. draft-ietf-avtcore-feedback-suppression-rtp-06 . . . . . . 16 A.6. draft-ietf-avtcore-feedback-suppression-rtp-12 . . . . . . 15
A.7. draft-ietf-avtcore-feedback-suppression-rtp-07 . . . . . . 16 A.7. draft-ietf-avtcore-feedback-suppression-rtp-11 . . . . . . 15
A.8. draft-ietf-avtcore-feedback-suppression-rtp-08 . . . . . . 16 A.8. draft-ietf-avtcore-feedback-suppression-rtp-10 . . . . . . 15
A.9. draft-ietf-avtcore-feedback-suppression-rtp-09 . . . . . . 16 A.9. draft-ietf-avtcore-feedback-suppression-rtp-09 . . . . . . 15
A.10. draft-ietf-avtcore-feedback-suppression-rtp-10 . . . . . . 17 A.10. draft-ietf-avtcore-feedback-suppression-rtp-08 . . . . . . 16
A.11. draft-ietf-avtcore-feedback-suppression-rtp-11 . . . . . . 17 A.11. draft-ietf-avtcore-feedback-suppression-rtp-07 . . . . . . 16
A.12. draft-ietf-avtcore-feedback-suppression-rtp-12 . . . . . . 17 A.12. draft-ietf-avtcore-feedback-suppression-rtp-06 . . . . . . 16
A.13. draft-ietf-avtcore-feedback-suppression-rtp-13 . . . . . . 17 A.13. draft-ietf-avtcore-feedback-suppression-rtp-05 . . . . . . 16
A.14. draft-ietf-avtcore-feedback-suppression-rtp-14 . . . . . . 17 A.14. draft-ietf-avtcore-feedback-suppression-rtp-04 . . . . . . 17
A.15. draft-ietf-avtcore-feedback-suppression-rtp-15 . . . . . . 18 A.15. draft-ietf-avtcore-feedback-suppression-rtp-03 . . . . . . 17
A.16. draft-ietf-avtcore-feedback-suppression-rtp-16 . . . . . . 18 A.16. draft-ietf-avtcore-feedback-suppression-rtp-02 . . . . . . 18
A.17. draft-ietf-avtcore-feedback-suppression-rtp-01 . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
RTCP feedback messages [RFC4585] allow the receivers in an RTP The RTP Control Protocol (RTCP) feedback messages [RFC4585] allow the
session to report events and ask for action from the media source (or receivers in an RTP session to report events and ask for action from
a delegated feedback target when using unicast RTCP feedback with SSM the media source (or a delegated feedback target when using unicast
[RFC5760]). There are cases where multiple receivers may initiate RTCP feedback with SSM [RFC5760]). There are cases where multiple
the same, or an equivalent message towards the same media source or receivers may initiate the same, or an equivalent message towards the
the same feedback target. When the receiver count is large, this same media source or the same feedback target. When the receiver
behavior may cause transient overload of the media source, the count is large, this behavior may cause transient overload of the
network or both. This is known as a "feedback storm" or a "NACK media source, the network or both. This is known as a "feedback
storm". One common cause of such a feedback storm is receivers storm" or a "NACK storm".
utilizing RTP retransmission [RFC4588] as a packet loss recovery
technique, sending feedback using RTCP NACK messages [RFC4585]
without proper dithering of the retransmission requests (e.g., not
implementing the RFC 4585 dithering rules or sending NACKs to a
feedback target that doesn't redistribute them to other receivers).
Another use case involves video Fast Update requests. A storm of One scenario that can cause such feedback storms involves video Fast
these feedback messages can occur in conversational multimedia Update requests. A storm of these feedback messages can occur in
scenarios like multipoint video switching conference [RFC4587]. In conversational multimedia scenarios like multipoint video switching
this scenario, the receiver may lose synchronization with the video conference [RFC4587], where many receivers may simultaneously lose
stream when speaker is changed in the middle of session. Poorly synchronization with the video stream when the speaker is changed in
designed receivers that blindly issue fast update requests (i.e., the middle of a session. Receivers that issue fast update requests
Full Intra Request (FIR) described in RFC5104 [RFC5104]), can cause (i.e., Full Intra Request (FIR) described in RFC5104 [RFC5104]), can
an implosion of FIR requests from receivers to the same media source. cause an implosion of FIR requests from receivers to the same media
source since these requests must currently be made blind, without
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 to 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 the use of RTCP NACK
packet and further is more precise in the uses where the network is packet and further is more precise in the uses where the network is
active to suppress feedback. It tells receivers explicitly that active to suppress feedback. It tells receivers explicitly that
feedback for a particular packet or frame loss is not needed and can feedback for a particular packet or frame loss is not needed and can
provide an early indication before the receiver reacts to the loss provide an early indication before the receiver reacts to the loss
and invokes its packet loss repair machinery. Section 6 provides and invokes its packet loss repair machinery. Section 3 provides
some examples of when to send the Third-Party Loss Report message. some example use cases of when to send the Third-Party Loss Report
message.
2. Requirements Notation 2. 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 RFC2119 [RFC2119].
2.1. Glossary 2.1. Glossary
TPLR - Third-Party Loss Report TPLR - Third-Party Loss Report
TLLEI - Transport Layer Third-Party Loss Early Indication TLLEI - Transport Layer Third-Party Loss Early Indication
PSLEI - Payload Specific Third-Party Loss Early Indication PSLEI - Payload Specific Third-Party Loss Early Indication
FCI - Feedback Control Information [RFC4585] FCI - Feedback Control Information [RFC4585]
AVPF - The Audio-Visual Profile with RTCP-based feedback [RFC4585] AVPF - The Audio-Visual Profile with RTCP-based feedback [RFC4585]
SSRC - Synchronization Source SSRC - Synchronization Source
BRS - Burst/Retransmission Sources [RFC6285] BRS - Burst/Retransmission Sources [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] SSM - Source Specific Multicast [RFC5760]
skipping to change at page 5, line 20 skipping to change at page 5, line 17
FCI - Feedback Control Information [RFC4585] FCI - Feedback Control Information [RFC4585]
AVPF - The Audio-Visual Profile with RTCP-based feedback [RFC4585] AVPF - The Audio-Visual Profile with RTCP-based feedback [RFC4585]
SSRC - Synchronization Source SSRC - Synchronization Source
BRS - Burst/Retransmission Sources [RFC6285] BRS - Burst/Retransmission Sources [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] SSM - Source Specific Multicast [RFC5760]
RAMS - Unicast based Rapid Acquisition of Multicast Stream [RFC6285] RAMS - Unicast based Rapid Acquisition of Multicast Stream [RFC6285]
MCU - Multipoint Control Unit [RFC5117] MCU - Multipoint Control Unit [RFC5117]
3. Protocol Overview 3. Example Use Cases
The operation of feedback suppression is similar for all types of RTP
sessions and topologies [RFC5117], however the exact messages used
and the scenarios in which suppression is employed differ for various
use cases. The following sections outline some of the intended use
cases for using the Third-Party Loss Report for feedback suppression
and give an overview of the particular mechanisms.
3.1. Source Specific Multicast (SSM) use case
In SSM RTP sessions as described in "RTP Control Protocol (RTCP)
Extensions for Single-Source Multicast Sessions with Unicast
Feedback" [RFC5760], one or more Media Sources send RTP packets to a
Distribution Source. The Distribution Source relays the RTP packets
to the receivers using a source-specific multicast group.
As outlined in the RFC5760 [RFC5760], there are two Unicast Feedback
models that may be used for reporting, the Simple Feedback model and
the Distribution Source Feedback Summary Model. In the simple
Feedback Model, there's no need for distribution source to create the
RTCP TPLRs, instead, RTCP NACKs are reflected by the distribution
source to the other Receivers. However in the Distribution Source
Feedback Summary model, the distribution source will not redistribute
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
to the systems that were unable to receive the NACK, and won't
receive the NACK via other means. The RTCP TPLR can be generated at
the distribution source when downstream loss is reported (e.g.,
downstream loss report is received), which indicates to the receivers
that they should not transmit feedback messages for the same loss
event for a certain time. Therefore the distribution source in the
feedback summary model can be reasonably certain that it will help
the situation (i.e., unable receive the NACK) by sending this RTCP
TPLR message to all the relevant receivers impacted by the packet
loss.
3.2. Unicast based Rapid Acquisition of Multicast Stream (RAMS) use
case
The typical RAMS architecture [RFC6285] may have several Burst/
Retransmission Sources(BRS) behind the multicast source (MS) placed
at the same level. These BRSes will receive the primary multicast
RTP stream from the media source and cache most recent packets after
joining multicast session. If packet loss happens at the upstream of
all the BRSs or the downstream of BRSes. One of the BRSes or all the
BRSes may send an RTCP NACK or RTCP TPLR message to the DS, where the
SSRC in this RTCP NACK or RTCP TPLR message is the BRS that is
sending the message. The DS forwards/reflects this message down on
the primary SSM. The details on how DS deal with this message is
specified in [RETRANSMISSION-FOR-SSM].
3.3. RTP Transport Translator use case
A Transport Translator (Topo-Trn-Translator), as defined in RFC5117
[RFC5117] is typically forwarding the RTP and RTCP traffic between
RTP clients, for example converting from multicast to unicast for
domains that do not support multicast. The translator may suffer a
loss of important video packets. In this case, the translator may
forward RTCP TPLR message received from upstream in the same way as
forwarding other RTCP traffic. If the translator acting as the
monitor [MONARCH] is aware of packet loss, it may use the SSRC of
monitor as packet sender SSRC to create NACK message and send it to
the receivers that are not aware of packet loss.
3.4. Multipoint Control Unit (MCU) use case
When the speaker is changed in a voice-activated multipoint video
switching conference [RFC4587], an RTP mixer can be used to select
the available input streams and forward them to each participants.
If the MCU is doing a blind switch without waiting for a
synchronization point on the new stream it can send a FIR to the new
video source. In this case the MCU should send a FIR suppression
message to the new receivers: e.g., when the RTP Mixer starts to
receive FIR from some participants it can suppress the remaining
session participants from sending FIR by sending out an RTCP TPLR
message.
3.5. Mixer use case
A Mixer, in accordance with RFC5117 [RFC5117], aggregates multiple
RTP streams from other session participants and generates a new RTP
stream sent to the session participants. In some cases, the video
frames delivery may get damaged, for example due to packet loss or
delayed delivery, between media source and the mixer. In such case,
the mixer need to check if the packet loss will result in PLI or FIR
transmissions from most of the group by analyzing the received video.
If so the mixer may initiate FIR or PLI towards the media source on
behalf of all the session participants and send out an RTCP TPLR
message to these session participants that may or are expected to
send a PLI or FIR. Alternatively, when the mixer starts to receive
FIR or PLI from some participants and like to suppress the remaining
session participants from sending FIR or PLI by forwarding the FIR/
PLI from one session participant to others.
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 a RTCP Third-Party Loss Report (TPLR) AVPF [RFC4585] 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 asks the receiver
not to send feedback to it regarding these packets. Intermediaries not to send feedback to it regarding these packets. Intermediaries
are variously referred to as Distribution source, Burst/ are variously referred to as Distribution source, Burst/
Retransmission Sources (BRS), MCUs, RTP translator, or RTP mixers, Retransmission Sources (BRS), MCUs, RTP translator, or RTP mixers,
depending on the precise use case described Section 6. depending on the precise use case described Section 3.
RTCP TPLR follows the similar format of message type as RTCP NACK or RTCP TPLR follows the similar format of message type as RTCP NACK or
Full Intra Request Command. However, the RTCP TPLR is defined as an Full Intra Request Command. However, the 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 RFC4585 [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 a RTCP TPLR SHOULD 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 direction to the receiver(s), additionally,
they may generate their own RTCP TPLR that reports a set of the they may generate their own RTCP TPLR that reports a set of the
losses they see, which are different from ones reported in the RTCP losses they see, which are different from ones reported in the RTCP
TPLR they received. The RTCP TPLR does not have the retransmission TPLR they received. The RTCP TPLR does not have the retransmission
request [RFC4588] semantics. request [RFC4588] semantics.
When a receiver gets a 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 RFC4585 [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 NACK. in the message, which is dealt with in the same way as receiving
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 receiver, the
receiver SHOULD deal with the additional TPLR in the same way as 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 a RTCP scheduling algorithm of RFC4585 [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 therefore still send feedback according to the AVPF scheduling might therefore still send feedback according to the AVPF scheduling
algorithm of RFC4585 [RFC4585]. The media source or intermediate algorithm of RFC4585 [RFC4585]. The media source or intermediate
nodes cannot be certain that the use of a 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 it receives.
4. 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 for an application-specific subset of the RTP packets in a or for an application-specific subset of the RTP packets in a
session. session.
The following two sections each define a 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 RFC4585
[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.
4.1. 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 value PT=RTPFB
and FMT=TBA1. and FMT=TBA1.
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 RFC4585 [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 denotes the media sender of the flow for which the indicated losses
are being suppressed. are being suppressed.
The Feedback Control Information (FCI) field MUST contain one or more The Feedback Control Information (FCI) field MUST contain one or more
entries of transport layer third-party loss Early Indication (TLLEI). entries of Transport Layer Third-Party loss Early Indication (TLLEI).
Each entry applies to the same media source identified by the SSRC Each entry applies to the same media source identified by the SSRC
contained in the SSRC of media source field of Feedback header. The contained in the SSRC of media source field of Feedback header. The
length field in the TLLEI feedback message MUST be set to 2+1*N, length field in the TLLEI feedback message MUST be set to N+2, where
where N is the number of FCI entries. 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 the similar format of message Types
defined in the section 6.2.1 of RFC4585 [RFC4585]. The format is defined in the section 6.2.1 of RFC4585 [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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 7, line 34 skipping to change at page 9, line 34
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 the section 6.2.1
of [RFC4585]. of [RFC4585].
4.2. 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 value PT=PSFB and
FMT=TBA2, which is used to suppress FIR [RFC5104] and PLI [RFC4585]. FMT=TBA2, which is 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 RFC4585 [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 applies 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 2+1*N, 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.
5. 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 the Section 4 of RFC4585 [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
RFC4585 [RFC4585]. In this section, we extend the rtcp-fb attribute RFC4585 [RFC4585]. In this section, we extend the rtcp-fb attribute
to include the commands and indications that are described for third- to include the commands and indications that are described for third-
party loss report in the present document. party loss report 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 RFC4585 [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 6.2.1of RFC4585
[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 "nack" is defined here (please
refer to section 4.2 of RFC4585 [RFC4585] for complete ABNF syntax). 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 4.2 of [RFC4585] >
Refer to Section 4.2 of RFC4585 [RFC4585] for a detailed description Refer to Section 4.2 of RFC4585 [RFC4585] for a detailed description
and the full syntax of the "rtcp-fb" attribute. and the full syntax of the "rtcp-fb" attribute.
6. Example Use Cases
The operation of feedback suppression is similar for all types of RTP
sessions and topologies [RFC5117], however the exact messages used
and the scenarios in which suppression is employed differ for various
use cases. The following sections outline some of the intended use
cases for using the Third-Party Loss Report for feedback suppression
and give an overview of the particular mechanisms.
6.1. Source Specific Multicast (SSM) use case
In SSM RTP sessions as described in "RTP Control Protocol (RTCP)
Extensions for Single-Source Multicast Sessions with Unicast
Feedback" [RFC5760], one or more Media Sources send RTP packets to a
Distribution Source. The Distribution Source relays the RTP packets
to the receivers using a source- specific multicast group.
As outlined in the RFC5760 [RFC5760], there are two Unicast Feedback
models that may be used for reporting, the Simple Feedback model and
the Distribution Source Feedback Summary Model. In the simple
Feedback Model, there's no need for distribution source to create the
RTCP TPLRs, instead, RTCP NACKs are reflected by the distribution
source to the other Receivers. However in the Distribution Source
Feedback Summary model, the distribution source will not redistribute
the NACK for some reason(e.g., to prevent revealing the identity or
existence of a system sending NACK)and may send a RTCP TPLR message
to the systems that were unable to receive the NACK, and won't
receive the NACK via other means. The RTCP TPLR can be generated at
the distribution source when downstream loss is reported (e.g.,
downstream loss report is received), which indicates to the receivers
that they should not transmit feedback messages for the same loss
event for a certain time. Therefore the distribution source in the
feedback summary model can be reasonably certain that it will help
the situation (i.e., unable receive the NACK) by sending this RTCP
TPLR message to all the relevant receivers impacted by the packet
loss.
6.2. Unicast based Rapid Acquisition of Multicast Stream (RAMS) use
case
The typical RAMS architecture [RFC6285] may have several Burst/
Retransmission Sources(BRS) behind the multicast source (MS) placed
at the same level. These BRSes will receive the primary multicast
RTP stream from the media source and cache most recent packets after
joining multicast session. If packet loss happens at the upstream of
all the BRSs or the downstream of BRSes. One of the BRSes or all the
BRSes may send a RTCP NACK or RTCP TPLR message to the DS, where the
SSRC in this RTCP NACK or RTCP TPLR message is the BRS that is
sending the message. The DS forwards/reflects this message down on
the primary SSM. The details on how DS deal with this message is
specified in [RETRANSMISSION-FOR-SSM].
6.3. RTP Transport Translator use case
A Transport Translator (Topo-Trn-Translator), as defined in RFC5117
[RFC5117] is typically forwarding the RTP and RTCP traffic between
RTP clients, for example converting from multicast to unicast for
domains that do not support multicast. The translator may suffer a
loss of important video packets. In this case, the translator may
forward RTCP TPLR message received from upstream in the same way as
forwarding other RTCP traffic. If the translator acting as the
monitor [MONARCH] is aware of packet loss, it may use the SSRC of
monitor as packet sender SSRC to create NACK message and send it to
the receivers that are not aware of packet loss.
6.4. Multipoint Control Unit (MCU) use case
When the speaker is changed in a voice-activated multipoint video
switching conference [RFC4587], an RTP mixer can be used to select
the available input streams and forward them to each participants.
If the MCU is doing a blind switch without waiting for a
synchronization point on the new stream it can send a FIR to the new
video source. In this case the MCU should send a FIR suppression
message to the new receivers. e.g., when the RTP Mixer starts to
receive FIR from some participants it can suppress the remaining
session participants from sending FIR by sending out a RTCP TPLR
message.
6.5. Mixer use case
A Mixer, in accordance with RFC5117 [RFC5117], aggregates multiple
RTP streams from other session participants and generates a new RTP
stream sent to the session participants. In some cases, the video
frames may get badly screwed up between media source and the mixer.
In such case, the mixer need to check if the packet loss will result
in PLI or FIR transmissions from most of the group by analyzing the
received video. If so the mixer may initiate FIR or PLI towards the
media source on behalf of all the session participants and send out a
RTCP TPLR message to these session participants that may or are
expected to send a PLI or FIR. Alternatively, when the mixer starts
to receive FIR or PLI from some participants and like to suppress the
remaining session participants from sending FIR or PLI by forwarding
the FIR/PLI from one session participant to others.
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 supression 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 and where this RTP receiver also receives a TPLR
message for the same missing packet(s), will negatively impact the message for the same missing packet(s), will negatively impact the
application that relies on the (timely) RTP retransmission application that relies on the (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, is to apply an authentication and integrity protection messages, is to apply an authentication and integrity protection
framework for the feedback messages. This can be accomplished using framework for the feedback messages. This can be accomplished using
the RTP profile that combines Secure RTP [RFC3711] and AVPF into the RTP profile that combines Secure RTP [RFC3711] and AVPF into
skipping to change at page 12, line 39 skipping to change at page 12, line 38
The following value have been registered as one FMT value in the "FMT The following value have 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 located at the time of
publication at: http://www.iana.org/assignments/rtp-parameters publication at: 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 TBA2 [RFCXXXX]
Loss Early Indication Loss Early Indication
9. Acknowledgement 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, Ingemar Johansson S, Colin Perkins, Ali C. Begen, Tom van Caenegem, Francis Dupont,
Bill Ver Steeg, Jonathan Lennox, WeeSan Lee for their valuable Ingemar Johansson, Bill Ver Steeg, Jonathan Lennox, WeeSan Lee for
comments and suggestions on this document. 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", 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,
skipping to change at page 14, line 17 skipping to change at page 14, line 17
[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 Appendix A. Change Log
Note to the RFC-Editor: please remove this section prior to Note to the RFC-Editor: please remove this section prior to
publication as an RFC. publication as an RFC.
A.1. draft-ietf-avtcore-feedback-suppression-rtp-01 A.1. draft-ietf-avtcore-feedback-suppression-rtp-17
The following are the major changes compared to previous version: The following are the major changes compared to previous version:
o Remove the merge report from SSM use case and additional text to o Editorial changes based on Gen-ART review.
address report merging issue.
o Revise section 3 and section 6 to address FEC packet dealing issue o removes the discussion of improper dithering that is less of
and Leave how to repair packet loss beyond the scope. motivation of the current version.
o Modify the SSM use case and RAMS use case to focus on uses. o change of the normative language from SHOULD NOT to MUST NOT in
the protocol overview section.
o Other Editorial changes. o Move Example use case section right after Introduction section.
A.2. draft-ietf-avtcore-feedback-suppression-rtp-02 A.2. draft-ietf-avtcore-feedback-suppression-rtp-16
The following are the major changes compared to previous version: 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 o Some Editorial changes.
[RFC5104] to section 6.2.1 of [RFC4585].
o In Section 3: Clarify how to deal with downstream loss using A.3. draft-ietf-avtcore-feedback-suppression-rtp-15
Third-party loss report and upstream loss using NACK.
o Update title and abstract to focus on third-party loss report. The following are the major changes compared to previous version:
o In Section 6.1: Update this section to explain how third party o Some Editorial changes.
loss report is used to deal with downstream loss.
o In section 6.1.2: Update this section to explain how third party A.4. draft-ietf-avtcore-feedback-suppression-rtp-14
loss report is used to deal with downstream loss.
o In section 6.2: Rephrase the text to discuss how BRS deal with the The following are the major changes compared to previous version:
third-party loss report.
A.3. draft-ietf-avtcore-feedback-suppression-rtp-03 o Two References moving to normative references.
The following are the major changes compared to previous version: o Revise IANA section to clarify whether to create new registry or
add new value to the existing registry.
o In Appendix A, fix typo: Appendix A. Appendix A. -> Appendix A. o Revise Security section to clarify ill effect of accepting
unauthenticated messages.
o Update abstract to clarify when third-party loss reports should be o Add a glossary to fix acronym issue.
sent instead of NACKs.
o Update section 3 Paragraph 2 to differentiate when a third-party o Other Editorial changes.
loss report should be used compared to a NACK.
o Update section 3 Paragraph 3 to explain when media source to send A.5. draft-ietf-avtcore-feedback-suppression-rtp-13
a third-party loss.
o Move specific rules for section 6.1.1 and section 6.1.2 to section The following are the major changes compared to previous version:
6.1 as generic rules and delete section 6.1.1.
A.4. draft-ietf-avtcore-feedback-suppression-rtp-04 o Additional Editorial changes.
A.6. draft-ietf-avtcore-feedback-suppression-rtp-12
The following are the major changes compared to previous version: 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 o Additional Editorial changes.
section 6.1.1.
A.5. draft-ietf-avtcore-feedback-suppression-rtp-05 A.7. draft-ietf-avtcore-feedback-suppression-rtp-11
The following are the major changes compared to previous version: 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 Additional Editorial changes.
o Revise the last paragraph of section 1 to clarify the rationale of A.8. draft-ietf-avtcore-feedback-suppression-rtp-10
using new message.
o Update RTP transport translator case in section 6.3 to correct the The following are the major changes compared to previous version:
use of the third-party loss report.
o Update MCU case in section 6.4 to correct the use of the third o Fix the definition of Synchronization source for TPLR in section
party loss report. 4.2.
o Revise SSM use case to address multiple DS issue. o Associate SDP parameters tllei and pslei with "nack".
o References Update. o Remove the packet loss recovery from TPLR loss handling part.
o Move one rationale on preventing sending unicast NACK in o Other typo fixed.
introduction section to SSM case section.
o Other Editorial changes to section 6.1, 6.1.1, 6.2. A.9. draft-ietf-avtcore-feedback-suppression-rtp-09
A.6. draft-ietf-avtcore-feedback-suppression-rtp-06 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: The following are the major changes compared to previous version:
o A few Editorial changes to the whole document. o Clarify which RTT is used and how timer is refreshed in the
section 3.
A.7. draft-ietf-avtcore-feedback-suppression-rtp-07 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: The following are the major changes compared to previous version:
o Restructuring the protocol overview section to clarify the round o Restructuring the protocol overview section to clarify the round
trip trip
time calculation and receiver behavior to the additional TPLR. time calculation and receiver behavior to the additional TPLR.
o Restructuring the SSM use case section to focus on the use of o Restructuring the SSM use case section to focus on the use of
TPLR. TPLR.
o Editorial changes to the abstract, introduction, message format, o Editorial changes to the abstract, introduction, message format,
use cases and IANA sections. use cases and IANA sections.
o References update o References update
A.8. draft-ietf-avtcore-feedback-suppression-rtp-08 A.12. draft-ietf-avtcore-feedback-suppression-rtp-06
The following are the major changes compared to previous version: The following are the major changes compared to previous version:
o Clarify which RTT is used and how timer is refreshed in the o A few Editorial changes to the whole document.
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.9. draft-ietf-avtcore-feedback-suppression-rtp-09 A.13. draft-ietf-avtcore-feedback-suppression-rtp-05
The following are the major changes compared to previous version: 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 Clarify to suppression interval with regard to how long to receive o Remove section 6.1.1.1.
the
retransmitted packet. Treating TPLR in the same way as receiving
NACK.
o Replace timer based approach with timeless based approach. o Revise the last paragraph of section 1 to clarify the rationale of
using new message.
A.10. draft-ietf-avtcore-feedback-suppression-rtp-10 o Update RTP transport translator case in section 6.3 to correct the
use of the third-party loss report.
The following are the major changes compared to previous version: o Update MCU case in section 6.4 to correct the use of the third
party loss report.
o Fix the definition of Synchronization source for TPLR in section o Revise SSM use case to address multiple DS issue.
4.2.
o Associate SDP parameters tllei and pslei with "nack". o References Update.
o Remove the packet loss recovery from TPLR loss handling part. o Move one rationale on preventing sending unicast NACK in
introduction section to SSM case section.
o Other typo fixed. o Other Editorial changes to section 6.1, 6.1.1, 6.2.
A.11. draft-ietf-avtcore-feedback-suppression-rtp-11 A.14. draft-ietf-avtcore-feedback-suppression-rtp-04
The following are the major changes compared to previous version: The following are the major changes compared to previous version:
o Reference Update.
o Additional Editorial changes. o Clarify the use of the third-party loss report in section 3 and
section 6.1.1.
A.12. draft-ietf-avtcore-feedback-suppression-rtp-12 A.15. draft-ietf-avtcore-feedback-suppression-rtp-03
The following are the major changes compared to previous version: The following are the major changes compared to previous version:
o Additional Editorial changes. o In Appendix A, fix typo: Appendix A. Appendix A. -> Appendix A.
A.13. draft-ietf-avtcore-feedback-suppression-rtp-13 o Update abstract to clarify when third-party loss reports should be
sent instead of NACKs.
The following are the major changes compared to previous version: o Update section 3 Paragraph 2 to differentiate when a third-party
loss report should be used compared to a NACK.
o Additional Editorial changes. o Update section 3 Paragraph 3 to explain when media source to send
a third-party loss.
A.14. draft-ietf-avtcore-feedback-suppression-rtp-14 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: The following are the major changes compared to previous version:
o Two References moving to normative refereces. o In Section 4.1, fix typo: change Section 4.3.1.1 of section
[RFC5104] to section 6.2.1 of [RFC4585].
o Revise IANA section to clarify whether to create new registry or o In Section 3: Clarify how to deal with downstream loss using
add new value to the existing registry. Third-party loss report and upstream loss using NACK.
o Revise Security section to clarify ill effect of accepting o Update title and abstract to focus on third-party loss report.
unauthenticated messages.
o Add a glossary to fix acronym issue. o In Section 6.1: Update this section to explain how third party
loss report is used to deal with downstream loss.
o Other Editorial changes. o In section 6.1.2: Update this section to explain how third party
loss report is used to deal with downstream loss.
A.15. draft-ietf-avtcore-feedback-suppression-rtp-15 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: The following are the major changes compared to previous version:
o Some Editorial changes. o Remove the merge report from SSM use case and additional text to
address report merging issue.
A.16. draft-ietf-avtcore-feedback-suppression-rtp-16 o Revise section 3 and section 6 to address FEC packet dealing issue
and Leave how to repair packet loss beyond the scope.
The following are the major changes compared to previous version: o Modify the SSM use case and RAMS use case to focus on uses.
o Some Editorial changes. o Other Editorial changes.
Authors' Addresses Authors' Addresses
Qin Wu Qin Wu
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
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