RFC 7509 PROPOSED STANDARD RTP · RTCP · LOSS METRICS
RTP Control Protocol (RTCP) Extended Report (XR) for Post-Repair Loss Count Metrics
A compact RTCP report that tells a sender how many lost packets were fixed and how many stayed lost.
RFC EDITOR
Huang, R. and V. Singh, "RTP Control Protocol (RTCP) Extended Report (XR) for Post-Repair Loss Count Metrics", RFC 7509, DOI 10.17487/RFC7509, May 2015, <https://www.rfc-editor.org/info/rfc7509>.
BIBTEX
@misc{rfc7509,
series = {Request for Comments},
number = 7509,
howpublished = {RFC 7509},
publisher = {RFC Editor},
doi = {10.17487/RFC7509},
url = {https://www.rfc-editor.org/info/rfc7509},
author = {R. Huang and V. Singh},
title = {{RTP Control Protocol (RTCP) Extended Report (XR) for Post-Repair Loss Count Metrics}},
pagetotal = 11,
year = 2015,
month = may,
} RFC text
Contents
Internet Engineering Task Force (IETF) R. Huang
Request for Comments: 7509 Huawei
Category: Standards Track V. Singh
ISSN: 2070-1721 Aalto University
May 2015
RTP Control Protocol (RTCP) Extended Report (XR)
for Post-Repair Loss Count Metrics
Abstract
This document defines an RTP Control Protocol (RTCP) Extended Report
(XR) block that allows reporting of a post-repair loss count metric
for a range of RTP applications. In addition, another metric,
repaired loss count, is also introduced in this report block for
calculating the pre-repair loss count when needed, so that the RTP
sender or a third-party entity is able to evaluate the effectiveness
of the repair methods used by the system.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
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/rfc7509.
Copyright Notice
Copyright (c) 2015 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
(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.
Table of Contents
1. Introduction ....................................................2
2. Terminology .....................................................3
3. Post-Repair Loss Count Metrics Report Block .....................3
3.1. Report Block Structure .....................................4
3.2. Example Usage ..............................................5
4. SDP Signaling ...................................................6
4.1. SDP rtcp-xr-attrib Attribute Extension .....................6
4.2. Offer/Answer Usage .........................................7
5. Security Considerations .........................................7
6. IANA Considerations .............................................7
6.1. New RTCP XR Block Type Value ...............................7
6.2. New RTCP XR SDP Parameter ..................................7
6.3. Contact Information for Registrations ......................7
7. References ......................................................8
7.1. Normative References .......................................8
7.2. Informative References .....................................9
Appendix A. Metrics Represented Using the Template from RFC 6390 ..10
Acknowledgments ...................................................11
Authors' Addresses ................................................11
1. Introduction
RTCP Sender Reports (SRs) / Receiver Reports (RRs) [RFC3550] contain
some rough statistics about the data received from the particular
source indicated in that block. One of them is the cumulative number
of packets lost, which is called the pre-repair loss metric in this
document. This metric conveys information regarding the total number
of RTP data packets that have been lost since the beginning of the
RTP session.
However, this metric is measured on the media stream before any loss-
repair mechanism, e.g., retransmission [RFC4588] or Forward Error
Correction (FEC) [RFC5109], is applied. Using a repair mechanism
usually results in recovering some or all of the lost packets. The
recovery process does not reduce the values reported by the two loss
metrics in RTCP RR [RFC3550] -- namely, the fraction lost and the
cumulative loss. Hence, the sending endpoint cannot infer the
performance of the repair mechanism based on the aforementioned
metrics in [RFC3550].
Consequently, [RFC5725] specifies a post-repair loss Run-Length
Encoding (RLE) XR report block to address this issue. The sending
endpoint is able to infer which packets were repaired from the RLE
report block, but the reporting overhead for the packet-by-packet
report block is higher compared to other report blocks.
When applications use multiple XR blocks, the endpoints may require
more concise reporting to save bandwidth. This document defines a
new XR block type to augment those defined in [RFC3611] and
complement the report block defined in [RFC5725] for use in a range
of RTP applications. This new block type reports the post-repair
loss count metric, which records the number of primary source RTP
packets that are still lost after applying one or more loss-repair
mechanisms. In addition, another metric, repaired loss count, is
also introduced in this report block for calculating the pre-repair
loss count during this range, so that the RTP sender or a third-party
entity is able to evaluate the effectiveness of the repair methods
used by the system. The metrics defined in this document are packet
level rather than slice/picture level; this means the partial
recovery of a packet will not be regarded as a repaired packet.
The metrics defined in this document belong to the class of
transport-related metrics defined in [RFC6792] and are specified in
accordance with the guidelines in [RFC6390] and [RFC6792]. These
metrics are applicable to any RTP application, especially those that
use loss-repair mechanisms.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [KEYWORDS].
primary source RTP packet: The original RTP packet sent from the RTP
sender for the first time. A lost primary source RTP packet may
be repaired by some other RTP packets used in repair mechanisms
like FEC or retransmission.
3. Post-Repair Loss Count Metrics Report Block
This block reports the number of packets lost after applying repair
mechanisms (e.g., FEC). It complements the RTCP XR metrics defined
in [RFC5725]. As noted in [RFC5725], ambiguity may occur when
comparing this metric with a pre-repair loss metric reported in an
RTCP SR/RR, i.e., some packets were not repaired in the current RTCP
interval, but they may be repaired later. Therefore, this block uses
a begin sequence number and an end sequence number to explicitly
indicate the actual sequence number range reported by this RTCP XR.
Accordingly, only packets that have no further chance of being
repaired and that have been repaired are included in this report
block.
3.1. Report Block Structure
The Post-Repair Loss Count Metrics Report Block has the following
format:
0 1 2 3 4
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT=33 | Reserved | Block length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| begin_seq | end_seq |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Post-repair loss count | Repaired loss count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Block Type (BT): 8 bits
A Post-Repair Loss Count Metrics Report Block is identified by the
constant 33.
Reserved: 8 bits
These bits are reserved for future use. They MUST be set to zero
by senders and ignored by receivers (see Section 4.2 of
[RFC6709]).
Block length: 16 bits
This field is in accordance with the definition in [RFC3611]. In
this report block, it MUST be set to 4. The block MUST be
discarded if the block length is set to a different value.
SSRC of source: 32 bits
As defined in Section 4.1 of [RFC3611].
begin_seq: 16 bits
The first sequence number that this block reports on. It can
remain fixed when calculating metrics over several RTCP reporting
intervals.
end_seq: 16 bits
The last sequence number that this block reports on plus one.
Post-repair loss count: 16 bits
Total number of packets finally lost after applying one or more
loss-repair methods, e.g., FEC and/or retransmission, during the
actual sequence number range indicated by begin_seq and end_seq.
This metric MUST NOT count the lost packets for which repair might
still be possible. Note that this metric MUST measure only
primary source RTP packets.
Repaired loss count: 16 bits
Total number of packets fully repaired after applying one or more
loss-repair methods, e.g., FEC and/or retransmission, during the
actual sequence number range indicated by begin_seq and end_seq.
Note that this metric MUST measure only primary source RTP
packets.
3.2 Example Usage
The metrics defined in this report block are all measured at the RTP
receiver. However, the receiving endpoint can report the metrics in
two different ways:
1) Cumulative report
In this case, implementations may set begin_seq to the first packet
in the RTP session, and it will remain fixed across all reports.
Hence, the "Post-repair loss count" and "Repaired loss count",
respectively, will correspond to "Cumulative post-repair loss count"
and "Cumulative repaired loss count" in this case. These cumulative
metrics when combined with the cumulative loss metrics reported in an
RTCP RR (pre-repair) assist in calculating the "Still-to-be-repaired
lost packets":
Still-to-be-repaired lost packets =
Cumulative number of packets lost -
Cumulative post-repair loss count -
Cumulative repaired loss count
2) Interval report
Some implementations may align the begin_seq and end_seq number with
the highest sequence numbers of consecutive RTCP RRs (RTCP interval).
This is NOT RECOMMENDED as packets that are not yet repaired in this
current RTCP interval and may be repaired in the subsequent intervals
will not be reported. An interval report is illustrated in the
following example:
Interval A: The extended highest sequence number received in RTCP
RR is 20. Begin_seq is 10 and end_seq is 20.
Interval B: The extended highest sequence number received in RTCP
RR is 30. Begin_seq is 20 and end_seq is 30.
If packets 17 and 19 are lost and not yet repaired in interval A and
subsequently repaired in interval B, they will not be reported
because their sequence numbers do not belong in interval B.
Therefore, if implementations want these packets to be reported as
repaired, they MUST NOT align the begin_seq and end_seq to the RTCP
intervals.
Alternatively, implementations may choose the begin_seq and end_seq
numbers that cover several RTCP intervals. Additionally, the
reported range of sequence numbers may overlap with the previous
report blocks, so that the packets that were not yet repaired in one
interval, but were subsequently repaired or deemed unrepairable, were
reported in subsequent intervals.
In this case, the "Cumulative number of packets lost" cannot be
easily compared with the post-repair metrics. However, the sending
endpoint can calculate the efficiency of the error resilience
algorithm using the post-repair and repaired loss count,
respectively.
4. SDP Signaling
[RFC3611] defines the use of SDP (Session Description Protocol) for
signaling the use of RTCP XR blocks. However, XR blocks MAY be used
without prior signaling (see Section 5 of [RFC3611]).
4.1. SDP rtcp-xr-attrib Attribute Extension
This session augments the SDP attribute "rtcp-xr" defined in Section
5.1 of [RFC3611] by providing an additional value of "xr-format" to
signal the use of the report block defined in this document. The
ABNF [RFC5234] syntax is as follows.
xr-format =/ xr-prlr-block
xr-prlr-block = "post-repair-loss-count"
4.2. Offer/Answer Usage
When SDP is used in offer/answer context, the SDP Offer/Answer usage
defined in [RFC3611] for the unilateral "rtcp-xr" attribute
parameters applies. For detailed usage of Offer/Answer for
unilateral parameters, refer to Section 5.2 of [RFC3611].
5. Security Considerations
This proposed RTCP XR block introduces no new security considerations
beyond those described in [RFC3611]. This block does not provide
per-packet statistics, so the risk to confidentiality documented in
Section 7, paragraph 3 of [RFC3611] does not apply.
An attacker may put incorrect information in the Post-Repair Loss
Count reports, which will affect the performance of loss-repair
mechanisms. Implementers should consider the guidance in [RFC7202]
for using appropriate security mechanisms, i.e., where security is a
concern, the implementation should apply encryption and
authentication to the report block. For example, this can be
achieved by using the AVPF profile together with the Secure RTP
profile as defined in [RFC3711]; an appropriate combination of the
two profiles (an "SAVPF") is specified in [RFC5124]. However, other
mechanisms also exist (documented in [RFC7201]) and might be more
suitable.
6. IANA Considerations
New block types for RTCP XR are subject to IANA registration. For
general guidelines on IANA considerations for RTCP XR, refer to
[RFC3611].
6.1. New RTCP XR Block Type Value
This document assigns the block type value 33 in the IANA "RTP
Control Protocol Extended Reports (RTCP XR) Block Type Registry" to
the "Post-Repair Loss Count Metrics Report Block".
6.2. New RTCP XR SDP Parameter
This document also registers a new parameter "post-repair-loss-count"
in the "RTP Control Protocol Extended Reports (RTCP XR) Session
Description Protocol (SDP) Parameters Registry".
6.3. Contact Information for Registrations
The contact information for the registrations is:
RAI Area Directors <rai-ads@ietf.org>
7. References
7.1. Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>.
[RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed.,
"RTP Control Protocol Extended Reports (RTCP XR)",
RFC 3611, DOI 10.17487/RFC3611, November 2003,
<http://www.rfc-editor.org/info/rfc3611>.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, DOI 10.17487/RFC3711, March 2004,
<http://www.rfc-editor.org/info/rfc3711>.
[RFC5124] Ott, J. and E. Carrara, "Extended Secure RTP Profile for
Real-time Transport Control Protocol (RTCP)-Based Feedback
(RTP/SAVPF)", RFC 5124, DOI 10.17487/RFC5124, February
2008, <http://www.rfc-editor.org/info/rfc5124>.
[RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC5725] Begen, A., Hsu, D., and M. Lague, "Post-Repair Loss RLE
Report Block Type for RTP Control Protocol (RTCP) Extended
Reports (XRs)", RFC 5725, DOI 10.17487/RFC5725, February
2010, <http://www.rfc-editor.org/info/rfc5725>.
7.2. Informative References
[RFC4588] Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R.
Hakenberg, "RTP Retransmission Payload Format", RFC 4588,
DOI 10.17487/RFC4588, July 2006,
<http://www.rfc-editor.org/info/rfc4588>.
[RFC5109] Li, A., Ed., "RTP Payload Format for Generic Forward Error
Correction", RFC 5109, DOI 10.17487/RFC5109, December
2007, <http://www.rfc-editor.org/info/rfc5109>.
[RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New
Performance Metric Development", BCP 170, RFC 6390,
DOI 10.17487/RFC6390, October 2011,
<http://www.rfc-editor.org/info/rfc6390>.
[RFC6709] Carpenter, B., Aboba, B., Ed., and S. Cheshire, "Design
Considerations for Protocol Extensions", RFC 6709, DOI
10.17487/RFC6709, September 2012,
<http://www.rfc-editor.org/info/rfc6709>.
[RFC6792] Wu, Q., Ed., Hunt, G., and P. Arden, "Guidelines for Use
of the RTP Monitoring Framework", RFC 6792,
DOI 10.17487/RFC6792, November 2012,
<http://www.rfc-editor.org/info/rfc6792>.
[RFC7201] Westerlund, M. and C. Perkins, "Options for Securing RTP
Sessions", RFC 7201, DOI 10.17487/RFC7201, April 2014,
<http://www.rfc-editor.org/info/rfc7201>.
[RFC7202] Perkins, C. and M. Westerlund, "Securing the RTP
Framework: Why RTP Does Not Mandate a Single Media
Security Solution", RFC 7202, DOI 10.17487/RFC7202, April
2014, <http://www.rfc-editor.org/info/rfc7202>.
Appendix A. Metrics Represented Using the Template from RFC 6390
a. Post-Repair RTP Packet Loss Count Metric
* Metric Name: Post-Repair RTP Packet Loss Count Metric.
* Metric Description: Total number of RTP packets still lost
after loss-repair methods are applied.
* Method of Measurement or Calculation: See the "Post-repair
loss count" definition in Section 3.1. It is directly
measured and must be measured for the primary source RTP
packets with no further chance of repair.
* Units of Measurement: This metric is expressed as a 16-bit
unsigned integer value giving the number of RTP packets.
* Measurement Point(s) with Potential Measurement Domain: It is
measured at the receiving end of the RTP stream.
* Measurement Timing: This metric relies on the sequence number
interval to determine measurement timing. See the Cumulative
and Interval reports defined in Section 3.2.
* Use and Applications: These metrics are applicable to any RTP
application, especially those that use loss-repair mechanisms.
See Section 1 for details.
* Reporting Model: See RFC 3611.
b. Repaired RTP Packet Loss Count Metric
* Metric Name: Repaired RTP Packet Count Metric.
* Metric Description: The number of RTP packets lost but
repaired after applying loss-repair methods.
* Method of Measurement or Calculation: See the "Repaired loss
count" in Section 3.1. It is directly measured and must be
measured for the primary source RTP packets with no further
chance of repair.
* Units of Measurement: This metric is expressed as a 16-bit
unsigned integer value giving the number of RTP packets.
* Measurement Point(s) with Potential Measurement Domain: It is
measured at the receiving end of the RTP stream.
* Measurement Timing: This metric relies on the sequence number
interval to determine measurement timing. See the Cumulative
and Interval reports defined in Section 3.2.
* Use and Applications: These metrics are applicable to any RTP
application, especially those that use loss-repair mechanisms.
See Section 1 for details.
* Reporting Model: See RFC 3611.
Acknowledgments
The authors would like to thank Roni Even, Colin Perkins, and Qin Wu
for giving valuable comments and suggestions.
Authors' Addresses
Rachel Huang
Huawei
101 Software Avenue, Yuhua District
Nanjing 210012
China
EMail: rachel.huang@huawei.com
Varun Singh
Aalto University
School of Electrical Engineering
Otakaari 5 A
Espoo, FIN 02150
Finland
EMail: varun@comnet.tkk.fi
URI: http://www.netlab.tkk.fi/~varun/
AI ELI5
On this page
PROBLEMStandard RTCP reports count packets lost before any repair, so a sender cannot tell how well retransmission or forward error correction is working. The existing per-packet report from RFC 5725 costs more bandwidth.
MECHANISMRFC 7509 defines an RTCP XR block, block type 33, that carries a post-repair loss count and a repaired loss count over an explicit range of sequence numbers.
WHY IT MATTERSThe sender or a third party can work out how many packets are still lost, how many were repaired and so how effective the repair methods are.
§1Why Pre-Repair Counts Are Not Enough
RTCP Sender and Receiver Reports (RFC 3550) include the cumulative number of packets lost. This document calls that the pre-repair loss metric, because it is measured on the media stream before any loss-repair mechanism, such as retransmission (RFC 4588) or Forward Error Correction (RFC 5109), is applied.
Recovering a packet does not lower the fraction lost or the cumulative loss in those reports. So the sender cannot judge how well its repair mechanism performs from them alone. RFC 5725 addressed this with a run-length encoded block, but its packet-by-packet reporting has a higher overhead than other report blocks.
Normal reports only say how many packets went missing, even if some were later replaced. It is like a score sheet that never erases a mistake after you fix it.
§2The Two New Metrics
The new block reports a post-repair loss count: the number of packets still lost after one or more repair mechanisms have been applied. It also reports a repaired loss count, which is the number of packets fully repaired. With the pre-repair count, the repaired count lets a sender or third-party entity calculate the pre-repair loss over the same range.
Both metrics count only primary source RTP packets, meaning the original packets the sender sent for the first time. They work at packet level, not slice or picture level, so partly recovering a packet does not count as repairing it. The metrics are measured at the RTP receiver and apply to any RTP application, especially one that uses loss repair.
One number says how many lost things stayed lost. The other says how many were found again. Only the first copy of each thing counts, and half-fixed does not count as fixed.
§3The Report Block Format
The block is identified by block type (BT) 33. Its fields are:
Reserved(8 bits): MUST be set to zero by senders and ignored by receivers.Block length(16 bits): MUST be 4. A block with any other value MUST be discarded.SSRC of source(32 bits): as defined in RFC 3611.begin_seq(16 bits): the first sequence number the block reports on.end_seq(16 bits): the last sequence number reported on, plus one.Post-repair loss count(16 bits): packets finally lost in that range. It MUST NOT count lost packets that could still be repaired.Repaired loss count(16 bits): packets fully repaired in that range.
The report is a small form. It names the stream, gives the first and last packet numbers it covers, and fills in two boxes: still lost and fixed.
| Field | Name | Size | Value | Description |
|---|---|---|---|---|
BT | BT | 1 byte | 33 | Block type, the constant 33. |
RESERVED | Reserved | 1 byte | Set to zero by senders, ignored by receivers. | |
BLOCK-LENGTH | Block length | 2 bytes | 4 | Must be 4; other values mean discard. |
SSRC | SSRC of Source | 4 bytes | The media source the block reports on. | |
BEGIN-SEQ | begin_seq | 2 bytes | First sequence number reported on. | |
END-SEQ | end_seq | 2 bytes | Last sequence number reported on, plus one. | |
POST-REPAIR | Post-repair loss count | 2 bytes | Packets finally lost after repair. | |
REPAIRED | Repaired loss count | 2 bytes | Packets fully repaired. |
§4Cumulative and Interval Reports
Because some packets missing in one RTCP interval may be repaired later, the block states its sequence number range explicitly. Only packets that have no further chance of being repaired, and packets that have been repaired, are included.
In a cumulative report, begin_seq is set to the first packet of the session and stays fixed. Combined with the cumulative loss from an RTCP Receiver Report, the sender can compute: still-to-be-repaired lost packets = cumulative number of packets lost - cumulative post-repair loss count - cumulative repaired loss count.
In an interval report, begin_seq and end_seq follow the highest sequence numbers of consecutive Receiver Reports. This is NOT RECOMMENDED: in the RFC's example, packets 17 and 19 are lost in interval A and repaired in interval B, but interval B starts at 20, so they are never reported. Implementations that want those reported MUST NOT align the range to RTCP intervals. They may instead choose a range that covers several intervals and overlaps earlier reports.
If you only count what happened this week, a toy lost on Friday and found on Monday gets missed. So the report should look at a longer stretch of packets, not just one short window.
§5Signaling with SDP
RFC 3611 lets endpoints announce XR blocks in SDP with the rtcp-xr attribute, although XR blocks MAY also be used without prior signaling. This document adds a new xr-format value, post-repair-loss-count, to that attribute. In an offer/answer exchange, the rules for unilateral rtcp-xr parameters in RFC 3611 apply.
Before a call, each side can say 'I can send this kind of report' using a short agreed word.
§6Security and IANA Registrations
The block adds no new security considerations beyond RFC 3611, and because it carries no per-packet statistics, the confidentiality risk noted there does not apply. An attacker could still put incorrect numbers in these reports, which would affect the performance of loss-repair mechanisms. Where security matters, implementations should apply encryption and authentication, following the guidance in RFC 7202, for example with the AVPF profile together with Secure RTP (SAVPF, RFC 5124).
IANA assigned block type value 33 in the RTCP XR Block Type Registry and registered the SDP parameter post-repair-loss-count.
A sneaky person could write false numbers on the form, so important reports should be locked and signed.
§7References
[RFC3550]RFC 3550Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003.July 2003[RFC3611]RFC 3611Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed., "RTP Control Protocol Extended Reports (RTCP XR)", RFC 3611, November 2003.November 2003[RFC5725]RFC 5725Begen, A., Hsu, D., and M. Lague, "Post-Repair Loss RLE Report Block Type for RTP Control Protocol (RTCP) Extended Reports (XRs)", RFC 5725, February 2010.February 2010[RFC4588]RFC 4588Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R. Hakenberg, "RTP Retransmission Payload Format", RFC 4588, July 2006.July 2006[RFC5109]RFC 5109Li, A., Ed., "RTP Payload Format for Generic Forward Error Correction", RFC 5109, December 2007.December 2007[RFC7202]RFC 7202Perkins, C. and M. Westerlund, "Securing the RTP Framework: Why RTP Does Not Mandate a Single Media Security Solution", RFC 7202, April 2014.April 2014