Prefer Header for HTTP
RFC 7240

 
Document Type RFC - Proposed Standard (June 2014; Errata)
Was draft-snell-http-prefer (individual in app area)
Last updated 2015-03-30
Stream IETF
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Stream WG state (None)
Consensus Unknown
Document shepherd No shepherd assigned
IESG IESG state RFC 7240 (Proposed Standard)
Telechat date
Responsible AD Barry Leiba
IESG note Mark Nottingham is the document shepherd.
Send notices to jasnell@gmail.com, mnot@mnot.net, draft-snell-http-prefer@ietf.org
Internet Engineering Task Force (IETF)                          J. Snell
Request for Comments: 7240                                     June 2014
Category: Standards Track
ISSN: 2070-1721

                         Prefer Header for HTTP

Abstract

   This specification defines an HTTP header field that can be used by a
   client to request that certain behaviors be employed by a server
   while processing a request.

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/rfc7240.

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.

Snell                        Standards Track                    [Page 1]
RFC 7240                       HTTP Prefer                     June 2014

Table of Contents

   1. Introduction ....................................................2
      1.1. Syntax Notation ............................................4
   2. The Prefer Request Header Field .................................4
      2.1. Examples ...................................................6
   3. The Preference-Applied Response Header Field ....................7
   4. Preference Definitions ..........................................8
      4.1. The "respond-async" Preference .............................8
      4.2. The "return=representation" and "return=minimal"
           Preferences ................................................9
      4.3. The "wait" Preference .....................................11
      4.4. The "handling=strict" and "handling=lenient" Processing ...12
   5. IANA Considerations ............................................13
      5.1. The Registry of Preferences ...............................13
      5.2. Initial Registry Contents .................................15
   6. Security Considerations ........................................16
   7. References .....................................................16
      7.1. Normative References ......................................16
      7.2. Informative References ....................................16

1.  Introduction

   Within the course of processing an HTTP request, there are typically
   a range of required and optional behaviors that a server or
   intermediary can employ.  These often manifest in a variety of subtle
   and not-so-subtle ways within the response.

   For example, when using the HTTP PUT method to modify a resource --
   similar to that defined for the Atom Publishing Protocol [RFC5023] --
   the server is given the option of returning either a complete
   representation of a modified resource or a minimal response that
   indicates only the successful completion of the operation.  The
   selection of which type of response to return to the client generally
   has no bearing on the successful processing of the request but could,
   for instance, have an impact on what actions the client must take
   after receiving the response.  That is, returning a representation of
   the modified resource within the response can allow the client to
   avoid sending an additional subsequent GET request.

   Similarly, servers that process requests are often faced with
   decisions about how to process requests that may be technically
   invalid or incorrect but are still understandable.  It might be the
   case that the server is able to overlook the technical errors in the
   request but still successfully process the request.  Depending on the

Snell                        Standards Track                    [Page 2]
RFC 7240                       HTTP Prefer                     June 2014

   specific requirements of the application and the nature of the
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