Network Time Protocol (NTP) Server Option for DHCPv6
RFC 5908

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Internet Engineering Task Force (IETF)                        R. Gayraud
Request for Comments: 5908                                  Unaffiliated
Category: Standards Track                                   B. Lourdelet
ISSN: 2070-1721                                      Cisco Systems, Inc.
                                                               June 2010

          Network Time Protocol (NTP) Server Option for DHCPv6

Abstract

   The NTP Server Option for Dynamic Host Configuration Protocol for
   IPv6 (DHCPv6) provides NTPv4 (Network Time Protocol version 4) server
   location information to DHCPv6 hosts.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5908.

Copyright Notice

   Copyright (c) 2010 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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Gayraud & Lourdelet          Standards Track                    [Page 1]
RFC 5908              NTP Server Option for DHCPv6             June 2010

Table of Contents

   1. Introduction ....................................................2
   2. Requirements Notation ...........................................2
   3. Related Work and Usage Model ....................................2
   4. NTP Server Option for DHCPv6 ....................................3
      4.1. NTP Server Address Suboption ...............................4
      4.2. NTP Multicast Address Suboption ............................5
      4.3. NTP Server FQDN Suboption ..................................6
   5. Appearance of This Option .......................................6
   6. Security Considerations .........................................7
   7. RFC 4075 Deprecation ............................................7
   8. IANA Considerations .............................................7
   9. References ......................................................8
      9.1. Normative References .......................................8
      9.2. Informative References .....................................8

1.  Introduction

   This document defines a DHCPv6 option and associated suboptions to
   provide Network Time Protocol version 4 [RFC5905] or greater server
   location information to DHCPv6 hosts.

2.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Related Work and Usage Model

   The NTP service is publicly offered on the Internet by a number of
   organizations.  Those servers can be used but should not be abused,
   so any method that is tasked to disseminate locations of NTP servers
   must act responsibly in a manner that does not lead to public server
   overloading.  When using DHCPv6 to offer NTP server location, and if
   there is a need to distribute a host with a hardcoded configuration,
   this configuration MUST NOT include server location that is not part
   of the organization that distributes this device.  Typical usage of
   this option is to specify an NTP server that is part of the
   organization that operates the DHCPv6 server.

   The location of the NTP service, like any other Internet service, can
   be specified by an IP address or a Fully Qualified Domain Name
   (FQDN).  By design, DHCP offers information to multiple devices and
   is prone to amplification of mistakes, so great care must be taken to
   define its configuration.  Specification of the NTP service by FQDN
   offers a level of indirection that works as a possible mitigation

Gayraud & Lourdelet          Standards Track                    [Page 2]
RFC 5908              NTP Server Option for DHCPv6             June 2010

   tool in case of misconfiguration.  DNS can be used to redirect
   misconfigured clients to an IPv6 address that is not configured on
   any host instead of having to change the address of the NTP server