One document matched: draft-ietf-xrblock-rtcp-xr-burst-gap-loss-01.xml
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<front>
<title abbrev="RTCP XR Burst/Gap Loss">RTCP XR Report Block for Burst/Gap
Loss metric Reporting</title>
<author fullname="Geoff Hunt" initials="G." surname="Hunt">
<organization>Unaffiliated</organization>
<address>
<email>r.geoff.hunt@gmail.com</email>
</address>
</author>
<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="Sunshine Zhang" initials="S." role="editor"
surname="Zhang">
<organization abbrev="STTRI">Shanghai Research Institure of China
Telecom Corporation Limited</organization>
<address>
<postal>
<street>No.1835,South Pudong Road</street>
<city>Shanghai</city>
<code>200122</code>
<country>China</country>
</postal>
<email>zhangyx@sttri.com.cn</email>
</address>
</author>
<author fullname="Jing Zhao" initials="J." surname="Zhao">
<organization abbrev="STTRI">Shanghai Research Institure of China
Telecom Corporation Limited</organization>
<address>
<postal>
<street>No.1835,South Pudong Road</street>
<city>Shanghai</city>
<code>200122</code>
<country>China</country>
</postal>
<email>zhaojing@sttri.com.cn</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 month="January" year="2012" />
<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 RTCP XR Report Block that allows the
reporting of Burst and Gap Loss metrics for use in a range of RTP
applications.</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<section title="Burst and Gap Loss Report Block">
<t>This draft 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 proportion of packets
lost by the network. The losses during loss bursts are reported,
together with the number of bursts and additional data allowing the
calculation of statistical parameters (mean and variance) of the
distribution of burst lengths. Some uses of these metrics depend on
the availability of the metric "cumulative number of packets lost"
from RTCP <xref target="RFC3550"></xref>.</t>
<t>This block provides information on transient IP problems. Burst/Gap
metrics are typically used in Cumulative reports however MAY be used
in Interval reports. The burstiness of packet loss affects user
experience, may influence any sender strategies to mitigate the
problem, and may also have diagnostic value.</t>
<t>The metric belongs to the class of transport-related terminal
metrics defined in <xref target="MONARCH"></xref> (work in
progress).</t>
<t>The definitions of Burst, Gap, Loss and Discard are consistent with
definitions in <xref target="RFC3611"></xref>. To accommodate the
range of jitter buffer algorithms and packet discard logic that may be
used by implementors, the method used to distinguish between bursts
and gaps may be an equivalent method to that defined in <xref
target="RFC3611"></xref>. The method used SHOULD produce the same
result as that defined in [RFC3611] for conditions of burst packet
loss, but MAY produce different results for conditions of time varying
jitter.</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 draft defines a new Extended Report block that MUST be used as
defined in <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. Metrics described in this draft either reference external
definitions or define metrics generally in accordance with the
guidelines in <xref target="RFC6390"></xref>.</t>
</section>
<section title="Applicability">
<t>These metrics are applicable to a range of RTP applications.</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 too early or late to
be played out shall be regarded as discarded. A packet shall be
classified as one of received (or OK), discarded or lost. <vspace
blankLines="1" /></t>
<t hangText="Bursts and Gaps"><vspace blankLines="1" />The terms
Burst and Gap are used in a manner consistent with that of RTCP XR
[RFC3611]. RTCP XR views a RTP stream as being divided into
bursts, which are periods during which the loss rate is high
enough to cause noticeable quality degradation (generally over 5
percent loss rate), and gaps, which are periods during which lost
packets are infrequent and hence quality is generally acceptable.
<vspace blankLines="1" /></t>
</list></t>
</section>
</section>
<section title="Burst/Gap Loss Block">
<t>Metrics in this block report on Burst/Gap Loss in the stream arriving
at the RTP system.</t>
<section title="Report Block Structure">
<t>Burst/Gap Loss metrics block<figure
title="Figure 1: Report Block Structure">
<artwork>
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT=NBGL |I|C| resv. | block length = 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSRC of Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Threshold | Sum of Burst Durations (ms) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packets Lost in Bursts | Total... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...Packets expected in bursts | Number of bursts | Sum of|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...Squares of Burst Durations (ms-squared) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork>
</figure></t>
</section>
<section title="Definition of Fields in Burst/Gap Loss Report Block">
<t><list style="hanging">
<t hangText="Block type (BT): 8 bits"><vspace blankLines="1" />A
Burst/Gap Loss Report Block is identified by the constant
NBGL.<vspace blankLines="1" />[Note to RFC Editor: please replace
NBGL with the IANA provided RTCP XR block type for this
block.]<vspace blankLines="1" /></t>
<t hangText="Interval Metric flag (I): 1 bit"><vspace
blankLines="1" /> This field is used to indicate whether the
Packet Delay Variation metrics block is an Interval or a
Cumulative report, that is, whether the reported values apply to
the most recent measurement interval duration between successive
metrics reports (I=1) (the Interval Duration) or to the
accumulation period characteristic of cumulative measurements
(I=0) (the Cumulative Duration). <vspace blankLines="1" /></t>
<t
hangText=" Loss and Discard Combination flag (C): 1 bit"><vspace
blankLines="1" />The 'C' flag is used to indicate whether
combining loss/discard report is needed. This field MUST be set to
'1' if the burst gap loss report is present in conjunction with
the burst gap discard report in the same compound RTCP packet and
MUST be set to '0' otherwise. If the burst gap discard is not sent
with burst gap loss, then the receiver should discard burst gap
loss with 'C' flag set to 1. If the 'C' flag is set to 0, then
receiver should not discard burst gap loss metric block when burst
gap discard is not received. <vspace blankLines="1" /></t>
<t hangText="Reserved (resv): 7 bits"><vspace
blankLines="1" />These bits are reserved. They SHOULD be set to
zero by senders and MUST be ignored by receivers.<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. For the
Delay block, the block length is equal to 5.<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="Threshold: 8 bits"><vspace blankLines="1" />The
Threshold is equivalent to Gmin in <xref target="RFC3611"></xref>,
i.e. the number of successive packets that must be received prior
to and following a lost frame in order for this lost frame to be
regarded as part of a gap. <vspace blankLines="1" /></t>
<t hangText="Sum of Burst Durations (ms): 24 bits"><vspace
blankLines="1" />The total duration of bursts of lost frames in
the period of the report (Interval or Cumulative). <vspace
blankLines="1" />If the measured value exceeds 0xFFFFFD, the value
0xFFFFFE SHOULD be reported to indicate an over-range measurement.
If the measurement is unavailable, the value 0xFFFFFF SHOULD be
reported. <vspace blankLines="1" /></t>
<t hangText="Packets lost in bursts: 24 bits"><vspace
blankLines="1" />The total number of packets lost during loss
bursts.<vspace blankLines="1" />If the measured value exceeds
0xFFFFFD, the value 0xFFFFFE SHOULD be reported to indicate an
over-range measurement. If the measurement is unavailable, the
value 0xFFFFFF SHOULD be reported. <vspace blankLines="1" /></t>
<t hangText="Total packets expected in bursts: 24 bits"><vspace
blankLines="1" />The total number of packets expected during loss
bursts (that is, the sum of received packets and lost packets).
<vspace blankLines="1" />If the measured value exceeds 0xFFFFFD,
the value 0xFFFFFE SHOULD be reported to indicate an over-range
measurement. If the measurement is unavailable, the value 0xFFFFFF
SHOULD be reported. <vspace blankLines="1" /></t>
<t hangText="Number of bursts: 16 bits"><vspace
blankLines="1" />The number of bursts in the period of the report
(Interval or Cumulative). <vspace blankLines="1" />If the measured
value exceeds 0xFFFD, the value 0xFFFE SHOULD be reported to
indicate an over-range measurement. If the measurement is
unavailable, the value 0xFFFF SHOULD be reported. <vspace
blankLines="1" /></t>
<t
hangText="Sum of Squares of Burst Durations (ms-squared): 36 bits"><vspace
blankLines="1" />The sum of the squares of burst durations (where
individual burst durations are expressed in ms) over in the period
of the report (Interval or Cumulative). The units for this
quantity are milliseconds-squared. <vspace blankLines="1" />If the
measured value exceeds 0xFFFFFFFFD, the value 0xFFFFFFFFE SHOULD
be reported to indicate an over-range measurement. If the
measurement is unavailable, the value 0xFFFFFFFFF SHOULD be
reported. <vspace blankLines="1" /></t>
</list></t>
</section>
<section title="Derived metrics based on reported metrics">
<t>The metrics described here are intended to be used as described in
this section, in conjunction with information from the Measurement
Information block <xref target="MEASID"></xref> (which MUST be present
in the same RTCP packet as the Burst/Gap Loss block) and also with the
metric "cumulative number of packets lost" provided in standard RTCP
<xref target="RFC3550"></xref>.</t>
<t>These metrics provides information relevant to statistical
parameters, including:<list style="symbols">
<t>The fraction of packets lost during bursts (i.e., Burst Loss
Rate in <xref target="SUMSTAT"></xref>)</t>
<t>The fraction of packets lost during gaps (i.e., Gap Loss Rate
in <xref target="SUMSTAT"></xref>)</t>
<t>burst duration mean <xref target="SUMSTAT"></xref></t>
<t>burst duration variance <xref target="SUMSTAT"></xref></t>
</list></t>
<t>The details on calculation these parameters in the metrics are
described in <xref target="SUMSTAT"></xref>.</t>
</section>
</section>
<section title="Considerations for Voice-over-IP applications">
<t>This metric block is applicable to a broad range of RTP applications.
Where the metric is used with a Voice-overIP (VoIP) application, the
following considerations apply.</t>
<t>RTCP XR views a call as being divided into bursts, which are periods
during which the loss rate is high enough to cause noticeable call
quality degradation (generally over 5 percent loss rate), and gaps,
which are periods during which lost packets are infrequent and hence
call quality is generally acceptable.</t>
<t>If Voice Activity Detection is used the Burst and Gap Duration shall
be determined as if silence frames had been sent, i.e. a period of
silence in excess of Gmin frames MUST terminate a burst condition.</t>
<t>The recommended value for the threshold Gmin in [RFC3611] results in
a Burst being a period of time during which the call quality is degraded
to a similar extent to a typical PCM Severely Errored Second <xref
target="PSES"></xref>.</t>
</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. XR blocks
MAY be used without prior signaling.</t>
<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>
rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF
(defined in [RFC3611])
xr-format =/ xr-bgl-block
xr-bgl-block = "brst-gap-loss"
</artwork>
</figure></t>
</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 NDEL in the IANA "RTCP
XR Block Type Registry" to the "Burst/Gap Loss Metrics Block".</t>
<t>[Note to RFC Editor: please replace NBGL 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 "brst-gap-loss" in the
"RTCP XR SDP Parameters Registry".</t>
</section>
<section title="Contact information for registrations">
<t><figure>
<artwork>
The contact information for the registrations is:
Geoff Hunt (r.geoff.hunt@gmail.com)
Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United
Kingdom
</artwork>
</figure><vspace blankLines="1" /></t>
</section>
</section>
<section title="Security Considerations">
<t>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>The authors gratefully acknowledge the comments and contributions
made 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.</t>
</section>
<section title="Changes from previous version">
<t>Changed BNF for SDP following Christian Groves' and Tom Taylor's
comments (4th and 5th May 2009), now aligned with RFC 5234 section 3.3
"Incremental Alternatives".</t>
<t>Updated references.</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>
</references>
<references title="Informative References">
<reference anchor="DISCARD">
<front>
<title>RTCP XR Report Block for Discard metric Reporting</title>
<author fullname="Geoff Hunt" initials="G." surname="Hunt">
<organization></organization>
</author>
<date month="May" year="2009" />
</front>
<seriesInfo name="ID" value="draft-ietf-rtcp-xr-discard-02" />
<format type="TXT" />
</reference>
<reference anchor="SUMSTAT">
<front>
<title>RTCP XR for Summary Statistics Metrics Reporting</title>
<author fullname="Glen Zorn" initials="G." surname="Zorn">
<organization></organization>
</author>
<date month="October" year="2011" />
</front>
<seriesInfo name="ID" value="draft-zorn-xrblock-rtcp-xr-al-stat-03" />
<format type="TXT" />
</reference>
<reference anchor="MEASID">
<front>
<title>Measurement Identity and information Reporting using SDES
item and XR Block</title>
<author fullname="Qin Wu" initials="Q." surname="Wu">
<organization></organization>
</author>
<date month="October" year="2011" />
</front>
<seriesInfo name="ID"
value="draft-ietf-xrblock-rtcp-xr-meas-identity-01" />
<format type="TXT" />
</reference>
<reference anchor="MONARCH">
<front>
<title>Monitoring Architectures for RTP</title>
<author fullname="Geoff Hunt" initials="G." surname="Hunt">
<organization></organization>
</author>
<date month="August" year="2011" />
</front>
<seriesInfo name="ID" value="draft-ietf-avtcore-monarch-04" />
<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="July" year="2011" />
</front>
<seriesInfo name="RFC" value="6390" />
</reference>
<reference anchor="PSES">
<front>
<title>URL</title>
<author>
<organization></organization>
</author>
<date month="October" year="2011" />
</front>
<seriesInfo name=""
value="http://www.its.bldrdoc.gov/projects/devglossary/_severely_errored_second.html" />
</reference>
</references>
</back>
</rfc>
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