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

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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   This Internet-Draft will expire on September 25, 2015.

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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
   improves support for responding to range requests for 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

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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, with the value "1", 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       = byte-content-range
                         / other-content-range

     byte-content-range  = bytes-unit SP
                           ( byte-range-resp / unsatisfied-range )

     byte-range-resp     = byte-range "/" ( complete-length / "*" )
     byte-range          = first-byte-pos "-" (last-byte-pos / "*" )
     unsatisfied-range   = "*/" ( complete-length / "*" )

     complete-length     = 1*DIGIT

     other-content-range = other-range-unit SP other-range-resp
     other-range-resp    = *CHAR

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   For byte ranges, a sender SHOULD indicate the complete length of the
   representation from which the range has been extracted, unless the
   complete length is unknown or difficult to determine. An asterisk
   character ("*") in place of the complete-length indicates that the
   representation length was unknown when the header field was
   generated.

   An asterisk character in place of the last-byte-pos indicates that
   the response length was unknown when the header was generated, and
   that the entire requested range of the resource will be sent. An
   asterisk character may be used in place of the last-byte-pos ONLY
   if the Accept-Indefinite-Ranges header was sent, and requires use
   of the RFC 7230 Chunked Transfer-Encoding

   The following example illustrates when the complete length of the
   selected representation is known by the sender to be 1234 bytes:

     Content-Range: bytes 42-1233/1234

   and this second example illustrates when the complete length is
   unknown:

     Content-Range: bytes 42-1233/*
    OR
     Content-Range: bytes 42-*/*
    (if the Accept-Indefinite-Ranges request header was sent)

   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: rodger@plex.tv

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