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Versions: 00 01 02 03 04 05 RFC 7003

Audio/Video Transport Working Group                              G. Hunt
Internet-Draft                                              Unaffiliated
Intended status: Standards Track                                A. Clark
Expires: July 22, 2012                                          Telchemy
                                                                R. Huang
                                                              Q. Wu, Ed.
                                                                  Huawei
                                                        January 19, 2012


      RTCP XR Report Block for Burst/Gap Discard metric Reporting
          draft-ietf-xrblock-rtcp-xr-burst-gap-discard-01.txt

Abstract

   This document defines an RTCP XR Report Block that allows the
   reporting of Burst and Gap Discard metrics for use in a range of RTP
   applications.

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 22, 2012.

Copyright Notice

   Copyright (c) 2012 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



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Burst and Gap Discard Report Block . . . . . . . . . . . .  3
     1.2.  RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . .  3
     1.3.  Performance Metrics Framework  . . . . . . . . . . . . . .  3
     1.4.  Applicability  . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Standards Language . . . . . . . . . . . . . . . . . . . .  5
   3.  Burst/Gap Discard Block  . . . . . . . . . . . . . . . . . . .  6
     3.1.  Report Block Structure . . . . . . . . . . . . . . . . . .  6
     3.2.  Definition of Fields in Burst/Gap Loss Report Block  . . .  6
     3.3.  Derived metrics based on reported metrics  . . . . . . . .  7
   4.  Considerations for Voice-over-IP applications  . . . . . . . .  9
   5.  SDP Signaling  . . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
     6.1.  New RTCP XR Block Type value . . . . . . . . . . . . . . . 11
     6.2.  New RTCP XR SDP Parameter  . . . . . . . . . . . . . . . . 11
     6.3.  Contact information for registrations  . . . . . . . . . . 11
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   8.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 13
   9.  Changes from previous version  . . . . . . . . . . . . . . . . 14
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     10.2. Informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16





















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1.  Introduction

1.1.  Burst and Gap Discard Report Block

   This draft 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 discarded by the
   receiver due to jitter.  The discards during discard 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.  This block is
   intended to be used in conjunction with [DISCARD] which provides the
   total packets discarded, and on which this block therefore depends.
   However the metric in [DISCARD] may be used independently of the
   metrics in this block.

   This block provides information on transient IP problems.  Burst/Gap
   metrics are typically used in Cumulative reports however MAY be used
   in Interval reports.  The burstiness of packet discard affects user
   experience, may influence any sender strategies to mitigate the
   problem, and may also have diagnostic value.

   The metric belongs to the class of transport-related terminal metrics
   defined in [MONARCH] (work in progress).

   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] .

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.  Metrics
   described in this draft either reference external definitions or
   define metrics generally in accordance with the guidelines in
   [RFC6390].






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1.4.  Applicability

   These metrics are applicable to a range of RTP applications.
















































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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 RFC 2119 [RFC2119].

   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 shall
      be regarded as discarded.  A packet shall be classified as one of
      received (or OK), discarded or lost.


   Bursts and Gaps

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
























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3.  Burst/Gap Discard Block

   Metrics in this block report on Burst/Gap Discard in the stream
   arriving at the RTP system.

3.1.  Report Block Structure

   Burst/Gap Discard 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=NBGD    |I|   resv.     |      block length = 2         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        SSRC of Source                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            Packets Discarded in Bursts        |    Total...   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | ...Packets expected in bursts |           Reserved.           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 1: Report Block Structure

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

   Block type (BT): 8 bits

      A Burst/Gap Discard Report Block is identified by the constant
      NBGD.

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


   Interval Metric flag (I): 1 bit

      This field is used to indicate whether the Packet Delay Variation
      metrics block is an Interval or a Cumulative report, that is,
      whether the reported values apply to the most recent measurement
      interval duration between successive metrics reports (I=1) (the
      Interval Duration) or to the accumulation period characteristic of
      cumulative measurements (I=0) (the Cumulative Duration).








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   Reserved (resv): 7 bits

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


   block length: 16 bits

      The length of this report block in 32-bit words, minus one.  For
      the Delay block, the block length is equal to 2.


   SSRC of source: 32 bits

      As defined in Section 4.1 of [RFC3611].


   Packets lost in bursts: 24 bits

      The total number of packets lost during loss bursts.

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

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


   Reserved (resv): 16 bits

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


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 [MEASID], discard block [DISCARD] (which MUST be
   present in the same RTCP packet as the Burst/Gap Discard block).



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   These metrics provides the following information relevant to
   statistical parameters, including:

   o  The fraction of packets discarded during bursts (burst discard
      rate in [SUMSTAT])

   o  The fraction of packets discarded during gaps (gap discard rate in
      [SUMSTAT])

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








































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4.  Considerations for Voice-over-IP applications

   This metric block is applicable to a broad range of RTP applications.
   Where the metric is used with a Voice-overIP (VoIP) application, the
   following considerations apply.

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

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

   The recommended value for the threshold Gmin in [RFC3611] results in
   a Burst being a period of time during which the call quality is
   degraded to a similar extent to a typical PCM Severely Errored Second
   [PSES].































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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.

   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.

   rtcp-xr-attrib = "a=" "rtcp-xr" ":" [xr-format *(SP xr-format)] CRLF

   (defined in [RFC3611])

   xr-format =/ xr-bgd-block

   xr-bgd-block = "brst-gap-dscrd"


































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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 value

   This document assigns the block type value NDEL in the IANA "RTCP XR
   Block Type Registry" to the "Burst/Gap Discard Metrics Block".

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

6.2.  New RTCP XR SDP Parameter

   This document also registers a new parameter "brst-gap-dscrd" in the
   "RTCP XR SDP Parameters Registry".

6.3.  Contact information for registrations


   The contact information for the registrations is:

   Geoff Hunt (r.geoff.hunt@gmail.com)

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























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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

   The authors gratefully acknowledge the comments and contributions
   made by Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin
   Connor, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert
   Higashi, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith
   Lantz, Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho,
   Ravi Raviraj, Albrecht Schwarz, Tom Taylor, and Hideaki Yamada.











































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9.  Changes from previous version

   Changed BNF for SDP following Christian Groves' and Tom Taylor's
   comments (4th and 5th May 2009), now aligned with RFC 5234 section 
   3.3 "Incremental Alternatives".

   Updated references.












































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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

   [DISCARD]  Hunt, G., "RTCP XR Report Block for Discard metric
              Reporting", ID draft-ietf-xrblock-rtcp-xr-discard-01,
              December 2011.

   [MEASID]   Wu, Q., "Measurement Identity and information Reporting
              using SDES item and XR Block",
              ID draft-ietf-xrblock-rtcp-xr-meas-identity-01,
              October 2011.

   [MONARCH]  Hunt, G., "Monitoring Architectures for RTP",
              ID draft-ietf-avtcore-monarch-04, August 2011.

   [PSES]     "URL",  http://www.its.bldrdoc.gov/projects/devglossary/
              _severely_errored_second.html, October 2011.

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

   [SUMSTAT]  Zorn, G., "RTCP XR for Summary Statistics Metrics
              Reporting", ID draft-zorn-xrblock-rtcp-xr-al-stat-03,
              October 2011.












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Authors' Addresses

   Geoff Hunt
   Unaffiliated

   Email: r.geoff.hunt@gmail.com


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

   Email: alan.d.clark@telchemy.com


   Rachel Huang
   Huawei Technologies Co., Ltd.
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: Rachel@huawei.com


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

   Email: sunseawq@huawei.com


















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