Network Working Group Vijayabhaskar A Kalusivalingam Internet-Draft Hewlett-Packard Expires: May 2004 Nov 2003 Timezone Specifier Option for DHCPv6 draft-ietf-dhc-dhcpv6-opt-tz-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 the client's timezone information. 1. Introduction This document describes a new option called Timezone option for passing the client's timezone information information 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 Timezone Specifier 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. Timezone option The Timezone option is used by the server to convey the timezone in which the client resides. The client is expected to set the timezone in its system on receiving this option from the server. The format of the Timezone option is: 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_TIME_ZONE | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | time-zone | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code: OPTION_TIME_ZONE (tbd) option-len: Length of the 'time-zone' field in octets time-zone: Time zone of the client in the NVT-ASCII string format. The format of this string is explained below: Std[Offset[Dst[Offset],[Start[/Time],End[/Time]]]] where '[' and ']' enclose optional fields, '|' indicates choice of exactly one of the alternatives, ',' and '/' represent literal characters present in the string. If "Offset" is specified, then the time-zone is represented in the IEEE 1003.1 POSIX timezone format [3]. Std Three or more octets for the standard timezone (Std). Any character (or case) except a leading colon, digits, comma, minus or plus sign is allowed. If there is no Offset followed by the Std, then the timezone is not represented in IEEE 1003.1 format. In this case, the Std is treated as the index to the timezone database, for example, a file name, from where additional information about the timezone may be obtained. Offset Indicates the value one must add to local time to arrive at UTC, of the form: [+|-]hh[:mm[:ss]]. Offset following Std is required, if the timezone is represented in IEEE 1003.1 POSIX timezone format. Digits are always interpreted as decimal number. If preceded by a '-', the timezone is east of the Prime Meridian, otherwise it is west ('+' is optional) The permissible values for hh[:mm[:ss]] are as follows: Vijay Expires May, 2004 [Page 2] Internet-Draft Timezone Specifier Option for DHCPv6 Nov 2003 hh 0 <= hh <= 23 mm 0 <= mm <= 60 ss 0 <= ss <= 60 Dst Three or more octets for the daylight savings timezone. If Dst is missing, then daylight savings time does not apply in this locale. If no Offset follows Dst, then Dst is assumed to be one hour ahead of standard time. Any character (or case) except a leading colon, digits, comma, minus or plus sign is allowed. Start Indicates the day of the year, in one of the formats indicated below, when to change to daylight savings time. The ``Time'' field (which follows immediately after a ``/'' character, if present) indicates when the change is made, in local time. End Indicates the day of the year, in one of the formats indicated below, when to change back from daylight savings time. The ``Time'' field (which follows immediately after a ``/'' character, if present) indicates when the change is made, in local time. Time Time has the same format as Offset, except that no leading ``-'' or ``+'' is permitted. The default is 02:00:00. The day of the year needs to be given in any of the following formats: Jn The julian day n, (1 <= n <= 365). Leap days are not counted. n Zero-based julian day, (0 <= n <= 365). Leap days are counted so it is possible to refer to Feb 29. Mm.n.d The ``d''th day, (0 <= d <= 6) of week ``n'' of month ``m'' of the year (1 <= n <= 5, 1 <= m <= 12, where week 5 means last ``d'' day in month ``m'' which may occur in either the fourth or the fifth week. Week ``1'' is the first week in which the ``d'' day occurs. Day ``0'' refers Sunday, day ``1'' refers Monday and so on. Examples: i) Indian Standard Time zone is represented as: IST-5:30 Here, ``IST'' refers the standard timezone and ``-5:30'' is the offset. `-' sign in the offset says that the timezone is 5 hours and 30 minutes ahead of UTC. Absence of ``Dst'' says that daylight savings doesn't apply to this locale. Vijay Expires May, 2004 [Page 3] Internet-Draft Timezone Specifier Option for DHCPv6 Nov 2003 ii) For Eastern USA time zone, 1986, the timezone string is as shown below: EST5EDT4,116/02:00:00,298/02:00:00 It says: The standard time zone is in 5 hours behind UTC. The Daylight Savings Timezone is 4 hours behind UTC. Day light savings starts at 116 day, i.e., April 27 02:00 AM standard time and ends at 298th day, i.e., October 26 02:00 AM daylight time. It can also represented as: EST5EDT,116/02:00:00,298/02:00:00 Since no offset follows the ``Dst'', daylight savings time is 1 hour ahead of standard time, thus, it is 4 hours behind UTC. iii) Representing ii) in the non POSIX standard way is: America/New-York It says that the locale belongs to New-York timezone in America, which will be used as the index in to a timezone database to get more information of the timezone. 5. Usage of Timezone option The Timezone option has the flexibility of providing timezone information in formats other than POSIX timezone, because some vendor specific databases can provide more information than POSIX Timezone string. The server SHOULD be configurable to send any of the format specified in Section 5. The timezone option can be used along with the Vendor Class Option [1] to make sure that the client and server agree upon the meaning of the string. For example, the clients running in different OS expect the string in different formats. Here, the Vendor Class Option [1] sent by clients can be used by the server to distinguish between the clients to return the proper timezone string. If the client is not able to interpret the timezone option sent by the server, then it SHOULD ignore the option. It MAY contact alternative DHCPv6 servers to obtain the timezone information. 6. Appearance of these options The Timezone option MUST NOT appear in other than the following the following messages: Solicit, Advertise, Request, Renew, Rebind, Information-Request and Reply. The option number for these options 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 4] Internet-Draft Timezone Specifier Option for DHCPv6 Nov 2003 7. Security Considerations The Timezone option may be used by an intruder DHCPv6 server to assign invalid time zones, leading to timing issues for the applications running on the client machine. For example, because of wrongly configured timezone, there is a possibility that some critical applications, which are supposed to start at a particular time don't get started at that time. A delayed start of OS security update will leave the client's machine vulnerable to security attacks. To avoid attacks through these options, the DHCPv6 client SHOULD use authenticated DHCPv6 (see "Authentication of DHCP messages" section in the DHCPv6 specification [1]). 8. 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_TIME_ZONE tbd Section 4. 9. 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. 10. Informative References [3] IEEE, "1003.1 POSIX Timezone Specification", 1988. 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 5] Internet-Draft Timezone Specifier 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. Special thanks to Robert Elz for his suggestions and help in making this document more readable. Thanks to Mike Carney for his abstract on Timezone option. Vijay Expires May, 2004 [Page 6]