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Audio/Video Transport Working                                    G. Hunt
Group                                                                 BT
Internet-Draft                                                  A. Clark
Intended status: Standards Track                                Telchemy
Expires: November 16, 2009                                  May 15, 2009


             RTCP XR Report Block for Measurement Identity
              draft-ietf-avt-rtcp-xr-meas-identity-02.txt

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Abstract

   This document defines an RTCP XR Report Block carrying parameters
   which identify a measurement, to which one or more other RTCP XR
   Report Blocks may refer.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Measurement Identity Report Block  . . . . . . . . . . . .  3
     1.2.  RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . .  4
     1.3.  Performance Metrics Framework  . . . . . . . . . . . . . .  4
     1.4.  Applicability  . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Measurement Identity Block . . . . . . . . . . . . . . . . . .  5
     2.1.  Report Block Structure . . . . . . . . . . . . . . . . . .  5
     2.2.  Definition of Fields in Measurement Identity Report
           Block  . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  SDP Signaling  . . . . . . . . . . . . . . . . . . . . . . . .  8
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
     4.1.  New RTCP XR Block Type value . . . . . . . . . . . . . . .  9
     4.2.  Contact information for registration . . . . . . . . . . .  9
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   6.  Changes since last version . . . . . . . . . . . . . . . . . . 11
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13























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1.  Introduction

1.1.  Measurement Identity Report Block

   This draft defines a new block type to augment those defined in
   [RFC3611] for use in a range of RTP applications.  This block type
   does not itself contain any measurement results (metrics).  However,
   this new block type provides information relevant to a measurement
   reported in one or more other block types, including

   o  a tag or key by which other blocks (containing metrics
      information) may refer to this block

   o  the SSRC of the measured stream,

   o  a field for incorporation of an application-specific auxiliary
      identifier,

   o  the sequence number of the first packet of the RTP session,

   o  the extended sequence numbers of the first packet of the current
      measurement interval, and the last packet included in the
      measurement,

   o  the duration of the most recent measurement interval and

   o  the duration of the interval applicable to cumulative measurements
      (which may be the duration of the RTP session to date).

   The method for calculation of the extended RTP sequence number is
   provide in [RFC3550].

   This block is intended to provide a single copy of the information
   necessary to relate measurement data in other blocks to the stream,
   and measurement period, to which they refer.  Commonly, multiple
   other small blocks contain measurement data for the same stream and
   period, and it would be a large overhead if all of these blocks
   carried duplicated data for measurement identification.  Other blocks
   make a reference to this block (by tag).

   A Measurement Identity block is associated with the set of RTCP XR
   metrics blocks which share its tag value.  There MAY be several such
   sets in an RTCP packet, up to a limit of 8 arising from the use of
   3-bit tags.  There MAY also be RTCP XR blocks in the packet which are
   not associated with a Measurement Identity block, for example blocks
   which were defined before the Measurement Identity mechanism was
   introduced by this document.




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1.2.  RTCP and RTCP XR Reports

   The use of RTCP for reporting is defined in [RFC3550].  [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 [RFC3550] and [RFC3611].

1.3.  Performance Metrics Framework

   The Performance Metrics Framework [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
   [PMOLFRAME].

1.4.  Applicability

   This block provides identification information for members of a
   family of RTCP XR metrics blocks which are designed to use it.  To
   use the mechanism defined here, a metrics block must be in the same
   RTCP packet as the Measurement Identity block and must refer to the
   Measurement Identity block via the 3-bit tag field defined below.





























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2.  Measurement Identity Block

2.1.  Report Block Structure

        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=NMI    |0| tag | resv  |      block length = 7         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    SSRC of stream source                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        sub-identifier                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            reserved           |         first seq num         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           extended first sequence number of interval          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 extended last sequence number                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          Measurement Duration (Cumulative) (ms)               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           Measurement Duration (Interval) (ms)                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: Report Block Structure

2.2.  Definition of Fields in Measurement Identity Report Block

   Bits shown as '0' in the figure SHOULD be set to zero.

   block type (BT): 8 bits

      A Measurement Identity Report Block is identified by the constant
      NMI.

   [Note to RFC Editor: please replace NMI with the IANA provided RTCP
   XR block type for this block.]

   tag: 3 bits

      This field is a tag or key which identifies this Measurement
      Identity block within the scope of an RTCP packet.  If an RTCP
      packet contains more than one Measurement Identity block, each
      Measurement Identity block MUST have a unique tag field to enable
      metrics blocks in the same RTCP packet to refer unambiguously to
      the correct Measurement Identity block.  The 3-bit field allows up
      to 8 Measurement Identity blocks in each RTCP packet.  If
      additional metrics must be sent at a given time, and they require



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      more than 8 blocks of Measurement Identity information, then the
      metrics must be sent in multiple RTCP packets.

   resv: 4 bits

      These bits are reserved.  They MUST be set to zero by senders.
      They MUST be ignored by receivers.

   block length: 16 bits

      The length of this report block in 32-bit words minus one.  For
      the Measurement Identity block, the block length is equal to 7.

   SSRC of source: 32 bits

      The SSRC [RFC3550] of the source of the stream being reported.
      Note that the SSRC of the reporting RTP system (the originator of
      the report block) is present in the RTCP XR header defined in
      Section 2 of [RFC3611].

   sub-identifier: 32 bits

      An additional identifier which is useful in the context of a
      specific application, e.g. an MPEG-2 transport identifier [MPEG2].
      Where the identifier is less than 32 bits, the identifier SHOULD
      be mapped into the most significant bits of the field.  If no
      additional identifier is provided, all bits of the field MUST be
      set to zero.  This field MUST be ignored by applications which are
      not configured to make use of it.

   reserved: 16 bits

      These bits are reserved.  They MUST be ignored by receivers.  They
      MUST be set to zero by senders.

   first seq num: 16 bits

      The RTP sequence number of the first received RTP packet of the
      session, used to determine the number of packets contributing to
      cumulative measurements.

   extended first sequence number of interval: 32 bits

      The extended RTP sequence number of the first received RTP packet
      of the current measurement interval.

   extended last sequence number: 32 bits




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      The extended RTP sequence number of the last received RTP packet
      which contributed to this measurement.

   Measurement Duration (Cumulative) (ms): 32 bits

      The duration in ms of the reporting interval applicable to
      Cumulative reports which use this Measurement Identity block.

   Measurement Duration (Interval) (ms): 32 bits

      The duration in ms of the reporting interval applicable to
      Interval reports which use this Measurement Identity block.







































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3.  SDP Signaling

   [RFC3611] defines the use of SDP (Session Description Protocol)
   [RFC4566] for signaling the use of XR blocks.  XR blocks MAY be used
   without prior signaling.

   No additional SDP signaling is defined for this block.  Instead, the
   need for this block SHOULD be inferred from a request in SDP
   signalling for a block type (such as [DISCARD]) which depends on it.










































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4.  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].

4.1.  New RTCP XR Block Type value

   This document assigns the block type value NMI in the IANA "RTCP XR
   Block Type Registry" to the "Measurement Identity Block".

   [Note to RFC Editor: please replace NMI with the IANA provided RTCP
   XR block type for this block.]

4.2.  Contact information for registration

   The contact information for the registration is:

   Geoff Hunt (geoff.hunt@bt.com)

   Orion 2 PP3, Adastral Park, Martlesham Heath, Ipswich IP5 3RE, United
   Kingdom





























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5.  Security Considerations

   RTCP reports can contain sensitive information since they can provide
   information about the nature and duration of a session established
   between two or more endpoints.














































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6.  Changes since last version

   Updated references.
















































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7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, BCP 14, March 1997.

   [RFC3550]  Schulzrinne, H., "RTP: A Transport Protocol for Real-Time
              Applications", RFC 3550, July 2003.

   [RFC3611]  Friedman, T., "RTP Control Protocol Extended Reports (RTCP
              XR)", RFC 3611, November 2003.

   [RFC4566]  Handley, M., "SDP: Session Description Protocol",
              RFC 4566, July 2006.

7.2.  Informative References

   [DISCARD]  Hunt, G., "RTCP XR Report Block for Discard metric
              Reporting", ID draft-ietf-avt-rtcp-xr-discard-02,
              May 2009.

   [MONARCH]  Hunt, G., "Monitoring Architectures for RTP",
              ID draft-hunt-avt-monarch-01, August 2008.

   [MPEG2]    ISO/IEC, "Standard 13818-1", December 2000.

   [PMOLFRAME]
              Clark, A., "Framework for Performance Metric Development",
              ID draft-ietf-pmol-metrics-framework-02, March 2009.





















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Authors' Addresses

   Geoff Hunt
   BT
   Orion 2 PP3
   Adastral Park
   Martlesham Heath
   Ipswich, Suffolk  IP5 3RE
   United Kingdom

   Phone: +44 1473 651704
   Email: geoff.hunt@bt.com


   Alan Clark
   Telchemy Incorporated
   2905 Premiere Parkway, Suite 280
   Duluth, GA  30097
   USA

   Email: alan.d.clark@telchemy.com






























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