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Versions: (draft-ietf-xrblock-rtcp-xr-concsec) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 7294

Audio/Video Transport Working Group                             A. Clark
Internet-Draft                                                  Telchemy
Intended status: Standards Track                            G. Zorn, Ed.
Expires: July 28, 2013                                       Network Zen
                                                                   C. Bi
                                                                   STTRI
                                                              Q. Wu, Ed.
                                                                  Huawei
                                                        January 24, 2013


    RTCP XR Report Block for Concealment metrics Reporting on Audio
                              Applications
             draft-ietf-xrblock-rtcp-xr-loss-conceal-04.txt

Abstract

   This document defines two RTCP XR Report Blocks that allows the
   reporting of loss concealment metrics for audio applications of RTP.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 28, 2013.

Copyright Notice

   Copyright (c) 2013 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



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   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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Loss Concealment and Concealment Seconds Metrics
           Reporting Block  . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . .  4
     1.3.  Performance Metrics Framework  . . . . . . . . . . . . . .  4
     1.4.  Applicability  . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Standards Language . . . . . . . . . . . . . . . . . . . .  5
   3.  Loss Concealment Block . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Report Block Structure . . . . . . . . . . . . . . . . . .  6
     3.2.  Definition of Fields in Loss Concealment Report Block  . .  6
   4.  Concealment Seconds Block  . . . . . . . . . . . . . . . . . . 10
     4.1.  Report Block Structure . . . . . . . . . . . . . . . . . . 10
     4.2.  Definition of Fields in Concealed Seconds Metrics Block  . 10
   5.  SDP Signaling  . . . . . . . . . . . . . . . . . . . . . . . . 15
     5.1.  SDP rtcp-xr-attrib Attribute Extension . . . . . . . . . . 15
     5.2.  Offer/Answer Usage . . . . . . . . . . . . . . . . . . . . 15
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
     6.1.  New RTCP XR Block Type values  . . . . . . . . . . . . . . 16
     6.2.  New RTCP XR SDP Parameters . . . . . . . . . . . . . . . . 16
     6.3.  Contact information for registrations  . . . . . . . . . . 16
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   8.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 18
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 20
     10.2. Informative References . . . . . . . . . . . . . . . . . . 20
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . . 21
     A.1.  draft-ietf-xrblock-rtcp-xr-loss-conceal-04 . . . . . . . . 21
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22














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1.  Introduction

1.1.  Loss Concealment and Concealment Seconds Metrics Reporting Block

   At any instant, the audio output at a receiver may be classified as
   either 'normal' or 'concealed'.  'Normal' refers to playout of audio
   payload received from the remote end, and also includes locally
   generated signals such as announcements, tones and comfort noise.
   Concealment refers to playout of locally-generated signals used to
   mask the impact of network impairments or to reduce the audibility of
   jitter buffer adaptations.

   This draft defines two new concealment related block types to augment
   those defined in [RFC3611] for use in a range of RTP applications.

   The first block type provides metrics for actions taken by the
   receiver to mitigate the effect of packet loss and packet discard.
   Specifically, the first metric (On-Time Playout Duration) reports the
   duration of normal playout of data which the receiver obtained from
   the sender's stream.  A second metric (Loss Concealment Duration)
   reports the total time during which the receiver played out media
   data which was manufactured locally, because the sender's data for
   these periods was not available due to packet loss or discard.  A
   similar metric (Buffer Adjustment Concealment Duration) reports the
   duration of playout of locally-manufactured data replacing data which
   is unavailable due to adaptation of an adaptive de-jitter buffer.
   Further metrics (Playout Interrupt Count and Mean Playout Interrupt
   Size) report the number of times normal playout was interrupted, and
   the mean duration of these interruptions.

   Loss Concealment Duration and Buffer Adjustment Concealment Duration
   are reported separately because buffer adjustment is typically
   arranged to occur in silence periods so may have very little impact
   on user experience, whilst loss concealment may occur at any time.

   The second block type provides metrics for concealment.
   Specifically, the first metric (Unimpaired Seconds) reports the
   number of whole seconds occupied only with normal playout of data
   which the receiver obtained from the sender's stream.  The second
   metric (Concealed Seconds) reports the number of whole seconds during
   which the receiver played out any locally-generated media data.  A
   third metric (Severely Concealed Seconds) reports the number of whole
   seconds during which the receiver played out locally-generated data
   for more than SCS Threshold (ms).

   These metrics belongs to the class of transport-related terminal
   metrics defined in [RFC6792].




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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 [RFC6390] provides guidance on the
   definition and specification of performance metrics.  The RTP
   Monitoring Architectures [RFC6792] provides guideline for reporting
   block format using RTCP XR.  The Metrics Block described in this
   document are in accordance with those guidelines.

1.4.  Applicability

   These metrics are only applicable to audio applications of RTP.

































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2.  Terminology

2.1.  Standards Language

   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 RFC2119 [RFC2119].












































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3.  Loss Concealment Block

3.1.  Report Block Structure

   Loss Concealment metrics block

        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=NLC     | I |plc|  rsv. |       block length=5          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         SSRC of Source                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 On-time Playout Duration                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  Loss Concealment Duration                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              Buffer Adjustment Concealment Duration           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Playout Interrupt Count    |  Mean Playout Interrupt Size  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: Report Block Structure

3.2.  Definition of Fields in Loss Concealment Report Block

   Block type (BT): 8 bits

      A Loss Concealment Metrics Report Block is identified by the
      constant NLC.

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


   Interval Metric flag (I): 2 bit

      This field is used to indicate whether the Loss Concealment
      metrics are Sampled, Interval or Cumulative metrics:

         I=10: Interval Duration - the reported value applies to the
         most recent measurement interval duration between successive
         metrics reports.

         I=11: Cumulative Duration - the reported value applies to the
         accumulation period characteristic of cumulative measurements.





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         I=01: Sampled Value - the reported value is a sampled
         instantaneous value.


   Packet Loss Concealment Method (plc): 2 bits

      This field is used to identify the packet loss concealment method
      in use at the receiver, according to the following code:

         bits 014-015

            0 = silence insertion

            1 = simple replay, no attenuation

            2 = simple replay, with attenuation

            3 = enhanced

            Other values reserved


   Reserved (resv): 4 bits

      These bits are reserved.  They MUST be set to zero by senders and
      ignored by receivers (See [RFC6709] section 4.2).


   block length: 16 bits

      The length of this report block in 32-bit words, minus one.  For
      the Loss Concealment block, the block length is equal to 5.


   SSRC of source: 32 bits

      As defined in Section 4.1 of [RFC3611].


   On-time Playout Duration (ms): 32 bits

      'On-time' playout is the uninterrupted, in-sequence playout of
      valid decoded audio information originating from the remote
      endpoint.  This includes comfort noise during periods of remote
      talker silence, if VAD is used, and locally generated or
      regenerated tones and announcements.

      An equivalent definition is that on-time playout is playout of any



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      signal other than those used for concealment.

      On-time playout duration MUST include both speech and silence
      intervals, whether VAD is used or not.  This duration is reported
      in millisecond units.

      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.


   Loss Concealment Duration (ms): 32 bits

      The duration, in milliseconds, of audio playout corresponding to
      Loss-type concealment.

      Loss-type concealment is reactive insertion or deletion of samples
      in the audio playout stream due to effective frame loss at the
      audio decoder.  "Effective frame loss" is the event in which a
      frame of coded audio is simply not present at the audio decoder
      when required.  In this case, substitute audio samples are
      generally formed, at the decoder or elsewhere, to reduce audible
      impairment.

      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.


   Buffer Adjustment Concealment Duration (ms): 32 bits

      The duration, in milliseconds, of audio playout corresponding to
      Buffer Adjustment-type concealment, if known.

      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.

      Buffer Adjustment-type concealment is proactive or controlled
      insertion or deletion of samples in the audio playout stream due
      to jitter buffer adaptation, re-sizing or re-centering decisions
      within the endpoint.

      Because this insertion is controlled, rather than occurring
      randomly in response to losses, it is typically less audible than
      loss-type concealment.  For example, jitter buffer adaptation
      events may be constrained to occur during periods of talker
      silence, in which case only silence duration is affected, or



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      sophisticated time-stretching methods for insertion/deletion
      during favorable periods in active speech may be employed.

      Concealment events which cannot be classified as Buffer
      Adjustment- type MUST be classified as Loss-type.


   Playout Interrupt Count: 16 bits

      The number of interruptions to normal playout which occurred
      during the reporting period.

      If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be
      reported to indicate an over-range measurement.  If the
      measurement is unavailable, the value 0xFFFF MUST be reported.


   Mean Playout Interrupt Size (ms): 16 bits

      The mean duration, in ms, of interruptions to normal playout which
      occurred during the reporting period.

      If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be
      reported to indicate an over-range measurement.  If the
      measurement is unavailable, the value 0xFFFF MUST be reported.


























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4.  Concealment Seconds Block

   This sub-block provides a description of potentially audible
   impairments due to lost and discarded packets at the endpoint,
   expressed on a time basis analogous to a traditional PSTN T1/E1
   errored seconds metric.

   The following metrics are based on successive one second intervals as
   declared by a local clock.  This local clock does NOT need to be
   synchronized to any external time reference.  The starting time of
   this clock is unspecified.  Note that this implies that the same loss
   pattern could result in slightly different count values, depending on
   where the losses occur relative to the particular one-second
   demarcation points.  For example, two loss events occurring 50ms
   apart could result in either one concealed second or two, depending
   on the particular 1000 ms boundaries used.

   The seconds in this sub-block are not necessarily calendar seconds.
   At the tail end of a session, periods of time of less than 1000ms
   shall be incorporated into these counts if they exceed 500ms and
   shall be disregarded if they are less than 500ms.

4.1.  Report Block Structure

   Concealed Seconds metrics block

        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=NCS     | I |plc|Rserved|       block length=4          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         SSRC of Source                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    Unimpaired Seconds                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    Concealed Seconds                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Severely Concealed Seconds    | RESERVED      | SCS Threshold |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: Report Block Structure

4.2.  Definition of Fields in Concealed Seconds Metrics Block








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   Block type (BT): 8 bits

      A Concealed Seconds Metrics Report Block is identified by the
      constant NCS.

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


   Interval Metric flag (I): 2 bit

      This field is used to indicate whether the Concealment Seconds
      metrics are Sampled, Interval or Cumulative metrics:

         I=10: Interval Duration - the reported value applies to the
         most recent measurement interval duration between successive
         metrics reports.

         I=11: Cumulative Duration - the reported value applies to the
         accumulation period characteristic of cumulative measurements.

         I=01: Sampled Value - the reported value is a sampled
         instantaneous value.


   Packet Loss Concealment Method (plc): 2 bits

      This field is used to identify the packet loss concealment method
      in use at the receiver, according to the following code:

         bits 014-015

            0 = silence insertion

            1 = simple replay, no attenuation

            2 = simple replay, with attenuation

            3 = enhanced

            Other values reserved


   Reserved (resv): 4 bits

      These bits are reserved.  They MUST be set to zero by senders and
      ignored by receivers (See [RFC6709] section 4.2).




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   Block Length: 16 bits

      The length of this report block in 32-bit words, minus one.  For
      the Concealment Seconds block, the block length is equal to 4.


   SSRC of source: 32 bits

      As defined in Section 4.1 of [RFC3611].


   Unimpaired Seconds: 32 bits

      A count of the number of unimpaired Seconds that have occurred.

      An unimpaired Second is defined as a continuous period of 1000ms
      during which no frame loss or discard due to late arrival has
      occurred.  Every second in a session must be classified as either
      OK or Concealed.

      Normal playout of comfort noise or other silence concealment
      signal during periods of talker silence, if VAD [VAD] is used,
      shall be counted as unimpaired seconds.

      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.


   Concealed Seconds: 32 bits

      A count of the number of Concealed Seconds that have occurred.

      A Concealed Second is defined as a continuous period of 1000ms
      during which any frame loss or discard due to late arrival has
      occurred.

      Equivalently, a concealed second is one in which some Loss-type
      concealment has occurred.  Buffer adjustment-type concealment
      SHALL not cause Concealed Seconds to be incremented, with the
      following exception.  An implementation MAY cause Concealed
      Seconds to be incremented for 'emergency' buffer adjustments made
      during talkspurts.

      Loss-type concealment is reactive insertion or deletion of samples
      in the audio playout stream due to effective frame loss at the
      audio decoder.  "Effective frame loss" is the event in which a
      frame of coded audio is simply not present at the audio decoder



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      when required.  In this case, substitute audio samples are
      generally formed, at the decoder or elsewhere, to reduce audible
      impairment.

      Buffer Adjustment-type concealment is proactive or controlled
      insertion or deletion of samples in the audio playout stream due
      to jitter buffer adaptation, re-sizing or re-centering decisions
      within the endpoint.

      Because this insertion is controlled, rather than occurring
      randomly in response to losses, it is typically less audible than
      loss-type concealment.  For example, jitter buffer adaptation
      events may be constrained to occur during periods of talker
      silence, in which case only silence duration is affected, or
      sophisticated time-stretching methods for insertion/deletion
      during favorable periods in active speech may be employed.  For
      these reasons, buffer adjustment-type concealment MAY be exempted
      from inclusion in calculations of Concealed Seconds and Severely
      Concealed Seconds.

      However, an implementation SHOULD include buffer-type concealment
      in counts of Concealed Seconds and Severely Concealed Seconds if
      the event occurs at an 'inopportune' moment, with an emergency or
      large, immediate adaptation during active speech, or for
      unsophisticated adaptation during speech without regard for the
      underlying signal, in which cases the assumption of low-audibility
      cannot hold.  In other words, jitter buffer adaptation events
      which may be presumed to be audible SHOULD be included in
      Concealed Seconds and Severely Concealed Seconds counts.

      Concealment events which cannot be classified as Buffer
      Adjustment- type MUST be classified as Loss-type.

      For clarification, the count of Concealed Seconds MUST include the
      count of Severely Concealed Seconds.

      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.

   Severely Concealed Seconds: 16 bits

      A count of the number of Severely Concealed Seconds.

      A Severely Concealed Second is defined as a non-overlapping period
      of 1000 ms during which the cumulative amount of time that has
      been subject to frame loss or discard due to late arrival, exceeds
      the SCS Threshold.



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      If the measured value exceeds 0xFFFD, the value 0xFFFE MUST be
      reported to indicate an over-range measurement.  If the
      measurement is unavailable, the value 0xFFFF MUST be reported.


   Reserved: 8 bits

      These bits are reserved.  They MUST be set to zero by senders and
      ignored by receivers (See [RFC6709] section 4.2).


   SCS Threshold: 8 bits

      The SCS Threshold defines the amount of time corresponding to lost
      or discarded frames that must occur within a one second period in
      order for the second to be classified as a Severely Concealed
      Second.  This is expressed in milliseconds and hence can represent
      a range of 0.1 to 25.5 percent loss or discard.

      A default threshold of 50ms (5% effective frame loss per second)
      is suggested.






























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5.  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.

5.1.  SDP rtcp-xr-attrib Attribute Extension

   This section augments the SDP attribute "rtcp-xr" [RFC3611] by
   providing two additional values of "xr-format" to signal the use of
   the report block defined in this document.

   xr-format =/ xr-conceal-block
   xr-format =/ xr-conc-sec-block

   xr-conceal-block = "loss-conceal"
   xr-conc-sec-block = "conc-sec" ["=" thresh]

   thresh      = 1*DIGIT          ; threshold for SCS (ms)
   DIGIT          = %x30-39

5.2.  Offer/Answer Usage

   When SDP is used in offer-answer context, the SDP Offer/Answer usage
   defined in [RFC3611] applies.


























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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 values

   This document assigns two block type values in the IANA "RTCP XR
   Block Type Registry":

   Name:       NLC
   Long Name:  Loss Concealment Block
   Value       <NLC>
   Reference:  Section 3.1

   Name:       NCS
   Long Name:  Concealment Seconds Block
   Value       <NCS>
   Reference:  Section 4.1

   [Note to RFC Editor: please replace <NLC> and <NCS> with the RTCP XR
   block type assigned by IANA for this block.]

6.2.  New RTCP XR SDP Parameters

   This document also registers two new parameters in the "RTCP XR SDP
   Parameters Registry":

   o  "loss-conceal"

   o  "conc-sec"

6.3.  Contact information for registrations


   The contact information for the registrations is:

   Qin Wu (sunseawq@huawei.com)
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China









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7.  Security Considerations

   It is believed that this proposed RTCP XR report 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.












































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8.  Contributors

   Geoff Hunt wrote the initial draft of this document.
















































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9.  Acknowledgements

   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.











































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10.  References

10.1.  Normative References

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

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

   [RFC3611]  Friedman, T., Caceres, R., and A. Clark, "RTP Control
              Protocol Extended Reports (RTCP XR)", November 2003.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", July 2006.

10.2.  Informative References

   [RFC6390]  Clark, A. and B. Claise, "Framework for Performance Metric
              Development", RFC 6390, October 2011.

   [RFC6709]  Carpenter, B., Aboba, B., and S. Cheshire, "Design
              Considerations for Protocol Extensions", RFC 6709,
              September 2012.

   [RFC6792]  Hunt, G., "Monitoring Architectures for RTP", RFC 6792,
              November 2012.

   [VAD]      "http://en.wikipedia.org/wiki/Voice_activity_detection".






















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Appendix A.  Change Log

   Note to the RFC-Editor: please remove this section prior to
   publication as an RFC.

A.1.  draft-ietf-xrblock-rtcp-xr-loss-conceal-04

   The following are the major changes to previous version :

   o  Merge Concealment Seconds draft into this draft (i.e.,Loss
      Concealment draft).

   o  Updated references.






































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Authors' Addresses

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

   Email: alan.d.clark@telchemy.com


   Glen Zorn (editor)
   Network Zen
   77/440 Soi Phoomjit, Rama IV Road
   Phra Khanong, Khlong Toie
   Bangkok  10110
   Thailand

   Phone: +66 (0) 87 502 4274
   Email: gwz@net-zen.net


   Claire Bi
   Shanghai Research Institure of China Telecom Corporation Limited
   No.1835,South Pudong Road
   Shanghai  200122
   China

   Email: bijy@sttri.com.cn


   Qin Wu (editor)
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: sunseawq@huawei.com













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