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RTCP XR Blocks for Synchronization Delay and Offset Metrics Reporting
draft-asaeda-xrblock-rtcp-xr-synchronization-04

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This is an older version of an Internet-Draft whose latest revision state is "Expired".
Authors Hitoshi Asaeda , Rachel Huang
Last updated 2012-02-21 (Latest revision 2012-02-02)
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draft-asaeda-xrblock-rtcp-xr-synchronization-04
Network Working Group                                          H. Asaeda
Internet-Draft                                           Keio University
Intended status: Standards Track                                R. Huang
Expires: August 25, 2012                                           Q. Wu
                                                                  Huawei
                                                       February 22, 2012

 RTCP XR Blocks for Synchronization Delay and Offset Metrics Reporting
            draft-asaeda-xrblock-rtcp-xr-synchronization-04

Abstract

   This document defines two RTCP XR Report Blocks and associated SDP
   parameters that allow the reporting of synchronization delay and
   offset 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.

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   This Internet-Draft will expire on August 25, 2012.

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   document authors.  All rights reserved.

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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Standards Language . . . . . . . . . . . . . . . . . . . .  3
   3.  Applicability  . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  RTP Flows Initial Synchronization Delay Report Block . . . . .  4
     4.1.  Metric Block Structure . . . . . . . . . . . . . . . . . .  4
     4.2.  Definition of Fields in RTP Flow Initial
           Synchronization Delay Metrics Block  . . . . . . . . . . .  5
   5.  RTP Flows General Synchronization Offset Metrics Block . . . .  5
     5.1.  Metric Block Structure . . . . . . . . . . . . . . . . . .  6
     5.2.  Definition of Fields in RTP Flow General
           Synchronization Offset Metrics Block . . . . . . . . . . .  6
   6.  SDP Signaling  . . . . . . . . . . . . . . . . . . . . . . . .  7
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  8
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     10.1. Normative References . . . . . . . . . . . . . . . . . . .  9
     10.2. Informative References . . . . . . . . . . . . . . . . . .  9
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . .  9
     A.1.  draft-asaeda-xrblock-rtcp-xr-syncronization-00 . . . . . .  9
     A.2.  draft-asaeda-xrblock-rtcp-xr-syncronization-01 . . . . . . 10
     A.3.  draft-asaeda-xrblock-rtcp-xr-syncronization-02 . . . . . . 10
     A.4.  draft-asaeda-xrblock-rtcp-xr-syncronization-03 . . . . . . 10
     A.5.  draft-asaeda-xrblock-rtcp-xr-syncronization-04 . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10

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1.  Introduction

   This draft defines a new block type to augment those defined in
   [RFC3611], for use in a range of RTP applications.

   This new block type supports reporting of Initial synchronization
   Delay to establish multimedia session.  Information is recorded about
   time difference between the start of RTP sessions and the time the
   RTP receiver acquires all components of RTP sessions in the
   multimedia session [RFC6051].

   It also supports reporting of the relative Synchronization offset
   time of two arbitrary streams (e.g., between audio and video
   streams), with the same RTCP CNAME included in RTCP SDES packets
   [RFC3550].  Information is recorded about the synchronization offset
   time of each RTP stream relative to the reference RTP stream with the
   same CNAME and General Synchronization Offset of zero.

   These metrics belong to the class of terminal related transport level
   metrics defined in [MONARCH].

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:

   Synchronization offset:

      The time difference of the actual delay of the measured RTP stream
      relative to the expected delay of the reference RTP stream with
      the same CNAME.

3.  Applicability

   The report blocks defined in this document could be used by dedicated
   network monitoring applications.

   When joining each session in layered video sessions [RFC6190] or the
   multimedia sessions, a receiver may not synchronize playout across
   the multimedia sessions or layered video sessions until RTCP SR

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   packets have been received on all the components of RTP sessions.
   The components of RTP sessions are referred to as each RTP stream for
   each media type in multimedia sessions or each RTP stream at each
   layer in the layered video sessions.  For unicast session, the delay
   due to negotiation of NAT pinholes, firewall holes, quality-of-
   service, and media security keys is contributed to such initial
   synchronization playout.  For multicast session, such initial
   synchronization delay varies with the session bandwidth,the number of
   members, and the number of senders in the session.  The RTP flow
   Initial synchronization delay block can be used to report the initial
   synchronization delay to receive all the RTP streams belonging to the
   same multimedia session or layered video session. beyond the
   information carried in the standard RTCP packet format.  In the
   absence of packet loss, the initial synchronization delay equals to
   the average time taken to receive the first RTCP packet in the RTP
   session with the longest RTCP reporting interval.  In the presence of
   packet loss, the media synchronization needs to based on the in-band
   mapping of RTP and NTP- format timestamps [RFC6051] or wait until the
   reporting interval has passed, and the next RTCP SR packet is sent.

   In an RTP multimedia session, there can be an arbitrary number of
   streams carried in different RTP streams, with the same RTCP CNAME.
   These streams may be not synchronized with each other.  For example,
   one audio stream and one video stream belong to the same session and
   audio stream are transmitted lag behind video stream for multiple
   tens of milliseconds.  The RTP Flows General Synchronization Offset
   block can be used to report such synchronization offset between video
   stream and audio stream.

4.  RTP Flows Initial Synchronization Delay Report Block

   This block is sent by RTP receivers and reports Initial
   synchronization delay beyond the information carried in the standard
   RTCP packet format.  Information is recorded about time difference
   between the start of RTP sessions and the time the RTP receiver
   acquires all components of RTP sessions [RFC6051].

4.1.  Metric Block Structure

   The RTP Flows Initial Synchronization Delay Report Block has the
   following format:

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       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=TBD    |   Reserved    |          Block length         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      SSRC of Source                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               Initial Synchronization Delay                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.2.  Definition of Fields in RTP Flow Initial Synchronization Delay
      Metrics Block

   Block type (BT): 8 bits

      The Statistics Summary Report Block is identified by the constant
      <RFISD>.

   Block length: 16 bits

      The constant 2, in accordance with the definition of this field in
      Section 3 of RFC 3611 [RFC3611].

   SSRC of Source: 32 bits

      The SSRC of the media source SHALL be set to the value of the SSRC
      identifier carried in the arbitrary RTP stream belonging to the
      same multimedia session.

   Initial Synchronization Delay: 32 bits

      The average delay, expressed in units of 1/65536 seconds, between
      the RTCP packets received on all of the components RTP sessions
      and the beginning of session [RFC6051].  The value is calculated
      based on the information contained in RTCP SR packets or the in-
      band mapping of RTP and NTP- format timestamps [RFC6051].  If
      there is no packet loss, the initial synchronisation delay is
      expected to be equal to the average time taken to receive the
      first RTCP packet in the RTP session with the longest RTCP
      reporting interval.

5.  RTP Flows General Synchronization Offset Metrics Block

   In the RTP multimedia sessions, there can be an arbitrary number of
   streams and each stream (e.g., audio stream or video stream) is sent
   in a separate RTP stream.  The receiver associates RTP streams to be
   synchronised by means of RTCP CNAME contained in the RTCP Source

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   Description (SDES) packets [RFC3550].

   This block is sent by RTP receivers and reports the general
   synchronization offset time of these RTP streams to be synchronized.
   Information is recorded about the time difference of the actual delay
   of the measured RTP stream relative to the expected delay of the
   reference RTP stream with the same CNAME.  The expected delay of the
   reference RTP stream can be chosen as the first stream delay or the
   average delay of all the streams in the same session according to the
   similar rule defined in section 6.2.2.1 of [Y.1540].

5.1.  Metric Block Structure

   The RTP Flow General Synchronization Offset Report Block has the
   following format:

       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=TBD    |   Reserved    |         Block length          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        SSRC of source                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           begin_seq           |          end_seq              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    General Synchronization Offset of packet begin_seq         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | General Synchronization Offset of packet begin_seq+1 mod 65536|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         .......................
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | General Synchronization Offset of packet end_seq-1 mod 65536  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.2.  Definition of Fields in RTP Flow General Synchronization Offset
      Metrics Block

   Block type (BT): 8 bits

      The RTP Flow General Synchronization Offset Report Block is
      identified by the constant <RFGSO>.

   Block length: 16 bits

      The constant end_seq-begin_seq-1+2, in accordance with the
      definition of this field in Section 3 of RFC 3611 [RFC3611].

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   SSRC of Source: 32 bits

      The SSRC of the media source SHALL be set to the value of the SSRC
      identifier of the reference RTP stream to which the XR relates.

   begin_seq: 16 bits

      The first sequence number that this block reports on.

   end_seq: 16bits

      The last sequence number that this block reports on plus one.

   Packet i General synchronization offset: 32 bits

      This field represents the synchronization offset time of one RTP
      stream in milliseconds relative to the reference RTP stream with
      the same CNAME and General Synchronisation Offset of zero
      [RFC6051] This value is calculated based on the interarrival time
      between an arbitrary RTP packet and the reference RTP packet with
      the same CNAME , and timestamps of this arbitrary RTP packet and
      the reference RTP packet with the same CNAME.

6.  SDP Signaling

   Two new parameters are defined for the two report blocks defined in
   this document to be used with Session Description Protocol (SDP)
   [RFC4566] using the Augmented Backus-Naur Form (ABNF) [RFC5234].
   They have the following syntax within the "rtcp-xr" attribute
   [RFC3611]:

        rtcp-xr-attrib =  "a=rtcp-xr:"
                          [xr-format *(SP xr-format)] CRLF
             xr-format = RTP-flows-init-syn
                       / RTP-flows-general-syn
              RTP-flows-init-syn = "RTP-flows-init-syn"
                              ["=" max-size]
              RTP-flow-general-syn = "RTP-flows-general-syn"
                                ["=" max-size]
              max-size = 1*DIGIT ; maximum block size in octets

   Refer to Section 5.1 of RFC 3611 [RFC3611] for a detailed description
   and the full syntax of the "rtcp-xr" attribute.

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7.  IANA Considerations

   New report block types for RTCP XR are subject to IANA registration.
   For general guidelines on IANA allocations for RTCP XR, refer to
   Section 6.2 of [RFC3611].

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

      Name:       RFISD
      Long Name:  RTP Flows Initial Synchronization Delay
      Value       <RFISD>
      Reference:  Section 4

      Name:       RFGSO
      Long Name:  RTP Flows General Synchronization Offset Metrics Block
      Value       <RFGSO>
      Reference:  Section 5

   This document also registers two new SDP [RFC4566] parameters for the
   "rtcp-xr" attribute in the RTCP XR SDP Parameters Registry:

      *  "RTP-flows-init-syn"
      *  "RTP-flows-general-syn"

   The contact information for the registrations is:

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

8.  Security Considerations

   The new RTCP XR report blocks proposed in this document introduces no
   new security considerations beyond those described in [RFC3611].

9.  Acknowledgements

   The authors would like to thank Bill Ver Steeg, David R Oran, Ali
   Begen, Colin Perkins, Roni Even, Youqing Yang, Wenxiao Yu and
   Yinliang Hu for their valuable comments and suggestions on this
   document.

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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.

   [RFC6051]  Perkins, C. and T. Schierl, "Rapid Synchronisation of RTP
              Flows", RFC 6051, November 2010.

   [RFC6190]  Wenger, S., Wang, Y., Schierl, T., and A. Eleftheriadis,
              "RTP Payload Format for Scalable Video Coding", RFC 6190,
              May 2011.

10.2.  Informative References

   [MONARCH]  Wu, Q., "Monitoring Architectures for RTP",
              ID draft-ietf-avtcore-monarch-00, April 2011.

   [Y.1540]   ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and
              availability performance parameters", November 2007.

Appendix A.  Change Log

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

A.1.  draft-asaeda-xrblock-rtcp-xr-syncronization-00

   This document is separated from
   draft-wu-xrblock-rtcp-xr-quality-monitoring-01 with some editorial
   changes and focuses on RTP Flow Initial Synchronization Delay and RTP
   Flows General Synchronization Offset.

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A.2.  draft-asaeda-xrblock-rtcp-xr-syncronization-01

   Separate Synchronization Delay and Offset Metrics Block into two
   independent block based on comments on the list.

A.3.  draft-asaeda-xrblock-rtcp-xr-syncronization-02

   The following are the major changes compared to previous version 01:

   o  Clarify which synchronization is reported in section 4 and 5.
   o  Allow calculating the synchronization delay based on RTP header
      extension defined in RFC6051
   o  Explain what the components of RTP session are in section 3.

A.4.  draft-asaeda-xrblock-rtcp-xr-syncronization-03

   The following are the major changes compared to previous version 02:

   o  Support multiple general synchronization offset reporting.
   o  Other Editorial Changes.

A.5.  draft-asaeda-xrblock-rtcp-xr-syncronization-04

   The following are the major changes compared to previous version 03:

   o  Add a definition for synchronization offset.
   o  Use additional text in applicability section to clarify the
      difference between synchronization delay and offset.
   o  Add a reference to tell how to select the reference stream.
   o  Other Editorial Changes.

Authors' Addresses

   Hitoshi Asaeda
   Keio University
   Graduate School of Media and Governance
   5322 Endo
   Fujisawa, Kanagawa  252-0882
   Japan

   Email: asaeda@wide.ad.jp

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

   Email: Rachel@huawei.com

   Qin Wu
   Huawei Technologies Co., Ltd.
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: sunseawq@huawei.com

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