RTP and Leap Seconds
RFC 7164
Document | Type |
RFC - Proposed Standard
(March 2014; No errata)
Updates RFC 3550
|
|
---|---|---|---|
Authors | Kevin Gross , Ray van Brandenburg | ||
Last updated | 2015-10-14 | ||
Replaces | draft-gross-leap-second, draft-gross-avtcore-leap-second | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Magnus Westerlund | ||
Shepherd write-up | Show (last changed 2013-11-18) | ||
IESG | IESG state | RFC 7164 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Richard Barnes | ||
Send notices to | (None) | ||
IANA | IANA review state | Version Changed - Review Needed | |
IANA action state | No IANA Actions |
Internet Engineering Task Force (IETF) K. Gross Request for Comments: 7164 AVA Networks Updates: 3550 R. van Brandenburg Category: Standards Track TNO ISSN: 2070-1721 March 2014 RTP and Leap Seconds Abstract This document discusses issues that arise when RTP sessions span Coordinated Universal Time (UTC) leap seconds. It updates RFC 3550 by describing how RTP senders and receivers should behave in the presence of leap seconds. 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/rfc7164. 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. Gross & van Brandenburg Standards Track [Page 1] RFC 7164 RTP and Leap Seconds March 2014 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Leap Seconds . . . . . . . . . . . . . . . . . . . . . . . . 2 3.1. UTC Behavior during a Positive Leap Second . . . . . . . 3 3.2. NTP Behavior during a Positive Leap Second . . . . . . . 3 3.3. POSIX Behavior during a Positive Leap Second . . . . . . 3 3.4. Example of Leap-Second Behaviors . . . . . . . . . . . . 4 4. Receiver Behavior during a Leap Second . . . . . . . . . . . 5 5. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 5 5.1. Sender Reports . . . . . . . . . . . . . . . . . . . . . 6 5.2. RTP Packet Playout . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 8.2. Informative References . . . . . . . . . . . . . . . . . 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 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 that are not rendered smoothly. This document updates RFC 3550 [1] by providing recommendations for smoothly rendering streamed media referenced to common wall clocks that 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 The world's scientific time standard is International Atomic Time (TAI), which is based on vibrations of cesium atoms in an atomic clock. The world's civil time is based on the rotation of the Earth. Gross & van Brandenburg Standards Track [Page 2] RFC 7164 RTP and Leap Seconds March 2014 In 1972, the civil time standard, Coordinated Universal Time (UTC), was redefined in terms of TAI and the concept of leap seconds was introduced to allow UTC to remain synchronized with the rotation of the Earth.Show full document text