Hypertext Transfer Protocol (HTTP) Client-Initiated Content-Encoding
RFC 7694

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Internet Engineering Task Force (IETF)                        J. Reschke
Request for Comments: 7694                                    greenbytes
Category: Standards Track                                  November 2015
ISSN: 2070-1721

  Hypertext Transfer Protocol (HTTP) Client-Initiated Content-Encoding

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,
   to indicate the content codings that are supported in requests.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7694.

Copyright Notice

   Copyright (c) 2015 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.

Reschke                      Standards Track                    [Page 1]
RFC 7694                        HTTP CICE                  November 2015

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . .   2
   3.  Using the 'Accept-Encoding' Header Field in Responses . . . .   3
   4.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Deployment Considerations . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Header Field Registry . . . . . . . . . . . . . . . . . .   5
     7.2.  Status Code Registry  . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   In HTTP, content codings allow for payload encodings such as for
   compression or integrity checks ([RFC7231], Section 3.1.2).  In
   particular, the "gzip" content coding ([RFC7230], Section 4.2) 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 ([RFC7231],
   Section 5.3.4) for use in responses, to indicate the content codings
   that are supported in requests.  It furthermore updates the
   definition of status code 415 (Unsupported Media Type) ([RFC7231],
   Section 6.5.13), recommending that the "Accept-Encoding" header field
   be included when appropriate.

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 defined in the base HTTP
   specifications, namely Section 2 of [RFC7230] and Section 3.1.2 of
   [RFC7231].

Reschke                      Standards Track                    [Page 2]
RFC 7694                        HTTP CICE                  November 2015

3.  Using the 'Accept-Encoding' Header Field in Responses

   Section 5.3.4 of [RFC7231] defines "Accept-Encoding" as a request
   header field only.

   This specification expands that definition to allow "Accept-Encoding"
   as a response header field as well.  When present in a response, it
   indicates what content codings the resource was willing to accept in
   the associated request.  A field value that only contains "identity"