RTP and Leap Seconds
draft-ietf-avtcore-leap-second-00

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Document Type Active Internet-Draft (avtcore WG)
Last updated 2012-08-03 (latest revision 2012-06-21)
Replaces draft-gross-avtcore-leap-second
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AVTCore                                                         K. Gross
Internet-Draft                                              AVA Networks
Updates: 3550 (if approved)                           R. van Brandenburg
Intended status: Standards Track                                     TNO
Expires: December 23, 2012                                 June 21, 2012

                          RTP and Leap Seconds
                   draft-ietf-avtcore-leap-second-00

Abstract

   This document discusses issues that arise when RTP sessions span
   (UTC) leap seconds.  It updates RFC 3550 to describe how RTP senders
   and receivers should behave in the presence of leap seconds.

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 December 23, 2012.

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

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Gross & van Brandenburg  Expires December 23, 2012              [Page 1]
Internet-Draft              RTP Leap Seconds                   June 2012

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Leap seconds  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     3.1.  UTC behavior during leap second . . . . . . . . . . . . . . 3
     3.2.  NTP behavior during leap second . . . . . . . . . . . . . . 4
     3.3.  POSIX behavior during leap second . . . . . . . . . . . . . 4
   4.  Recommendations . . . . . . . . . . . . . . . . . . . . . . . . 4
     4.1.  RTP Sender Reports and Receiver Reports . . . . . . . . . . 5
     4.2.  RTP Packet Playout  . . . . . . . . . . . . . . . . . . . . 5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   8.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6

Gross & van Brandenburg  Expires December 23, 2012              [Page 2]
Internet-Draft              RTP Leap Seconds                   June 2012

1.  Introduction

   In some applications, RTP streams are referenced to a walllock time
   (absolute date and time).  This is typically accomplished through use
   of the NTP timestamp field in the RTCP sender report (SR) to create a
   mapping between RTP timestamps and the wallclock.  When a wallclock
   reference is used, the playout time for RTP packets is referenced to
   the wallclock.  Smooth and continuous media playout requires a smooth
   and continuous timebase.  The timebase used by the wallclock may
   include leap seconds which, in many cases, are not rendered smoothly.

   This document provides recommendations for smoothly rendering
   streamed media referenced to common wallclocks which may not have
   smooth or continuous behavior in the presence of leap seconds.

2.  Terminology

   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 [RFC2119] and indicate
   requirement levels for compliant implementations.

3.  Leap seconds

   Leap seconds are intended to keep UTC time synchronized with the
   rotation of the earth.  Leap seconds are scheduled by the
   International Earth Rotation and Reference Systems Service.  Leap
   seconds may be scheduled at the last day of any month but are
   preferentially scheduled for December and June and secondarily March
   and September.[TF.460-6] Because earth's rotation is unpredictable,
   leap seconds are typically not scheduled more than six months in
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