[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 7002

Audio/Video Transport Working Group                              G. Hunt
Internet-Draft                                              Unaffiliated
Intended status: Standards Track                                A. Clark
Expires: October 20, 2012                                       Telchemy
                                                                 G. Zorn
                                                             Network Zen
                                                                   Q. Wu
                                                                  Huawei
                                                          April 18, 2012


           RTCP XR Report Block for Discard metric Reporting
               draft-ietf-xrblock-rtcp-xr-discard-02.txt

Abstract

   This document defines an RTCP XR Report Block that allows the
   reporting of a simple discard count metric 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 October 20, 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



Hunt, et al.            Expires October 20, 2012                [Page 1]


Internet-Draft               RTCP XR Discard                  April 2012


   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.  Discard Report Block . . . . . . . . . . . . . . . . . . .  3
     1.2.  RTCP and RTCP XR Reports . . . . . . . . . . . . . . . . .  3
     1.3.  Performance Metrics Framework  . . . . . . . . . . . . . .  3
     1.4.  Applicability  . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Standards Language . . . . . . . . . . . . . . . . . . . .  4
   3.  Discard Metric Report Block  . . . . . . . . . . . . . . . . .  5
     3.1.  Report Block Structure . . . . . . . . . . . . . . . . . .  5
     3.2.  Definition of Fields in Discard Metric Report Block  . . .  5
   4.  SDP Signaling  . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  New RTCP XR Block Type value . . . . . . . . . . . . . . .  8
     5.2.  New RTCP XR SDP Parameter  . . . . . . . . . . . . . . . .  8
     5.3.  Contact information for registrations  . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   7.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10
   8.  Changes from previous version  . . . . . . . . . . . . . . . . 11
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13






















Hunt, et al.            Expires October 20, 2012                [Page 2]


Internet-Draft               RTCP XR Discard                  April 2012


1.  Introduction

1.1.  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 number of packets which are received
   correctly but are never played out, typically because they arrive too
   late to be played out (buffer underflow) or too early (buffer
   overflow).  The metric is applicable both to systems which use packet
   loss repair techniques (such as forward error correction [RFC5109] or
   retransmission [RFC4588]) and to those which do not.

   This metric is useful for identifying the existence, and
   characterising the severity, of a packet transport problem which may
   affect users' perception of a service delivered over RTP.

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

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].

1.4.  Applicability

   This metric is believed to be applicable to a large class of RTP
   applications which use a jitter buffer.












Hunt, et al.            Expires October 20, 2012                [Page 3]


Internet-Draft               RTCP XR Discard                  April 2012


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.  The Discard Metric counts
      only discarded packets.  The metric "cumulative number of packets
      lost" defined in [RFC3550] reports a count of packets lost from
      the media stream (single SSRC within single RTP session).
      Similarly the metric "number of packets discarded" reports a count
      of packets discarded from the media stream (single SSRC within
      single RTP session) arriving at the receiver.  Another metric
      defined in [RFC5725] is available to report on packets which are
      not recovered by any repair techniques which may be in use.


























Hunt, et al.            Expires October 20, 2012                [Page 4]


Internet-Draft               RTCP XR Discard                  April 2012


3.  Discard Metric Report Block

3.1.  Report Block Structure


        0               1               2               3
        0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    BT=NBGD    | I |DT |  resv.|      block length = 2         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        SSRC of Source                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    number of packets discarded                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: Report Block Structure

3.2.  Definition of Fields in Discard Metric Report Block

   Block type (BT): 8 bits

      A Discard Metric Report Block is identified by the constant ND.

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


   Interval Metric flag (I): 2 bits

      This field is used to indicate whether the Discard metric is an
      sampled,Interval or Cumulative metric, that is, whether the
      reported values applies to the most recent measurement interval
      duration between successive metrics reports (I=10) (the Interval
      Duration) or to the accumulation period characteristic of
      cumulative measurements (I=11) (the Cumulative Duration) or to the
      value of a continuously measured or calculated that has been
      sampled at end of the interval (I=01) (Sampled Value).


   Discard Type (DT): 2bits

      This field is used to identify the discard type used in this
      report block.  The discard type is defined as follows:

         01: packets are discarded due to too early arrival.






Hunt, et al.            Expires October 20, 2012                [Page 5]


Internet-Draft               RTCP XR Discard                  April 2012


         10: packets are discarded due to too late arrival.

         11: packets are discarded due to both early arrival and late
         arrival.


   Reserved (resv): 5 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].


   number of packets discarded: 32 bits

      Number of packets discarded over the period (Interval or
      Cumulative) covered by this report.

      If the measured value exceeds 0xFFFFFFFD, the value 0xFFFFFFFE
      SHOULD be reported to indicate an over-range measurement.  If the
      measurement is unavailable, the value 0xFFFFFFFF SHOULD be
      reported.

      Note that the number of packets expected in the period covered by
      the metric (whether interval or cumulative) is available from the
      difference between a pair of extended sequence numbers in the
      Measurement Identity block, so need not be repeated in this block.














Hunt, et al.            Expires October 20, 2012                [Page 6]


Internet-Draft               RTCP XR Discard                  April 2012


4.  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-pd-block

    xr-pd-block = "pkt-dscrd"


































Hunt, et al.            Expires October 20, 2012                [Page 7]


Internet-Draft               RTCP XR Discard                  April 2012


5.  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].

5.1.  New RTCP XR Block Type value

   This document assigns the block type value ND in the IANA "RTCP XR
   Block Type Registry" to the "Discard Metrics Block".

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

5.2.  New RTCP XR SDP Parameter

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

5.3.  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























Hunt, et al.            Expires October 20, 2012                [Page 8]


Internet-Draft               RTCP XR Discard                  April 2012


6.  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.












































Hunt, et al.            Expires October 20, 2012                [Page 9]


Internet-Draft               RTCP XR Discard                  April 2012


7.  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.











































Hunt, et al.            Expires October 20, 2012               [Page 10]


Internet-Draft               RTCP XR Discard                  April 2012


8.  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.

   Allocate 1 bit to distinguish early discard from later discard.

   Expand Interval Metric flag to 2 bit to allow using sampled metric.








































Hunt, et al.            Expires October 20, 2012               [Page 11]


Internet-Draft               RTCP XR Discard                  April 2012


9.  References

9.1.  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.

9.2.  Informative References

   [MONARCH]  Wu, Q., "Monitoring Architectures for RTP",
              ID draft-ietf-avtcore-monarch-12, April 2012.

   [RFC4588]  Rey, J., "RTP Retransmission Payload Format", RFC 4588,
              July 2006.

   [RFC5109]  Li, A., "RTP Payload Format for Generic Forward Error
              Correction", RFC 5109, July 2006.

   [RFC5725]  Begen, A., "RTCP XR Report Block for Post-Repair Loss
              metric Reporting", RFC 5725, February 2010.

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



















Hunt, et al.            Expires October 20, 2012               [Page 12]


Internet-Draft               RTCP XR Discard                  April 2012


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


   Glen Zorn
   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


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

   Email: sunseawq@huawei.com
















Hunt, et al.            Expires October 20, 2012               [Page 13]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/