[Search] [txt|pdfized|bibtex] [Tracker] [Email] [Diff1] [Diff2] [Nits]
Versions: 00 01 02 03 04 05                                             
Network Working Group                                      S. Harhalakis
Internet-Draft                                       TEI of Thessaloniki
Intended status: Experimental                                 April 2008
Expires: October 3, 2008


                      Timezone Information in HTTP
                    draft-sharhalakis-httptz-04.txt

Status of this Memo

   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 becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   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 October 3, 2008.


















Harhalakis               Expires October 3, 2008                [Page 1]


Internet-Draft        Timezone Information in HTTP            April 2008


Abstract

   This document defines a HTTP header for clients to provide timezone
   information to web servers.  An ABNF description of the corresponding
   header is provided.














































Harhalakis               Expires October 3, 2008                [Page 2]


Internet-Draft        Timezone Information in HTTP            April 2008


Discussion

   Discussion about this document takes place in http-wg mailing list
   (ietf-http-wg@w3.org).  Please CC v13@v13.gr too.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Purpose  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Requirements . . . . . . . . . . . . . . . . . . . . . . .  4
     1.3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.4.  Considerations . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Definition . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     2.1.  Client support . . . . . . . . . . . . . . . . . . . . . .  7
     2.2.  Server support . . . . . . . . . . . . . . . . . . . . . .  7
     2.3.  Proxy considerations . . . . . . . . . . . . . . . . . . .  8
   3.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
     3.1.  Client side  . . . . . . . . . . . . . . . . . . . . . . .  9
     3.2.  Server side  . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.1.  Normative  . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.2.  Informative  . . . . . . . . . . . . . . . . . . . . . . . 12
   Appendix A.  Examples  . . . . . . . . . . . . . . . . . . . . . . 13
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
   Intellectual Property and Copyright Statements . . . . . . . . . . 15























Harhalakis               Expires October 3, 2008                [Page 3]


Internet-Draft        Timezone Information in HTTP            April 2008


1.  Introduction

1.1.  Purpose

   Many web based applications could benefit from knowing the timezone
   of their visiting clients.  Most of the dynamic content provider
   applications depend on user accounts to display time and date in the
   client's native timezone.  Even this is not always adequate since
   people may travel across timezone boundaries and they currently need
   to update their web accounts to reflect their actual timezone
   information.  Furthermore, this is also the case for all HTTP-like or
   HTTP based protocols that make use of timestamps.

   This document addresses this need by describing a header to be used
   by HTTP [RFC2616] so that interested clients may provide their
   current timezone information to web servers and thus to web based
   applications.

1.2.  Requirements

   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].

   An implementation is not compliant if it fails to satisfy one or more
   of the MUST or REQUIRED level requirements.  An implementation that
   satisfies all the MUST or REQUIRED level and all the SHOULD level
   requirements is said to be "unconditionally compliant"; one that
   satisfies all the MUST level requirements but not all the SHOULD
   level requirements is said to be "conditionally compliant".

1.3.  Terminology

   This document uses the following terms:

   HTTP client
      Every client of the HTTP protocol.  Commonly referred to as a web
      browser.

   Timezone string
      A timezone string as described in this document.

   HTTP header
      An HTTP header as described in [RFC2616].

   The HTTP header specification of this document is presented in the
   augmented Backus-Naur Form that is described in [RFC2616].




Harhalakis               Expires October 3, 2008                [Page 4]


Internet-Draft        Timezone Information in HTTP            April 2008


1.4.  Considerations

   Because of the variety of systems on the Internet and the non-
   technical nature of timezone, there is no simple method for a client
   to provide timezone information to HTTP servers.  During the writing
   of this document the following were considered:

   o  Simplicity is a must.  The specification needs to be as simple as
      possible or allow for partial handling in a simple manter.

   o  There is a variety of timezone styles.  Some countries don't
      experience Daylight Saving Time (DST).  Other countries have very
      unstable DST.

   o  Politics affect DST.  This makes it a moving target.

   o  DST settings may change from year to year.

   o  Complete past and future timezone information cannot be described
      using a simple string.

   o  End user systems may have an invalid timezone configured.

   o  There are systems without timezone information.

   o  Not all systems have a time source.

   This document tries to provide adequate data for applications that
   can take advantage of the Timezone information to fulfill their
   needs.  There are different levels of requirements that applications
   may have and HTTP clients may be able to satisfy.  Thus this document
   introduces a way for HTTP clients to provide:

   o  The current client time.

   o  The current time offset.

   o  The current year's timezone information.

   o  Complete timezone information.

   depending on their abilities.

   Simple server side applications may just use the current time offset
   and hope that it is correctly set.  More advanced applications (like
   calendars) need to know when a DST change will occur to correctly
   represent future or past times.  Even more advanced applications may
   need to know the exact client timezone which can only be described



Harhalakis               Expires October 3, 2008                [Page 5]


Internet-Draft        Timezone Information in HTTP            April 2008


   using a reference to a timezone database entry.  Finally,
   applications may choose to use the client's current time as reference
   time and optionally ignore client timezone information.

   Paragraph 4.4 of [RFC3339] "Unqualified Local Time" considers systems
   with invalid timezone information as inappropriate for Internet
   communications.












































Harhalakis               Expires October 3, 2008                [Page 6]


Internet-Draft        Timezone Information in HTTP            April 2008


2.  Definition

2.1.  Client support

   HTTP clients MAY provide local timezone information to visiting web
   sites.  This information is sent using the client-timezone HTTP
   header:


      client-timezone  =  "Timezone" ":" tzdescr

      tzdescr          =  rfctime [ ";" posixtz [ ";" tznames ] ]

      rfctime          =  <local time>

      posixtz          =  <a POSIX 1003.1 timezone string>

      tznames          =  tzname *( "," tzname )

      tzname           =  <a timezone string from a timezone database>

   Where:

   rfctime    A local time string as specified in [RFC3339].  It
              includes the current time offset.

   posixtz    A POSIX 1003.1 timezone string as specified in [POSIXTZ].

   tzname     A timezone name.  Many systems use a timezone name from a
              timezone database.  This is one such string.  More than
              one such strings may be provided.  All of them MUST
              identify the same timezone.

   HTTP clients SHOULD provide all three parts of the header unless they
   aren't able to do so or they are configured not to send timezone
   information.

   Clients that don't have a clock source MUST use zeroes for all digits
   of the datetime string except from the offset.  "Z" MUST by used when
   the offset is also unavailable.

2.2.  Server support

   Compliant servers MAY validate the format of the provided
   information.  Timezone strings that are not in a valid format MAY not
   be accepted.  Validation checks MUST NOT be performed on the content
   of the Timezone string by servers.  Only the format of the string may
   be checked.  This way outdated servers will not filter out proper



Harhalakis               Expires October 3, 2008                [Page 7]


Internet-Draft        Timezone Information in HTTP            April 2008


   information.

2.3.  Proxy considerations

   HTTP proxy servers MUST NOT alter this information.

   Server side scripts that produce customized results based on the
   timezone information MUST return an appropriate "Vary" header as
   specified in paragraph 14.44 of [RFC2616].










































Harhalakis               Expires October 3, 2008                [Page 8]


Internet-Draft        Timezone Information in HTTP            April 2008


3.  Security Considerations

3.1.  Client side

   Timezone information may consist personal information regarding the
   location of a person.  HTTP clients MUST NOT provide this information
   without letting the user prevent it.  Clients must either ask users
   or provide an option for enabling/disabling this feature.  The later
   is RECOMMENDED.

   In most cases, Timezone information will not disclose more personal
   information than an IP address.  HTTP clients MAY default in enabling
   this to improve user experience.

3.2.  Server side

   Web based applications MUST treat this information as user input that
   may be invalid or malicious.

































Harhalakis               Expires October 3, 2008                [Page 9]


Internet-Draft        Timezone Information in HTTP            April 2008


4.  IANA Considerations

   This specification requires registration of a Message Header Field
   for HTTP [RFC3864].

   Header field:  Timezone

   Applicable protocol:  HTTP

   Status:  Experimental

   Author/change controller:
       IETF (iesg@ietf.org)
       Internet Engineering Task Force

   Specification document:
       [ this document ]


































Harhalakis               Expires October 3, 2008               [Page 10]


Internet-Draft        Timezone Information in HTTP            April 2008


5.  Acknowledgements

   Timezone information in HTTP was also proposed by David Robinson in
   an email at HTTP Working Group back in 1995 but the replies he got
   were negative.  It was believed that timezone information should be
   handled by CGI scripts and not by the Hypertext Transfer Protocol.
   The discussion can be found at http-wg mailing list archives: <http:/
   /www.hpl.hp.com/personal/ange/archives/archives-95/http-wg-archive/
   0521.html>.

   This document was properly formed thanks to the remarks of Julian
   Reschke.







































Harhalakis               Expires October 3, 2008               [Page 11]


Internet-Draft        Timezone Information in HTTP            April 2008


6.  References

6.1.  Normative

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3339]  Klyne, G., Ed. and C. Newman, "Date and Time on the
              Internet: Timestamps", RFC 3339, July 2002.

   [RFC3864]  Klyne, G., Nottingham, M., and J. Mogul, "Registration
              Procedures for Message Header Fields", BCP 90, RFC 3864,
              September 2004.

   [POSIXTZ]  IEEE, The Open Group, "IEEE Std 1003.1", 2004.

6.2.  Informative

   [I-D.rfc-editor-rfc2223bis]
              Reynolds, J. and R. Braden, "Instructions to Request for
              Comments (RFC) Authors", draft-rfc-editor-rfc2223bis-08
              (work in progress), July 2004.

























Harhalakis               Expires October 3, 2008               [Page 12]


Internet-Draft        Timezone Information in HTTP            April 2008


Appendix A.  Examples

   A complete timezone information header:

   Current time is 12:00, Jul 30, 1977. time offset is +2 hours.  The
   full timezone string is EET2EEST3,M3.2.0/02:00,M11.1.0/02:00.  The
   timezone database identifier string is Europe/Athens.

   Timezone: 1977-07-30T12:00+0200;
       EET2EEST3,M3.2.0/02:00,M11.1.0/02:00;
       Europe/Athens

   A partial one:

   GMT/UTC timezone is noted as Z(ulu).

   Timezone: 2007-06-12T23:48Z

   A header from a clock-less client without current offset information:

   Timezone: 0000-00-00T00:00Z;
       EET2EEST3,M3.2.0/02:00,M11.1.0/02:00;
       Europe/Athens




























Harhalakis               Expires October 3, 2008               [Page 13]


Internet-Draft        Timezone Information in HTTP            April 2008


Author's Address

   Stefanos Harhalakis
   Technological Educational Institute of Thessaloniki
   Department of Information Technology
   Thessaloniki, Greece
   GR

   Email: v13@v13.gr, v13@it.teithe.gr










































Harhalakis               Expires October 3, 2008               [Page 14]


Internet-Draft        Timezone Information in HTTP            April 2008


Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   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, THE IETF TRUST 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-ipr@ietf.org.


Acknowledgment

   This document was produced using xml2rfc v1.33 (of
   http://xml.resource.org/) from a source in RFC-2629 XML format.





Harhalakis               Expires October 3, 2008               [Page 15]