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Versions: 00 01 02 draft-ietf-httpbis-cice

Network Working Group                                         J. Reschke
Internet-Draft                                                greenbytes
Intended status: Standards Track                            May 10, 2014
Expires: November 11, 2014


  Hypertext Transfer Protocol (HTTP) Client-Initiated Content-Encoding
                       draft-reschke-http-cice-00

Abstract

   In HTTP, "Content Codings" allow for payload encodings such as for
   compression or integrity checks.  In particular, the "gzip" content
   coding is widely used for payload data sent in response messages.

   Content Codings can be used in request messages as well, however
   discoverability is not on par with response messages.  This document
   extends the HTTP "Accept-Encoding" header field for use in responses.

Editorial Note (To be removed by RFC Editor before publication)

   Distribution of this document is unlimited.  Although this is not a
   work item of the HTTPbis Working Group, comments should be sent to
   the Hypertext Transfer Protocol (HTTP) mailing list at
   ietf-http-wg@w3.org [1], which may be joined by sending a message
   with subject "subscribe" to ietf-http-wg-request@w3.org [2].

   Discussions of the HTTPbis Working Group are archived at
   <http://lists.w3.org/Archives/Public/ietf-http-wg/>.

   XML versions, latest edits, and the issues list for this document are
   available from
   <http://greenbytes.de/tech/webdav/#draft-reschke-http-cice>.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."



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   This Internet-Draft will expire on November 11, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . . . 3
   3.  Extensions to 'Accept-Encoding' Header Field  . . . . . . . . . 3
   4.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
   Appendix A.  Open issues (to be removed by RFC Editor prior to
                publication) . . . . . . . . . . . . . . . . . . . . . 5
     A.1.  edit  . . . . . . . . . . . . . . . . . . . . . . . . . . . 6




















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1.  Introduction

   In HTTP, "Content Codings" allow for payload encodings such as for
   compression or integrity checks ([HTTPSEM], Section 3.1.2).  In
   particular, the "gzip" content coding is widely used for payload data
   sent in response messages.

   Content Codings can be used in request messages as well, however
   discoverability is not on par with response messages.  This document
   extends the HTTP "Accept-Encoding" header field ([HTTPSEM], Section
   5.3.4) for use in responses.

2.  Notational Conventions

   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].

   This document reuses terminology used in the base HTTP
   specifications, namely Section 2 of [HTTPMSG] and Section 3.1.2 of
   [HTTPSEM].

3.  Extensions to 'Accept-Encoding' Header Field

   Section 5.3.4 of [HTTPSEM] defines "Accept-Encoding" as a request
   header field only.

   This specification extends that definition to allow "Accept-Encoding"
   as response header field as well.  When present, it indicates what
   content codings a server is willing to accept in requests.  In
   particular, a field value that contains "identity" only implies that
   no content codings are supported at all.

   Note that this information applies to the resource to which the
   request was addressed.  The set of supported encodings might vary for
   different resources on the same server, and could also vary depending
   on other aspects of the request (such as the request method).

   Section 6.5.13 of [HTTPSEM] defines status code 415 (Unsupported
   Media Type) to apply to both media type and content coding related
   problems.

   Servers that fail a request due to an unsupported content coding
   SHOULD respond with a 415 status and SHOULD include an "Accept-
   Encoding" header in that response, allowing clients to distinguish
   between content coding related issues and media type related issues.





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4.  Example

   Client submits a POST request using Content-Encoding "compress"
   ([HTTPSEM], Section 3.1.2.1):

     POST /edit/ HTTP/1.1
     Host: example.org
     Content-Type: application/atom+xml;type=entry
     Content-Encoding: compress

     ...compressed payload...

   Server rejects request because it only allows the "gzip" content
   coding:

     HTTP/1.1 415 Unsupported Media Type
     Date: Fri, 09 May 2014 11:43:53 GMT
     Accept-Encoding: gzip
     Content-Length: 68
     Content-Type: text/plain

     This resource only supports the "gzip" content coding in requests.

   ...at which point the client can retry the request with the supported
   "gzip" content coding.

   Alternatively, a server that does not support any content codings in
   requests could answer with:

     HTTP/1.1 415 Unsupported Media Type
     Date: Fri, 09 May 2014 11:43:53 GMT
     Accept-Encoding: identity
     Content-Length: 61
     Content-Type: text/plain

     This resource does not support content codings in requests.

5.  Security Considerations

   This specification does not introduce any new security considerations
   beyond those discussed in Section 9 of [HTTPSEM].

6.  IANA Considerations

   HTTP header fields are registered within the "Message Headers"
   registry located at
   <http://www.iana.org/assignments/message-headers>, as defined by
   [BCP90].



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   This document updates the definition of the "Accept-Encoding" header
   field, so the "Permanent Message Header Field Names" registry shall
   be updated accordingly:

   +-----------------+----------+----------+---------------------------+
   | Header Field    | Protocol | Status   | Reference                 |
   | Name            |          |          |                           |
   +-----------------+----------+----------+---------------------------+
   | Accept-Encoding | http     | standard | [HTTPSEM], Section 5.3.4, |
   |                 |          |          | extended by Section 3 of  |
   |                 |          |          | this document             |
   +-----------------+----------+----------+---------------------------+

7.  References

7.1.  Normative References

   [HTTPMSG]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              draft-ietf-httpbis-p1-messaging-26 (work in progress),
              February 2014.

   [HTTPSEM]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content",
              draft-ietf-httpbis-p2-semantics-26 (work in progress),
              February 2014.

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

7.2.  Informative References

   [BCP90]    Klyne, G., Nottingham, M., and J. Mogul, "Registration
              Procedures for Message Header Fields", BCP 90, RFC 3864,
              September 2004.

URIs

   [1]  <mailto:ietf-http-wg@w3.org>

   [2]  <mailto:ietf-http-wg-request@w3.org?subject=subscribe>

Appendix A.  Open issues (to be removed by RFC Editor prior to
             publication)







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A.1.  edit

   Type: edit

   julian.reschke@greenbytes.de (2011-04-15): Umbrella issue for
   editorial fixes/enhancements.

Author's Address

   Julian F. Reschke
   greenbytes GmbH
   Hafenweg 16
   Muenster, NW  48155
   Germany

   EMail: julian.reschke@greenbytes.de
   URI:   http://greenbytes.de/tech/webdav/


































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