Network Working Group                                  V. Kalusivalingam
Request for Comments: 4075         Cisco Systems (India) Private Limited
Category: Standards Track                                       May 2005


 Simple Network Time Protocol (SNTP) Configuration Option for DHCPv6

Status of This Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (2005).

Abstract

  This document describes a new DHCPv6 option for passing a list of
  Simple Network Time Protocol (SNTP) server addresses to a client.

1.  Introduction

  This document describes a new option, called the SNTP [3] servers
  option, for passing information about SNTP servers in DHCPv6 [1].

2.  Requirements

  The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
  SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
  document, are to be interpreted as described in RFC 2119 [2].

3.  Terminology

  This document uses terminology specific to IPv6 and DHCPv6 as defined
  in the "Terminology" section of the DHCPv6 specification [1].

4.  Simple Network Time Protocol (SNTP) Servers Option

  The Simple Network Time Protocol servers option provides a list of
  one or more IPv6 addresses of SNTP [3] servers available to the
  client for synchronization.  The clients use these SNTP servers to
  synchronize their system time to that of the standard time servers.
  Clients MUST treat the list of SNTP servers as an ordered list.  The
  server MAY list the SNTP servers in decreasing order of preference.



Kalusivalingam              Standards Track                     [Page 1]

RFC 4075          SNTP Configuration Option for DHCPv6          May 2005


  The option defined in this document can only be used to configure
  information about SNTP servers that can be reached using IPv6.  The
  DHCP option to configure information about IPv4 SNTP servers can be
  found in RFC 2132 [4].  Mechanisms for configuring IPv4/IPv6 dual-
  stack applications are being considered, but are not specified in
  this document.

  The format of the Simple Network Time Protocol servers option is as
  shown below:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      OPTION_SNTP_SERVERS       |        option-len            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |                  SNTP server (IPv6 address)                   |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |                  SNTP server (IPv6 address)                   |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                              ...                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


     option-code: OPTION_SNTP_SERVERS (31)

     option-len:  Length of the 'SNTP server' fields, in octets;
                  it must be a multiple of 16

     SNTP server: IPv6 address of SNTP server

5.  Appearance of This Option

  The SNTP servers option MUST NOT appear in messages other than the
  following: Solicit, Advertise, Request, Renew, Rebind, Information-
  Request, and Reply.  If this option appears in messages other than
  those specified above, the receiver SHOULD ignore it.

  The option number for this option MAY appear in the Option Request
  Option [1] in the following messages:  Solicit, Request, Renew,
  Rebind, Information-Request, and Reconfigure.  If this option number
  appears in the Option Request Option in messages other than those
  specified above, the receiver SHOULD ignore it.



Kalusivalingam              Standards Track                     [Page 2]

RFC 4075          SNTP Configuration Option for DHCPv6          May 2005


6.  Security Considerations

  The SNTP servers option may be used by an intruder DHCPv6 server to
  cause DHCPv6 clients to contact a rogue SNTP server, resulting in
  invalid synchronization of time in the client, finally leading to
  time-critical applications running inaccurately in the client
  machine.  Time accuracy can be crucial to some security algorithms.
  For example, expired certificates may gain a new life, making the
  applications running on the client machine less secure.  The
  inaccuracy can even cause clients to set their time incorrectly,
  making them vulnerable to replay attacks in protocols that use time
  stamps to detect replays.

  To avoid attacks through these options, the DHCPv6 client SHOULD use
  authenticated DHCPv6 (see the "Authentication of DHCP messages"
  section in the DHCPv6 specification [1]).

7.  IANA Considerations

  The IANA has assigned an option code to the following from the
  option-code space defined in the "DHCPv6 Options" section of the
  DHCPv6 specification [1].

  Option Name            Value    Described in
  OPTION_SNTP_SERVERS    31       Section 4.

8.  Acknowledgements

  Thanks to the DHC Working Group for their time and input on the
  specification.  In particular, thanks to (in alphabetical order)
  Bernie Volz, Jim Bound, Margaret Wasserman, Pekka Savola, Ralph
  Droms, Robert Elz, and Thomas Narten for their thorough review.



















Kalusivalingam              Standards Track                     [Page 3]

RFC 4075          SNTP Configuration Option for DHCPv6          May 2005


9.  Normative References

  [1]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
       Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
       RFC 3315, July 2003.

  [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.

10.  Informative References

  [3]  Mills, D., "Simple Network Time Protocol (SNTP) Version 4 for
       IPv4, IPv6 and OSI", RFC 2030, October 1996.

  [4]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
       Extensions", RFC 2132, March 1997.

Author's Address

  Vijayabhaskar A. Kalusivalingam
  Cisco Systems (India) Private Limited,
  No: 9, Brunton Road,
  Bangalore - 560025
  India

  Phone: +91-80-51036615
  EMail: [email protected]
























Kalusivalingam              Standards Track                     [Page 4]

RFC 4075          SNTP Configuration Option for DHCPv6          May 2005


Full Copyright Statement

  Copyright (C) The Internet Society (2005).

  This document is subject to the rights, licenses and restrictions
  contained in BCP 78, and except as set forth therein, the authors
  retain all their rights.

  This document and the information contained herein are provided on an
  "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
  OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
  ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
  INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
  INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
  WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

  The IETF takes no position regarding the validity or scope of any
  Intellectual Property Rights or other rights that might be claimed to
  pertain to the implementation or use of the technology described in
  this document or the extent to which any license under such rights
  might or might not be available; nor does it represent that it has
  made any independent effort to identify any such rights.  Information
  on the procedures with respect to rights in RFC documents can be
  found in BCP 78 and BCP 79.

  Copies of IPR disclosures made to the IETF Secretariat and any
  assurances of licenses to be made available, or the result of an
  attempt made to obtain a general license or permission for the use of
  such proprietary rights by implementers or users of this
  specification can be obtained from the IETF on-line IPR repository at
  http://www.ietf.org/ipr.

  The IETF invites any interested party to bring to its attention any
  copyrights, patents or patent applications, or other proprietary
  rights that may cover technology that may be required to implement
  this standard.  Please address the information to the IETF at ietf-
  [email protected].

Acknowledgement

  Funding for the RFC Editor function is currently provided by the
  Internet Society.







Kalusivalingam              Standards Track                     [Page 5]


You are viewing proxied material from gopher.fnord.one. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.