Network Time Protocol Suggested REFID Extension Field
draft-stenn-ntp-suggest-refid-05

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Last updated 2019-03-25
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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 Suggested REFID Extension Field
                    draft-stenn-ntp-suggest-refid-05

Abstract

   NTP's Reference ID, or REFID, identifies the source of time in a
   timestamp or time packet.  In NTP packets sent over the network the
   REFID is used to identify the "system peer", and in the long-term
   general case its fundamental purpose is to prevent a one-degree
   timing loop.  Each instance of NTP decides for itself what REFID it
   will put in its outgoing packets, and there is currently no way for
   an external time source to tell or recommend this value in the case
   where that external time source is selected as the "system peer."

   The SUGGESTED-REFID NTP Extension Field proposal is a backward-
   compatible way for a time source to tell its peers or clients "If you
   use me as your system peer, use this nonce as your REFID."

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on September 26, 2019.

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   Copyright (c) 2019 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
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Stenn                  Expires September 26, 2019               [Page 1]
Internet-Draft    Network Time Protocol Suggested REFID       March 2019

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  The REFID . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  The Suggested REFID Extension Field . . . . . . . . . . . . .   4
   4.  Generating and Sending a Nonce as the Suggested REFID
       Extension Field . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Remembering a Nonce Suggested REFID Extension Field . . . . .   5
   6.  The Suggested REFID Extension Field and Leap Smear REFIDs . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   NTP has been widely used through several revisions, with the latest
   being RFC 5905 [RFC5905].  A core component of the protocol and the
   algorithms is the Reference ID, or REFID, which is used to identify
   the time source.  Traditionally, when the source of time was another
   system the REFID was the IPv4 address of that other system.  If the
   remote system was using IPv6 for its connection, a 4 octet digest
   value of the IPv6 address was used.  The general case core purpose of
   the REFID is to prevent a one-degree timing loop (where if A has
   several timing sources that include B, if B decides to get its time
   from A we don't want A then deciding to get its time from B).  The
   REFID is considered to be "public data" and is a vital core-component
   of the base NTP packet.  In an increasingly hostile Internet,
   knowledge of a system's time source is abusable information.  If a
   system's REFID is the IPv4 address of its system peer, an attacker
   can try to use that information to send spoofed time packets to
   either or both the target or the target's server, attempting to cause
   a disruption in time service.  There is also a clear use-case for
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