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Network Working Group R. Fielding, Ed.
Internet-Draft Day Software
Obsoletes: 2616 (if approved) J. Gettys
Intended status: Standards Track One Laptop per Child
Expires: March 2, 2009 J. Mogul
HP
H. Frystyk
Microsoft
L. Masinter
Adobe Systems
P. Leach
Microsoft
T. Berners-Lee
W3C/MIT
Y. Lafon, Ed.
W3C
J. Reschke, Ed.
greenbytes
August 29, 2008
HTTP/1.1, part 5: Range Requests and Partial Responses
draft-ietf-httpbis-p5-range-04
Status of this Memo
By submitting this Internet-Draft, each author represents that any
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This Internet-Draft will expire on March 2, 2009.
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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 is Part 5 of the
seven-part specification that defines the protocol referred to as
"HTTP/1.1" and, taken together, obsoletes RFC 2616. Part 5 defines
range-specific requests and the rules for constructing and combining
responses to those requests.
Editorial Note (To be removed by RFC Editor)
Discussion of this draft should take place on the HTTPBIS working
group mailing list (ietf-http-wg@w3.org). The current issues list is
at <http://www.tools.ietf.org/wg/httpbis/trac/report/11> and related
documents (including fancy diffs) can be found at
<http://www.tools.ietf.org/wg/httpbis/>.
The changes in this draft are summarized in Appendix C.4.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 4
2. Notational Conventions and Generic Grammar . . . . . . . . . . 4
3. Range Units . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Status Code Definitions . . . . . . . . . . . . . . . . . . . 5
4.1. 206 Partial Content . . . . . . . . . . . . . . . . . . . 5
4.2. 416 Requested Range Not Satisfiable . . . . . . . . . . . 6
5. Combining Byte Ranges . . . . . . . . . . . . . . . . . . . . 6
6. Header Field Definitions . . . . . . . . . . . . . . . . . . . 7
6.1. Accept-Ranges . . . . . . . . . . . . . . . . . . . . . . 7
6.2. Content-Range . . . . . . . . . . . . . . . . . . . . . . 8
6.3. If-Range . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.4. Range . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.4.1. Byte Ranges . . . . . . . . . . . . . . . . . . . . . 10
6.4.2. Range Retrieval Requests . . . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
7.1. Message Header Registration . . . . . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . . 15
Appendix A. Internet Media Type multipart/byteranges . . . . . . 15
Appendix B. Compatibility with Previous Versions . . . . . . . . 17
B.1. Changes from RFC 2068 . . . . . . . . . . . . . . . . . . 17
B.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 17
Appendix C. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 17
C.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 17
C.2. Since draft-ietf-httpbis-p5-range-00 . . . . . . . . . . . 18
C.3. Since draft-ietf-httpbis-p5-range-01 . . . . . . . . . . . 18
C.4. Since draft-ietf-httpbis-p5-range-02 . . . . . . . . . . . 18
C.5. Since draft-ietf-httpbis-p5-range-03 . . . . . . . . . . . 18
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
Intellectual Property and Copyright Statements . . . . . . . . . . 23
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1. Introduction
HTTP clients often encounter interrupted data transfers as a result
of cancelled requests or dropped connections. When a cache 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 benefit from being able to request only a subset of
a larger representation, such as a single page of a very large
document or only part of an image to be rendered by a device with
limited local storage.
This document defines HTTP/1.1 range requests, partial responses, and
the multipart/byteranges media type. The protocol for range requests
is an OPTIONAL feature of HTTP, designed so resources or recipients
that do not implement this feature 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. Requirements
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].
An implementation is not compliant if it fails to satisfy one or more
of the MUST or REQUIRED level requirements for the protocols it
implements. An implementation that satisfies all the MUST or
REQUIRED level and all the SHOULD level requirements for its
protocols is said to be "unconditionally compliant"; one that
satisfies all the MUST level requirements but not all the SHOULD
level requirements for its protocols is said to be "conditionally
compliant."
2. Notational Conventions and Generic Grammar
This specification uses the ABNF syntax defined in Section 2.1 of
[Part1] and the core rules defined in Section 2.2 of [Part1]:
[[abnf.dep: ABNF syntax and basic rules will be adopted from RFC
5234, see <http://tools.ietf.org/wg/httpbis/trac/ticket/36>.]]
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DIGIT = <DIGIT, defined in [Part1], Section 2.2>
SP = <SP, defined in [Part1], Section 2.2>
token = <token, defined in [Part1], Section 2.2>
The ABNF rules below are defined in other parts:
HTTP-date = <HTTP-date, defined in [Part1], Section 3.3.1>
entity-tag = <entity-tag, defined in [Part4], Section 3>
3. Range Units
HTTP/1.1 allows a client to request that only part (a range of) the
response entity be included within the response. HTTP/1.1 uses range
units in the Range (Section 6.4) and Content-Range (Section 6.2)
header fields. An entity can be broken down into subranges according
to various structural units.
range-unit = bytes-unit | other-range-unit
bytes-unit = "bytes"
other-range-unit = token
The only range unit defined by HTTP/1.1 is "bytes". HTTP/1.1
implementations MAY ignore ranges specified using other units.
HTTP/1.1 has been designed to allow implementations of applications
that do not depend on knowledge of ranges.
4. Status Code Definitions
4.1. 206 Partial Content
The server has fulfilled the partial GET request for the resource.
The request MUST have included a Range header field (Section 6.4)
indicating the desired range, and MAY have included an If-Range
header field (Section 6.3) to make the request conditional.
The response MUST include the following header fields:
o Either a Content-Range header field (Section 6.2) indicating the
range included with this response, or a multipart/byteranges
Content-Type including Content-Range fields for each part. If a
Content-Length header field is present in the response, its value
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MUST match the actual number of OCTETs transmitted in the message-
body.
o Date
o ETag and/or Content-Location, if the header would have been sent
in a 200 response to the same request
o Expires, Cache-Control, and/or Vary, if the field-value might
differ from that sent in any previous response for the same
variant
If the 206 response is the result of an If-Range request, the
response SHOULD NOT include other entity-headers. Otherwise, the
response MUST include all of the entity-headers that would have been
returned with a 200 (OK) response to the same request.
A cache MUST NOT combine a 206 response with other previously cached
content if the ETag or Last-Modified headers do not match exactly,
see Section 5.
A cache that does not support the Range and Content-Range headers
MUST NOT cache 206 (Partial Content) responses.
4.2. 416 Requested Range Not Satisfiable
A server SHOULD return a response with this status code if a request
included a Range request-header field (Section 6.4), and none of the
range-specifier values in this field overlap the current extent of
the selected resource, and the request did not include an If-Range
request-header field. (For byte-ranges, this means that the first-
byte-pos of all of the byte-range-spec values were greater than the
current length of the selected resource.)
When this status code is returned for a byte-range request, the
response SHOULD include a Content-Range entity-header field
specifying the current length of the selected resource (see
Section 6.2). This response MUST NOT use the multipart/byteranges
content-type.
5. Combining Byte Ranges
A response might transfer only a subrange of the bytes of an entity-
body, either because the request included one or more Range
specifications, or because a connection was broken prematurely.
After several such transfers, a cache might have received several
ranges of the same entity-body.
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If a cache has a stored non-empty set of subranges for an entity, and
an incoming response transfers another subrange, the cache MAY
combine the new subrange with the existing set if both the following
conditions are met:
o Both the incoming response and the cache entry have a cache
validator.
o The two cache validators match using the strong comparison
function (see Section 5 of [Part4]).
If either requirement is not met, the cache MUST use only the most
recent partial response (based on the Date values transmitted with
every response, and using the incoming response if these values are
equal or missing), and MUST discard the other partial information.
6. Header Field Definitions
This section defines the syntax and semantics of HTTP/1.1 header
fields related to range requests and partial responses.
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.
6.1. Accept-Ranges
The Accept-Ranges response-header field allows the server to indicate
its acceptance of range requests for a resource:
Accept-Ranges = "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 generate byte-range
requests without having received this header for the resource
involved. Range units are defined in Section 3.
Servers that do not accept any kind of range request for a resource
MAY send
Accept-Ranges: none
to advise the client not to attempt a range request.
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6.2. 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. Range units are defined in Section 3.
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
The header SHOULD indicate the total length of the full entity-body,
unless this length is unknown or difficult to determine. The
asterisk "*" character means that the instance-length is unknown at
the time when the response was generated.
Unlike byte-ranges-specifier values (see Section 6.4.1), a byte-
range-resp-spec MUST only specify one range, and MUST contain
absolute byte positions for both the first and last byte of the
range.
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
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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
When an HTTP message includes the content of a single range (for
example, a response to a request for a single range, or to a request
for a set of ranges that overlap without any holes), this content is
transmitted with a Content-Range header, and a Content-Length header
showing the number 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, a response to a request for multiple non-overlapping
ranges), these are transmitted as a multipart message. The multipart
media type used for this purpose is "multipart/byteranges" as defined
in Appendix A. See Appendix B.1 for a compatibility issue.
A response to a request for a single range MUST NOT be sent using the
multipart/byteranges media type. A response to a request for
multiple ranges, whose result is a single range, MAY be sent as a
multipart/byteranges media type with one part. A client that cannot
decode a multipart/byteranges message MUST NOT ask for multiple byte-
ranges in a single request.
When a client requests multiple byte-ranges in one request, the
server SHOULD return them in the order that they appeared in the
request.
If the server ignores a byte-range-spec because it is syntactically
invalid, the server SHOULD treat the request as if the invalid Range
header field did not exist. (Normally, this means return a 200
response containing the full entity).
If the server receives a request (other than one including an If-
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Range request-header field) with an unsatisfiable Range request-
header field (that is, all of whose byte-range-spec values have a
first-byte-pos value greater than the current length of the selected
resource), it SHOULD return a response code of 416 (Requested range
not satisfiable) (Section 4.2).
Note: clients cannot depend on servers to send a 416 (Requested
range not satisfiable) response instead of a 200 (OK) response for
an unsatisfiable Range request-header, since not all servers
implement this request-header.
6.3. If-Range
If a client has a partial copy of an entity in its cache, and wishes
to have an up-to-date copy of the entire entity in its cache, it
could use the Range request-header with a conditional GET (using
either or both of If-Unmodified-Since and If-Match.) However, if the
condition fails because the entity has been modified, the client
would then have to make a second request to obtain the entire current
entity-body.
The If-Range header allows a client to "short-circuit" the second
request. Informally, its meaning is `if the entity is unchanged,
send me the part(s) that I am missing; otherwise, send me the entire
new entity'.
If-Range = "If-Range" ":" ( entity-tag | HTTP-date )
If the client has no entity tag for an entity, but does have a Last-
Modified date, it MAY use that date in an If-Range header. (The
server can distinguish between a valid HTTP-date and any form of
entity-tag by examining no more than two characters.) The If-Range
header SHOULD only be used together with a Range header, and MUST be
ignored if the request does not include a Range header, or if the
server does not support the sub-range operation.
If the entity tag given in the If-Range header matches the current
entity tag for the entity, then the server SHOULD provide the
specified sub-range of the entity using a 206 (Partial Content)
response. If the entity tag does not match, then the server SHOULD
return the entire entity using a 200 (OK) response.
6.4. Range
6.4.1. Byte Ranges
Since all HTTP entities are represented in HTTP messages as sequences
of bytes, the concept of a byte range is meaningful for any HTTP
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entity. (However, not all clients and servers need to support byte-
range operations.)
Byte range specifications in HTTP apply to the sequence of bytes in
the entity-body (not necessarily the same as the message-body).
A byte range operation MAY specify a single range of bytes, or a set
of ranges within a single entity.
ranges-specifier = byte-ranges-specifier
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 byte-range-spec gives the byte-offset
of the first byte in a range. 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 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 the last-byte-pos value is absent, or if the value is greater than
or equal to the current length of the entity-body, last-byte-pos is
taken to be equal to one less than the current length of the entity-
body in bytes.
By its choice of last-byte-pos, a client can limit the number of
bytes retrieved without knowing the size of the entity.
suffix-byte-range-spec = "-" suffix-length
suffix-length = 1*DIGIT
A suffix-byte-range-spec is used to specify the suffix of the entity-
body, of a length given by the suffix-length value. (That is, this
form specifies the last N bytes of an entity-body.) If the entity is
shorter than the specified suffix-length, the entire entity-body is
used.
If a syntactically valid byte-range-set includes at least one byte-
range-spec whose first-byte-pos is less than the current length of
the entity-body, or at least one suffix-byte-range-spec with a non-
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zero suffix-length, then the byte-range-set is satisfiable.
Otherwise, the byte-range-set is unsatisfiable. If the byte-range-
set is unsatisfiable, the server SHOULD return a response with a
status of 416 (Requested range not satisfiable). Otherwise, the
server SHOULD return a response with a status of 206 (Partial
Content) containing the satisfiable ranges of the entity-body.
Examples of byte-ranges-specifier values (assuming an entity-body 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
o Or bytes=9500-
o The first and last bytes only (bytes 0 and 9999): bytes=0-0,-1
o Several legal but not canonical specifications of the second 500
bytes (byte offsets 500-999, inclusive):
bytes=500-600,601-999
bytes=500-700,601-999
6.4.2. Range Retrieval Requests
HTTP retrieval requests using conditional or unconditional GET
methods MAY request one or more sub-ranges of the entity, instead of
the entire entity, using the Range request header, which applies to
the entity returned as the result of the request:
Range = "Range" ":" ranges-specifier
A server MAY ignore the Range header. However, HTTP/1.1 origin
servers and intermediate caches ought to support byte ranges when
possible, since Range supports efficient recovery from partially
failed transfers, and supports efficient partial retrieval of large
entities.
If the server supports the Range header and the specified range or
ranges are appropriate for the entity:
o The presence of a Range header in an unconditional GET modifies
what is returned if the GET is otherwise successful. In other
words, the response carries a status code of 206 (Partial Content)
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instead of 200 (OK).
o The presence of a Range header 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 the condition is
true. It does not affect the 304 (Not Modified) response returned
if the conditional is false.
In some cases, it might be more appropriate to use the If-Range
header (see Section 6.3) in addition to the Range header.
If a proxy that supports ranges receives a Range request, forwards
the request to an inbound server, and receives an entire entity in
reply, it SHOULD only return the requested range to its client. It
SHOULD store the entire received response in its cache if that is
consistent with its cache allocation policies.
7. IANA Considerations
7.1. Message Header Registration
The Message Header Registry located at <http://www.iana.org/
assignments/message-headers/message-header-index.html> should be
updated with the permanent registrations below (see [RFC3864]):
+-------------------+----------+----------+-------------+
| Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+-------------+
| Accept-Ranges | http | standard | Section 6.1 |
| Content-Range | http | standard | Section 6.2 |
| If-Range | http | standard | Section 6.3 |
| Range | http | standard | Section 6.4 |
+-------------------+----------+----------+-------------+
The change controller is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force".
8. Security Considerations
No additional security considerations have been identified beyond
those applicable to HTTP in general [Part1].
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9. Acknowledgments
Most of the specification of ranges is based on work originally done
by Ari Luotonen and John Franks, with additional input from Steve
Zilles, Daniel W. Connolly, Roy T. Fielding, Jim Gettys, Martin
Hamilton, Koen Holtman, Shel Kaplan, Paul Leach, Alex Lopez-Ortiz,
Larry Masinter, Jeff Mogul, Lou Montulli, David W. Morris, Luigi
Rizzo, and Bill Weihl.
10. References
10.1. Normative References
[Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections,
and Message Parsing", draft-ietf-httpbis-p1-messaging-04
(work in progress), August 2008.
[Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 3: Message Payload
and Content Negotiation", draft-ietf-httpbis-p3-payload-04
(work in progress), August 2008.
[Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional
Requests", draft-ietf-httpbis-p4-conditional-04 (work in
progress), August 2008.
[Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 6: Caching",
draft-ietf-httpbis-p6-cache-04 (work in progress),
August 2008.
[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.
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10.2. Informative References
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC3864] 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 and
Registration Procedures", BCP 13, RFC 4288, December 2005.
Appendix A. Internet Media Type multipart/byteranges
When an HTTP 206 (Partial Content) response message includes the
content of multiple ranges (a response to a request for multiple non-
overlapping ranges), these are transmitted as a multipart message-
body [RFC2046]. The media type for this purpose is called
"multipart/byteranges". The following is to be registered with IANA
[RFC4288].
The multipart/byteranges media type includes two or more 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.
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).
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Applications that use this media type:
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
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--
Notes:
1. Additional CRLFs may precede the first boundary string in the
entity.
2. Although [RFC2046] permits the boundary string to be quoted, some
existing implementations handle a quoted boundary string
incorrectly.
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3. A number of browsers and servers were coded to an early draft of
the byteranges specification to use a media type of multipart/
x-byteranges, which is almost, but not quite compatible with the
version documented in HTTP/1.1.
Appendix B. Compatibility with Previous Versions
B.1. Changes from RFC 2068
Transfer-coding and message lengths all interact in ways that
required fixing exactly when chunked encoding is used (to allow for
transfer encoding that may not be self delimiting); it was important
to straighten out exactly how message lengths are computed.
(Section 6.2, see also [Part1], [Part3] and [Part6])
There are situations where a server (especially a proxy) does not
know the full length of a response but is capable of serving a
byterange request. We therefore need a mechanism to allow byteranges
with a content-range not indicating the full length of the message.
(Section 6.2)
Range request responses would become very verbose if all meta-data
were always returned; by allowing the server to only send needed
headers in a 206 response, this problem can be avoided. (Section 4.1
and 6.3)
Fix problem with unsatisfiable range requests; there are two cases:
syntactic problems, and range doesn't exist in the document. The 416
status code was needed to resolve this ambiguity needed to indicate
an error for a byte range request that falls outside of the actual
contents of a document. (Section 4.2, 6.2)
B.2. Changes from RFC 2616
Clarify that it is not ok to use a weak cache validator in a 206
response. (Section 4.1)
Appendix C. Change Log (to be removed by RFC Editor before publication)
C.1. Since RFC2616
Extracted relevant partitions from [RFC2616].
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C.2. Since draft-ietf-httpbis-p5-range-00
Closed issues:
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/18>: "Cache
validators in 206 responses"
(<http://purl.org/NET/http-errata#ifrange206>)
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35>: "Normative
and Informative references"
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/86>: "Normative
up-to-date references"
C.3. Since draft-ietf-httpbis-p5-range-01
Closed issues:
o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/55>: "Updating
to RFC4288"
Ongoing work on ABNF conversion
(<http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36>):
o Add explicit references to BNF syntax and rules imported from
other parts of the specification.
C.4. Since draft-ietf-httpbis-p5-range-02
Ongoing work on IANA Message Header Registration
(<http://www3.tools.ietf.org/wg/httpbis/trac/ticket/40>):
o Reference RFC 3984, and update header registrations for headers
defined in this document.
C.5. Since draft-ietf-httpbis-p5-range-03
Index
2
206 Partial Content (status code) 5
4
416 Requested Range Not Satisfiable (status code) 6
A
Accept-Ranges header 7
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C
Content-Range header 8
G
Grammar
Accept-Ranges 7
acceptable-ranges 7
byte-content-range-spec 8
byte-range-resp-spec 8
byte-range-set 11
byte-range-spec 11
byte-ranges-specifier 11
bytes-unit 5
Content-Range 8
content-range-spec 8
first-byte-pos 11
If-Range 10
instance-length 8
last-byte-pos 11
other-range-unit 5
Range 12
range-unit 5
ranges-specifier 11
suffix-byte-range-spec 11
suffix-length 11
H
Headers
Accept-Ranges 7
Content-Range 8
If-Range 10
Range 10
I
If-Range header 10
M
Media Type
multipart/byteranges 15
multipart/x-byteranges 17
multipart/byteranges Media Type 15
multipart/x-byteranges Media Type 17
R
Range header 10
S
Status Codes
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206 Partial Content 5
416 Requested Range Not Satisfiable 6
Authors' Addresses
Roy T. Fielding (editor)
Day Software
23 Corporate Plaza DR, Suite 280
Newport Beach, CA 92660
USA
Phone: +1-949-706-5300
Fax: +1-949-706-5305
Email: fielding@gbiv.com
URI: http://roy.gbiv.com/
Jim Gettys
One Laptop per Child
21 Oak Knoll Road
Carlisle, MA 01741
USA
Email: jg@laptop.org
URI: http://www.laptop.org/
Jeffrey C. Mogul
Hewlett-Packard Company
HP Labs, Large Scale Systems Group
1501 Page Mill Road, MS 1177
Palo Alto, CA 94304
USA
Email: JeffMogul@acm.org
Henrik Frystyk Nielsen
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
USA
Email: henrikn@microsoft.com
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Larry Masinter
Adobe Systems, Incorporated
345 Park Ave
San Jose, CA 95110
USA
Email: LMM@acm.org
URI: http://larry.masinter.net/
Paul J. Leach
Microsoft Corporation
1 Microsoft Way
Redmond, WA 98052
Email: paulle@microsoft.com
Tim Berners-Lee
World Wide Web Consortium
MIT Computer Science and Artificial Intelligence Laboratory
The Stata Center, Building 32
32 Vassar Street
Cambridge, MA 02139
USA
Email: timbl@w3.org
URI: http://www.w3.org/People/Berners-Lee/
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/
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Julian F. Reschke (editor)
greenbytes GmbH
Hafenweg 16
Muenster, NW 48155
Germany
Phone: +49 251 2807760
Fax: +49 251 2807761
Email: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/
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