draft-combs-http-indeterminate-range-00.txt

Network Working Group                                   J. R. Combs, Ed.
Internet-Draft                                                      Plex
Updates: 7233                                             March 24, 2015
(if approved)
Intended status: Standards Track
Expires: September 25, 2015


            HTTP/1.1: Range Responses of Indeterminate Length
                draft-combs-http-indeterminate-range-00

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Copyright Notice

   Copyright (C) The IETF Trust (2007).


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Abstract

   The Hypertext Transfer Protocol (HTTP) is an application-level
   protocol for distributed, collaborative, hypermedia information
   systems. HTTP has been in use by the World Wide Web global
   information initiative since 1990. This document updates Part 5 of the
   eight-part specification that defines the protocol referred to as
   "HTTP/1.1". Part 5 defines range-specific requests and the rules for
   constructing and combining responses to those requests. This document
   adds support for using range requests with resources of indeterminate
   size.

Table of Contents

   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2. Header Field Definitions . . . . . . . . . . . . . . . . . . . 3
     2.1. Accept-Indefinite-Ranges . . . . . . . . . . . . . . . . . 3
     2.2. Content-Range  . . . . . . . . . . . . . . . . . . . . . . 3
   3. Security Considerations  . . . . . . . . . . . . . . . . . . . 5
   4. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 5
   5. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 5
   Intellectual Property and Copyright Statements  . . . . . . . . . 6


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1. Introduction

   This document will define changes to RFC 7233 HTTP/1.1 designed to
   allow range requests to be used to retrieve parts of resources whose
   lengths are unknown at the time of the first request.


2. Header Field Definitions

   This section defines the syntax and semantics of all standard
   HTTP/1.1 header fields. For entity-header fields, both sender and
   recipient refer to either the client or the server, depending on who
   sends and who receives the entity.

2.1. Accept-Indefinite-Ranges

   The Accept-Indefinite-Ranges request-header field allows the client
   to indicate its acceptance of indefinite-sized range requests for a
   resource:

      Accept-Indefinite-Ranges = "Accept-Indefinite-Ranges" ":" "1"

   Servers MUST NOT generate indefinite-sized byte-range replies without
   having received this header for the resource involved.

2.2. Content-Range

   The Content-Range entity-header is sent with a partial entity-body to
   specify where in the full entity-body the partial body should be
   applied. This section updates Section 4.2 of RFC 7233.


       Content-Range = "Content-Range" ":" content-range-spec

       content-range-spec      = byte-content-range-spec
       byte-content-range-spec = bytes-unit SP
                                 byte-range-resp-spec "/"
                                 ( instance-length | "*" )

       byte-range-resp-spec = (first-byte-pos "-" last-byte-pos)
                                      | "*"
       instance-length           = 1*DIGIT
       first-byte-pos  = 1*DIGIT
       last-byte-pos   = ( 1*DIGIT | "*" )


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   The header SHOULD indicate the total length of the full entity-body,
   unless this length is unknown or difficult to determine. The
   asterisk "*" character as instance-length's value means that the
   instance-length is unknown at the time when the response was generated.
   The asterisk "*" character as last-byte-pos's value means that the
   length of the response is unknown or difficult to determine.

   Unlike byte-ranges-specifier values (see Section 6.4.1), a byte-
   range-resp-spec MUST only specify one range, and MUST contain
   an absolute byte positions for the first byte of the range. The
   last-byte-pos MAY be set to "*" only if the client has sent the
   Accept-Indefinite-Ranges header for the resource involved.

   If the server returns a last-byte-pos of "*", it MUST send the entire
   resource in the response body, and MUST use the RFC 7230 Chunked
   Transfer-Encoding.

   A byte-content-range-spec with a byte-range-resp-spec whose last-
   byte-pos value is less than its first-byte-pos value, or whose
   instance-length value is less than or equal to its last-byte-pos
   value, is invalid. The recipient of an invalid byte-content-range-
   spec MUST ignore it and any content transferred along with it.

   A server sending a response with status code 416 (Requested range not
   satisfiable) SHOULD include a Content-Range field with a byte-range-
   resp-spec of "*". The instance-length specifies the current length
   of the selected resource. A response with status code 206 (Partial
   Content) MUST NOT include a Content-Range field with a byte-range-
   resp-spec of "*".

   Examples of byte-content-range-spec values, assuming that the entity
   contains a total of 1234 bytes:

   o  The first 500 bytes:

      bytes 0-499/1234

   o  The second 500 bytes:

      bytes 500-999/1234

   o  All except for the first 500 bytes:

      bytes 500-1233/1234


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   o  The last 500 bytes:

      bytes 734-1233/1234

   o  The last 500 bytes, Chunked, where the length was unknown:

      bytes 734-*/*


3. Security Considerations

   No additional security considerations have been identified beyond
   those applicable to HTTP in general [Part 1].


4. IANA Considerations

   TBD

5. Acknowledgments

   Parts of this document are based on RFC 7233 and its drafts.


Authors' Addresses

   J. Rodger Combs (editor)
   Plex, Inc.

   Email: [email protected]


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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   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.

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Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).


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