Network Working Group Vijayabhaskar A Kalusivalingam Internet-Draft Hewlett-Packard Expires: May 2004 Nov 2003 Simple Network Time Protocol Configuration Option for DHCPv6 draft-ietf-dhc-dhcpv6-opt-sntp-00 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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 May, 2004. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This document describes a new DHCPv6 option for passing a list of 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 May, 2004 [Page 1] Internet-Draft SNTP Configuration Option for DHCPv6 Nov 2003 3. Terminology This document uses terminology specific to IPv6 and DHCPv6 as defined in "Terminology" section of the DHCPv6 specification. 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 SNTP servers SHOULD be listed in the order of preference. The clients use these SNTP servers to synchronize their system time to that of the standard time servers. 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 these options The SNTP servers option MUST NOT appear in other than the following messages: Solicit, Advertise, Request, Renew, Rebind, Information-Request and Reply. 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. Vijay Expires May, 2004 [Page 2] Internet-Draft SNTP Configuration Option for DHCPv6 Nov 2003 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. Author's Address Vijayabhaskar A Kalusivalingam Hewlett-Packard STSD-I 29, Cunningham Road Bangalore - 560052 India Phone: +91-80-2053085 E-Mail: vijayak@india.hp.com Vijay Expires May, 2004 [Page 3] Internet-Draft SNTP Configuration Option for DHCPv6 Nov 2003 Full Copyright Statement Copyright (C) The Internet Society (2003). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. 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, Ralph Droms, Robert Elz and Thomas Narten for their thorough review. Vijay Expires May, 2004 [Page 4]