RTP and Leap Seconds
draft-ietf-avtcore-leap-second-06

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AVTCore                                                         K. Gross
Internet-Draft                                              AVA Networks
Updates: 3550 (if approved)                           R. van Brandenburg
Intended status: Standards Track                                     TNO
Expires: May 19, 2014                                  November 15, 2013

                          RTP and Leap Seconds
                   draft-ietf-avtcore-leap-second-06

Abstract

   This document discusses issues that arise when RTP sessions span
   Coordinated Universal Time (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.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on May 19, 2014.

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
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Leap seconds  . . . . . . . . . . . . . . . . . . . . . . . .   2
     3.1.  UTC behavior during positive leap second  . . . . . . . .   3
     3.2.  NTP behavior during positive leap second  . . . . . . . .   3
     3.3.  POSIX behavior during positive leap second  . . . . . . .   3
     3.4.  Example of leap-second behaviors  . . . . . . . . . . . .   4
   4.  Receiver behavior during leap second  . . . . . . . . . . . .   5
   5.  Recommendations . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  RTP Sender Reports  . . . . . . . . . . . . . . . . . . .   6
     5.2.  RTP Packet Playout  . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

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

   This document updates RFC 3550 [1] providing recommendations for
   smoothly rendering streamed media referenced to common wall clocks
   which do 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 RFC 2119 [2] and
   indicate requirement levels for compliant implementations.

3.  Leap seconds

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   The world scientific time standard is International Atomic Time (TAI)
   which is based on vibrations of cesium atoms in an atomic clock.  The