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RTP Clock Source Signalling
RFC 7273

Document type: RFC - Proposed Standard (June 2014; No errata)
Document stream: IETF
Last updated: 2014-06-30
Other versions: plain text, pdf, html

IETF State: Submitted to IESG for Publication Oct 2013
Consensus: Unknown
Document shepherd: Roni Even
Shepherd Write-Up: Last changed 2013-12-06

IESG State: RFC 7273 (Proposed Standard)
IANA Action State: RFC-Ed-Ack
Responsible AD: Alissa Cooper
Send notices to: avtcore-chairs@ietf.org, draft-ietf-avtcore-clksrc@ietf.org

Internet Engineering Task Force (IETF)                       A. Williams
Request for Comments: 7273                                      Audinate
Category: Standards Track                                       K. Gross
ISSN: 2070-1721                                             AVA Networks
                                                      R. van Brandenburg
                                                             H. Stokking
                                                                     TNO
                                                               June 2014

                      RTP Clock Source Signalling

Abstract

   NTP format timestamps are used by several RTP protocols for
   synchronisation and statistical measurements.  This memo specifies
   Session Description Protocol (SDP) signalling that identifies
   timestamp reference clock sources and SDP signalling that identifies
   the media clock sources in a multimedia session.

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/rfc7273.

Copyright Notice

   Copyright (c) 2014 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.

Williams, et al.             Standards Track                    [Page 1]
RFC 7273               RTP Clock Source Signalling             June 2014

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Applications  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Timestamp Reference Clock Source Signalling . . . . . . . . .   5
     4.1.  Clock Synchronisation . . . . . . . . . . . . . . . . . .   5
     4.2.  Identifying NTP Reference Clocks  . . . . . . . . . . . .   6
     4.3.  Identifying PTP Reference Clocks  . . . . . . . . . . . .   6
     4.4.  Identifying Global Reference Clocks . . . . . . . . . . .   8
     4.5.  Private Reference Clocks  . . . . . . . . . . . . . . . .   8
     4.6.  Local Reference Clocks  . . . . . . . . . . . . . . . . .   8
     4.7.  Traceable Reference Clocks  . . . . . . . . . . . . . . .   8
     4.8.  SDP Signalling of Timestamp Reference Clock Source  . . .   9
       4.8.1.  Examples  . . . . . . . . . . . . . . . . . . . . . .  11
   5.  Media Clock Source Signalling . . . . . . . . . . . . . . . .  12
     5.1.  Asynchronously Generated Media Clock  . . . . . . . . . .  12
     5.2.  Direct-Referenced Media Clock . . . . . . . . . . . . . .  12
     5.3.  Stream-Referenced Media Clock . . . . . . . . . . . . . .  14
     5.4.  SDP Signalling of Media Clock Source  . . . . . . . . . .  15
     5.5.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  17
   6.  Signalling Considerations . . . . . . . . . . . . . . . . . .  19
     6.1.  Usage in Offer/Answer . . . . . . . . . . . . . . . . . .  19
       6.1.1.  Indicating Support for Clock Source Signalling  . . .  20
       6.1.2.  Timestamp Reference Clock . . . . . . . . . . . . . .  20
       6.1.3.  Media Clock . . . . . . . . . . . . . . . . . . . . .  20
     6.2.  Usage Outside of Offer/Answer . . . . . . . . . . . . . .  21
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22
     8.1.  Reference Clock SDP Parameter . . . . . . . . . . . . . .  22
     8.2.  Media Clock SDP Parameter . . . . . . . . . . . . . . . .  23
     8.3.  Timestamp Reference Clock Source Parameters Registry  . .  23
     8.4.  Media Clock Source Parameters Registry  . . . . . . . . .  24
     8.5.  Source-Level Attributes . . . . . . . . . . . . . . . . .  25
       8.5.1.  Source-Level Timestamp Reference Clock Attribute  . .  25

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