One document matched: draft-ietf-xrblock-rtcp-xr-discard-15.xml
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<front>
<title abbrev="RTCP XR Discard">RTP Control Protocol (RTCP) Extended
Report (XR) Block for Discard Count metric Reporting</title>
<author fullname="Alan Clark" initials="A." surname="Clark">
<organization abbrev="Telchemy">Telchemy Incorporated</organization>
<address>
<postal>
<street>2905 Premiere Parkway, Suite 280</street>
<city>Duluth</city>
<region>GA</region>
<code>30097</code>
<country>USA</country>
</postal>
<email>alan.d.clark@telchemy.com</email>
</address>
</author>
<author fullname="Glen Zorn" initials="G." surname="Zorn">
<organization>Network Zen</organization>
<address>
<postal>
<street>77/440 Soi Phoomjit, Rama IV Road</street>
<street>Phra Khanong, Khlong Toie</street>
<city>Bangkok</city>
<code>10110</code>
<country>Thailand</country>
</postal>
<phone>+66 (0) 87 502 4274</phone>
<email>gwz@net-zen.net</email>
</address>
</author>
<author fullname="Qin Wu" initials="Q." surname="Wu">
<organization>Huawei</organization>
<address>
<postal>
<street>101 Software Avenue, Yuhua District</street>
<city>Nanjing</city>
<region>Jiangsu</region>
<code>210012</code>
<country>China</country>
</postal>
<email>sunseawq@huawei.com</email>
</address>
</author>
<date year="2013" />
<area>Real-time Applications and Infrastructure Area</area>
<workgroup>Audio/Video Transport Working Group</workgroup>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>Real Time Control Protocol</keyword>
<abstract>
<t>This document defines an RTP Control Protocol(RTCP) Extended Report
(XR) Block that allows the reporting of a simple discard count metric
for use in a range of RTP applications.</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<section title="Discard Count Report Block">
<t>This document defines a new block type to augment those defined in
<xref target="RFC3611"></xref> for use in a range of RTP applications.
The new block type supports the reporting of the number of packets
which are received correctly but are never played out, typically
because they arrive too late to be played out (buffer underflow) or
too early (buffer overflow). The metric is applicable both to systems
which use packet loss repair techniques (such as forward error
correction <xref target="RFC5109"></xref> or retransmission <xref
target="RFC4588"></xref>) and to those which do not.</t>
<t>This metric is useful for identifying the existence, and
characterizing the severity, of a packet transport problem which may
affect users' perception of a service delivered over RTP.</t>
<t>This block may be used in conjunction with <xref
target="BGDISCARD"></xref> which provides additional information on
the pattern of discarded packets. However the metric in <xref
target="BGDISCARD"></xref> may be used independently of the metrics in
this block.</t>
<t>When a Discard Count Metrics Block is sent together with a Burst
Gap Discard Metrics Block (defined in <xref target="BGDISCARD"></xref>
) to the media sender or RTP based network management system, the
information carried in the Discard Count Metrics Block and the Burst
Gap Discard Metrics Block allows systems receiving the blocks to
calculate burst gap summary statistics (e.g., the gap discard
rate).</t>
<t>The metric belongs to the class of transport-related end system
metrics defined in <xref target="RFC6792"></xref>.</t>
</section>
<section title="RTCP and RTCP XR Reports">
<t>The use of RTCP for reporting is defined in <xref
target="RFC3550"></xref>. <xref target="RFC3611"></xref> defined an
extensible structure for reporting using an RTCP Extended Report (XR).
This document defines a new Extended Report block for use with <xref
target="RFC3550"></xref> and <xref target="RFC3611"></xref>.</t>
</section>
<section title="Performance Metrics Framework">
<t>The Performance Metrics Framework <xref target="RFC6390"></xref>
provides guidance on the definition and specification of performance
metrics. The RTP Monitoring Architectures <xref
target="RFC6792"></xref> provides guideline for reporting block format
using RTCP XR. The metrics block described in this document are in
accordance with the guidelines in <xref target="RFC6390"></xref> and
<xref target="RFC6792"></xref>.</t>
</section>
<section title="Applicability">
<t>This metric is believed to be applicable to a large class of RTP
applications which use a de-jitter buffer [RFC5481].</t>
<t>Discards due to late or early arriving packets affects user
experience. The reporting of discards alerts senders and other
receivers to the need to adjust their transmission or reception
strategies. The reports allow network managers to diagnose these user
experience problems.</t>
<t>The ability to detect duplicate packets can be used by managers to
detect network layer or sender behavior which may indicate network or
device issues. Based on the reports, these issues may be addressed
prior to any impact on user experience.</t>
</section>
</section>
<section title="Terminology">
<section title="Standards Language">
<t>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 <xref
target="RFC2119">RFC 2119</xref>.</t>
<t>In addition, the following terms are defined:</t>
<t><list style="hanging">
<t hangText="Received, Lost and Discarded"><vspace
blankLines="1" />A packet shall be regarded as lost if it fails to
arrive within an implementation-specific time window. A packet
that arrives within this time window but is either too early to be
played out or too late to be played out or thrown away before
playout due to packet duplication or redundancy shall be regarded
as discarded. A packet shall not be regarded as discarded if it
arrives within this time window but is dropped during decoding by
some higher layer decoder, e.g., due to a decoding error. A packet
shall be classified as one of received (or OK), discarded or lost.
The Discard Count Metric counts only discarded packets. The metric
"cumulative number of packets lost" defined in <xref
target="RFC3550"></xref> reports a count of packets lost from the
media stream (single Synchronization source (SSRC) within single
RTP session). Similarly the metric "number of packets discarded"
reports a count of packets discarded from the media stream (single
SSRC within single RTP session) arriving at the receiver. Another
metric defined in <xref target="RFC5725"></xref> is available to
report on packets which are not recovered by any repair techniques
which may be in use. <vspace blankLines="1" /></t>
</list></t>
</section>
</section>
<section title="Discard Count Metric Report Block">
<t>Metrics in this block report on the number of packets discarded in
the stream arriving at the RTP end system. The measurement of these
metrics is made at the receiving end of the RTP stream. Instances of
this metrics block refer by SSRC to the separate auxiliary Measurement
Information Block <xref target="RFC6776"></xref> which describes
measurement Intervals in use. This metrics block relies on the
measurement interval in the Measurement Information Block indicating the
span of the report and MUST be sent in the same compound RTCP packet as
the measurement information block. If the measurement interval is not
received in the same compound RTCP packet as this metrics block, this
metrics block MUST be discarded.</t>
<section title="Report Block Structure">
<t><figure title="Figure 1: Report Block Structure">
<artwork>
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT=PDC | I |DT | resv.| block length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| discard count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork>
</figure></t>
</section>
<section title="Definition of Fields in Discard Count Metric Report Block">
<t><list style="hanging">
<t hangText="Block type (BT): 8 bits"><vspace blankLines="1" />A
Discard Count Metric Report Block is identified by the constant
PDC.<vspace blankLines="1" /> [Note to RFC Editor: please replace
PDC with the IANA provided RTCP XR block type for this block.]
<vspace blankLines="1" /></t>
<t hangText="Interval Metric Flag (I): 2 bits"><vspace
blankLines="1" />This field indicates whether the reported metric
is an interval, cumulative, or sampled metric <xref
target="RFC6792"></xref>: <list>
<t>I=10: Interval Duration - the reported value applies to the
most recent measurement interval duration between successive
metrics reports.</t>
<t>I=11: Cumulative Duration - the reported value applies to
the accumulation period characteristic of cumulative
measurements.</t>
<t>I=01: Sampled Value - the reported value is a sampled
instantaneous value.</t>
</list>In this document, the Discard Count Metric can only be
measured over definite intervals, and cannot be sampled.
Accordingly, the value I=01, indicating a sampled value, MUST NOT
be sent, and MUST be discarded when received. In addition, the
value I=00 is reserved and also MUST NOT be sent, and MUST be
discarded when received. <vspace blankLines="1" /></t>
<t hangText="Discard Type (DT): 2bits"><vspace
blankLines="1" />This field is used to identify the discard type
used in this report block. The discard type is defined as
follows:<list>
<t>00: Report packet discarded or being thrown away before
playout due to packets duplication.</t>
<t>01: Report packet discarded due to too early to be played
out.</t>
<t>10: Report packet discarded due to too late to be played
out.</t>
</list><vspace blankLines="1" />The value DT=11 is reserved for
future definition and MUST NOT be Sent,and MUST be discarded when
received.<vspace blankLines="1" />An endpoint MAY report any
combination of discard types in each reporting interval by
including several Discard Count Metric Report Blocks in a single
RTCP XR packet.<vspace blankLines="1" />Some systems send
duplicate RTP packets for robustness or error resilience. This is
NOT RECOMMENDED since it breaks RTCP packet statistics. If
duplication is desired for error resilience, the mechanism
described in <xref target="RTPDUP"></xref> can be used, since this
will not cause breakage of RTP streams or RTCP statistics.<vspace
blankLines="1" /></t>
<t hangText="Reserved (resv): 4 bits"><vspace
blankLines="1" />These bits are reserved. They MUST be set to zero
by senders and ignored by receivers (See RFC6709 section 4.2).
<vspace blankLines="1" /></t>
<t hangText="block length: 16 bits"><vspace blankLines="1" />The
length of this report block in 32-bit words, minus one, in
accordance with the definition in <xref target="RFC3611"></xref>.
This field MUST be set to 2 to match the fixed length of the
report block. The block MUST be discarded if the block length is
set to a different value. <vspace blankLines="1" /></t>
<t hangText="SSRC of source: 32 bits"><vspace blankLines="1" />As
defined in Section 4.1 of <xref target="RFC3611"></xref>.<vspace
blankLines="1" /></t>
<t hangText="discard count"><vspace blankLines="1" />Number of
packets discarded over the period (Interval or Cumulative) covered
by this report. <vspace blankLines="1" />The measured value is
unsigned value. If the measured value exceeds 0xFFFFFFFD, the
value 0xFFFFFFFE MUST be reported to indicate an over-range
measurement. If the measurement is unavailable, the value
0xFFFFFFFF MUST be reported. <vspace blankLines="1" />Note that
the number of packets expected in the period associated with this
metric (whether interval or cumulative) is available from the
difference between a pair of extended sequence numbers in the
Measurement Information block <xref target="RFC6776"></xref>, so
need not be repeated in this block. <vspace blankLines="1" /></t>
</list></t>
</section>
</section>
<section title="SDP Signaling">
<t>[RFC3611] defines the use of SDP (Session Description Protocol) <xref
target="RFC4566"></xref> for signaling the use of XR blocks. However XR
blocks MAY be used without prior signaling (see section 5 of
RFC3611).</t>
<section title="SDP rtcp-xr-attrib Attribute Extension">
<t>This section augments the SDP <xref target="RFC4566"></xref>
attribute "rtcp-xr" defined in <xref target="RFC3611"></xref> by
providing an additional value of "xr-format" to signal the use of the
report block defined in this document.<figure>
<artwork>
xr-format =/ xr-pdc-block
xr-pdc-block = "pkt-discard-count"
</artwork>
</figure></t>
</section>
<section title="Offer/Answer Usage">
<t>When SDP is used in offer-answer context, the SDP Offer/Answer
usage defined in <xref target="RFC3611"></xref> for unilateral
"rtcp-xr" attribute parameters applies. For detailed usage of
Offer/Answer for unilateral parameter, refer to section 5.2 of <xref
target="RFC3611"></xref>.</t>
</section>
</section>
<section title="IANA Considerations">
<t>New block types for RTCP XR are subject to IANA registration. For
general guidelines on IANA considerations for RTCP XR, refer to <xref
target="RFC3611"></xref>.</t>
<section title="New RTCP XR Block Type value">
<t>This document assigns the block type value PDC in the IANA " RTP
Control Protocol Extended Reports (RTCP XR) Block Type Registry " to
the "Discard Count Metrics Block".</t>
<t>[Note to RFC Editor: please replace PDC with the IANA provided RTCP
XR block type for this block.]</t>
</section>
<section title="New RTCP XR SDP Parameter">
<t>This document also registers a new parameter "pkt-discard-count" in
the " RTP Control Protocol Extended Reports (RTCP XR) Session
Description Protocol (SDP) Parameters Registry ".</t>
</section>
<section title="Contact information for registrations">
<t>The following contact information is provided for all registrations
in this document:<figure>
<artwork>
Qin Wu (sunseawq@huawei.com)
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
</artwork>
</figure><vspace blankLines="1" /></t>
</section>
</section>
<section title="Security Considerations">
<t>In some situations, returning very detailed error information
(e.g.,over-range measurement or measurement unavailable) using this
report block can provide an attacker with insight into the security
processing. Where this is a concern, the implementation should apply
authentication to this report block. This can be achieved by using the
AVPF profile together with the Secure RTP profile as defined in
[RFC3711]; as a prerequisite, an appropriate combination of those two
profiles (an "SAVPF") is being specified [RFC5124].</t>
<t>Besides this, it is believed that this proposed RTCP XR report block
introduces no new security considerations beyond those described in
<xref target="RFC3611"></xref>. This block does not provide per-packet
statistics so the risk to confidentiality documented in Section 7,
paragraph 3 of <xref target="RFC3611"></xref> does not apply.</t>
</section>
<section title="Contributors">
<t>Geoff Hunt wrote the initial draft of this document.</t>
</section>
<section title="Acknowledgments">
<t>The authors gratefully acknowledge reviews and feedback provided by
Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, Claus
Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, Tom Hock,
Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, Mohamed Mostafa,
Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi Raviraj, Albrecht
Schwarz, Tom Taylor, and Hideaki Yamada, Kevin Gross, Varun Singh,
Claire Bi, Roni Even, Dan Romascanu and Jonathan Lennox.</t>
</section>
</middle>
<back>
<references title="Normative References">
<reference anchor="RFC2119">
<front>
<title abbrev="RFC Key Words">Key words for use in RFCs to Indicate
Requirement Levels</title>
<author fullname="Scott Bradner" initials="S." surname="Bradner">
<organization>Harvard University</organization>
<address>
<postal>
<street>1350 Mass. Ave.</street>
<street>Cambridge</street>
<street>MA 02138</street>
</postal>
<phone>- +1 617 495 3864</phone>
<email>sob@harvard.edu</email>
</address>
</author>
<date month="March" year="1997" />
<area>General</area>
<keyword>keyword</keyword>
<abstract>
<t>In many standards track documents several words are used to
signify the requirements in the specification. These words are
often capitalized. This document defines these words as they
should be interpreted in IETF documents. Authors who follow these
guidelines should incorporate this phrase near the beginning of
their document: <list>
<t>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 RFC 2119.</t>
</list></t>
<t>Note that the force of these words is modified by the
requirement level of the document in which they are used.</t>
</abstract>
</front>
</reference>
<reference anchor="RFC3611">
<front>
<title>RTP Control Protocol Extended Reports (RTCP XR)</title>
<author fullname="T. Friedman" initials="T." surname="Friedman">
<organization></organization>
</author>
<author fullname="R. Caceres" initials="R." surname="Caceres">
<organization></organization>
</author>
<author fullname="A. Clark" initials="A." surname="Clark">
<organization></organization>
</author>
<date month="November" year="2003" />
<abstract>
<t>This document defines the Extended Report (XR) packet type for
the RTP Control Protocol (RTCP), and defines how the use of XR
packets can be signaled by an application if it employs the
Session Description Protocol (SDP). XR packets are composed of
report blocks, and seven block types are defined here. The purpose
of the extended reporting format is to convey information that
supplements the six statistics that are contained in the report
blocks used by RTCP's Sender Report (SR) and Receiver Report (RR)
packets. Some applications, such as multicast inference of network
characteristics (MINC) or voice over IP (VoIP) monitoring, require
other and more detailed statistics. In addition to the block types
defined here, additional block types may be defined in the future
by adhering to the framework that this document provides.</t>
</abstract>
</front>
</reference>
<reference anchor="RFC4566">
<front>
<title>SDP: Session Description Protocol</title>
<author fullname="M. Handley" initials="M." surname="Handley">
<organization></organization>
</author>
<author fullname="V. Jacobson" initials="V." surname="Jacobson">
<organization></organization>
</author>
<author fullname="C. Perkins" initials="C." surname="Perkins">
<organization></organization>
</author>
<date month="July" year="2006" />
<abstract>
<t>This memo defines the Session Description Protocol (SDP). SDP
is intended for describing multimedia sessions for the purposes of
session announcement, session invitation, and other forms of
multimedia session initiation. [STANDARDS-TRACK]</t>
</abstract>
</front>
</reference>
<reference anchor="RFC3550">
<front>
<title>RTP: A Transport Protocol for Real-Time Applications</title>
<author fullname="Henning Schulzrinne" initials="H."
surname="Schulzrinne">
<organization>Columbia University</organization>
</author>
<date month="July" year="2003" />
</front>
<seriesInfo name="RFC" value="3550" />
<format type="TXT" />
</reference>
<reference anchor="RFC6776">
<front>
<title>Measurement Identity and information Reporting using SDES
item and XR Block</title>
<author fullname="Geoff Hunt" initials="G." surname="Hunt">
<organization></organization>
</author>
<date month="October" year="2012" />
</front>
<seriesInfo name="RFC" value="6776" />
<format type="TXT" />
</reference>
<reference anchor="RFC6709">
<front>
<title>Design Considerations for Protocol Extensions</title>
<author fullname="B.Carpenter" initials="B." surname="Carpenter">
<organization></organization>
</author>
<author fullname="B.Aboba" initials="B." surname="Aboba">
<organization></organization>
</author>
<author fullname="S.Cheshire" initials="S." surname="Cheshire">
<organization></organization>
</author>
<date month="September" year="2012" />
</front>
<seriesInfo name="RFC" value="6709" />
<format type="TXT" />
</reference>
</references>
<references title="Informative References">
<reference anchor="RFC6792">
<front>
<title>Monitoring Architectures for RTP</title>
<author fullname="Qin Wu" initials="Q." surname="Wu">
<organization></organization>
</author>
<date month="November" year="2012" />
</front>
<seriesInfo name="RFC" value="6792" />
<format type="TXT" />
</reference>
<reference anchor="BGDISCARD">
<front>
<title>RTCP XR Report Block for Burst Gap Discard metric
Reporting</title>
<author fullname="Geoff Hunt" initials="G." surname="Hunt">
<organization></organization>
</author>
<date month="April" year="2013" />
</front>
<seriesInfo name="ID"
value="draft-ietf-xrblock-rtcp-xr-burst-gap-discard-14" />
<format type="TXT" />
</reference>
<reference anchor="RTPDUP">
<front>
<title>Duplicating RTP Streams</title>
<author fullname="Ali Begen " initials="A." surname="Begen">
<organization></organization>
</author>
<author fullname="Colin Perkins" initials="C." surname="Perkins">
<organization></organization>
</author>
<date month="March" year="2013" />
</front>
<seriesInfo name="ID" value="draft-ietf-avtext-rtp-duplication-02" />
<format type="TXT" />
</reference>
<reference anchor="RFC6390">
<front>
<title>Framework for Performance Metric Development</title>
<author fullname="Alan Clark" initials="A." surname="Clark">
<organization></organization>
</author>
<author fullname="Benoit Claise " initials="B." surname="Claise">
<organization></organization>
</author>
<date month="October" year="2011" />
</front>
<seriesInfo name="RFC" value="6390" />
</reference>
<reference anchor="RFC5725">
<front>
<title>RTCP XR Report Block for Post-Repair Loss metric
Reporting</title>
<author fullname="Ali Begen" initials="A." surname="Begen">
<organization></organization>
</author>
<date month="February" year="2010" />
</front>
<seriesInfo name="RFC" value="5725" />
</reference>
<reference anchor="RFC4588">
<front>
<title>RTP Retransmission Payload Format</title>
<author fullname="J.Rey" initials="J." surname="Rey">
<organization></organization>
</author>
<date month="July" year="2006" />
</front>
<seriesInfo name="RFC" value="4588" />
<format type="TXT" />
</reference>
<reference anchor="RFC5109">
<front>
<title>RTP Payload Format for Generic Forward Error
Correction</title>
<author fullname="A.Li" initials="A." surname="Li">
<organization></organization>
</author>
<date month="July" year="2006" />
</front>
<seriesInfo name="RFC" value="5109" />
<format type="TXT" />
</reference>
</references>
<section title="Metrics represented using RFC6390 Template">
<t>RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC
number, when assigned.</t>
<t><list style="letters">
<t>Number of packets discarded Metric<vspace blankLines="1" /><list
style="symbols">
<t>Metric Name: Number of RTP packets discarded Metric<vspace
blankLines="1" /></t>
<t>Metric Description: Number of RTP packets discarded over the
period covered by this report.<vspace blankLines="1" /></t>
<t>Method of Measurement or Calculation: See section 3.2, number
of packets discarded definition [RFCXXXX].<vspace
blankLines="1" /></t>
<t>Units of Measurement: See section 3.2, number of packets
discarded definition [RFCXXXX].<vspace blankLines="1" /></t>
<t>Measurement Point(s) with Potential Measurement Domain: See
section 3, 1st paragraph [RFCXXXX]. <vspace
blankLines="1" /></t>
<t>Measurement Timing: See section 3, 1st paragraph [RFCXXXX]
for measurement timing and section 3.2 [RFCXXXX] for Interval
Metric flag. <vspace blankLines="1" /></t>
<t>Use and applications: See section 1.4 [RFCXXXX].<vspace
blankLines="1" /></t>
<t>Reporting model: See RFC3611.<vspace blankLines="1" /></t>
</list></t>
</list></t>
</section>
<section title="Change Log">
<t>Note to the RFC-Editor: please remove this section prior to
publication as an RFC.</t>
<section title="draft-ietf-xrblock-rtcp-xr-discard-14">
<t>The following are the major changes compared to previous
version:<list style="symbols">
<t>Editorial changes to paragraph 4 of section 1.1.</t>
</list></t>
</section>
<section title="draft-ietf-xrblock-rtcp-xr-discard-13">
<t>The following are the major changes compared to previous
version:<list style="symbols">
<t>Some editorial changes to get in line with burst gap
drafts.</t>
</list></t>
</section>
<section title="draft-ietf-xrblock-rtcp-xr-discard-12">
<t>The following are the major changes compared to previous
version:<list style="symbols">
<t>Incorporate some changes to burst gap draft that applies to
this document.</t>
<t>Use RFC6390 template to the metrics in the appendix.</t>
</list></t>
</section>
</section>
</back>
</rfc>
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