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rfc:rfc6776

Internet Engineering Task Force (IETF) A. Clark Request for Comments: 6776 Telchemy Category: Standards Track Q. Wu ISSN: 2070-1721 Huawei

                                                          October 2012
       Measurement Identity and Information Reporting Using a

Source Description (SDES) Item and an RTCP Extended Report (XR) Block

Abstract

 This document defines an RTP Control Protocol (RTCP) Source
 Description (SDES) item and an RTCP Extended Report (XR) block
 carrying parameters that identify and describe a measurement period
 to which one or more other RTCP XR blocks may refer.

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/rfc6776.

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

Clark & Wu Standards Track [Page 1] RFC 6776 Measurement Identity and Duration October 2012

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   1.1.  RTCP and RTCP XRs . . . . . . . . . . . . . . . . . . . . . 3
   1.2.  Performance Metrics Framework . . . . . . . . . . . . . . . 3
   1.3.  Applicability . . . . . . . . . . . . . . . . . . . . . . . 3
 2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   2.1.  Standards Language  . . . . . . . . . . . . . . . . . . . . 4
 3.  Measurement Identity SDES Item  . . . . . . . . . . . . . . . . 4
   3.1.  APSI: Application-Specific Identifier SDES Item . . . . . . 4
 4.  Measurement Information XR Block  . . . . . . . . . . . . . . . 5
   4.1.  Report Block Structure  . . . . . . . . . . . . . . . . . . 5
   4.2.  Definition of Fields in Measurement Information Report
         Block . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
 5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   5.1.  New RTCP SDES Item Type Value . . . . . . . . . . . . . . . 7
   5.2.  New RTCP XR Block Type Value  . . . . . . . . . . . . . . . 7
   5.3.  Contact Information for Registrations . . . . . . . . . . . 7
 6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
 7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
   7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
   7.2.  Informative References  . . . . . . . . . . . . . . . . . . 8

1. Introduction

 This document defines one new RTP Control Protocol (RTCP) Source
 Description (SDES) [RFC3550] item and one new Extended Report (XR)
 block carrying parameters that identify and describe a measurement
 period to which one or more other RTCP XR blocks may refer.
 The SDES item provides a field for an application-specific auxiliary
 identifier.  This identifier may be used to correlate data in XR
 blocks within an RTP session with data from a non-RTP session.
 An RTCP Measurement Identity SDES packet may be associated with a set
 of RTCP XR metrics blocks that share the same application-specific
 measurement identifier.
 The XR block does not contain any measurement results (metrics).
 Instead, it provides information relevant to a measurement reported
 in one or more other block types, including:
 o  the sequence number of the first packet of the RTP session,
 o  the extended sequence numbers of the first packet of the current
    measurement interval, and the last packet included in the
    measurement,

Clark & Wu Standards Track [Page 2] RFC 6776 Measurement Identity and Duration October 2012

 o  the duration of the most recent measurement interval, and
 o  the duration of the interval applicable to cumulative measurements
    (which may be the duration of the RTP session to date).
 The calculation method of the extended RTP sequence number is
 provided in the Real-time Transport Protocol (RTP) [RFC3550].
 The RTCP XR block containing the measurement information is intended
 to provide a single copy of the information necessary to relate
 measurement data in the RTCP XR blocks to the stream and measurement
 period to which they refer.  Commonly, multiple other small metric
 blocks contain measurement data for the same stream and period, and
 overhead would be large if all of these metric blocks carried
 duplicated data for measurement identification.
 The RTCP XR block may be associated with a set of RTCP XR metrics
 blocks that share the same information relevant to a reported
 measurement.  There may be several such sets in an RTCP packet, in
 which each set shares the same information relevant to a reported
 measurement.  There may also be RTCP XR blocks in the packet that are
 not associated with a Measurement Information block, for example,
 blocks that were defined before the Measurement Identity and
 information mechanism were introduced by this document.

1.1. RTCP and RTCP XRs

 The use of RTCP for reporting is defined in [RFC3550].  [RFC3611]
 defines an extensible structure for reporting by using an RTCP XR.
 [RFC3611] also defines the use of XR blocks.  This document defines a
 new Extended Report block.

1.2. Performance Metrics Framework

 The Performance Metrics Framework [RFC6390] provides guidance on the
 definition and specification of performance metrics.  The RTP
 Monitoring Architectures [MONARCH] provides guidelines for reporting
 block format using RTCP XR.  The SDES item and XR block described in
 this document are in accordance with [RFC6390] and [MONARCH].

1.3. Applicability

 The RTCP SDES item and the RTCP XR block defined in this document
 provide information relevant to the measurements for members of a
 family of RTCP XR metrics blocks that are designed to use it.  To use
 the mechanism defined here, the RTCP XR block containing measurement
 information is not required to be in the same RTCP packet as the SDES
 item containing measurement identity.

Clark & Wu Standards Track [Page 3] RFC 6776 Measurement Identity and Duration October 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].

3. Measurement Identity SDES Item

 This section defines the format of the Measurement Identity SDES
 item.  The SDES item is carried in the RTCP SDES packet.  The packet
 format for the RTCP SDES is defined in Section 6.5 of [RFC3550].
 Each SDES packet is composed of a header with fixed-length fields for
 version, source count, packet type (PT), and length, followed by zero
 or more SDES items.  In the SDES packet, the PT field is set to SDES
 (202).

3.1. APSI: Application-Specific Identifier SDES Item

  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    APSI=10    |     length    |application-specific identifier
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   ....
 +-+-+-+-+-+-+-+-+
 The application-specific identifier is an additional identifier that
 is useful in the context of a specific application, e.g., an MPEG-2
 transport identifier [MPEG2].  This item MUST be ignored by
 applications that are not configured to make use of it.  The
 identifier is variable length.  Its length is described by the length
 field.  The value of the length field does not include the two-octet
 SDES item header.

Clark & Wu Standards Track [Page 4] RFC 6776 Measurement Identity and Duration October 2012

4. Measurement Information XR Block

4.1. 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=14     |    Reserved   |      block length = 7         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                    SSRC of stream source                      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |            Reserved           |    first sequence number      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |           extended first sequence number of interval          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                 extended last sequence number                 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              Measurement Duration (Interval)                  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Measurement Duration (Cumulative) - Seconds (bit 0-31)    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Measurement Duration (Cumulative) - Fraction (bit 0-31)   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Report Block Structure

4.2. Definition of Fields in Measurement Information Report Block

 Block type (BT): 8 bits
    A Measurement Information Block is identified by the constant 14.
 Reserved: 8 bits
    These bits are reserved.  They MUST be set to zero by senders and
    ignored by receivers.
 Block Length: 16 bits
    The length of this report block in 32-bit words minus one.  For
    the Measurement Information Block, the block length is equal to 7.
 SSRC of source: 32 bits
    As defined in Section 4.1 of [RFC3611].

Clark & Wu Standards Track [Page 5] RFC 6776 Measurement Identity and Duration October 2012

 Reserved: 16 bits
    These bits are reserved.  They MUST be set to zero by senders and
    ignored by receivers.
 First sequence number: 16 bits
    The RTP sequence number of the first received RTP packet of the
    session, used to determine the number of packets contributing to
    cumulative measurements.
 Extended first sequence number of interval: 32 bits
    The extended RTP sequence number of the first received RTP packet
    of the current measurement interval.  The extended sequence number
    is expressed as the low 16-bit value containing the sequence
    number received in an RTP data packet and the most significant
    16-bit value containing the corresponding count of sequence number
    cycles.  For additional information on extended sequence numbers,
    see the "extended highest sequence number received" definition in
    Section 6.4.1 of RFC 3550 and Appendix A.1 of RFC 3550.
 Extended last sequence number: 32 bits
    The extended RTP sequence number of the last received RTP packet
    that contributed to this measurement.  The extended sequence
    number is expressed as the low 16-bit value containing the
    sequence number received in an RTP data packet and the most
    significant 16-bit value containing the corresponding count of
    sequence number cycles.  For additional information on extended
    sequence numbers, see the "extended highest sequence number
    received" definition in Section 6.4.1 of RFC 3550 and Appendix A.1
    of RFC 3550.
 Measurement Duration (Interval): 32 bits
    The duration, expressed in units of 1/65536 seconds, of the
    reporting interval applicable to Interval reports that use this
    Measurement Information Block.  The value of this field can be
    calculated by the receiver of the RTP media stream, for example,
    based on received RTP media packets or using the RTCP method
    described in [RFC3550].

Clark & Wu Standards Track [Page 6] RFC 6776 Measurement Identity and Duration October 2012

 Measurement Duration (Cumulative): 64 bits
    The duration of the reporting interval applicable to Cumulative
    reports that use this Measurement Information Block.  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.  It can be calculated by the
    receiver of the RTP media stream, for example, based on received
    RTP media packets or using the RTCP method described in [RFC3550].

5. IANA Considerations

 A new SDES item type for RTCP SDES and a new XR block type for RTCP
 XR have been registered with IANA.  For general guidelines on IANA
 considerations, refer to [RFC3550] for RTCP SDES and [RFC3611] for
 RTCP XR.

5.1. New RTCP SDES Item Type Value

 This document adds the Measurement Identity SDES item to the IANA
 "RTP SDES item types" registry as follows:
 abbrev.      name                               value
 APSI         Application-Specific Identifier    10

5.2. New RTCP XR Block Type Value

 This document assigns the block type value 14 in the IANA "RTCP XR
 Block Type Registry" to the "Measurement Information Block".

5.3. Contact Information for Registrations

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

6. Security Considerations

 RTCP reports can contain sensitive information, including information
 about the nature and duration of a session established between two or
 more endpoints.  Therefore, the use of security mechanisms with RTP,
 as documented in Section 9 of [RFC3550], applies.

Clark & Wu Standards Track [Page 7] RFC 6776 Measurement Identity and Duration October 2012

7. References

7.1. 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., Ed., Caceres, R., Ed., and A. Clark, Ed.,
            "RTP Control Protocol Extended Reports (RTCP XR)",
            RFC 3611, November 2003.
 [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
            "Network Time Protocol Version 4: Protocol and Algorithms
            Specification", RFC 5905, June 2010.

7.2. Informative References

 [MONARCH]  Wu, Q., Hunt, G., and P. Arden, "Monitoring Architectures
            for RTP", Work in Progress, September 2012.
 [MPEG2]    ISO/IEC, "Standard 13818-1, Information technology --
            Generic coding of moving pictures and associated audio
            information: Systems", October 2007.
 [RFC6390]  Clark, A. and B. Claise, "Guidelines for Considering New
            Performance Metric Development", BCP 170, RFC 6390,
            October 2011.

Clark & Wu Standards Track [Page 8] RFC 6776 Measurement Identity and Duration October 2012

Authors' Addresses

 Alan Clark
 Telchemy Incorporated
 2905 Premiere Parkway, Suite 280
 Duluth, GA  30097
 United States
 EMail: alan.d.clark@telchemy.com
 Qin Wu
 Huawei
 101 Software Avenue, Yuhua District
 Nanjing, Jiangsu  210012
 China
 EMail: sunseawq@huawei.com

Clark & Wu Standards Track [Page 9]

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