Network Time Protocol REFID Updates
draft-ietf-ntp-refid-updates-04

Document Type Active Internet-Draft (ntp WG)
Last updated 2018-11-06 (latest revision 2018-10-04)
Replaces draft-stenn-ntp-ipv6-refid-hash, draft-stenn-ntp-not-you-refid
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Internet Engineering Task Force                                 H. Stenn
Internet-Draft                                   Network Time Foundation
Intended status: Standards Track                             S. Goldberg
Expires: April 7, 2019                                 Boston University
                                                         October 4, 2018

                  Network Time Protocol REFID Updates
                    draft-ietf-ntp-refid-updates-04

Abstract

   RFC 5905 [RFC5905], section 7.3, "Packet Header Variables", defines
   the value of the REFID, the system peer for the responding host.  In
   the past, for IPv4 associations the IPv4 address is used, and for
   IPv6 associations the first four octets of the MD5 hash of the IPv6
   are used.  There are two recognized shortcomings to this approach,
   and this proposal addresses them.  One is that knowledge of the
   system peer is "abusable" information and should not be generally
   available.  The second is that the four octet hash of the IPv6
   address looks very much like an IPv4 address, and this is confusing.

Status of This Memo

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   This Internet-Draft will expire on April 7, 2019.

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   Copyright (c) 2018 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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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents

Stenn & Goldberg          Expires April 7, 2019                 [Page 1]
Internet-Draft     Network Time Protocol REFID Updates      October 2018

   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  The REFID . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.2.  NOT-YOU REFID . . . . . . . . . . . . . . . . . . . . . .   3
     1.3.  IPv6 REFID  . . . . . . . . . . . . . . . . . . . . . . .   3
     1.4.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  The NOT-YOU REFID . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Proposal  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Augmenting the IPv6 REFID Hash  . . . . . . . . . . . . . . .   5
     3.1.  Background  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Potential Problems  . . . . . . . . . . . . . . . . . . .   6
     3.3.  Questions . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

1.1.  The REFID

   The interpretation of a REFID is based on the stratum, as documented
   in RFC 5905 [RFC5905], section 7.3, "Packet Header Variables".  The
   core reason for the REFID in the NTP Protocol is to prevent a degree-
   one timing loop, where server B decides to follow A as its time
   source, and A then decides to follow B as its time source.

   At Stratum 2+, which will be the case if two servers A and B are
   exchanging timing information, then if server B follows A as its time
   source, A's address will be B's REFID.  When A uses IPv4, the default
   REFID is A's IPv4 address.  When A uses IPv6, the default REFID is a
   four-octet digest of A's IPv6 address.  Now, if A queries B for its
   time, then A will learn that B is using A as its time source by
   observing A's address in the REFID field of the response packet sent
   by B.  Thus, A will not select B as a potential time source, as this
   would cause a timing loop.

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