Network Time Protocol Best Current Practices
draft-ietf-ntp-bcp-04

Document Type Active Internet-Draft (ntp WG)
Last updated 2017-05-22
Replaces draft-reilly-ntp-bcp
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Internet Engineering Task Force                           D. Reilly, Ed.
Internet-Draft                                                Spectracom
Intended status: Best Current Practice                          H. Stenn
Expires: November 22, 2017                       Network Time Foundation
                                                               D. Sibold
                                                                     PTB
                                                            May 21, 2017

              Network Time Protocol Best Current Practices
                         draft-ietf-ntp-bcp-04

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
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   Drafts is at http://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 November 22, 2017.

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
   (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

Reilly, et al.          Expires November 22, 2017               [Page 1]
Internet-Draft          Network Time Protocol BCP               May 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.  Broadcast Mode Should Only Be Used On Trusted Networks  .  15
     6.5.  Symmetric Mode Should Only Be Used With Trusted Peers . .  15
   7.  NTP in Embedded Devices . . . . . . . . . . . . . . . . . . .  16
     7.1.  Updating Embedded Devices . . . . . . . . . . . . . . . .  16
     7.2.  KISS Packets  . . . . . . . . . . . . . . . . . . . . . .  17
     7.3.  Server configuration  . . . . . . . . . . . . . . . . . .  17
       7.3.1.  Get a vendor subdomain for pool.ntp.org . . . . . . .  17
   8.  NTP over Anycast  . . . . . . . . . . . . . . . . . . . . . .  17
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  19
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  19
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
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