





Internet Engineering Task Force (IETF)                          A. Clark
Request for Comments: 6958                                      Telchemy
Category: Standards Track                                       S. Zhang
ISSN: 2070-1721                                                  J. Zhao
                                                                   STTRI
                                                              Q. Wu, Ed.
                                                                  Huawei
                                                                May 2013


       RTP Control Protocol (RTCP) Extended Report (XR) Block for
                    Burst/Gap Loss Metric Reporting

Abstract

   This document defines an RTP Control Protocol (RTCP) Extended Report
   (XR) Block that allows the reporting of burst and gap loss metrics
   for use in a range of RTP applications.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6958.

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
   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.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Burst/Gap Loss Metrics Block  . . . . . . . . . . . . . .   2
     1.2.  RTCP and RTCP XR Reports  . . . . . . . . . . . . . . . .   3
     1.3.  Performance Metrics Framework . . . . . . . . . . . . . .   3
     1.4.  Applicability . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Burst/Gap Loss Metrics Block  . . . . . . . . . . . . . . . .   4
     3.1.  Report Block Structure  . . . . . . . . . . . . . . . . .   5
     3.2.  Definition of Fields in Burst/Gap Loss Metrics Block  . .   5
     3.3.  Derived Metrics Based on Reported Metrics . . . . . . . .   7
   4.  Considerations for Voice-over-IP Applications . . . . . . . .   8
   5.  SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  SDP rtcp-xr-attrib Attribute Extension  . . . . . . . . .   9
     5.2.  Offer/Answer Usage  . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  New RTCP XR Block Type Value  . . . . . . . . . . . . . .   9
     6.2.  New RTCP XR SDP Parameter . . . . . . . . . . . . . . . .   9
     6.3.  Contact Information for Registrations . . . . . . . . . .  10
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  10
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     10.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Appendix A.  Metrics Represented Using the Template from RFC 6390  13

1.  Introduction

1.1.  Burst/Gap Loss Metrics Block

   This document defines a new block type to augment those defined in
   [RFC3611] 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
   [RFC3550].

   This block provides information on transient IP problems.  Burst/gap
   metrics are typically used in Cumulative reports; however, they also
   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.




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   The metric belongs to the class of transport-related end system
   metrics defined in [RFC6792].

   The definitions of "burst", "gap", "loss", and "discard" are
   consistent with definitions in [RFC3611].  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 [RFC3611].  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.

1.2.  RTCP and RTCP XR Reports

   The use of RTCP for reporting is defined in [RFC3550].  [RFC3611]
   defines an extensible structure for reporting by using an RTCP
   Extended Report (XR).  This document defines a new Extended Report
   block for use with [RFC3550] and [RFC3611].

1.3.  Performance Metrics Framework

   The Performance Metrics Framework [RFC6390] provides guidance on the
   definition and specification of performance metrics.  The "Guidelines
   for Use of the RTP Monitoring Framework" [RFC6792] provides
   guidelines for reporting block format using RTCP XR.  The Metrics
   Block described in this document is in accordance with the guidelines
   in [RFC6390] and [RFC6792].

1.4.  Applicability

   These metrics are applicable to a range of RTP applications that
   contain jitter buffers and don't use stream repair means, e.g.,
   Forward Error Correction (FEC) [RFC5109] and/or retransmission
   [RFC4588].

2.  Terminology

   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 [RFC2119].











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   In addition, the following terms are defined:

   Received, Lost, and Discarded

      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 or
      thrown away before playout due to packet duplication or redundancy
      shall be regarded as discarded.  A packet shall be classified as
      one of received (or OK), discarded, or lost.  The metric
      "cumulative number of packets lost" defined in [RFC3550] reports a
      count of packets lost from the media stream (single
      Synchronization Source (SSRC) within a single RTP session).
      Similarly, the metric "number of packets discarded" defined in
      [DISCARD] reports a count of packets discarded from the media
      stream (single SSRC within single RTP session) arriving at the
      receiver.  The post-repair Loss RLE metric, which is defined in
      [RFC5725], can be used to report the number of packets that are
      not recovered by any repair techniques that are in use.

   Bursts and Gaps

      The terms "burst" and "gap" are used in a manner consistent with
      that of RTCP XR [RFC3611].  RTCP XR views an RTP stream as being
      divided into bursts, which are periods when the loss rate is high
      enough to cause noticeable quality degradation (generally over 5
      percent loss rate) and gaps, which are periods when lost packets
      are infrequent and hence quality is generally acceptable.

3.  Burst/Gap Loss Metrics Block

   Metrics in this block report on burst/gap loss in the stream arriving
   at the RTP system.  The measurement of these metrics is made at the
   receiving end of the RTP stream.  Each instance of this Metrics Block
   refers by SSRC to a separate auxiliary Measurement Information Block
   [RFC6776], which describes the measurement periods in use (see RFC
   6776, Section 4.2).

   This Metrics Block relies on the measurement period in the
   Measurement Information Block indicating the span of the report.
   Senders MUST send this block in the same compound RTCP packet as the
   Measurement Information Block.  Receivers MUST verify that the
   measurement period is received in the same compound RTCP packet as
   this Metrics Block.  If not, this Metrics Block MUST be discarded.







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3.1.  Report Block Structure

   The structure of the Burst/Gap Loss Metrics Block is as follows.

       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=20     | 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)     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: Report Block Structure

3.2.  Definition of Fields in Burst/Gap Loss Metrics Block

   Block Type (BT): 8 bits

      A Burst/Gap Loss Metrics Block is identified by the constant 20.

   Interval Metric flag (I): 2 bits

      This field is used to indicate whether the burst/gap loss 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.

      In this document, burst/gap loss metrics can only be measured over
      definite intervals and cannot be sampled.  Also, the value I=00 is
      reserved for future use.  Senders MUST NOT use the values I=00 or
      I=01.  If a block is received with I=00 or I=01, the receiver MUST
      discard the block.



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    Loss and Discard Combination flag (C): 1 bit

      The 'C' flag is used to indicate whether the loss/discard report
      is combined with the burst/gap loss report in the same compound
      RTCP packet.  The value is set to '1' if the loss/discard report
      and the burst gap loss report are combined.  Otherwise, the value
      is set to '0'.  If the 'C' flag is set to '1' but the burst/gap
      discard was not sent, the receiver MUST discard the burst/gap
      loss.

   Reserved (resv.): 5 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 Burst/Gap Loss Metrics Block, the block length is equal to 5.
      The block MUST be discarded if the block length is set to a
      different value.

   SSRC of Source: 32 bits

      As defined in Section 4.1 of [RFC3611].

   Threshold: 8 bits

      The Threshold is equivalent to Gmin in [RFC3611], i.e., the number
      of successive packets that must be received prior to and following
      a lost packet in order for this lost packet to be regarded as part
      of a gap.  Note that the threshold is calculated in accordance
      with the Gmin Calculation defined in Section 4.7.2 of RFC 3611.

   Sum of Burst Durations (ms): 24 bits

      The total duration of bursts of lost packets in the period of the
      report (Interval or Cumulative).

      The measured value is an unsigned value.  If the measured value
      exceeds 0xFFFFFD, the value 0xFFFFFE MUST be reported to indicate
      an over-range measurement.  If the measurement is unavailable, the
      value 0xFFFFFF MUST be reported.








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   Packets Lost in Bursts: 24 bits

      The total number of packets lost during loss bursts.

      The measured value is an unsigned value.  If the measured value
      exceeds 0xFFFFFD, the value 0xFFFFFE MUST be reported to indicate
      an over-range measurement.  If the measurement is unavailable, the
      value 0xFFFFFF MUST be reported.

   Total Packets Expected in Bursts: 24 bits

      The total number of packets expected during loss bursts (that is,
      the sum of received packets and lost packets).

      The measured value is an unsigned value.  If the measured value
      exceeds 0xFFFFFD, the value 0xFFFFFE MUST be reported to indicate
      an over-range measurement.  If the measurement is unavailable, the
      value 0xFFFFFF MUST be reported.

   Number of Bursts: 16 bits

      The number of bursts in the period of the report (Interval or
      Cumulative).

      The measured value is an unsigned value.  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.

   Sum of Squares of Burst Durations (ms-squared): 36 bits

      The sum of the squares of burst durations (where individual burst
      durations are expressed in ms) in the period of the report
      (Interval or Cumulative).  The units for this quantity are
      milliseconds-squared.

      The measured value is an unsigned value.  If the measured value
      exceeds 0xFFFFFFFFD, the value 0xFFFFFFFFE MUST be reported to
      indicate an over-range measurement.  If the measurement is
      unavailable, the value 0xFFFFFFFFF MUST be reported.

3.3.  Derived Metrics Based on Reported Metrics

   The metrics described here are intended to be used as described in
   this section, in conjunction with information from the Measurement
   Information Block [RFC6776] and also with the metric "cumulative
   number of packets lost" provided in standard RTCP [RFC3550].




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   These metrics provide information relevant to statistical parameters,
   including:

   o  the fraction of packets lost during bursts (i.e., Burst Loss Rate
      in [SUMSTAT]), which can be calculated using the metric "Packets
      Loss in Bursts" and the metric "Total Packets Expected in Bursts"
      provided in the Burst/Gap Loss Metrics Block.

   o  the fraction of packets lost during gaps (i.e., Gap Loss Rate in
      [SUMSTAT]), which can be calculated using the metric "Packets Loss
      in Bursts" and the metric "Total Packets Expected in Bursts"
      provided in the Burst/Gap Loss Metrics Block.

   o  burst duration mean [SUMSTAT], which can be calculated using the
      metric "Packets Loss in Bursts" and the metric "Total Packets
      Expected in Bursts" provided in the Burst/Gap Loss Metrics Block.

   o  burst duration variance [SUMSTAT], which can be calculated using
      the metric "Packets Loss in Bursts" and the metric "Total Packets
      Expected in Bursts" provided in the Burst/Gap Loss Metrics Block.

   The details on calculation of these parameters in the metrics are
   described in [SUMSTAT].

4.  Considerations for Voice-over-IP Applications

   This Metrics Block is applicable to a broad range of RTP
   applications.  Where the metric is used with a Voice-over-IP (VoIP)
   application and the stream repair means is not available, the
   following considerations apply.

   RTCP XR views a call as being divided into bursts, which are periods
   when the loss rate is high enough to cause noticeable call quality
   degradation (generally over 5 percent loss rate), and gaps, which are
   periods when lost packets are infrequent and hence call quality is
   generally acceptable.

   If Voice Activity Detection is used, the Burst and Gap Durations
   shall be determined as if silence packets had been sent, i.e., a
   period of silence in excess of Gmin packets will terminate a burst
   condition.

   The recommended value for the threshold Gmin in [RFC3611] causes a
   burst during which the call quality is degraded to a similar extent
   as it would be during a typical Pulse Code Modulation (PCM) Severely
   Errored Second.





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5.  SDP Signaling

   [RFC3611] defines the use of the Session Description Protocol (SDP)
   [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 [RFC4566] attribute "rtcp-xr" defined
   in [RFC3611] by providing an additional value of "xr-format" to
   signal the use of the report block defined in this document.  The
   ABNF [RFC5234] syntax is below.

   xr-format =/ xr-bgl-block

   xr-bgl-block = "burst-gap-loss"

5.2.  Offer/Answer Usage

   When SDP is used in the offer/answer context, the SDP Offer/Answer
   usage defined in [RFC3611] for unilateral "rtcp-xr" attribute
   parameters applies.  For detailed usage of offer/answer for
   unilateral parameters, refer to Section 5.2 of [RFC3611].

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 Value

   This document assigns the block type value 20 in the IANA "RTP
   Control Protocol Extended Reports (RTCP XR) Block Type Registry" to
   the "Burst/Gap Loss Metrics Block".

6.2.  New RTCP XR SDP Parameter

   This document also registers a new parameter "burst-gap-loss" in the
   "RTP Control Protocol Extended Reports (RTCP XR) Session Description
   Protocol (SDP) Parameters Registry".










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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

7.  Security Considerations

   This block does not provide per-packet statistics, so the risk to
   confidentiality documented in Section 7, paragraph 3 of [RFC3611]
   does not apply.  However, the gaps indicated within this block could
   be used to detect the timing of other events on the path between the
   sender and receiver.  For example, a competing multimedia stream
   might cause a loss burst for the duration of the stream, allowing the
   receiver of this block to know when the competing stream was active.
   This risk is not a significant threat since the only information
   leaked is the timing of the loss, not the cause.  Besides this, it is
   believed that this proposed RTCP XR report block introduces no other
   new security considerations beyond those described in [RFC3611].

8.  Contributors

   Geoff Hunt wrote the initial draft of this document.

9.  Acknowledgments

   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, Hideaki Yamada, Adam Roach,
   Dan Romascanu, Chris Lonvick, Alfred C. Morton Jr., Pete Resnick, Ted
   Lemon, Stephen Farrell, Richard Barnes, and Benoit Claise.













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10.  References

10.1.  Normative References

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

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, July 2003.

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

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, July 2006.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [RFC5725]  Begen, A., Hsu, D., and M. Lague, "Post-Repair Loss RLE
              Report Block Type for RTP Control Protocol (RTCP) Extended
              Reports (XRs)", RFC 5725, February 2010.

10.2.  Informative References

   [DISCARD]  Clark, A., Huang, R., and Q. Wu, Ed., "RTP Control
              Protocol (RTCP) Extended Report (XR) Block for Discard
              Count metric Reporting", Work in Progress, April 2013.

   [RFC4588]  Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R.
              Hakenberg, "RTP Retransmission Payload Format", RFC 4588,
              July 2006.

   [RFC5109]  Li, A., "RTP Payload Format for Generic Forward Error
              Correction", RFC 5109, December 2007.

   [RFC6390]  Clark, A. and B. Claise, "Guidelines for Considering New
              Performance Metric Development", BCP 170, RFC 6390,
              October 2011.

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






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   [RFC6776]  Clark, A. and Q. Wu, "Measurement Identity and Information
              Reporting Using a Source Description (SDES) Item and an
              RTCP Extended Report (XR) Block", RFC 6776, October 2012.

   [RFC6792]  Wu, Q., Hunt, G., and P. Arden, "Guidelines for Use of the
              RTP Monitoring Framework", RFC 6792, November 2012.

   [SUMSTAT]  Zorn, G., Schott, R., Wu, Q., Ed., and R. Huang, "RTP
              Control Protocol (RTCP) Extended Report (XR) Blocks for
              Summary Statistics Metrics Reporting", Work in Progress,
              March 2013.








































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Appendix A.  Metrics Represented Using the Template from RFC 6390

   The six metrics defined in this document are described below using
   the template from Section 5.4.4 of RFC 6390.

   a.  Threshold Metric

       *  Metric Name: Threshold in RTP

       *  Metric Description: The Threshold is equivalent to Gmin in
          [RFC3611], i.e., the number of successive RTP packets that
          must be received prior to and following a lost RTP packet in
          order for this lost RTP packet to be regarded as part of a
          gap.

       *  Method of Measurement or Calculation: See Section 3.2,
          Threshold definition.

       *  Units of Measurement: See Section 3.2, Threshold definition.

       *  Measurement Point(s) with Potential Measurement Domain: See
          Section 3, 1st paragraph.

       *  Measurement Timing: See Section 3, 2nd paragraph for
          measurement timing and Section 3.2 for Interval Metric flag.

       *  Use and Applications: See Section 1.4.

       *  Reporting Model: See RFC 3611.

   b.  Sum of Burst Durations Metric

       *  Metric Name: Sum of Burst Durations in RTP

       *  Metric Description: The total duration of bursts of lost RTP
          packets in the period of the report.

       *  Method of Measurement or Calculation: See Section 3.2, Sum of
          Burst Durations definition.

       *  Units of Measurement: See Section 3.2, Sum of Burst Durations
          definition.

       *  Measurement Point(s) with Potential Measurement Domain: See
          Section 3, 1st paragraph.

       *  Measurement Timing: See Section 3, 2nd paragraph for
          measurement timing and Section 3.2 for Interval Metric flag.



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       *  Use and Applications: See Section 1.4.

       *  Reporting Model: See RFC 3611.

   c.  Packets Lost in Bursts Metric

       *  Metric Name: RTP Packets lost in bursts

       *  Metric Description: The total number of RTP packets lost
          during loss bursts.

       *  Method of Measurement or Calculation: See Section 3.2, Packets
          Lost in Bursts definition.

       *  Units of Measurement: See Section 3.2, Packets lost in bursts
          definition.

       *  Measurement Point(s) with Potential Measurement Domain: See
          Section 3, 1st paragraph.

       *  Measurement Timing: See Section 3, 2nd paragraph for
          measurement timing and Section 3.2 for Interval Metric flag.

       *  Use and Applications: See Section 1.4.

       *  Reporting Model: See RFC 3611.

   d.  Total Packets Expected in Bursts Metric

       *  Metric Name: Total RTP packets expected in bursts

       *  Metric Description: The total number of RTP packets expected
          during loss bursts (that is, the sum of received RTP packets
          and lost RTP packets).

       *  Method of Measurement or Calculation: See Section 3.2, Total
          packets expected in bursts definition.

       *  Units of Measurement: See Section 3.2, Total packets expected
          in bursts definition.

       *  Measurement Point(s) with Potential Measurement Domain: See
          Section 3, 1st paragraph.

       *  Measurement Timing: See Section 3, 2nd paragraph for
          measurement timing and Section 3.2 for Interval Metric flag.

       *  Use and Applications: See Section 1.4.



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       *  Reporting Model: See RFC 3611.

   e.  Number of Bursts Metric

       *  Metric Name: Number of bursts in RTP

       *  Metric Description: The total duration of bursts of lost RTP
          packets in the period of the report.

       *  Method of Measurement or Calculation: See Section 3.2, Number
          of bursts definition.

       *  Units of Measurement: See Section 3.2, Number of bursts
          definition.

       *  Measurement Point(s) with Potential Measurement Domain: See
          Section 3, 1st paragraph.

       *  Measurement Timing: See Section 3, 2nd paragraph for
          measurement timing and Section 3.2 for Interval Metric flag.

       *  Use and Applications: See Section 1.4.

       *  Reporting Model: See RFC 3611.

   f.  Sum of Squares of Burst Durations Metric

       *  Metric Name: Sum of Squares of Burst Durations in RTP

       *  Metric Description: The sum of the squares of burst durations
          (where individual burst durations are expressed in ms) over in
          the period of the report.

       *  Method of Measurement or Calculation: See Section 3.2, Sum of
          Squares of Burst Durations definition.

       *  Units of Measurement: See Section 3.2, Sum of Squares of Burst
          Durations definition.

       *  Measurement Point(s) with Potential Measurement Domain: See
          Section 3, 1st paragraph.

       *  Measurement Timing: See Section 3, 2nd paragraph for
          measurement timing and Section 3.2 for Interval Metric flag.

       *  Use and Applications: See Section 1.4.

       *  Reporting Model: See RFC 3611.



Clark, et al.                Standards Track                   [Page 15]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013


Authors' Addresses

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

   EMail: alan.d.clark@telchemy.com


   Sunshine Zhang
   Shanghai Research Institute of China Telecom Corporation Limited
   No. 1835, South Pudong Road
   Shanghai  200122
   China

   EMail: zhangyx@sttri.com.cn


   Jing Zhao
   Shanghai Research Institute of China Telecom Corporation Limited
   No. 1835, South Pudong Road
   Shanghai  200122
   China

   EMail: zhaojing@sttri.com.cn


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

   EMail: sunseawq@huawei.com















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