Network Working Group Q. Wu
Internet-Draft F. Xia
Intended status: Standards Track R. Even
Expires: January 12, 2012 Huawei
July 11, 2011
RTCP Extension for Third-party Loss Report
draft-ietf-avtcore-feedback-supression-rtp-05
Abstract
In a large RTP session using the RTCP feedback mechanism defined in
RFC 4585, a feedback target may experience transient overload if some
event causes a large number of receivers to send feedback at once.
This overload is usually avoided by ensuring that feedback reports
are forwarded to all receivers, allowing them to avoid sending
duplicate feedback reports. However, there are cases where it is not
recommended to forward feedback reports, and this may allow feedback
implosion. This memo discusses these cases and defines a new RTCP
third-party loss report that can be used to inform receivers that a
feedback target is aware of some loss event, allowing them to
suppress feedback. Associated SDP signalling is also defined.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 12, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
Wu, et al. Expires January 12, 2012 [Page 1]
Internet-Draft Third Party Loss Report July 2011
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Wu, et al. Expires January 12, 2012 [Page 2]
Internet-Draft Third Party Loss Report July 2011
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 5
4. Format of RTCP Feedback Messages . . . . . . . . . . . . . . . 6
4.1. Transport Layer Feedback: Third-party Loss Report . . . . 6
4.2. Payload Specific Feedback: Third-party Loss Report . . . . 7
5. SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Example Use Cases . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Source Specific Multicast (SSM) use case . . . . . . . . . 9
6.2. Unicast based Rapid Acquisition of Multicast Stream
(RAMS) use case . . . . . . . . . . . . . . . . . . . . . 10
6.3. RTP transport translator use case . . . . . . . . . . . . 11
6.4. Multipoint Control Unit (MCU) use case . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 12
9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 13
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 15
A.1. draft-ietf-avtcore-feedback-suppression-rtp-01 . . . . . . 15
A.2. draft-ietf-avtcore-feedback-suppression-rtp-02 . . . . . . 15
A.3. draft-ietf-avtcore-feedback-suppression-rtp-03 . . . . . . 16
A.4. draft-ietf-avtcore-feedback-suppression-rtp-04 . . . . . . 16
A.5. draft-ietf-avtcore-feedback-suppression-rtp-05 . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
Wu, et al. Expires January 12, 2012 [Page 3]
Internet-Draft Third Party Loss Report July 2011
1. Introduction
RTCP feedback messages [RFC4585] allow the receivers in an RTP
session to report events and ask for action from the media source (or
a delegated feedback target when using unicast RTCP feedback with SSM
[RFC5760]). There are cases where multiple receivers may initiate
the same, or an equivalent message towards the same media source.
When the receiver count is large, this behavior may cause transient
overload of the media source, the network or both. This is known as
a "feedback storm" or a "NACK storm". One common cause of such a
feedback storm is receivers utilizing RTP retransmission [RFC4588] as
a packet loss recovery technique based, sending feedback using RTCP
NACK messages [RFC4585] without proper dithering of the
retransmission requests.
Another use case involves video Fast Update requests. A storm of
these feedback messages can occur in conversational multimedia
scenarios like Topo-Video-switch-MCU [RFC5117]. In this scenario,
packet loss may happen on an upstream link of an intermediate network
element such as a Multipoint Control Unit(MCU). Poorly designed
receivers that blindly issue fast update requests (i.e., Full Intra
Request (FIR) described in [RFC5104]), can cause an implosion of FIR
requests from receivers to the same media source.
RTCP feedback storms may cause short term overload, and in extreme
cases to pose a possible risk of increasing network congestion on the
control channel (e.g. RTCP feedback), the data channel, or both. It
is therefore desirable to provide a way of suppressing unneeded
feedback.
One approach to this, suggested in [DVB-IPTV], involves sending a
NACK message to the other clients (or receiver) in the same group as
the sender of NACK. However NACK is defined as a receiver report
sent from a receiver observing a packet loss, therefore it only
inform others that sender of NACK detected loss while the case the
sender of the feedback has received reports that the indicated
packets were lost is not covered. This document specifies a new
third-party loss report for this function. It further is more
precise in the intended uses and less likely to be confusing to
receivers. It tells receivers explicitly that feedback for a
particular packet or frame loss is not needed for a period of time
and can provide an early indication before the receiver reacts to the
loss and invokes its packet loss repair machinery. Section 6
provides some examples of when to send the third party loss report
message.
Wu, et al. Expires January 12, 2012 [Page 4]
Internet-Draft Third Party Loss Report July 2011
2. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Protocol Overview
This document extends the RTCP feedback messages defined in the
Audio-Visual Profile with feedback (RTP/AVPF) [RFC4585] defining a
Third Party Loss Report message. The Third Party Loss Report message
can be used by the media source or intermediaries to inform the
receiver that the sender of the Third Party Loss Report has received
reports that the indicated packets were lost, and asks the receiver
not to send feedback to it regarding these packets.
When a receiver gets a Third Party Loss Report message, it should
refrain from sending a feedback request (e.g., NACK or FIR) for the
missing packets reported in the message for a period of time. A
receiver may still have sent a Feedback message according to the RTP/
AVPF scheduling algorithm of [RFC4585]before receiving a Third Party
Loss Report message, but further feedback messages for those sequence
numbers will be suppressed by this technique for a period of time.
Nodes that do not understand the Third Party Loss Report message will
ignore it, and might therefore still send feedback according to the
AVPF scheduling algorithm of [RFC4585]. The media source or
intermediate nodes cannot assume that the use of a Third Party Loss
Report message actually reduces the amount of feedback it receives.
RTCP Third Party Loss Report follows the similar format of message
type as RTCP NACK. However, the third party loss report is defined
as an indication that the sender of the feedback has received reports
that the indicated packets were lost, while NACK [RFC4585] just
indicates that the sender of the NACK observed that these packets
were lost. The Third Party Loss Report message is generated by a
system that has not seen the actual packet loss. Systems that
receive a third party loss report SHOULD NOT initiate their own
additional Third Party Loss Report messages for the same packet
sequence numbers. They may either simply forward the Third Party
Loss Report message, or they may generate their own Third Party Loss
Report that reports a superset of the loss reported in the Third
Party Loss report they received. The Third Party Loss Report does
not have the retransmission request [RFC4588] semantics.
Since Third Party Loss Report interacts strongly with repair timing,
it has to work together with feedback to not adversely impact the
repair of lost source packets. One example is the middle box gets
Wu, et al. Expires January 12, 2012 [Page 5]
Internet-Draft Third Party Loss Report July 2011
the retransmitted packet by sending a NACK upstream and sent it
downstream. This retransmitted packet was lost on the downstream
link. In order to deal with this, the downstream receiver can start
a timeout in which it expected to get a retransmission packet. When
this timeout expires and there is no retransmitted packet or a new
third party loss report message, it can take its normal behavior as
if there is no current retransmission suppression. In this case when
the loss was detected and repair initiated much closer to the source,
the delay for the receiver to recover from packet loss can be reduced
through the combination of intermediary feedback to the source and
Third Party Loss Report downstream.
4. Format of RTCP Feedback Messages
This document registers two new RTCP Feedback messages for Third
Party Loss Report. Applications that are employing one or more loss-
repair methods MAY use Third Party Loss Report together with their
existing loss-repair methods either for every packet they expect to
receive, or for an application-specific subset of the RTP packets in
a session. In other words, receivers MAY ignore Third Party Loss
Report messages, but SHOULD react to them unless they have good
reason to still send feedback messages despite having been requested
to suppress them.
4.1. Transport Layer Feedback: Third-party Loss Report
This Third Party Loss Report message is an extension to the RTCP
Transport Layer Feedback Report and identified by RTCP packet type
value PT=RTPFB and FMT=TBD.
The FCI field MUST contain one or more entries of transport layer
third party loss Early Indication (TLLEI). Each entry applies to a
different media source, identified by its SSRC.
The Feedback Control Information (FCI) for TLLEI uses the similar
format of message Types defined in the section 6.2.1 of [RFC4585].
The format is shown in Figure 1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PID | BLP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Message Format for the Third Party Loss Report
Wu, et al. Expires January 12, 2012 [Page 6]
Internet-Draft Third Party Loss Report July 2011
Packet ID (PID): 16 bits
The PID field is used to specify a lost packet. The PID field
refers to the RTP sequence number of the lost packet.
bitmask of proceeding lost packets (BLP): 16 bits
The BLP allows for reporting losses of any of the 16 RTP packets
immediately following the RTP packet indicated by the PID. The
BLP's definition is identical to that given in [RFC4585].
4.2. Payload Specific Feedback: Third-party Loss Report
This message is an extension to the RTCP Payload Specific Feedback
report and identified by RTCP packet type value PT=PSFB and FMT=TBD.
The FCI field MUST contain a Payload Specific Third Party Loss Early
Indication (PSLEI) entry. Each entry applies to a different media
source, identified by its SSRC.
The Feedback Control Information (FCI) for PSLEI uses the similar
format of message Types defined in the section 4.3.1.1 of [RFC5104].
The format is shown in Figure 2.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Seq nr. | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Message Format for the Third Party Loss Report
SSRC (32 bits):
The SSRC value of the media source that is requested to send a
decoder refresh point.
Seq nr:8bits Command sequence number. The sequence number space is
unique for each pairing of the SSRC of command source and the SSRC
of the command target. The sequence number SHALL be increased by
1 modulo 256 for each new request.
Wu, et al. Expires January 12, 2012 [Page 7]
Internet-Draft Third Party Loss Report July 2011
Reserved: 24 bits
All bits SHALL be set to 0 by the media source and SHALL be
ignored on reception.
5. SDP Signaling
A new feedback value "tplr" needs to be defined for the Third Party
Loss Report message to be used with Session Description Protocol
(SDP) [RFC4566] using the Augmented Backus-Naur Form (ABNF)
[RFC4585].
The "tplr" feedback value SHOULD be used with parameters that
indicate the third party loss supported. In this document, we define
two such parameter, namely:
o "tllei" denotes support of transport layer third party loss early
indication (fsei).
o "pslei" denotes support of payload specific third party loss early
indication.
In the ABNF for rtcp-fb-val defined in [RFC4585], there is a
placeholder called rtcp-fb-id to define new feedback types. "tplr" is
defined as a new feedback type in this document, and the ABNF for the
parameters for tplr is defined here (please refer to section 4.2 of
[RFC4585] for complete ABNF syntax).
rtcp-fb-val =/ "tplr" rtcp-fb-tplr-param
rtcp-fb-tplr-param = SP "tllei";transport layer third party loss early indication
/ SP "pslei";payload specific third party loss early indication
/ SP token [SP byte-string]
; for future commands/indications
byte-string = <as defined in section 4.2 of [RFC4585] >
Refer to Section 4.2 of [RFC4585] for a detailed description 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 Third Party Loss Report for feedback suppression and
Wu, et al. Expires January 12, 2012 [Page 8]
Internet-Draft Third Party Loss Report July 2011
give an overview of the particular mechanisms.
6.1. Source Specific Multicast (SSM) use case
In SSM RTP sessions as described in [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. Note that each receiver sending multicast
NACK to its group may still need to send unicast NACK addressed to
the media source or distribution source , this may lead to a NACK
storm if feedback suppression is not performed and if the RTCP
bandwidth limit is misconfigured.
As outlined in the [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, NACKs are reflected by the distribution source to the other
receivers, and there's no need for distribution source to create the
third-party loss report. The third-party loss report may be
generated at the distribution source when downstream loss report is
received in the Distribution Source Feedback Summary model, since
this summary feedback does not mandate the forwarding of NACK
downstream.
In order to observe packet loss before the receivers perceive it, one
or more intermediate nodes may be placed between the media source and
the receivers. These intermediaries monitor for upstream packet loss
. These intermediates may be Distribution source, MCUs, RTP
translator, or RTP mixers, depending on the precise implementation.
If an intermediary notices the loss itself, then it may send a NACK
both downstream towards the receivers and upstream towards the media
source, to indicate that it has noticed the loss, and to suppress
feedback from other downstream receivers. In the SSM case, If the
distribution source ,using the simple feedback model, receives a NACK
from another system (e.g.,an intermediary), it should redistribute
that NACK to all other systems that would not otherwise receive it.
If the distribution source, using the summary feedback model,
receives a NACK from another system, but, for some reason(e.g., to
prevent revealing the identity or existence of a system sending
NACK), cannot redistribute that NACK, then it may send a third-party
loss report to the systems that were unable to receive the NACK, and
won't receive the NACK via other means. . Therefore the intermediate
node can be reasonably certain that it will help the situation by
sending a Third Party Loss Report message to all the relevant
receivers, thereby indicating to the receivers that they should not
transmit feedback messages for a period of time. The intermediate
node needs to take into account such factors as the tolerable
application delay, packet loss recovery techniques, the network
Wu, et al. Expires January 12, 2012 [Page 9]
Internet-Draft Third Party Loss Report July 2011
dynamics, and the media type. Loss-repair methods such as
retransmission and Forward Error Correction may be used to recover
the missing packet.
Alternatively, the media source may directly monitor the amount of
feedback reports it receives from downstream. If the media source
notices the loss itself, then it may send a NACK downstream towards
the receivers to suppress feedback. If the media source receives a
NACK from another system, it should redistribute that NACK to all
other systems that would not otherwise receive it. If the media
source receives a NACK from another system, but, for some reason
(e.g., hiding identity or existing a system sending NACK, cannot
redistribute that NACK, then it may send a third-party loss report to
the systems that were unable to receive the NACK, and won't receive
the NACK via other means.
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 multicast SSM stream
from the media source. If one of the BRSes receives downstream loss
report (i.e., First loss in Figure 3) on its downstream link, but the
others BRSes have not, as the packet loss took place on the SSM tree
branch that does not impact the other BRSes. In such case, the BRSes
not being impacted are not aware of downstream loss at their
downstream link, therefore these BRSes will not create new Third
Party Loss Report message and send it to receivers in their
downstream path. If the BRS impacted by packet loss has been told
the actual packet loss, the BRS MAY choose to create new Third Party
Loss Report message and send it to the receivers in the downstream
link. Note that BRS must use its own SSRC as packet sender SSRC for
transmitting the feedback suppress message.
The BRS may also send a NACK upstream to request the retransmitted
packet. Upon receiving the retransmitted packet, the BRS sent it
downstream. Note that this retransmitted packet may get lost (i.e.,
second loss in the Figure 3) on the downstream link. In order to
deal with this issue, the downstream receiver can start a timeout
clock in which it expected to get a retransmission packet. When this
timeout expires and there is no retransmitted packet or a new Third
Party Loss Report message, it can take its normal behavior as if
there is no current retransmission suppression in place.
Wu, et al. Expires January 12, 2012 [Page 10]
Internet-Draft Third Party Loss Report July 2011
+------------+ First Loss +----------+
|Burst and |Second Loss | |
+-----------| Retrans. |----X--X--->| |
| Upstream |Source1(BRS)| Downstream | |
Link close | link 1 +------------+ link 1 | |
to multicast | | |
source | | |
| | | |
| | +------------+ | RTP |
+---------+ | +-----++ |Burst and | | Receiver |
|Multicast| V| | +----------| Retrans. |----------->| |
| Source +-----|Router|Upstream |Source2(BRS)| Downstream | RTP_Rx |
+---------+ | |link 2 +------------+ link 2 | |
+-----++ | |
| | |
| | |
| | |
| +------------+ | |
| |Burst and | | |
+-----------+ Retrans. |----------->| |
Upstream |Source k(BRS| Downstream | |
link k +------------+ link k +----------+
Figure 3: RAMS Use Case
6.3. RTP transport translator use case
A Transport Translator (Topo-Trn-Translator), as defined in [RFC5117]
is typically forwarding the RTP and RTCP traffic between RTP clients,
for example converting between multicast and unicast for domains that
do not support multicast. The translator can identify packet loss
using co-located monitor [I-D.ietf-avtcore-monarch] by receiving a
NACK from another system and then the monitor can use it's own SSRC
as packet sender SSRC for transmitting the Third Party Loss Report
message and send this message to the unicast receivers that is not
aware of packet loss.
6.4. Multipoint Control Unit (MCU) use case
In point to multipoint topologies using video switching MCU (Topo-
Video-switch-MCU) [RFC5117], the MCU typically forwards a single
media stream to each participant, selected from the available input
streams. The selection of the input stream is often based on voice
activity in the audio-visual conference, but other conference
management mechanisms (like presentation mode or explicit floor
control) exist as well.
In this case the MCU may identify packet loss by receiving a NACK
Wu, et al. Expires January 12, 2012 [Page 11]
Internet-Draft Third Party Loss Report July 2011
from another system or may decide to switch to a new source. In both
cases the receiver may lose synchronization with the video stream and
may send a FIR request. If the MCU itself can detect the mis-
synchronization of the video, the MCU can send the FIR suppression
message to the receivers and send a FIR request to the video source.
As suggested in RFC 5117, this topology is better implemented as an
Topo-mixer, in which case the mixer's SSRC is used as packet sender
SSRC for transmitting Third Party Loss Report message.
7. Security Considerations
The defined messages have certain properties that have security
implications. These must be addressed and taken into account by
users of this protocol.
Spoofed or maliciously created feedback messages of the type defined
in this specification can have the following implications:
Sending Third Party Loss Report with wrong sequence number of lost
packet that makes missing RTP packets can not be compensated.
To prevent these attacks, there is a need to apply authentication and
integrity protection of the feedback messages. This can be
accomplished against threats external to the current RTP session
using the RTP profile that combines Secure RTP [RFC3711] and AVPF
into SAVPF [RFC5124].
Note that middleboxes that are not visible at the RTP layer that wish
to send Third Party Loss Reports on behalf of the media 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 middlebox is visible at the
RTP layer, this is not an issue, provided the middlebox is part of
the security context for the session.
Also note that endpoints that receive a Third Party Loss Report would
be well-advised to ignore it, unless it is authenticated via SRTCP or
similar. Accepting un-authenticated Third Party Loss Report can lead
to a denial of service attack, where the endpoint accepts poor
quality media that could be repaired.
8. IANA Consideration
New feedback type and New parameters for RTCP Third Party Loss Report
are subject to IANA registration. For general guidelines on IANA
considerations for RTCP feedback, refer to [RFC4585].
Wu, et al. Expires January 12, 2012 [Page 12]
Internet-Draft Third Party Loss Report July 2011
This document assigns one new feedback type value x in the RTCP
feedback report registry to "Third Party Loss Report" with the
following registrations format:
Name: TPLR
Long Name: Third Party Loss Report
Value: TBD
Reference: This document.
This document also assigns the parameter value y in the RTCP TPLR
feedback report Registry to " Transport Layer Third Party Loss Early
Indication ", with the following registrations format:
Name: TLLEI
Long name: Transport Layer Third Party Loss Early Indication
Value: TBD
Reference: this document.
This document also assigns the parameter value z in the RTCP TPLR
feedback report Registry to "Payload Specific Third Party Loss Early
Indication ", with the following registrations format:
Name: PSLEI
Long name: Payload Specific Third Party Loss Early Indication
Value: TBD
Reference: this document.
The contact information for the registrations is:
Qin Wu
sunseawq@huawei.com
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012, China
9. Acknowledgement
The authors would like to thank David R Oran, Ali C. Begen, Colin
Perkins,Tom VAN CAENEGEM, Ingemar Johansson S, Bill Ver Steeg,
Jonathan Lennox, WeeSan Lee for their valuable comments and
suggestions on this document.
10. References
Wu, et al. Expires January 12, 2012 [Page 13]
Internet-Draft Third Party Loss Report July 2011
10.1. Normative References
[RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
Protocol (RTCP) Extensions for Single-Source Multicast
Sessions with Unicast Feedback", RFC 5760, February 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
"Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
July 2006.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC5117] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117,
January 2008.
[RFC4588] Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R.
Hakenberg, "RTP Retransmission Payload Format", RFC 4588,
July 2006.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
"Codec Control Messages in the RTP Audio-Visual Profile
with Feedback (AVPF)", RFC 5104, February 2008.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004.
[RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for
Real-time Transport Control Protocol (RTCP)-Based Feedback
(RTP/SAVPF)", RFC 5124, February 2008.
10.2. Informative References
[RFC5740] Adamson, B., Bormann, C., Handley, M., and J. Macker,
"NACK-Oriented Reliable Multicast (NORM) Transport
Protocol", November 2009.
Wu, et al. Expires January 12, 2012 [Page 14]
Internet-Draft Third Party Loss Report July 2011
[DVB-IPTV]
ETSI Standard, "Digital Video Broadcasting(DVB); Transport
of MPEG-2 TS Based DVB Services over IP Based Networks",
ETSI TS 102 034, V1.4.1 , August 2009.
[RFC6285] Steeg, B., Begen, A., Caenegem, T., and Z. Vax, "Unicast-
Based Rapid Acquisition of Multicast RTP Sessions",
June 2011.
[I-D.ietf-avtcore-monarch]
Wu, Q., Hunt, G., and P. Arden, "Monitoring Architectures
for RTP", June 2011.
[I-D.ietf-pmol-metrics-framework]
Clark, A. and B. Claise, "Framework for Performance Metric
Development", January 2011.
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-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.
A.2. draft-ietf-avtcore-feedback-suppression-rtp-02
The following are the major changes compared to previous version:
o In Section 4.1, fix typo: Section 4.3.1.1 of section [RFC5104]->
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.
Wu, et al. Expires January 12, 2012 [Page 15]
Internet-Draft Third Party Loss Report July 2011
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.3. 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.4. 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.5. 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.
Wu, et al. Expires January 12, 2012 [Page 16]
Internet-Draft Third Party Loss Report July 2011
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.
Authors' Addresses
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: sunseawq@huawei.com
Frank Xia
Huawei
1700 Alma Dr. Suite 500
Plano, TX 75075
USA
Phone: +1 972-509-5599
Email: xiayangsong@huawei.com
Roni Even
Huawei
14 David Hamelech
Tel Aviv 64953
Israel
Email: even.roni@huawei.com
Wu, et al. Expires January 12, 2012 [Page 17]
