Network Time Protocol Leap Smear REFID
draft-stenn-ntp-leap-smear-refid-02

Document Type Active Internet-Draft (ntp WG)
Last updated 2019-03-25
Stream IETF
Intended RFC status (None)
Formats plain text xml pdf html bibtex
Stream WG state Candidate for WG Adoption
Document shepherd No shepherd assigned
IESG IESG state I-D Exists
Consensus Boilerplate Unknown
Telechat date
Responsible AD (None)
Send notices to (None)
Internet Engineering Task Force                                 H. Stenn
Internet-Draft                                   Network Time Foundation
Intended status: Standards Track                          March 25, 2019
Expires: September 26, 2019

                 Network Time Protocol Leap Smear REFID
                  draft-stenn-ntp-leap-smear-refid-02

Abstract

   Leap Seconds are part of UTC.  NTP timestamps are based on POSIX
   timestamps, which require each day to have exactly 86,400 seconds per
   day.  Some applications and environments choose to "smear" leap
   second corrections over a period that can last up to 24 hours' time,
   and implement NTP servers that offer smeared time to clients asking
   them for the time.

   Both NTP clients and operators have no current way to tell if an NTP
   server is offering leap-smeared time or not.  This is a problem.

   Similarly, an NTP server may choose to offer leap-smeared time to
   clients that do not appear to know that a leap event is in-process.
   This is a problem.

   This proposal offers a mechanism that provides a simple and clean
   solution to problems, by giving a way that clients (and operators)
   can trivially ask for leap-smeared time and detect a server that is
   offering leap-smeared time.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 26, 2019.

Stenn                  Expires September 26, 2019               [Page 1]
Internet-Draft   Network Time Protocol Leap Smear REFID       March 2019

Copyright Notice

   Copyright (c) 2019 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
   (https://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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Leap Smear REFID  . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Leap Seconds are applied as needed to UTC in order to keep its time
   of day close to UT1's mean solar time.

   RFC 5905 [RFC5905] and earlier versions of NTP are the overwhelming
   method of distributing time on networks.  The timescale used by NTP
   is based on POSIX which, for better or worse, ignores any instances
   where there are not the ordinary 86,400 seconds per day.

   Leap Seconds will continue to exist for the foreseeable future, and
   similarly, POSIX can be expected to ignore leap seconds for the
   foreseeable future.

   Different applications have different requirements for the stability
   of time during the application of a leap second.  Some applications
   are tolerant of a fast application of the correction, while other
   applications prefer to "smear" the leap second over a longer period,
   where the time reported by leap-second aware servers is gradually
   applied so there is no abrupt change to time during the processing of
   a leap second.

Stenn                  Expires September 26, 2019               [Page 2]
Internet-Draft   Network Time Protocol Leap Smear REFID       March 2019

   While leap second processing can be expected to be properly handled
   by up-to-date software and by time servers, there are large numbers
   of out-of-date software installations and client systems that are
   just not able to properly handle a leap second correction.

   Additionally, some use-cases for calculating elapsed time (a
   "difference clock") that use POSIX timestamps are greatly complicated
Show full document text