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Internet Engineering Task Force (IETF)                          A. ClarkRequest for Comments: 6958                                      TelchemyCategory: Standards Track                                       S. ZhangISSN: 2070-1721                                                  J. Zhao                                                                   STTRI                                                              Q. Wu, Ed.                                                                  Huawei                                                                May 2013RTP Control Protocol (RTCP) Extended Report (XR) Block forBurst/Gap Loss Metric ReportingAbstract   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 inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://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 toBCP 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.Clark, et al.                Standards Track                    [Page 1]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .21.1.  Burst/Gap Loss Metrics Block  . . . . . . . . . . . . . .21.2.  RTCP and RTCP XR Reports  . . . . . . . . . . . . . . . .31.3.  Performance Metrics Framework . . . . . . . . . . . . . .31.4.  Applicability . . . . . . . . . . . . . . . . . . . . . .32.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .33.  Burst/Gap Loss Metrics Block  . . . . . . . . . . . . . . . .43.1.  Report Block Structure  . . . . . . . . . . . . . . . . .53.2.  Definition of Fields in Burst/Gap Loss Metrics Block  . .53.3.  Derived Metrics Based on Reported Metrics . . . . . . . .74.  Considerations for Voice-over-IP Applications . . . . . . . .85.  SDP Signaling . . . . . . . . . . . . . . . . . . . . . . . .95.1.  SDP rtcp-xr-attrib Attribute Extension  . . . . . . . . .95.2.  Offer/Answer Usage  . . . . . . . . . . . . . . . . . . .96.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .96.1.  New RTCP XR Block Type Value  . . . . . . . . . . . . . .96.2.  New RTCP XR SDP Parameter . . . . . . . . . . . . . . . .96.3.  Contact Information for Registrations . . . . . . . . . .107.  Security Considerations . . . . . . . . . . . . . . . . . . .108.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .109.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .1010. References  . . . . . . . . . . . . . . . . . . . . . . . . .1110.1.  Normative References . . . . . . . . . . . . . . . . . .1110.2.  Informative References . . . . . . . . . . . . . . . . .11Appendix A.  Metrics Represented Using the Template fromRFC 6390  131.  Introduction1.1.  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.Clark, et al.                Standards Track                    [Page 2]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013   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 inRFC 2119 [RFC2119].Clark, et al.                Standards Track                    [Page 3]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013   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 (seeRFC6776,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.Clark, et al.                Standards Track                    [Page 4]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 20133.1.  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 Structure3.2.  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.Clark, et al.                Standards Track                    [Page 5]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013    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 inSection 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 inSection 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.Clark, et al.                Standards Track                    [Page 6]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013   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].Clark, et al.                Standards Track                    [Page 7]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013   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.Clark, et al.                Standards Track                    [Page 8]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 20135.  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 toSection 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".Clark, et al.                Standards Track                    [Page 9]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 20136.3.  Contact Information for Registrations   The contact information for the registrations is:      Qin Wu (sunseawq@huawei.com)      101 Software Avenue, Yuhua District      Nanjing, Jiangsu  210012      China7.  Security Considerations   This block does not provide per-packet statistics, so the risk to   confidentiality documented inSection 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.Clark, et al.                Standards Track                   [Page 10]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 201310.  References10.1.  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.Clark, et al.                Standards Track                   [Page 11]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013   [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.Clark, et al.                Standards Track                   [Page 12]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013Appendix A.  Metrics Represented Using the Template fromRFC 6390   The six metrics defined in this document are described below using   the template fromSection 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: SeeSection 3.2,          Threshold definition.       *  Units of Measurement: SeeSection 3.2, Threshold definition.       *  Measurement Point(s) with Potential Measurement Domain: SeeSection 3, 1st paragraph.       *  Measurement Timing: SeeSection 3, 2nd paragraph for          measurement timing andSection 3.2 for Interval Metric flag.       *  Use and Applications: SeeSection 1.4.       *  Reporting Model: SeeRFC 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: SeeSection 3.2, Sum of          Burst Durations definition.       *  Units of Measurement: SeeSection 3.2, Sum of Burst Durations          definition.       *  Measurement Point(s) with Potential Measurement Domain: SeeSection 3, 1st paragraph.       *  Measurement Timing: SeeSection 3, 2nd paragraph for          measurement timing andSection 3.2 for Interval Metric flag.Clark, et al.                Standards Track                   [Page 13]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013       *  Use and Applications: SeeSection 1.4.       *  Reporting Model: SeeRFC 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: SeeSection 3.2, Packets          Lost in Bursts definition.       *  Units of Measurement: SeeSection 3.2, Packets lost in bursts          definition.       *  Measurement Point(s) with Potential Measurement Domain: SeeSection 3, 1st paragraph.       *  Measurement Timing: SeeSection 3, 2nd paragraph for          measurement timing andSection 3.2 for Interval Metric flag.       *  Use and Applications: SeeSection 1.4.       *  Reporting Model: SeeRFC 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: SeeSection 3.2, Total          packets expected in bursts definition.       *  Units of Measurement: SeeSection 3.2, Total packets expected          in bursts definition.       *  Measurement Point(s) with Potential Measurement Domain: SeeSection 3, 1st paragraph.       *  Measurement Timing: SeeSection 3, 2nd paragraph for          measurement timing andSection 3.2 for Interval Metric flag.       *  Use and Applications: SeeSection 1.4.Clark, et al.                Standards Track                   [Page 14]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013       *  Reporting Model: SeeRFC 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: SeeSection 3.2, Number          of bursts definition.       *  Units of Measurement: SeeSection 3.2, Number of bursts          definition.       *  Measurement Point(s) with Potential Measurement Domain: SeeSection 3, 1st paragraph.       *  Measurement Timing: SeeSection 3, 2nd paragraph for          measurement timing andSection 3.2 for Interval Metric flag.       *  Use and Applications: SeeSection 1.4.       *  Reporting Model: SeeRFC 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: SeeSection 3.2, Sum of          Squares of Burst Durations definition.       *  Units of Measurement: SeeSection 3.2, Sum of Squares of Burst          Durations definition.       *  Measurement Point(s) with Potential Measurement Domain: SeeSection 3, 1st paragraph.       *  Measurement Timing: SeeSection 3, 2nd paragraph for          measurement timing andSection 3.2 for Interval Metric flag.       *  Use and Applications: SeeSection 1.4.       *  Reporting Model: SeeRFC 3611.Clark, et al.                Standards Track                   [Page 15]

RFC 6958                 RTCP XR Burst/Gap Loss                 May 2013Authors' 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.comClark, et al.                Standards Track                   [Page 16]