One document matched: draft-ietf-avt-rtcp-xr-discard-02.xml

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    <front>
        <title abbrev='RTCP XR Discard'>RTCP XR Report Block for Discard metric Reporting</title>
        <author initials='G.' surname='Hunt' fullname='Geoff Hunt'>
            <organization abbrev='BT'>BT</organization>
		<address>
	    <postal>
        	<street>Orion 2 PP3</street>
        	<street>Adastral Park</street>
        	<street>Martlesham Heath</street>
        	<city>Ipswich</city> <region>Suffolk</region>
        	<code>IP5 3RE</code>
        	<country>United Kingdom</country>
    	    </postal>
	    <phone>+44 1473 651704</phone>
	    <email>geoff.hunt@bt.com</email>
	    </address>
        </author>
        <author initials='A.' surname='Clark' fullname='Alan 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>
        <date month='May' year='2009' />
       <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 a simple discard count metric for use in a range of RTP applications.
        </t>
        </abstract>
    </front>

    <middle>

<section anchor='intro' title="Introduction">
<section anchor='intro1' title="Discard Report Block">
<t>
   This draft defines a new block type to augment those defined
   in <xref target='RFC3611'/> 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'/>
 or retransmission <xref target='RFC4588'/>) and to those which do not.
</t>
<t>
This metric is useful for identifying the existence, and characterising the severity, of a packet transport 
problem 
which may affect users' perception of a service delivered over RTP.
</t>
<t>
The metric belongs to the class of transport-related terminal metrics defined in [MONARCH] (work in progress).
</t>
<t>
Instances of this Metrics Block refer by tag to the separate auxiliary Measurement Identity block 
<xref target='MEASIDENT'/> which contains information 
such as the SSRC of the measured stream, and RTP sequence numbers and time intervals indicating the span of the 
report.
</t>
<t>
The Measurement Identity block provides extended sequence numbers for the beginning and end of both Interval and 
Cumulative reporting periods. This allows systems receiving the report to calculate the number of packets 
expected.
</t>
</section>
<section anchor='intro2' title="RTCP and RTCP XR Reports">
<t>
   The use of RTCP for reporting is defined in <xref target='RFC3550'/>. 
   <xref target='RFC3611'/> 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'/> and <xref target='RFC3611'/>.
</t>
</section>
<section anchor='intro3' title="Performance Metrics Framework">
<t>
   The Performance Metrics Framework <xref target='PMOLFRAME'/> 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='PMOLFRAME'/>.
</t>
</section>
<section anchor='intro4' title="Applicability">
<t>
This metric is believed to be applicable to a large class of RTP applications which use a jitter buffer.
</t>
</section>
</section>

<section anchor='definitions' title='Definitions'>

<t>Received, Lost and Discarded</t>
<t><list style='empty'><t>
   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. The Discard Metric counts only discarded packets. 
The metric "cumulative number of packets lost" defined in <xref target='RFC3550'/> reports a count of packets lost from the 
media stream (single 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='POSTREPAIRLOSS'/> is available to report on packets which 
are not recovered by any repair techniques which may be in use. 
</t>
<t>
For Voice-over-IP applications of the metric, if Voice Activity Detection 
is used then the proportion of packets lost
   and discarded shall be determined based on transmitted packets, i.e.
   packets that contained silence and were not transmitted shall not be
   considered, because they do not form part of the RTP sequence.
</t></list></t>
</section>

<section anchor='blockdef' title="Discard Metric Report Block">
<section anchor='blockdef1' title="Report Block Structure">
    <figure anchor='blockdata' title="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=ND     |I| tag | resv  |       block length=1          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   number of packets discarded                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        </artwork>
    </figure>
</section>
<section anchor='blockdef2' title="Definition of Fields in Discard Metric Report Block">
<t>
   block type (BT): 8 bits
</t>
<t>
<list style='empty'>
<t>
         A Discard Metric Report Block is identified by the constant 
         ND. 
</t>
</list>
</t>
<t>
[Note to RFC Editor: please replace ND with the
         IANA provided RTCP XR block type for this block.]
</t>
<t>
   Interval Metric flag (I): 1 bit
</t>
<t>
<list style='empty'>
<t>
This field is used to indicate whether the Discard metric is an Interval or a Cumulative metric, 
that is, whether the reported value applies 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). Numerical values for both these intervals are provided in the Measurement Identifier block 
referenced by the tag field below.
</t>
</list>
</t>
<t>
   Measurement Identifier association (tag): 3 bits
</t>
<t>
<list style='empty'>
<t>
This field is used to identify the Measurement Identifier block <xref target='MEASIDENT'/> which describes this measurement. The relevant 
Measurement Identifier block has the same tag value as the Discard Metric block. Note that there may be 
more than one Measurement Identifier block per RTCP packet.
</t>
</list>
</t>
<t>
   Reserved (resv): 4 bits
</t>
<t>
<list style='empty'>
<t>
These bits are reserved. They SHOULD be set to zero by senders and MUST be ignored by receivers.
</t>
</list>
</t>
<t>
   block length: 16 bits
</t>
<t>
<list style='empty'>
<t>
The length of this report block in 32-bit words minus one. For the Discard Metric block, the block length 
is equal to 1.
</t>
</list>
</t>
<t>
   number of packets discarded: 32 bits
</t>
<t>
<list style='empty'>
<t>
Number of packets discarded over the period (Interval or Cumulative) covered by this report.
</t>
<t>
   If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE SHOULD be
   reported to indicate an over-range measurement.  If the measurement
   is unavailable, the value 0xFFFFFFFF SHOULD be reported.
</t>
<t>
Note that the number of packets expected in the period covered by the metric (whether interval or cumulative) 
is available from the difference between a pair of extended sequence numbers in the Measurement Identity block, 
so need not be repeated in this block.
</t>
</list>
</t>
</section>
</section>

<section anchor='sdp' title="SDP Signaling">
<t>
   <xref target='RFC3611'/> defines the use of SDP (Session Description Protocol) 
   <xref target='RFC4566'/> 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'/> attribute "rtcp-xr" defined in 
   <xref target='RFC3611'/> by providing an additional value of "xr-format" to signal the use of the report
   block defined in this document. 
</t><t>
     rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF
</t><t>
     (defined in RFC3611)
</t><t>
     xr-format =/ xr-pd-block
</t><t>
     xr-pd-block   = "pkt-dscrd"
</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
   [RFC3611].
</t>
<section title="New RTCP XR Block Type value">
<t>   
   This document assigns the block type value ND in the IANA "RTCP XR Block
   Type Registry" to the "Concealed Seconds Metrics Block".
</t>
<t>
[Note to RFC Editor: please replace ND 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-dscrd" in the "RTCP XR SDP Parameters Registry".
</t>
</section>
<section title="Contact information for registrations">
<t>
   The contact information for the registrations is:
</t>
<t>
   Geoff Hunt (geoff.hunt@bt.com)
</t>
<t>
   Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United Kingdom
</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'/>.  This block does not provide 
   per-packet statistics so the risk
   to confidentiality documented in Section 7, paragraph 3 of <xref target='RFC3611'/> 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>
Update references
</t>
</section>
</middle>

    <back>
<references title='Normative References'>
                <reference anchor='MEASIDENT'>
			<front> 
				<title>RTCP XR Measurement Identifier Block</title> 
				<author initials='G.' surname='Hunt' fullname='Geoff Hunt'> 
					<organization>BT</organization> 
				</author> 
				<date month='May' year='2009' /> 
			</front> 
			<seriesInfo name='ID' value='draft-ietf-avt-rtcp-xr-meas-identity-02' /> 	
			<format type='TXT' /> 
		</reference>
                <reference anchor='RFC3550'>
			<front> 
				<title>RTP: A Transport Protocol for Real-Time Applications</title> 
				<author initials='H.' surname='Schulzrinne' fullname='Henning Schulzrinne'> 
					<organization>Columbia University</organization> 
				</author> 
				<date month='July' year='2003' /> 
			</front> 
			<seriesInfo name='RFC' value='3550' /> 	
			<format type='TXT' /> 
		</reference>
                <reference anchor='RFC3611'>
			<front> 
				<title>RTP Control Protocol Extended Reports (RTCP XR)</title> 
				<author initials='T. (Ed)' surname='Friedman' fullname='Timur Friedman'> 
					<organization> Paris 6 </organization> 
				</author> 
				<date month='November' year='2003' /> 
			</front> 
			<seriesInfo name='RFC' value='3611' /> 	
			<format type='TXT' /> 
		</reference>
                <reference anchor='RFC2119'>
			<front> 
				<title>Key words for use in RFCs to Indicate Requirement Levels</title> 
				<author initials='S.' surname='Bradner' fullname='Scott Bradner'> 
					<organization>Harvard University</organization> 
				</author> 
				<date month='March' year='1997' /> 
			</front> 
			<seriesInfo name='RFC' value='2119' /> 	
			<seriesInfo name='BCP' value='14' /> 	
			<format type='TXT' /> 
		</reference>
                <reference anchor='RFC4566'>
			<front> 
				<title>SDP: Session Description Protocol</title> 
				<author initials='M.' surname='Handley' fullname='Mark Handley'> 
					<organization>UCL</organization> 
				</author> 
				<date month='July' year='2006' /> 
			</front> 
			<seriesInfo name='RFC' value='4566'/>
			<format type='TXT' /> 
		</reference>
</references>
        <references title='Informative References'>
		<reference anchor='PMOLFRAME'>
			<front>
                                <title>Framework for Performance Metric Development</title> 
                                <author initials='A.' surname='Clark' fullname='Alan Clark'> 
                                        <organization>Telchemy Incorporated</organization> 
				</author> 
                                <date month='March' year='2009' /> 
			</front> 
                        <seriesInfo name='ID' value='draft-ietf-pmol-metrics-framework-02' />  
			<format type='TXT' /> 
            </reference>
                <reference anchor='MONARCH'>
			<front> 
				<title>Monitoring Architectures for RTP</title> 
				<author initials='G.' surname='Hunt' fullname='Geoff Hunt'> 
					<organization>BT</organization> 
				</author> 
				<date month='August' year='2008' /> 
			</front> 
			<seriesInfo name='ID' value='draft-hunt-avt-monarch-01' /> 	
			<format type='TXT' /> 
		</reference>
                <reference anchor='POSTREPAIRLOSS'>
			<front> 
				<title>RTCP XR Report Block for Post-Repair Loss metric Reporting</title> 
				<author initials='G.' surname='Hunt' fullname='Geoff Hunt'> 
					<organization>BT</organization> 
				</author> 
				<date month='May' year='2009' /> 
			</front> 
			<seriesInfo name='ID' value='draft-ietf-rtcp-xr-postrepair-loss-02' /> 	
			<format type='TXT' /> 
		</reference>
                <reference anchor='RFC4588'>
			<front>
				<title>RTP Retransmission Payload Format</title> 
				<author initials='J. Rey' surname='Rey' fullname='Jose Rey'> 
					<organization>Panasonic</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 initials='A. Li' surname='Li' fullname='Adam H. Li'> 
					<organization></organization> 
				</author> 
				<date month='December' year='2007' /> 
			</front> 
			<seriesInfo name='RFC' value='5109' /> 	
			<format type='TXT' /> 
		</reference>
	</references>
    </back>

</rfc>