HTTPbis Working Group                                   R. Fielding, Ed.
Internet-Draft                                                     Adobe
Obsoletes: 2616 (if approved)                              Y. Lafon, Ed.
Intended status: Standards Track                                     W3C
Expires: April 7, August 27, 2013                                 J. Reschke, Ed.
                                                              greenbytes
                                                         October 4, 2012
                                                       February 23, 2013

         Hypertext Transfer Protocol (HTTP/1.1): Range Requests
                     draft-ietf-httpbis-p5-range-21
                     draft-ietf-httpbis-p5-range-22

Abstract

   The Hypertext Transfer Protocol (HTTP) is an application-level
   protocol for distributed, collaborative, hypertext information
   systems.  This document defines range requests and the rules for
   constructing and combining responses to those requests.

Editorial Note (To be removed by RFC Editor)

   Discussion of this draft takes place on the HTTPBIS working group
   mailing list (ietf-http-wg@w3.org), which is archived at
   <http://lists.w3.org/Archives/Public/ietf-http-wg/>.

   The current issues list is at
   <http://tools.ietf.org/wg/httpbis/trac/report/3> and related
   documents (including fancy diffs) can be found at
   <http://tools.ietf.org/wg/httpbis/>.

   The changes in this draft are summarized in Appendix E.2. E.3.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 7, August 27, 2013.

Copyright Notice

   Copyright (c) 2012 2013 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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Conformance and Error Handling . . . . . . . . . . . . . .  4
     1.2.  Syntax Notation  . . . . . . . . . . . . . . . . . . . . .  4
   2.  Range Units  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Range Specifier Registry  Byte Ranges  . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Status Code Definitions
     2.2.  Other Range Units  . . . . . . . . . . . . . . . . . . .  5
     3.1.  206 Partial Content .  7
     2.3.  Accept-Ranges  . . . . . . . . . . . . . . . . . .  5
     3.2.  416 Requested Range Not Satisfiable . . . .  7
   3.  Range Requests . . . . . . .  6
   4.  Responses to a Range Request . . . . . . . . . . . . . . . . .  7
     4.1.  Response to a Single and Multiple Ranges Request
     3.1.  Range  . . . . .  7
     4.2.  Combining Ranges . . . . . . . . . . . . . . . . . . . . .  7
   5.  Header Field Definitions
     3.2.  If-Range . . . . . . . . . . . . . . . . . . .  8
     5.1.  Accept-Ranges . . . . . .  9
   4.  Responses to a Range Request . . . . . . . . . . . . . . . .  8
     5.2.  Content-Range .  9
     4.1.  206 Partial Content  . . . . . . . . . . . . . . . . . . . 10
     4.2.  Content-Range  . .  9
     5.3.  If-Range . . . . . . . . . . . . . . . . . . . . 12
     4.3.  Combining Ranges . . . . . 10
     5.4.  Range . . . . . . . . . . . . . . . . 14
     4.4.  416 Range Not Satisfiable  . . . . . . . . . . 11
       5.4.1.  Byte Ranges . . . . . . 15
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . 11
       5.4.2. . . 15
     5.1.  Range Retrieval Requests Unit Registry  . . . . . . . . . . . . . . . 13
   6.  IANA Considerations . . . . 15
       5.1.1.  Procedure  . . . . . . . . . . . . . . . . . 14
     6.1.  Status Code Registration . . . . . 15
       5.1.2.  Registrations  . . . . . . . . . . . . 14
     6.2.  Header Field Registration . . . . . . . . 16
     5.2.  Status Code Registration . . . . . . . . 15
     6.3.  Range Specifier Registration . . . . . . . . . 16
     5.3.  Header Field Registration  . . . . . . 15
   7.  Security Considerations . . . . . . . . . . 16
   6.  Security Considerations  . . . . . . . . . 15
     7.1.  Overlapping Ranges . . . . . . . . . . 17
     6.1.  Denial of Service Attacks using Range  . . . . . . . . . . 16
   8. 17
   7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 16
   9. 17
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     9.1. 17
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
     9.2. 17
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 16 18
   Appendix A.  Internet Media Type multipart/byteranges  . . . . . . 17 18
   Appendix B.  Changes from RFC 2616 . . . . . . . . . . . . . . . . 19 20
   Appendix C.  Imported ABNF . . . . . . . . . . . . . . . . . . . . 19 21
   Appendix D.  Collected ABNF  . . . . . . . . . . . . . . . . . . . 21
   Appendix E.  Change Log (to be removed by RFC Editor before
                publication)  . . . . . . . . . . . . . . . . . . . . 22 23
     E.1.  Since draft-ietf-httpbis-p5-range-19 . . . . . . . . . . . 22 23
     E.2.  Since draft-ietf-httpbis-p5-range-20 . . . . . . . . . . . 22 23
     E.3.  Since draft-ietf-httpbis-p5-range-21 . . . . . . . . . . . 23
   Index  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 23

1.  Introduction

   HTTP

   Hypertext Transfer Protocol (HTTP) clients often encounter
   interrupted data transfers as a result of canceled requests or
   dropped connections.  When a client has stored a partial
   representation, it is desirable to request the remainder of that
   representation in a subsequent request rather than transfer the
   entire representation.  There are also a number of Web
   applications that  Likewise, devices with limited local storage
   might benefit from being able to request only a subset of a larger
   representation, such as a single page of a very large
   document document, or only part
   the dimensions of an image to be rendered by a device with
   limited local storage. embedded image.

   This document defines HTTP/1.1 range requests, partial responses, and
   the multipart/byteranges media type.  The protocol for range type, obsoleting those parts
   previously defined in [RFC2616].  Range requests
   is are an OPTIONAL
   feature of HTTP, designed so resources or recipients that do recipients not implement implementing this
   feature (or not supporting it for the target resource) can respond as
   if it is a normal GET request without impacting interoperability.
   Partial responses are indicated by a distinct status code to not be
   mistaken for full responses by intermediate caches that might not implement the
   feature.

   Although the HTTP range request mechanism is designed to allow for
   extensible range types, this specification only defines requests for
   byte ranges.

1.1.  Conformance and Error Handling

   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].

   Conformance criteria and considerations regarding error handling are
   defined in Section 2.5 of [Part1].

1.2.  Syntax Notation

   This specification uses the Augmented Backus-Naur Form (ABNF)
   notation of [RFC5234] with the list rule extension defined in Section
   1.2 of [Part1].  Appendix C describes rules imported from other
   documents.  Appendix D shows the collected ABNF with the list rule
   expanded.

2.  Range Units

   HTTP/1.1 allows a client to request that only part (a range) of the

   A representation can be included within partitioned into subranges according to
   various structural units, depending on the response.  HTTP/1.1 uses range
   units structure inherent in the
   representation's media type.  This "range unit" is used in the
   Accept-Ranges (Section 2.3) response header field to advertise
   support for range requests, the Range (Section 5.4) 3.1) request header
   field to delineate the parts of a representation that are requested,
   and the Content-Range (Section 5.2) 4.2) payload header fields.  A representation can be broken down into subranges
   according field to various structural units. describe
   which part of a representation is being transferred.

     range-unit       = bytes-unit / other-range-unit
     bytes-unit       = "bytes"
     other-range-unit = token

   HTTP/1.1 has been designed to allow implementations of applications
   that do not depend on knowledge of ranges.  The only range unit
   defined by HTTP/1.1

2.1.  Byte Ranges

   Since representation data is "bytes".  Additional specifiers can be defined
   as described transferred in Section 2.1.

   If payloads as a sequence of
   octets, a byte range unit is not understood in a request, a server MUST ignore
   the whole Range header field meaningful substructure for any
   representation transferable over HTTP (Section 5.4).  If a 3 of [Part2]).  We
   define the "bytes" range unit is not
   understood for expressing subranges of the data's
   octet sequence.

     bytes-unit       = "bytes"

   A byte range operation MAY specify a single range of bytes, or a set
   of ranges within a single representation.

     byte-ranges-specifier = bytes-unit "=" byte-range-set
     byte-range-set  = 1#( byte-range-spec / suffix-byte-range-spec )
     byte-range-spec = first-byte-pos "-" [ last-byte-pos ]
     first-byte-pos  = 1*DIGIT
     last-byte-pos   = 1*DIGIT

   The first-byte-pos value in a response, an intermediary SHOULD pass byte-range-spec gives the response to byte-offset
   of the client; first byte in a client MUST fail.

2.1.  Range Specifier Registry range.  The HTTP Range Specifier Registry defines last-byte-pos value gives the name space for
   byte-offset of the
   range specifier names.

   Registrations MUST include last byte in the following fields:

   o  Name range; that is, the byte
   positions specified are inclusive.  Byte offsets start at zero.

   Examples of byte-ranges-specifier values:

   o  Description  The first 500 bytes (byte offsets 0-499, inclusive):

        bytes=0-499

   o  Pointer to specification text

   Values to be added to this name space require IETF Review (see
   [RFC5226], Section 4.1).  The registry itself second 500 bytes (byte offsets 500-999, inclusive):

        bytes=500-999

   A byte-range-spec is maintained at
   <http://www.iana.org/assignments/http-range-specifiers>.

3.  Status Code Definitions

3.1.  206 Partial Content

   The server has fulfilled the partial GET request for the resource.
   The request MUST have included a Range header field (Section 5.4)
   indicating invalid if the desired range, last-byte-pos value is present
   and MAY have included an If-Range
   header field (Section 5.3) to make less than the request conditional.

   The response MUST include first-byte-pos.

   A client can limit the following header fields:

   o  Either a Content-Range header field (Section 5.2) indicating number of bytes requested without knowing the
      range included with this response, or a multipart/byteranges
      Content-Type including Content-Range fields for each part.
   size of the selected representation.  If a
      Content-Length header field the last-byte-pos value is present in
   absent, or if the response, its value
      MUST match is greater than or equal to the actual number current
   length of octets transmitted in the message
      body.

   o  Date

   o  Cache-Control, ETag, Expires, Content-Location and/or Vary, if the
      header field would have been sent in a 200 (OK) response to representation data, the
      same request

   If a 206 byte range is sent in response to a request with an If-Range header
   field, it SHOULD NOT include other representation header fields.
   Otherwise, interpreted as
   the response MUST include all remainder of the representation header
   fields that would have been returned (i.e., the server replaces the
   value of last-byte-pos with a 200 (OK) response to value that is one less than the
   same request.

   Caches MAY use a heuristic (see Section 4.1.2 current
   length of [Part6]) to
   determine freshness for 206 responses.

3.2.  416 Requested Range Not Satisfiable the selected representation).

   A server SHOULD return a response with this status code if a client can request
   included a Range header field (Section 5.4), and none of the ranges-
   specifier values in this field overlap the current extent last N bytes of the selected resource, and representation
   using a suffix-byte-range-spec.

     suffix-byte-range-spec = "-" suffix-length
     suffix-length = 1*DIGIT

   If the request did not include an If-Range header
   field (Section 5.3).  (For byte-ranges, this means that selected representation is shorter than the first-
   byte-pos specified suffix-
   length, the entire representation is used.  For example (assuming a
   representation of all length 10000):

   o  The final 500 bytes (byte offsets 9500-9999, inclusive):

        bytes=-500

      Or:

        bytes=9500-

   o  The first and last bytes only (bytes 0 and 9999):

        bytes=0-0,-1

   o  Other valid (but not canonical) specifications of the second 500
      bytes (byte offsets 500-999, inclusive):

        bytes=500-600,601-999
        bytes=500-700,601-999

   If a valid byte-range-set includes at least one byte-range-spec values were greater with
   a first-byte-pos that is less than the current length of the selected resource.)

   When this status code is returned for
   representation, or at least one suffix-byte-range-spec with a byte-range request, non-
   zero suffix-length, then the
   response SHOULD include a Content-Range header field specifying byte-range-set is satisfiable.
   Otherwise, the
   current byte-range-set is unsatisfiable.

   In the byte range syntax, first-byte-pos, last-byte-pos, and suffix-
   length are expressed as decimal number of the representation (see Section 5.2).  This
   response MUST NOT use the multipart/byteranges content-type.  For
   example,

     HTTP/1.1 416 Requested Range Not Satisfiable
     Date: Mon, 20 Jan 2012 15:41:54 GMT
     Content-Range: bytes */47022
     Content-Type: image/gif

      Note: Clients cannot depend on servers octets.  Since there is no
   predefined limit to send a 416 (Requested
      Range Not Satisfiable) response instead the length of a 200 (OK) response for
      an unsatisfiable Range header field, since not all servers
      implement this header field.

4.  Responses payload, recipients ought to a Range Request

4.1.  Response
   anticipate potentially large decimal numerals and prevent parsing
   errors due to integer conversion overflows.

2.2.  Other Range Units

   Range units are intended to be extensible.  New range units ought to
   be registered with IANA, as defined in Section 5.1.

     other-range-unit = token

2.3.  Accept-Ranges

   The "Accept-Ranges" header field allows a Single and Multiple Ranges Request

   When an HTTP message includes server to indicate that it
   supports range requests for the content target resource.

     Accept-Ranges     = acceptable-ranges
     acceptable-ranges = 1#range-unit / "none"

   Origin servers that support byte-range requests MAY send

     Accept-Ranges: bytes

   but are not required to do so.  Clients MAY generate range requests
   without having received this header field for the resource involved.
   Range units are defined in Section 2.

   Servers that do not support any kind of range request for the target
   resource resource MAY send

     Accept-Ranges: none

   to advise the client not to attempt a single range (for
   example, request.

3.  Range Requests

3.1.  Range

   The "Range" header field on a response GET request modifies the method
   semantics to request transfer of only one or more subranges of the
   selected representation data, rather than the entire selected
   representation data.

     Range = byte-ranges-specifier / other-ranges-specifier
     other-ranges-specifier = other-range-unit "=" other-range-set
     other-range-set = 1*CHAR

   A server MAY ignore the Range header field.  However, origin servers
   and intermediate caches ought to support byte ranges when possible,
   since Range supports efficient recovery from partially failed
   transfers and partial retrieval of large representations.  A server
   MUST ignore a Range header field received with a request for method other
   than GET.

   An origin server MUST ignore a single range, Range header field that contains a
   range unit it does not understand.  A proxy MAY either discard a
   Range header field that contains a range unit it does not understand
   or pass it to the next inbound server when forwarding the request.

   A server that supports range requests ought to ignore or reject a request
   for
   Range header field that consists of more than two overlapping ranges,
   or a set of many small ranges that overlap without any holes), this content are not listed in ascending order,
   since both are indications of either a broken client or a deliberate
   denial of service attack (Section 6.1).  A client SHOULD NOT request
   multiple ranges that are inherently less efficient to process and
   transfer than a single range that encompasses the same data.

   A client that is
   transmitted requesting multiple ranges SHOULD list those ranges
   in ascending order (the order in which they would typically be
   received in a complete representation) unless there is a specific
   need to request a later part earlier.  For example, a user agent
   processing a large representation with an internal catalog of parts
   might need to request later parts first, particularly if the
   representation consists of pages stored in reverse order and the user
   agent wishes to transfer one page at a Content-Range time.

   The Range header field, field is evaluated after evaluating the
   preconditions of [Part4] and only if the result of their evaluation
   is leading toward a Content-Length 200 (OK) response.  In other words, Range is
   ignored when a conditional GET would result in a 304 (Not Modified)
   response.

   The If-Range header field showing (Section 3.2) can be used as a precondition
   to applying the number Range header field.

   If all of bytes actually transferred.  For
   example,

     HTTP/1.1 206 Partial Content
     Date: Wed, 15 Nov 1995 06:25:24 GMT
     Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
     Content-Range: bytes 21010-47021/47022
     Content-Length: 26012
     Content-Type: image/gif

   When an HTTP message includes the content of multiple ranges (for
   example, preconditions are true, the server supports the Range
   header field for the target resource, and the specified range(s) are
   valid and satisfiable (as defined in Section 2.1), the server SHOULD
   send a 206 (Partial Content) response to a request for multiple non-overlapping
   ranges), these are transmitted as with a multipart message.  The multipart
   media type used for this purpose is "multipart/byteranges" payload containing one
   or more partial representations that correspond to the satisfiable
   ranges requested, as defined in Appendix A.

   A Section 4.

   If all of the preconditions are true, the server MAY combine requested ranges when those ranges supports the Range
   header field for the target resource, and the specified range(s) are
   overlapping (see Section 7.1).

   A response to
   invalid or unsatisfiable, the server SHOULD send a request for 416 (Range Not
   Satisfiable) response.

3.2.  If-Range

   If a single range MUST NOT be sent using client has a partial copy of a representation and wishes to have
   an up-to-date copy of the
   multipart/byteranges media type.  A response entire representation, it could use the
   Range header field with a conditional GET (using either or both of
   If-Unmodified-Since and If-Match.)  However, if the condition fails
   because the representation has been modified, the client would then
   have to make a second request for
   multiple ranges, whose result is a single range, MAY be sent as to obtain the entire current
   representation.

   The "If-Range" header field allows a
   multipart/byteranges media type with one part.  A client to "short-circuit" the
   second request.  Informally, its meaning is: if the representation is
   unchanged, send me the part(s) that cannot
   decode a multipart/byteranges message I am requesting in Range;
   otherwise, send me the entire representation.

     If-Range = entity-tag / HTTP-date

   Clients MUST NOT ask for multiple
   ranges use an entity-tag marked as weak in an If-Range
   field value and MUST NOT use a single request.

   When a client asks for multiple ranges Last-Modified date in one request, an If-Range
   field value unless it has no entity-tag for the server
   SHOULD return them in representation and
   the order that they appeared Last-Modified date it does have for the representation is strong
   in the request.

4.2.  Combining Ranges

   A response might transfer only a subrange sense defined by Section 2.2.2 of [Part4].

   A server that evaluates a representation if the
   connection closed prematurely or if the conditional range request used that is
   applicable to one or more
   Range specifications.  After several such transfers, a client might
   have received several ranges of its representations MUST evaluate the same representation.  These
   ranges can only be safely combined condition
   as false if they all have in common the
   same strong validator, where "strong validator" is defined to be
   either an entity-tag that used as a validator is not marked as weak (Section 2.3 of
   [Part4]) or, if no entity-tag
   when an HTTP-date is provided, a Last-Modified used as the validator, if the date value that is not
   strong in the sense defined by Section 2.2.2 of [Part4].

   When  (A server
   can distinguish between a client receives an incomplete 200 (OK) or 206 (Partial
   Content) response and already has one or more stored responses for
   the same method valid HTTP-date and effective request URI, all any form of entity-tag
   by examining the stored
   responses with the same strong validator MAY be combined with the
   partial content first two characters.)

   A client MUST NOT generate an If-Range header field in this new response.  If none of the stored
   responses a request that
   does not contain a Range header field.  A server MUST ignore an If-
   Range header field received in a request that does not contain the same strong validator, then this new response
   corresponds to a new representation and
   Range header field.  An origin server MUST NOT be combined with the
   existing stored responses.

   If the new response is ignore an incomplete 200 (OK) response, then the If-Range header fields of that new response are used
   field received in a request for any combined response
   and replace those of the matching stored responses.

   If the new response is a 206 (Partial Content) response and at least
   one of target resource that does not
   support Range requests.

   If the matching stored responses is a 200 (OK), then validator given in the combined
   response If-Range header fields consist of field matches the most recent 200 response's
   header fields.  If all
   current validator for the selected representation of the matching stored responses are 206
   responses, target
   resource, then the stored response with server SHOULD process the most Range header fields is
   used field as
   requested.  If the source of header fields for the combined response, except
   that validator does not match, then the client server MUST use other header fields provided in the new
   response, aside from Content-Range, to replace all instances of
   ignore the
   corresponding Range header fields in the stored response. field.

4.  Responses to a Range Request
4.1.  206 Partial Content

   The combined response message body consists of 206 (Partial Content) status code indicates that the union of partial
   content ranges in server is
   successfully fulfilling a range request for the new response and each target resource by
   transferring one or more parts of the selected
   responses.  If the union consists of the entire range of the
   representation, then representation that
   correspond to the combined response MUST be recorded as a
   complete 200 (OK) response with a Content-Length satisfiable ranges found in the requests's Range
   header field that
   reflects (Section 3.1).

   If a single part is being transferred, the complete length.  Otherwise, server generating the combined response(s) 206
   response MUST include generate a Content-Range header field field, describing what
   range of the included
   range(s) selected representation is enclosed, and be recorded as incomplete.  If the union consists of a
   discontinuous range payload
   consisting of the representation, then range.  For example:

     HTTP/1.1 206 Partial Content
     Date: Wed, 15 Nov 1995 06:25:24 GMT
     Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
     Content-Range: bytes 21010-47021/47022
     Content-Length: 26012
     Content-Type: image/gif

     ... 26012 bytes of partial image data ...

   If multiple parts are being transferred, the client MAY store
   it as either a multipart range server generating the
   206 response or MUST generate a "multipart/byteranges" payload, as multiple 206 responses
   with one continuous range each.

5.  Header Field Definitions

   This section defines the syntax and semantics of HTTP/1.1 header
   fields related to range requests
   defined in Appendix A, and partial responses.

5.1.  Accept-Ranges

   The "Accept-Ranges" a Content-Type header field allows a resource to indicate containing the
   multipart/byteranges media type and its
   acceptance of range requests.

     Accept-Ranges     = acceptable-ranges
     acceptable-ranges = 1#range-unit / "none"

   Origin servers that accept byte-range requests MAY send

     Accept-Ranges: bytes

   but are not required to do so.  Clients MAY boundary parameter.
   To avoid confusion with single part responses, a server MUST NOT
   generate range requests
   without having received this a Content-Range header field for the resource involved.
   Range units are defined in Section 2.

   Servers that do not accept any kind the HTTP header block of range request for a resource
   MAY send

     Accept-Ranges: none

   to advise
   multiple part response (this field will be sent in each part
   instead).

   Within the client not to attempt header area of each body part in the multipart payload,
   the server MUST generate a range request.

5.2. Content-Range

   The "Content-Range" header field is sent with a partial
   representation corresponding
   to specify where the range being enclosed in that body part.  If the full selected
   representation the
   payload body is intended to be applied.

   Range units are defined in Section 2.

     Content-Range           = byte-content-range-spec
                             / other-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

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

   The would have had a Content-Type header field in a 200
   (OK) response, the server SHOULD indicate generate that same Content-Type
   field in the total length header area of each body part.  For example:

     HTTP/1.1 206 Partial Content
     Date: Wed, 15 Nov 1995 06:25:24 GMT
     Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
     Content-Length: 1741
     Content-Type: multipart/byteranges; boundary=THIS_STRING_SEPARATES

     --THIS_STRING_SEPARATES
     Content-Type: application/pdf
     Content-Range: bytes 500-999/8000

     ...the first range...
     --THIS_STRING_SEPARATES
     Content-Type: application/pdf
     Content-Range: bytes 7000-7999/8000

     ...the second range
     --THIS_STRING_SEPARATES--

   When multiple ranges are requested, a server MAY coalesce any of the full
   representation, unless this length is unknown
   ranges that overlap or difficult to
   determine.  The asterisk "*" character means that the instance-length are separated by a gap that is unknown at smaller
   than the time when overhead of sending multiple parts, regardless of the response was generated.

   Unlike byte-ranges-specifier values (see Section 5.4.1), a byte-
   range-resp-spec MUST only specify one range, and MUST contain
   absolute byte positions for both order
   in which the first and last byte of corresponding byte-range-spec appeared in the
   range.

   A byte-content-range-spec with received
   Range header field.  Since the typical overhead between parts of a byte-range-resp-spec whose last-
   byte-pos value
   multipart/byteranges payload is around 80 bytes, depending on the
   selected representation's media type and the chosen boundary
   parameter length, it can be less efficient to transfer many small
   disjoint parts than its first-byte-pos value, or whose
   instance-length value it 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.

   In transfer the case of a byte range request: entire selected
   representation.

   A server sending MUST NOT generate a multipart response with
   status code 416 (Requested Range Not Satisfiable) SHOULD include to a
   Content-Range field request for a
   single range, since a client that does not request multiple parts
   might not support multipart responses.  However, a server MAY
   generate a multipart/byteranges payload with only a byte-range-resp-spec of "*".  The
   instance-length specifies the current length of the selected
   resource. single body part
   if multiple ranges were requested and only one range was found to be
   satisfiable or only one range remained after coalescing.  A client
   that cannot process a multipart/byteranges response with status code 206 (Partial Content) MUST NOT
   include ask for
   multiple ranges in a Content-Range field with single request.

   When a byte-range-resp-spec of "*".

   The "Content-Range" header field has no meaning for status codes multipart response payload is generated, the server SHOULD
   send the parts in the same order that
   do not explicitly describe its semantic.  Currently, only status
   codes 206 (Partial Content) and 416 (Requested Range Not Satisfiable)
   describe the meaning of this corresponding byte-range-
   spec appeared in the received Range header field.

   Examples of byte-content-range-spec values, assuming field, excluding those
   ranges that the
   representation contains were deemed unsatisfiable or that were coalesced into
   other ranges.  A client that receives 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

   o  The last 500 bytes:

        bytes 734-1233/1234

   If multipart response MUST
   inspect the server ignores Content-Range header field present in each body part in
   order to determine which range is contained in that body part; a byte-range-spec (for example if
   client cannot rely on receiving the same ranges that it is
   syntactically invalid, or if requested,
   nor the same order that it might be seen as requested.

   When a denial-of-service
   attack), 206 response is generated, the server SHOULD treat MUST generate the request as
   following header fields, in addition to those required above, if the invalid Range
   header
   field did not exist.  (Normally, this means return would have been sent in a 200 (OK) response containing to the full representation).

5.3.  If-Range same
   request: Date, Cache-Control, ETag, Expires, Content-Location, and
   Vary.

   If a client has a partial copy of a representation and wishes 206 is generated in response to have a request with an up-to-date copy of the entire representation, it could use If-Range
   header field, the
   Range sender SHOULD NOT generate other representation
   header field with fields beyond those required above, because the client is
   understood to already have a conditional GET (using either or both of
   If-Unmodified-Since and If-Match.)  However, if prior response containing those header
   fields.  Otherwise, the condition fails
   because sender MUST generate all of the
   representation has been modified, the client header fields that would then have to make been sent in a second request 200 (OK)
   response to obtain the entire current
   representation. same request.

   A 206 response is cacheable unless otherwise indicated by explicit
   cache controls (see Section 4.1.2 of [Part6]).

4.2.  Content-Range

   The "If-Range" "Content-Range" header field allows is sent in a client single part 206
   (Partial Content) response to "short-circuit" indicate the
   second request.  Informally, its meaning is "if partial range of the
   selected representation is
   unchanged, send me enclosed as the part(s) that I am missing; otherwise, send me message payload, sent in each
   part of a multipart 206 response to indicate the entire new representation".

     If-Range range enclosed
   within each body part, and sent in 416 (Range Not Satisfiable)
   responses to provide information about the selected representation.

     Content-Range       = entity-tag byte-content-range
                         / HTTP-date

   Clients MUST NOT use an entity-tag marked as weak in an If-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

   If a 206 (Partial Content) response contains a Content-Range header
   field value and with a range unit (Section 2) that the recipient does not
   understand, the recipient MUST NOT use attempt to recombine it with a Last-Modified date in an If-Range
   field value unless
   stored representation.  A proxy that receives such a message SHOULD
   forward it has no entity-tag for the representation and downstream.

   For byte ranges, a sender SHOULD indicate the Last-Modified date it does have for complete length of the
   representation is strong
   in from which the sense defined by Section 2.2.2 of [Part4].

   A server that evaluates a conditional range request that has been extracted, unless the
   complete length is
   applicable unknown or difficult to one determine.  An asterisk
   character ("*") in place of its representations MUST evaluate the condition
   as false if complete-length indicates that the entity-tag used as a validator is marked as weak or,
   representation length was unknown when an HTTP-date is used as the validator, if header field was
   generated.

   The following example illustrates when the date value is not
   strong in complete length of the sense defined
   selected representation is known by Section 2.2.2 of [Part4].  (A server
   can distinguish between a valid HTTP-date the sender to be 1234 bytes:

     Content-Range: bytes 42-1233/1234

   and any form of entity-tag
   by examining this second example illustrates when the first two characters.)

   The If-Range header complete length is
   unknown:

     Content-Range: bytes 42-1233/*

   A Content-Range field SHOULD only be sent by clients together
   with value is invalid if it contains a Range header field. byte-range-
   resp that has a last-byte-pos value less than its first-byte-pos
   value, or a complete-length value less than or equal to its last-
   byte-pos value.  The If-Range header field recipient of an invalid Content-Range MUST be ignored
   if it is NOT
   attempt to recombine the received in content with a stored
   representation.

   A server generating a 416 (Range Not Satisfiable) response to a byte
   range request that does not include SHOULD send a Range header
   field.  The If-Range Content-Range header field MUST be ignored by a server that
   does not support the sub-range operation.

   If the validator given with an
   unsatisfied-range value, as in the If-Range header field matches following example:

     Content-Range: bytes */1234

   The complete-length in a 416 response indicates the current validator for the selected representation length of
   the target
   resource, then the server SHOULD send the specified sub-range of selected representation.

   The "Content-Range" header field has no meaning for status codes that
   do not explicitly describe its semantic.  For this specification,
   only the
   representation using a 206 (Partial Content) response.  If the
   validator does not match, then the server SHOULD send the entire
   representation using a 200 (OK) response.

5.4.  Range

5.4.1.  Byte Ranges

   Since all HTTP representations are transferred as sequences of bytes,
   the concept of and 416 (Range Not Satisfiable) status
   codes describe a byte range is meaningful meaning for any HTTP
   representation.  (However, not all clients and servers need to
   support byte-range operations.)
   Byte range specifications in HTTP apply to the sequence Content-Range.

   The following are examples of bytes Content-Range values in which the
   selected representation data (not necessarily the same as the message
   body).

   A byte range operation MAY specify a single range of bytes, or contains a set total of ranges within a single representation.

     byte-ranges-specifier = bytes-unit "=" byte-range-set
     byte-range-set  = 1#( byte-range-spec / suffix-byte-range-spec )
     byte-range-spec = first-byte-pos "-" [ last-byte-pos ]
     first-byte-pos  = 1*DIGIT
     last-byte-pos   = 1*DIGIT 1234 bytes:

   o  The first-byte-pos value in a byte-range-spec gives the byte-offset
   of first 500 bytes:

        Content-Range: bytes 0-499/1234

   o  The second 500 bytes:

        Content-Range: bytes 500-999/1234

   o  All except for the first byte in a range. 500 bytes:

        Content-Range: bytes 500-1233/1234

   o  The last-byte-pos value gives the
   byte-offset of the last byte in the range; that is, the byte
   positions specified are inclusive.  Byte offsets start at zero.

   If the last-byte-pos value is present, it MUST be greater than or
   equal to the first-byte-pos in that byte-range-spec, or the byte-
   range-spec is syntactically invalid.  The recipient 500 bytes:

        Content-Range: bytes 734-1233/1234

4.3.  Combining Ranges

   A response might transfer only a subrange of a byte-range-
   set that includes one or more syntactically invalid byte-range-spec
   values MUST ignore the header field that includes that byte-range-
   set.

   If representation if the last-byte-pos value is absent,
   connection closed prematurely or if the value is greater than request used one or equal to the current length more
   Range specifications.  After several such transfers, a client might
   have received several ranges of the representation data, last-byte-
   pos same representation.  These
   ranges can only be safely combined if they all have in common the
   same strong validator, where "strong validator" is taken defined to be equal to one less than the current length of the
   representation in bytes.

   By its choice
   either an entity-tag that is not marked as weak (Section 2.3 of last-byte-pos,
   [Part4]) or, if no entity-tag is provided, a client can limit the number of
   bytes retrieved without knowing Last-Modified value that
   is strong in the size sense defined by Section 2.2.2 of the representation.

     suffix-byte-range-spec = "-" suffix-length
     suffix-length = 1*DIGIT [Part4].

   A suffix-byte-range-spec is used client that has received multiple partial responses to specify the suffix of the
   representation data, of GET requests
   on a length given by the suffix-length value.
   (That is, this form specifies the last N bytes of target resource MAY combine those responses into a representation.) larger
   continuous range if they share the same strong validator.

   If the representation most recent response is shorter than an incomplete 200 (OK) response, then
   the specified suffix-length, header fields of that response are used for any combined response
   and replace those of the entire representation is used. matching stored responses.

   If the most recent response is a syntactically valid byte-range-set includes 206 (Partial Content) response and
   at least one byte-
   range-spec whose first-byte-pos is less than the current length of the representation, or at least one suffix-byte-range-spec with matching stored responses is a
   non-zero suffix-length, 200 (OK), then the byte-range-set is satisfiable.
   Otherwise,
   combined response header fields consist of the byte-range-set is unsatisfiable. most recent 200
   response's header fields.  If all of the byte-range-
   set is unsatisfiable, matching stored responses
   are 206 responses, then the server SHOULD return a stored response with a 416
   (Requested Range Not Satisfiable) status code.  Otherwise, the server
   SHOULD return a response with a 206 (Partial Content) status code
   containing most recent
   header fields is used as the satisfiable ranges source of header fields for the representation.

   In combined
   response, except that the byte range syntax, first-byte-pos, last-byte-pos, and suffix-
   length are expressed as decimal number of octets.  Since there is no
   predefined limit to client MUST use other header fields
   provided in the length of an HTTP payload, recipients SHOULD
   anticipate potentially large decimal numerals and prevent parsing
   errors due new response, aside from Content-Range, to integer conversion overflows.

   Examples of byte-ranges-specifier values (assuming a representation replace
   all instances of length 10000):

   o  The first 500 bytes (byte offsets 0-499, inclusive):

        bytes=0-499

   o  The second 500 bytes (byte offsets 500-999, inclusive):

        bytes=500-999

   o  The final 500 bytes (byte offsets 9500-9999, inclusive):

        bytes=-500

      Or:

        bytes=9500-

   o the corresponding header fields in the stored
   response.

   The first and last bytes only (bytes 0 combined response message body consists of the union of partial
   content ranges in the new response and 9999):

        bytes=0-0,-1

   o  Several legal but not canonical specifications each of the second 500
      bytes (byte offsets 500-999, inclusive):

        bytes=500-600,601-999
        bytes=500-700,601-999

5.4.2.  Range Retrieval Requests

   The "Range" selected
   responses.  If the union consists of the entire range of the
   representation, then the client MUST record the combined response as
   if it were a complete 200 (OK) response, including a Content-Length
   header field defines that reflects the GET method (conditional or not)
   to request complete length.  Otherwise, the
   client MUST record the set of continuous ranges as one or more sub-ranges of the
   following: an incomplete 200 (OK) response representation
   data, instead of if the entire representation data.

     Range = byte-ranges-specifier / other-ranges-specifier
     other-ranges-specifier = other-range-unit "=" other-range-set
     other-range-set = 1*CHAR

   A server MAY ignore combined response
   is a prefix of the Range representation, a single 206 (Partial Content)
   response containing a multipart/byteranges body, or multiple 206
   (Partial Content) responses, each with one continuous range that is
   indicated by a Content-Range header field.  However, origin servers
   and intermediate caches ought to support byte ranges when possible,
   since

4.4.  416 Range supports efficient recovery from partially failed
   transfers, and supports efficient partial retrieval Not Satisfiable

   The 416 (Range Not Satisfiable) status code indicates that none of large
   representations.

   If
   the server supports ranges in the request's Range header field and (Section 3.1) overlap
   the specified range current extent of the selected resource or that the set of ranges are appropriate for
   requested has been rejected due to invalid ranges or an excessive
   request of small or overlapping ranges.

   For byte ranges, failing to overlap the current extent means that the
   first-byte-pos of all of the byte-range-spec values were greater than
   the representation:

   o  The presence current length of a Range header field in an unconditional GET
      modifies what is returned if the GET selected representation.  When this status
   code is otherwise successful.  In
      other words, the generated in response carries to a status code of 206 (Partial
      Content) instead of 200 (OK).

   o  The presence of byte range request, the sender
   SHOULD generate a Range Content-Range header field in a conditional GET (a
      request using one or both of If-Modified-Since and If-None-Match,
      or one or both of If-Unmodified-Since and If-Match) modifies what
      is returned if the GET is otherwise successful and specifying the condition
      is true.  It does not affect current
   length of the 304 (Not Modified) response
      returned selected representation (Section 4.2).

   For example:

     HTTP/1.1 416 Range Not Satisfiable
     Date: Mon, 20 Jan 2012 15:41:54 GMT
     Content-Range: bytes */47022

      Note: Because servers are free to ignore Range, many
      implementations will simply respond with 200 (OK) if the conditional requested
      ranges are invalid or not satisfiable.  That is false.

   In some cases, it might be more appropriate partly because
      most clients are prepared to use the If-Range
   header field (see Section 5.3) in addition receive a 200 (OK) to complete the Range header field.

   If
      task (albeit less efficiently) and partly because clients might
      not stop making an invalid partial request until they have
      received a proxy that supports ranges receives complete representation.  Thus, clients cannot depend
      on receiving a 416 (Range Not Satisfiable) response even when it
      is most appropriate.

5.  IANA Considerations

5.1.  Range request, forwards Unit Registry

   The HTTP Range Unit Registry defines the request to an inbound server, name space for the range
   unit names and receives refers to their corresponding specifications.  The
   registry is maintained at
   <http://www.iana.org/assignments/http-parameters>.

5.1.1.  Procedure

   Registration of an entire
   representation in reply, it MAY only return HTTP Range Unit MUST include the following fields:

   o  Name

   o  Description

   o  Pointer to specification text

   Values to be added to this name space require IETF Review (see
   [RFC5226], Section 4.1).

5.1.2.  Registrations

   The initial HTTP Range Unit Registry shall contain the requested registrations
   below:

   +-------------+---------------------------------------+-------------+
   | Range Unit  | Description                           | Reference   |
   | Name        |                                       |             |
   +-------------+---------------------------------------+-------------+
   | bytes       | a range to
   its client.

6.  IANA Considerations

6.1. of octets                     | Section 2.1 |
   | none        | reserved as keyword, indicating no    | Section 2.3 |
   |             | ranges are supported                  |             |
   +-------------+---------------------------------------+-------------+

   The change controller is: "IETF (iesg@ietf.org) - Internet
   Engineering Task Force".

5.2.  Status Code Registration

   The HTTP Status Code Registry located at
   <http://www.iana.org/assignments/http-status-codes> shall be updated
   with the registrations below:

   +-------+---------------------------------+-------------+

   +-------+-----------------------+-------------+
   | Value | Description           | Reference   |
   +-------+---------------------------------+-------------+
   +-------+-----------------------+-------------+
   | 206   | Partial Content       | Section 3.1 4.1 |
   | 416   | Requested Range Not Satisfiable | Section 3.2 4.4 |
   +-------+---------------------------------+-------------+

6.2.
   +-------+-----------------------+-------------+

5.3.  Header Field Registration

   The Message Header Field Registry located at <http://www.iana.org/
   assignments/message-headers/message-header-index.html> shall be
   updated with the permanent registrations below (see [RFC3864]): [BCP90]):

   +-------------------+----------+----------+-------------+
   | Header Field Name | Protocol | Status   | Reference   |
   +-------------------+----------+----------+-------------+
   | Accept-Ranges     | http     | standard | Section 5.1 2.3 |
   | Content-Range     | http     | standard | Section 5.2 4.2 |
   | If-Range          | http     | standard | Section 5.3 3.2 |
   | Range             | http     | standard | Section 5.4 3.1 |
   +-------------------+----------+----------+-------------+

   The change controller is: "IETF (iesg@ietf.org) - Internet
   Engineering Task Force".

6.3.  Range Specifier Registration

   The registration procedure for HTTP Range Specifiers is defined by
   Section 2.1 of this document.

   The HTTP Range Specifier Registry shall be created at
   <http://www.iana.org/assignments/http-range-specifiers> and be
   populated with the registrations below:

   +---------------+-------------------------------------+-------------+
   | Range         | Description                         | Reference   |
   | Specifier     |                                     |             |
   | Name          |                                     |             |
   +---------------+-------------------------------------+-------------+
   | bytes         | a range of octets                   | Section 2   |
   | none          | reserved as keyword, indicating no  | Section 5.1 |
   |               | ranges are supported                |             |
   +---------------+-------------------------------------+-------------+

   The change controller is: "IETF (iesg@ietf.org) - Internet
   Engineering Task Force".

7.

6.  Security Considerations

   This section is meant to inform application developers, information providers,
   and users of the known security limitations in HTTP/1.1 as
   described by this document.  The discussion does not include
   definitive solutions concerns specific to the problems revealed, though it does make
   some suggestions for reducing HTTP/1.1 range
   request mechanisms.  More general security risks.

7.1.  Overlapping Ranges considerations are
   addressed in HTTP messaging [Part1] and semantics [Part2].

6.1.  Denial of Service Attacks using Range

   Unconstrained multiple range requests containing are susceptible to denial of
   service attacks because the effort required to request many
   overlapping ranges can lead to of the
   situation where a server same data is sending far more tiny compared to the time,
   memory, and bandwidth consumed by attempting to serve the requested
   data in many parts.  Servers ought to ignore, coalesce, or reject
   egregious range requests, such as requests for more than two
   overlapping ranges or for many small ranges in a single set,
   particularly when the size ranges are requested out of
   the complete resource representation.

8. order for no
   apparent reason.  Multipart range requests are not designed to
   support random access.

7.  Acknowledgments

   See Section 9 of [Part1].

9.

8.  References

9.1.

8.1.  Normative References

   [Part1]    Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              draft-ietf-httpbis-p1-messaging-21
              draft-ietf-httpbis-p1-messaging-22 (work in progress),
              October 2012.
              February 2013.

   [Part2]    Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content",
              draft-ietf-httpbis-p2-semantics-21
              draft-ietf-httpbis-p2-semantics-22 (work in progress),
              October 2012.
              February 2013.

   [Part4]    Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Conditional Requests",
              draft-ietf-httpbis-p4-conditional-21
              draft-ietf-httpbis-p4-conditional-22 (work in progress),
              October 2012.
              February 2013.

   [Part6]    Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
              draft-ietf-httpbis-p6-cache-21
              draft-ietf-httpbis-p6-cache-22 (work in progress),
              October 2012.
              February 2013.

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              November 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

9.2.

8.2.  Informative References

   [RFC2616]  Fielding, R., Gettys, J., Mogul,

   [BCP13]    Freed, N., Klensin, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 2616, June 1999.

   [RFC3864] 6838, January 2013.

   [BCP90]    Klyne, G., Nottingham, M., and J. Mogul, "Registration
              Procedures for Message Header Fields", BCP 90, RFC 3864,
              September 2004.

   [RFC4288]  Freed, N. and J. Klensin, "Media Type Specifications

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and
              Registration Procedures", BCP 13, T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 4288, December 2005. 2616, June 1999.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

Appendix A.  Internet Media Type multipart/byteranges

   When an HTTP a 206 (Partial Content) response message includes the content of
   multiple ranges (a response to a request for multiple non-
   overlapping ranges), these ranges, they are transmitted as body parts in a multipart
   message body ([RFC2046], Section 5.1).  The 5.1) with the media type for this purpose is
   called of
   "multipart/byteranges".  The following definition is to be registered
   with IANA [RFC4288]. [BCP13].

   The multipart/byteranges media type includes one or more body parts,
   each with its own Content-Type and Content-Range fields.  The
   required boundary parameter specifies the boundary string used to
   separate each body-part. body part.

   Type name:  multipart

   Subtype name:  byteranges

   Required parameters:  boundary

   Optional parameters:  none

   Encoding considerations:  only "7bit", "8bit", or "binary" are
      permitted

   Security considerations:  none

   Interoperability considerations:  none

   Published specification:  This specification (see Appendix A).

   Applications that use this media type:  HTTP components supporting
      multiple ranges in a single request.

   Additional information:

      Magic number(s):  none

      File extension(s):  none

      Macintosh file type code(s):  none

   Person and email address to contact for further information:  See
      Authors Section.

   Intended usage:  COMMON

   Restrictions on usage:  none

   Author/Change controller:  IESG

      Note: Despite the name "multipart/byteranges" is not limited to
      the byte ranges only.

   For example:

     HTTP/1.1 206 Partial Content
     Date: Wed, 15 Nov 1995 06:25:24 GMT
     Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
     Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES

     --THIS_STRING_SEPARATES
     Content-type: application/pdf
     Content-range: bytes 500-999/8000

     ...the first range...
     --THIS_STRING_SEPARATES
     Content-type: application/pdf
     Content-range: bytes 7000-7999/8000

     ...the second range
     --THIS_STRING_SEPARATES--

   Another example, using the "exampleunit" range unit:

     HTTP/1.1 206 Partial Content
     Date: Tue, 14 Nov 1995 06:25:24 GMT
     Last-Modified: Tue, 14 July 04:58:08 GMT
     Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES

     --THIS_STRING_SEPARATES
     Content-type: video/example
     Content-range: exampleunit 1.2-4.3/25

     ...the first range...
     --THIS_STRING_SEPARATES
     Content-type: video/example
     Content-range: exampleunit 11.2-14.3/25

     ...the second range
     --THIS_STRING_SEPARATES-- specification:  This specification (see Appendix A).

   Applications that use this media type:  HTTP components supporting
      multiple ranges in a single request.

   Additional information:

      Magic number(s):  none

      File extension(s):  none

      Macintosh file type code(s):  none

   Person and email address to contact for further information:  See
      Authors Section.

   Intended usage:  COMMON

   Restrictions on usage:  none

   Author/Change controller:  IESG

   Implementation Notes:

   1.  Additional CRLFs MAY might precede the first boundary string in the
       body.

   2.  Although [RFC2046] permits the boundary string to be quoted, some
       existing implementations handle a quoted boundary string
       incorrectly.

   3.  A number of clients and servers were coded to an early draft of
       the byteranges specification to use that used a media type of multipart/
       x-byteranges, which is almost, but almost (but not quite quite) compatible with
       this type.

   Despite the
       version documented in HTTP/1.1. name, the "multipart/byteranges" media type is not
   limited to byte ranges.  The following example uses an "exampleunit"
   range unit:

     HTTP/1.1 206 Partial Content
     Date: Tue, 14 Nov 1995 06:25:24 GMT
     Last-Modified: Tue, 14 July 04:58:08 GMT
     Content-Length: 2331785
     Content-Type: multipart/byteranges; boundary=THIS_STRING_SEPARATES

     --THIS_STRING_SEPARATES
     Content-Type: video/example
     Content-Range: exampleunit 1.2-4.3/25

     ...the first range...
     --THIS_STRING_SEPARATES
     Content-Type: video/example
     Content-Range: exampleunit 11.2-14.3/25

     ...the second range
     --THIS_STRING_SEPARATES--

Appendix B.  Changes from RFC 2616

   Introduce Range Specifier Registry.  (Section 2.1)

   Clarify that it is not ok to use a

   A weak validator cannot be used in a 206 response.  (Section 3.1)

   Clarify that 4.1)

   The Content-Range header field only has meaning when the status code
   explicitly defines its use.  (Section 4.2)

   Servers are given more leeway in how they respond to a range request,
   in order to mitigate abuse by malicious (or just greedy) clients.

   multipart/byteranges can consist of a single part.  (Appendix A)

   This specification introduces a Range Unit Registry.  (Section 5.1)

Appendix C.  Imported ABNF

   The following core rules are included by reference, as defined in
   Appendix B.1 of [RFC5234]: ALPHA (letters), CR (carriage return),
   CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double
   quote), HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any
   8-bit sequence of data), SP (space), and VCHAR (any visible US-ASCII
   character).

   Note that all rules derived from token are to be compared case-
   insensitively, like range-unit and acceptable-ranges.

   The rules below are defined in [Part1]:

     OWS        = <OWS, defined in [Part1], Section 3.2.1> 3.2.3>
     token      = <token, defined in [Part1], Section 3.2.4> 3.2.6>

   The rules below are defined in other parts:

     HTTP-date  = <HTTP-date, defined in [Part2], Section 8.1.1.1> 7.1.1.1>
     entity-tag = <entity-tag, defined in [Part4], Section 2.3>

Appendix D.  Collected ABNF
   Accept-Ranges = acceptable-ranges

   Content-Range = byte-content-range-spec byte-content-range / other-content-range-spec other-content-range

   HTTP-date = <HTTP-date, defined in [Part2], Section 8.1.1.1> 7.1.1.1>

   If-Range = entity-tag / HTTP-date

   OWS = <OWS, defined in [Part1], Section 3.2.1> 3.2.3>

   Range = byte-ranges-specifier / other-ranges-specifier

   acceptable-ranges = ( *( "," OWS ) range-unit *( OWS "," [ OWS
    range-unit ] ) ) / "none"

   byte-content-range-spec

   byte-content-range = bytes-unit SP byte-range-resp-spec "/" (
    instance-length byte-range-resp / "*"
    unsatisfied-range )
   byte-range-resp-spec
   byte-range = ( first-byte-pos "-" last-byte-pos )
   byte-range-resp = byte-range "/" ( complete-length / "*" )
   byte-range-set = *( "," OWS ) ( byte-range-spec /
    suffix-byte-range-spec ) *( OWS "," [ OWS ( byte-range-spec /
    suffix-byte-range-spec ) ] )
   byte-range-spec = first-byte-pos "-" [ last-byte-pos ]
   byte-ranges-specifier = bytes-unit "=" byte-range-set
   bytes-unit = "bytes"

   complete-length = 1*DIGIT

   entity-tag = <entity-tag, defined in [Part4], Section 2.3>

   first-byte-pos = 1*DIGIT

   instance-length = 1*DIGIT

   last-byte-pos = 1*DIGIT

   other-content-range-spec

   other-content-range = other-range-unit SP other-range-resp-spec
   other-range-resp-spec other-range-resp
   other-range-resp = *CHAR
   other-range-set = 1*CHAR
   other-range-unit = token
   other-ranges-specifier = other-range-unit "=" other-range-set

   range-unit = bytes-unit / other-range-unit

   suffix-byte-range-spec = "-" suffix-length
   suffix-length = 1*DIGIT

   token = <token, defined in [Part1], Section 3.2.4> 3.2.6>

   unsatisfied-range = "*/" complete-length

Appendix E.  Change Log (to be removed by RFC Editor before publication)

   Changes up to the first Working Group Last Call draft are summarized
   in <http://tools.ietf.org/html/
   draft-ietf-httpbis-p5-range-19#appendix-D>.

E.1.  Since draft-ietf-httpbis-p5-range-19

   Closed issues:

   o  <http://tools.ietf.org/wg/httpbis/trac/ticket/358>: "ABNF list
      expansion code problem"

   o  <http://tools.ietf.org/wg/httpbis/trac/ticket/361>: "ABNF
      requirements for recipients"

   o  <http://tools.ietf.org/wg/httpbis/trac/ticket/367>: "reserve
      'none' as byte range unit"

   o  <http://tools.ietf.org/wg/httpbis/trac/ticket/368>: "note
      introduction of new IANA registries as normative changes"

   o  <http://tools.ietf.org/wg/httpbis/trac/ticket/369>: "range units
      vs leading zeroes vs size"

E.2.  Since draft-ietf-httpbis-p5-range-20

   o  Conformance criteria and considerations regarding error handling
      are now defined in Part 1.

E.3.  Since draft-ietf-httpbis-p5-range-21

   Closed issues:

   o  <http://tools.ietf.org/wg/httpbis/trac/ticket/175>: "Security
      consideration: range flooding"

   o  <http://tools.ietf.org/wg/httpbis/trac/ticket/223>: "Allowing
      heuristic caching for new status codes"

   o  <http://tools.ietf.org/wg/httpbis/trac/ticket/311>: "Add
      limitations to Range to reduce its use as a denial-of-service
      tool"

Index

   2
      206 Partial Content (status code)  5  10

   4
      416 Requested Range Not Satisfiable (status code)  6  15

   A
      Accept-Ranges header field  8  7

   C
      Content-Range header field  9  12

   G
      Grammar
         Accept-Ranges  8  7
         acceptable-ranges  8
         byte-content-range-spec  9
         byte-range-resp-spec  9
         byte-range-set  7
         byte-content-range  12
         byte-range-spec
         byte-range  12
         byte-ranges-specifier
         byte-range-resp  12
         byte-range-set  5
         byte-range-spec  5
         byte-ranges-specifier  5
         bytes-unit  5
         complete-length  12
         Content-Range  9
         first-byte-pos  12
         first-byte-pos  5
         If-Range  11
         instance-length  9
         last-byte-pos  5
         other-content-range  12
         other-range-resp  12
         other-range-unit  5  5, 7
         Range  13  7
         range-unit  5
         ranges-specifier  12  5
         suffix-byte-range-spec  12  6
         suffix-length  6
         unsatisfied-range  12

   I
      If-Range header field  10  9

   M
      Media Type
         multipart/byteranges  17  18
         multipart/x-byteranges  19  20
      multipart/byteranges Media Type  17  18
      multipart/x-byteranges Media Type  19  20

   R
      Range header field  11  7

Authors' Addresses

   Roy T. Fielding (editor)
   Adobe Systems Incorporated
   345 Park Ave
   San Jose, CA  95110
   USA

   EMail: fielding@gbiv.com
   URI:   http://roy.gbiv.com/

   Yves Lafon (editor)
   World Wide Web Consortium
   W3C / ERCIM
   2004, rte des Lucioles
   Sophia-Antipolis, AM  06902
   France

   EMail: ylafon@w3.org
   URI:   http://www.raubacapeu.net/people/yves/

   Julian F. Reschke (editor)
   greenbytes GmbH
   Hafenweg 16
   Muenster, NW  48155
   Germany

   EMail: julian.reschke@greenbytes.de
   URI:   http://greenbytes.de/tech/webdav/