Network Working Group V. Kalusivalingam Internet-Draft Cisco Systems (India) Private Limited Category: Standards Track October 2004 Simple Network Time Protocol Configuration Option for DHCPv6 draft-ietf-dhc-dhcpv6-opt-sntp-01 Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. 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 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]. Vijay Expires Apr, 2005 [Page 1] Internet-Draft SNTP Configuration Option for DHCPv6 Oct 2004 3. Terminology This document uses terminology specific to IPv6 and DHCPv6 as defined in "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 the order of preference. 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 (tbd) 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 other than the following messages: Solicit, Advertise, Request, Renew, Rebind, Information-Request and Reply. If this option appears in other than the Vijay Expires Apr, 2005 [Page 2] Internet-Draft SNTP Configuration Option for DHCPv6 Oct 2004 messages specified above, the receiver SHOULD ignore the option. 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 appear in the Option Request Option in other than the messages specified above, the receiver SHOULD ignore the option number. 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 client and finally leading to time critical applications running inaccurately in client machine. The time accuracy can be crucial to some security algorithms. For example, it may cause expired certificates to gain a new life, making the applications running on the client machine less secure. It 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 "Authentication of DHCP messages" section in the DHCPv6 specification [1]). 7. IANA Considerations IANA is requested to assign an option code to the following options from the option-code space defined in "DHCPv6 Options" section of the DHCPv6 specification [1]. Option Name Value Described in OPTION_SNTP_SERVERS tbd Section 4. 8. Normative References [1] Bound, J., Carney, M., Perkins, C., Lemon, T., Volz, B. and R. Droms (ed.), "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. 9. Informative References [3] D. Mills. Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI. Request for Comments (Informational) 2030, Internet Engineering Task Force, October 1996. [4] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, March 1997. Vijay Expires Apr, 2005 [Page 3] Internet-Draft SNTP Configuration Option for DHCPv6 Oct 2004 Acknowledgements Thanks to the DHC Working Group for their time and input into 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. Author's Address Vijayabhaskar A Kalusivalingam Cisco Systems (India) Private Limited, No: 9, Brunton Road, Bangalore - 560025 India Phone: +91-80-51036615 EMail: vibhaska@cisco.com Intellectual Property Statement 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. 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Disclaimer of Validity 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. Vijay Expires Apr, 2005 [Page 4] Internet-Draft SNTP Configuration Option for DHCPv6 Oct 2004 Copyright Statement Copyright (C) The Internet Society (2004). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Vijay Expires Apr, 2005 [Page 5]