RTP Clock Source Signalling
draft-ietf-avtcore-clksrc-00

The information below is for an old version of the document
Document Type Active Internet-Draft (avtcore WG)
Last updated 2012-08-03 (latest revision 2012-07-02)
Replaces draft-williams-avtcore-clksrc
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Audio/Video Transport Core                                   A. Williams
Maintenance                                                     Audinate
Internet-Draft                                                  K. Gross
Intended status: Standards Track                            AVA Networks
Expires: January 4, 2013                              R. van Brandenburg
                                                             H. Stokking
                                                                     TNO
                                                            July 3, 2012

                      RTP Clock Source Signalling
                      draft-ietf-avtcore-clksrc-00

Abstract

   NTP timestamps are used by several RTP protocols for synchronisation
   and statistical measurement.  This memo specifies SDP signalling
   identifying NTP timestamp clock sources and SDP signalling
   identifying the media clock sources in a multimedia session.

Requirements 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 [1].

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 January 4, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Williams, et al.         Expires January 4, 2013                [Page 1]
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   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Applications . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Timestamp Reference Clock Source Signalling  . . . . . . . . .  5
     4.1.  Clock synchronization  . . . . . . . . . . . . . . . . . .  5
     4.2.  Identifying NTP Reference Clocks . . . . . . . . . . . . .  6
     4.3.  Identifying PTP Reference Clocks . . . . . . . . . . . . .  6
     4.4.  Identifying Global Reference Clocks  . . . . . . . . . . .  7
     4.5.  Other Reference Clocks . . . . . . . . . . . . . . . . . .  8
     4.6.  Traceable Reference Clocks . . . . . . . . . . . . . . . .  8
     4.7.  Synchronisation Confidence . . . . . . . . . . . . . . . .  8
     4.8.  SDP Signalling of Timestamp Clock Source . . . . . . . . .  9
       4.8.1.  Examples . . . . . . . . . . . . . . . . . . . . . . . 11
   5.  Media Clock Source Signalling  . . . . . . . . . . . . . . . . 12
     5.1.  Asynchronously Generated Media Clock . . . . . . . . . . . 13
     5.2.  Direct-Referenced Media Clock  . . . . . . . . . . . . . . 13
     5.3.  Stream-Referenced Media Clock  . . . . . . . . . . . . . . 13
     5.4.  Signalling Grammar . . . . . . . . . . . . . . . . . . . . 14
     5.5.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . 16
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 19
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 19
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20

Williams, et al.         Expires January 4, 2013                [Page 2]
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1.  Introduction

   RTP protocols use NTP format timestamps to facilitate media stream
   synchronisation and for providing estimates of round trip time (RTT)
   and other statistical parameters.

   Information about media clock timing exchanged in NTP format
   timestamps may come from a clock which is synchronised to a global
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