Network Time Protocol Best Current Practices
draft-ietf-ntp-bcp-06

Document Type Active Internet-Draft (ntp WG)
Last updated 2018-05-30 (latest revision 2017-12-14)
Replaces draft-reilly-ntp-bcp
Stream IETF
Intended RFC status Best Current Practice
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Stream WG state Submitted to IESG for Publication
On Agenda ntp at IETF-102
Document shepherd Karen O'Donoghue
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Internet Engineering Task Force                           D. Reilly, Ed.
Internet-Draft                                                Spectracom
Intended status: Best Current Practice                          H. Stenn
Expires: June 17, 2018                           Network Time Foundation
                                                               D. Sibold
                                                                     PTB
                                                       December 14, 2017

              Network Time Protocol Best Current Practices
                         draft-ietf-ntp-bcp-06

Abstract

   NTP Version 4 (NTPv4) has been widely used since its publication as
   RFC 5905 [RFC5905].  This documentation is a collection of Best
   Practices from across the NTP community.

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 June 17, 2018.

Copyright Notice

   Copyright (c) 2017 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

Reilly, et al.            Expires June 17, 2018                 [Page 1]
Internet-Draft          Network Time Protocol BCP          December 2017

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Keeping NTP up to date  . . . . . . . . . . . . . . . . . . .   3
   3.  General Network Security Best Practices . . . . . . . . . . .   4
     3.1.  BCP 38  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  NTP Configuration Best Practices  . . . . . . . . . . . . . .   4
     4.1.  Use enough time sources . . . . . . . . . . . . . . . . .   4
     4.2.  Use a diversity of Reference Clocks . . . . . . . . . . .   5
     4.3.  Mode 6 and 7  . . . . . . . . . . . . . . . . . . . . . .   6
     4.4.  Monitoring  . . . . . . . . . . . . . . . . . . . . . . .   7
     4.5.  Using Pool Servers  . . . . . . . . . . . . . . . . . . .   8
     4.6.  Leap Second Handling  . . . . . . . . . . . . . . . . . .   8
       4.6.1.  Leap Smearing . . . . . . . . . . . . . . . . . . . .  10
     4.7.  Configuring ntpd  . . . . . . . . . . . . . . . . . . . .  11
   5.  NTP Security Mechanisms . . . . . . . . . . . . . . . . . . .  11
     5.1.  Pre-Shared Key Approach . . . . . . . . . . . . . . . . .  11
     5.2.  Autokey . . . . . . . . . . . . . . . . . . . . . . . . .  12
     5.3.  Network Time Security . . . . . . . . . . . . . . . . . .  12
   6.  NTP Security Best Practices . . . . . . . . . . . . . . . . .  12
     6.1.  Minimizing Information Leakage  . . . . . . . . . . . . .  12
     6.2.  Avoiding Daemon Restart Attacks . . . . . . . . . . . . .  13
     6.3.  Detection of Attacks Through Monitoring . . . . . . . . .  14
     6.4.  KISS Packets  . . . . . . . . . . . . . . . . . . . . . .  15
     6.5.  Broadcast Mode Should Only Be Used On Trusted Networks  .  15
     6.6.  Symmetric Mode Should Only Be Used With Trusted Peers . .  16
   7.  NTP in Embedded Devices . . . . . . . . . . . . . . . . . . .  17
     7.1.  Updating Embedded Devices . . . . . . . . . . . . . . . .  17
     7.2.  Server configuration  . . . . . . . . . . . . . . . . . .  17
       7.2.1.  Get a vendor subdomain for pool.ntp.org . . . . . . .  17
   8.  NTP over Anycast  . . . . . . . . . . . . . . . . . . . . . .  18
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  19
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  19
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  19
     12.2.  Informative References . . . . . . . . . . . . . . . . .  20
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