GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc6843

Internet Engineering Task Force (IETF) A. Clark Request for Comments: 6843 Telchemy Category: Standards Track K. Gross ISSN: 2070-1721 AVA Networks

                                                                 Q. Wu
                                                                Huawei
                                                          January 2013
          RTP Control Protocol (RTCP) Extended Report (XR)
                  Block for Delay Metric Reporting

Abstract

 This document defines an RTP Control Protocol (RTCP) Extended Report
 (XR) block that allows the reporting of delay metrics for use in a
 range of Real-time Transport Protocol (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/rfc6843.

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.

Clark, et al. Standards Track [Page 1] RFC 6843 RTCP XR Delay January 2013

Table of Contents

 1. Introduction ....................................................2
    1.1. Packet Delay Metrics Block .................................2
    1.2. RTCP and RTCP XR Reports ...................................2
    1.3. Performance Metrics Framework ..............................3
    1.4. Applicability ..............................................3
 2. Terminology .....................................................3
    2.1. Standards Language .........................................3
 3. Delay Block .....................................................3
    3.1. Report Block Structure .....................................4
    3.2. Definition of Fields in Delay Metrics Report Block .........4
 4. SDP Signaling ...................................................6
    4.1. SDP rtcp-xr-attrib Attribute Extension .....................7
    4.2. Offer/Answer Usage .........................................7
 5. IANA Considerations .............................................7
    5.1. New RTCP XR Block Type Value ...............................7
    5.2. New RTCP XR SDP Parameter ..................................7
    5.3. Contact Information for Registrations ......................7
 6. Security Considerations .........................................8
 7. Contributors ....................................................8
 8. Acknowledgments .................................................8
 9. References ......................................................8
    9.1. Normative References .......................................8
    9.2. Informative References .....................................9

1. Introduction

1.1. Packet Delay 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 mean, minimum, and maximum values of
 the network round-trip delay between RTP interfaces in peer RTP end
 systems as measured, for example, using the RTCP method described in
 [RFC3550].  It also supports reporting of the component of the round-
 trip delay internal to the local RTP system.
 The network metrics belong to the class of transport metrics defined
 in [RFC6792].

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 document defines a new Extended Report block for
 use with [RFC3550] and [RFC3611].

Clark, et al. Standards Track [Page 2] RFC 6843 RTCP XR Delay January 2013

1.3. Performance Metrics Framework

 The Performance Metrics Framework [RFC6390] provides guidance on the
 definition and specification of performance metrics.  The RTP
 Monitoring Architectures [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 in which
 this report block would be useful, such as multimedia conferencing
 and streaming audio and video.  Knowledge of the round-trip delay and
 delay characteristics can aid other receivers in sizing their receive
 buffers and selecting a playout delay.  The same information is also
 valuable to network managers in troubleshooting network and user
 experience issues.

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].

3. Delay Block

 Metrics in this block report on packet delay in the stream arriving
 at the RTP system.  The measurement of these metrics is made either
 at the receiving end of the RTP stream or at the sending end of the
 RTP stream.  Instances of this metrics block refer by synchronization
 source (SSRC) to the separate auxiliary Measurement Information block
 [RFC6776], which contains measurement periods (see [RFC6776], Section
 4.2).  This metrics block relies on the measurement period in the
 Measurement Information block indicating the span of the report and
 SHOULD be sent in the same compound RTCP packet as the Measurement
 Information block.  If the measurement period is not received in the
 same compound RTCP packet as this metrics block, this metrics block
 MUST be discarded.

Clark, et al. Standards Track [Page 3] RFC 6843 RTCP XR Delay January 2013

3.1. Report Block Structure

 Delay 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=16      | I |   resv.   |      block length = 6         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           SSRC of Source                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Mean Network Round-Trip Delay                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   Min Network Round-Trip Delay                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   Max Network Round-Trip Delay                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               End System Delay - Seconds (bit 0-31)           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              End System Delay - Fraction (bit 0-31)           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   Figure 1: Report Block Structure

3.2. Definition of Fields in Delay Metrics Report Block

 Block type (BT): 8 bits
    A Delay Report Block is identified by the constant 16.
 Interval Metric flag (I): 2 bit
    This field is used to indicate whether the delay 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.

Clark, et al. Standards Track [Page 4] RFC 6843 RTCP XR Delay January 2013

 Reserved (resv): 6 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 delay block, the block length is equal to 6.
 SSRC of source: 32 bits
    As defined in Section 4.1 of [RFC3611].
 Mean Network Round-Trip Delay: 32 bits
    The Mean Network Round-Trip Delay is the mean value of the RTP-to-
    RTP interface round-trip delay over the measurement period,
    expressed in units of 1/65536 seconds.  This value is typically
    determined using "the NTP timestamp field" in the RTCP sender
    report (SR) and "the last SR (LSR) field","delay since last SR
    (DLSR) field" in the RTCP receiver report (RR) (see [RFC3550],
    Section 6.4.1 and Figure 2).  It also can be determined using "the
    NTP timestamp field" in the RTCP Receiver Reference Time Report
    Block and "last RR (LRR) field", "delay since last RR (DLRR)
    field" in the DLRR Report Block (see [RFC3611], Section 4.5).
    If only one measurement of Round-Trip Delay is available for the
    time span of the report (i.e., the measurement period) (whether
    Interval or Cumulative), this single value SHOULD be reported as
    the mean value.
    If the measurement is unavailable, the value of this field with
    all bits set to 1 MUST be reported.
 Min Network Round-Trip Delay: 32 bits
    The Min Network Round Trip Delay is the minimum value of the RTP-
    to-RTP interface round-trip delay over the measurement period,
    expressed in units of 1/65536 seconds.  This value is typically
    determined using the NTP timestamp field in the RTCP SR and LSR
    field and DLSR field in the RTCP RR.  It also can be determined
    using the NTP timestamp field in the RTCP Receiver Reference Time
    Report Block and LRR field and DLRR field in the DLRR Report
    Block.

Clark, et al. Standards Track [Page 5] RFC 6843 RTCP XR Delay January 2013

    If only one measurement of Round Trip Delay is available for the
    time span of the report (i.e., the measurement period) (whether
    Interval or Cumulative), this single value SHOULD be reported as
    the minimum value.
    If the measurement is unavailable, the value of this field with
    all bits set to 1 MUST be reported.
 Max Network Round-Trip Delay: 32 bits
    The Max Network Round-Trip Delay is the maximum value of the RTP-
    to-RTP interface round-trip delay over the measurement period,
    expressed in units of 1/65536 seconds.  This value is typically
    determined using the NTP timestamp field in the RTCP SR and LSR
    field and DLSR field in the RTCP RR.  It also can be determined
    using the NTP timestamp field in the RTCP Receiver Reference Time
    Report Block and LRR field and DLRR field in the DLRR Report
    Block.
    If only one measurement of Round-Trip Delay is available for the
    time span of the report (i.e.,the measurement period) (whether
    Interval or Cumulative), this single value SHOULD be reported as
    the maximum value.
    If the measurement is unavailable, the value of this field with
    all bits set to 1 MUST be reported.
 End System Delay: 64 bits
    The End System Delay is the internal round-trip delay within the
    reporting endpoint, calculated using the nominal value of the
    jitter buffer delay plus the accumulation/encoding and decoding/
    playout delay associated with the codec being used.  The value of
    this field is represented using a 64-bit NTP-format timestamp as
    defined in [RFC5905], which is a 64-bit unsigned fixed-point
    number with the integer part in the first 32 bits and the
    fractional part in the last 32 bits.
    If the measurement is unavailable, the value of this field with
    all bits set to 1 MUST be reported.

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.

Clark, et al. Standards Track [Page 6] RFC 6843 RTCP XR Delay January 2013

4.1. 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.
 xr-format =/ xr-delay-block
 xr-delay-block ="delay"

4.2. Offer/Answer Usage

 When SDP is used in offer/answer context, the SDP Offer/Answer usage
 defined in [RFC3611] applies.

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 16 in the IANA "RTP
 Control Protocol Extended Reports (RTCP XR) Block Type Registry" to
 the "Delay Metrics Block".

5.2. New RTCP XR SDP Parameter

 This document also registers a new parameter "delay" in the "RTP
 Control Protocol Extended Reports (RTCP XR) Session Description
 Protocol (SDP) Parameters" registry.

5.3. Contact Information for Registrations

    The contact information for the registrations is:
    Qin Wu (sunseawq@huawei.com)
    Huawei
    101 Software Avenue, Yuhua District
    Nanjing, Jiangsu  210012
    China

Clark, et al. Standards Track [Page 7] RFC 6843 RTCP XR Delay January 2013

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.

7. Contributors

 Geoff Hunt wrote the initial version of this document.

8. Acknowledgments

 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, Jing
 Zhao, Kevin Gross, Colin Perkins, Charles Eckel, Glen Zorn, Shida
 Schubert, Barry Leiba, Sean Turner, Robert Sparks, Benoit Claise, and
 Stephen Farrell.

9. References

9.1. 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.
 [RFC5905]  Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
            Time Protocol Version 4: Protocol and Algorithms
            Specification", RFC 5905, June 2010.

Clark, et al. Standards Track [Page 8] RFC 6843 RTCP XR Delay January 2013

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

9.2. Informative References

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

Authors' Addresses

 Alan Clark
 Telchemy Incorporated
 2905 Premiere Parkway, Suite 280
 Duluth, GA  30097
 USA
 EMail: alan.d.clark@telchemy.com
 Kevin Gross
 AVA Networks
 EMail: kevin.gross@avanw.com
 Qin Wu
 Huawei
 101 Software Avenue, Yuhua District
 Nanjing, Jiangsu  210012
 China
 EMail: sunseawq@huawei.com

Clark, et al. Standards Track [Page 9]

/data/webs/external/dokuwiki/data/pages/rfc/rfc6843.txt · Last modified: 2013/01/15 00:49 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki