Prefer Header for HTTP
draft-snell-http-prefer-14

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Network Working Group                                           J. Snell
Internet-Draft                                           August 23, 2012
Intended status: Standards Track
Expires: February 24, 2013

                         Prefer Header for HTTP
                       draft-snell-http-prefer-14

Abstract

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

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on February 24, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Syntax Notation  . . . . . . . . . . . . . . . . . . . . .  4
   2.  The Prefer Request Header Field  . . . . . . . . . . . . . . .  4
     2.1.  Content Negotiation and Cache Considerations . . . . . . .  6
     2.2.  Examples . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Preference Definitions . . . . . . . . . . . . . . . . . . . .  7
     3.1.  The "return-asynch" Preference . . . . . . . . . . . . . .  7
     3.2.  The "return-representation" Preference . . . . . . . . . .  8
     3.3.  The "return-minimal" Preference  . . . . . . . . . . . . .  9
     3.4.  The "wait" Preference  . . . . . . . . . . . . . . . . . . 10
     3.5.  The "strict" and "lenient" Processing Preferences  . . . . 11
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
     4.1.  The Registry of Preferences  . . . . . . . . . . . . . . . 12
     4.2.  Initial Registry Contents  . . . . . . . . . . . . . . . . 13
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   6.  Normative References . . . . . . . . . . . . . . . . . . . . . 14
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16

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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 is 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 [RFC 5023]
   -- 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
   specific requirements of the application and the nature of the
   request being made, the client might or might not consider such