超文本传输​​协议（HTTP/1.1）：范围请求

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.  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, or    the dimensions of an embedded image.     This document defines HTTP/1.1 range requests, partial responses, and    the multipart/byteranges media type.  Range requests are an OPTIONAL    feature of HTTP, designed so that recipients not 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 caches that might not implement the    feature.     Although the range request mechanism is designed to allow for    extensible range types, this specification only defines requests for    byte ranges.  

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](https://tools.ietf.org/html/rfc2119)].     Conformance criteria and considerations regarding error handling are    defined in [Section 2.5 of [RFC7230]](https://tools.ietf.org/html/rfc7230#section-2.5).  

This specification uses the Augmented Backus-Naur Form (ABNF)    notation of [[RFC5234](https://tools.ietf.org/html/rfc5234)] with a list extension, defined in [Section 7 of    [RFC7230]](https://tools.ietf.org/html/rfc7230#section-7), that allows for compact definition of comma-separated    lists using a '#' operator (similar to how the '\*' operator indicates    repetition).  [Appendix C](about:blank#appendix-C) describes rules imported from other    documents.  [Appendix D](about:blank#appendix-D) shows the collected grammar with all list    operators expanded to standard ABNF notation.   

A representation can be partitioned into subranges according to    various structural units, depending on the structure inherent in the    representation's media type.  This "range unit" is used in the    Accept-Ranges ([Section 2.3](about:blank#section-2.3)) response header field to advertise    support for range requests, the Range ([Section 3.1](about:blank#section-3.1)) request header    field to delineate the parts of a representation that are requested,    and the Content-Range ([Section 4.2](about:blank#section-4.2)) payload header field to describe    which part of a representation is being transferred.       range-unit       = bytes-unit / other-range-unit  

Since representation data is transferred in payloads as a sequence of    octets, a byte range is a meaningful substructure for any    representation transferable over HTTP ([Section 3 of [RFC7231]](https://tools.ietf.org/html/rfc7231#section-3)).  The    "bytes" range unit is defined for expressing subranges of the data's    octet sequence.       bytes-unit       = "bytes"     A byte-range request can 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 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.     Examples of byte-ranges-specifier values:     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      A byte-range-spec is invalid if the last-byte-pos value is present    and less than the first-byte-pos.     A client can limit the number of bytes requested without knowing the    size of the selected representation.  If the last-byte-pos value is    absent, or if the value is greater than or equal to the current    length of the representation data, the byte range is interpreted as    the remainder of the representation (i.e., the server replaces the    value of last-byte-pos with a value that is one less than the current    length of the selected representation).     A client can request the last N bytes of the selected representation    using a suffix-byte-range-spec.       suffix-byte-range-spec = "-" suffix-length      suffix-length = 1\*DIGIT     If the selected representation is shorter than the specified    suffix-length, the entire representation is used.     Additional examples, assuming a representation of 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 with    a first-byte-pos that is less than the current length of the    representation, or at least one suffix-byte-range-spec with a    non-zero suffix-length, then the byte-range-set is satisfiable.    Otherwise, the 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 octets.  Since there    is no predefined limit to the length of a payload, recipients MUST    anticipate potentially large decimal numerals and prevent parsing    errors due to integer conversion overflows.  

Range units are intended to be extensible.  New range units ought to    be registered with IANA, as defined in [Section 5.1](about:blank#section-5.1).       other-range-unit = token  

The "Accept-Ranges" header field allows a server to indicate that it    supports range requests for the target resource.       Accept-Ranges     = acceptable-ranges      acceptable-ranges = 1#range-unit / "none"     An origin server that supports byte-range requests for a given target    resource MAY send       Accept-Ranges: bytes     to indicate what range units are supported.  A client MAY generate    range requests without having received this header field for the    resource involved.  Range units are defined in [Section 2](about:blank#section-2).     A server that does not support any kind of range request for the    target resource MAY send       Accept-Ranges: none     to advise the client not to attempt a range request.   

The "Range" header field on a 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\*VCHAR     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 method other    than GET.     An origin server MUST ignore a Range header field that contains a    range unit it does not understand.  A proxy MAY discard a Range    header field that contains a range unit it does not understand.     A server that supports range requests MAY ignore or reject a Range    header field that consists of more than two overlapping ranges, or a    set of many small ranges that 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](about:blank#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 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 time.     The Range header field is evaluated after evaluating the precondition    header fields defined in [[RFC7232](https://tools.ietf.org/html/rfc7232)], and only if the result in absence    of the Range header field would be a 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 ([Section 3.2](about:blank#section-3.2)) can be used as a precondition    to applying the Range header field.     If all of the 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](about:blank#section-2.1)), the server SHOULD    send a 206 (Partial Content) response with a payload containing one    or more partial representations that correspond to the satisfiable    ranges requested, as defined in [Section 4](about:blank#section-4).     If all of the preconditions are true, the server supports the Range    header field for the target resource, and the specified range(s) are    invalid or unsatisfiable, the server SHOULD send a 416 (Range Not    Satisfiable) response.  

If a client has a partial copy of a representation and wishes to have    an up-to-date copy of the 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 precondition    fails because the representation has been modified, the client would    then have to make a second request to obtain the entire current    representation.     The "If-Range" header field allows a client to "short-circuit" the    second request.  Informally, its meaning is as follows: if the    representation is unchanged, send me the part(s) that I am requesting    in Range; otherwise, send me the entire representation.       If-Range = entity-tag / HTTP-date     A client MUST NOT generate an If-Range header field in 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 a    Range header field.  An origin server MUST ignore an If-Range header    field received in a request for a target resource that does not    support Range requests.     A client MUST NOT generate an If-Range header field containing an    entity-tag that is marked as weak.  A client MUST NOT generate an    If-Range header field containing an HTTP-date unless the client has    no entity-tag for the corresponding representation and the date is a    strong validator in the sense defined by [Section 2.2.2 of [RFC7232]](https://tools.ietf.org/html/rfc7232#section-2.2.2).     A server that evaluates an If-Range precondition MUST use the strong    comparison function when comparing entity-tags ([Section 2.3.2 of    [RFC7232]](https://tools.ietf.org/html/rfc7232#section-2.3.2)) and MUST evaluate the condition as false if an HTTP-date      validator is provided that is not a strong validator in the sense    defined by [Section 2.2.2 of [RFC7232]](https://tools.ietf.org/html/rfc7232#section-2.2.2).  A valid entity-tag can be    distinguished from a valid HTTP-date by examining the first two    characters for a DQUOTE.     If the validator given in the If-Range header field matches the    current validator for the selected representation of the target    resource, then the server SHOULD process the Range header field as    requested.  If the validator does not match, the server MUST ignore    the Range header field.  Note that this comparison by exact match,    including when the validator is an HTTP-date, differs from the    "earlier than or equal to" comparison used when evaluating an    If-Unmodified-Since conditional.  

The 206 (Partial Content) status code indicates that the server is    successfully fulfilling a range request for the target resource by    transferring one or more parts of the selected representation that    correspond to the satisfiable ranges found in the request's Range    header field ([Section 3.1](about:blank#section-3.1)).     If a single part is being transferred, the server generating the 206    response MUST generate a Content-Range header field, describing what    range of the selected representation is enclosed, and a payload    consisting of the 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 server generating the    206 response MUST generate a "multipart/byteranges" payload, as    defined in [Appendix A](about:blank#appendix-A), and a Content-Type header field containing the    multipart/byteranges media type and its required boundary parameter.    To avoid confusion with single-part responses, a server MUST NOT    generate a Content-Range header field in the HTTP header section of a    multiple part response (this field will be sent in each part    instead).      Within the header area of each body part in the multipart payload,    the server MUST generate a Content-Range header field corresponding    to the range being enclosed in that body part.  If the selected    representation would have had a Content-Type header field in a 200    (OK) response, the server SHOULD generate that same Content-Type    field in the 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    ranges that overlap, or that are separated by a gap that is smaller    than the overhead of sending multiple parts, regardless of the order    in which the corresponding byte-range-spec appeared in the received    Range header field.  Since the typical overhead between parts of a    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 it is to transfer the entire selected    representation.     A server MUST NOT generate a multipart response to a 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 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 MUST NOT generate    a request that asks for multiple ranges.     When a multipart response payload is generated, the server SHOULD    send the parts in the same order that the corresponding    byte-range-spec appeared in the received Range header field,      excluding those ranges that were deemed unsatisfiable or that were    coalesced into other ranges.  A client that receives a multipart    response MUST inspect the Content-Range header field present in each    body part in order to determine which range is contained in that body    part; a client cannot rely on receiving the same ranges that it    requested, nor the same order that it requested.     When a 206 response is generated, the server MUST generate the    following header fields, in addition to those required above, if the    field would have been sent in a 200 (OK) response to the same    request: Date, Cache-Control, ETag, Expires, Content-Location, and    Vary.     If a 206 is generated in response to a request with an If-Range    header field, the sender SHOULD NOT generate other representation    header fields beyond those required above, because the client is    understood to already have a prior response containing those header    fields.  Otherwise, the sender MUST generate all of the    representation header fields that would have been sent in a 200 (OK)    response to the same request.     A 206 response is cacheable by default; i.e., unless otherwise    indicated by explicit cache controls (see [Section 4.2.2 of    [RFC7234]](https://tools.ietf.org/html/rfc7234#section-4.2.2)).  

The "Content-Range" header field is sent in a single part 206    (Partial Content) response to indicate the partial range of the    selected representation enclosed as the message payload, sent in each    part of a multipart 206 response to indicate the range enclosed    within each body part, and sent in 416 (Range Not Satisfiable)    responses to provide information about the selected representation.       Content-Range       = byte-content-range                          / other-content-range       byte-content-range  = bytes-unit SP                            ( byte-range-resp / unsatisfied-range )       byte-range-resp     = byte-range "/" ( complete-length / "\*" )      byte-range          = first-byte-pos "-" last-byte-pos      unsatisfied-range   = "\*/" complete-length       complete-length     = 1\*DIGIT       other-content-range = other-range-unit SP other-range-resp      other-range-resp    = \*CHAR      If a 206 (Partial Content) response contains a Content-Range header    field with a range unit ([Section 2](about:blank#section-2)) that the recipient does not    understand, the recipient MUST NOT attempt to recombine it with a    stored representation.  A proxy that receives such a message SHOULD    forward it downstream.     For byte ranges, a sender SHOULD indicate the complete length of the    representation from which the range has been extracted, unless the    complete length is unknown or difficult to determine.  An asterisk    character ("\*") in place of the complete-length indicates that the    representation length was unknown when the header field was    generated.     The following example illustrates when the complete length of the    selected representation is known by the sender to be 1234 bytes:       Content-Range: bytes 42-1233/1234     and this second example illustrates when the complete length is    unknown:       Content-Range: bytes 42-1233/\*     A Content-Range field value is invalid if it contains a    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 recipient of an invalid    Content-Range MUST NOT attempt to recombine the received content with    a stored representation.     A server generating a 416 (Range Not Satisfiable) response to a    byte-range request SHOULD send a Content-Range header field with an    unsatisfied-range value, as in the following example:       Content-Range: bytes \*/1234     The complete-length in a 416 response indicates the current length of    the 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 206 (Partial Content) and 416 (Range Not Satisfiable) status    codes describe a meaning for Content-Range.      The following are examples of Content-Range values in which the    selected representation contains a total of 1234 bytes:     o  The 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 500 bytes:          Content-Range: bytes 500-1233/1234     o  The last 500 bytes:          Content-Range: bytes 734-1233/1234  

A response might transfer only a subrange of a representation if the    connection closed prematurely or if the request used one or more    Range specifications.  After several such transfers, a client might    have received several ranges of the same representation.  These    ranges can only be safely combined if they all have in common the    same strong validator ([Section 2.1 of [RFC7232]](https://tools.ietf.org/html/rfc7232#section-2.1)).     A client that has received multiple partial responses to GET requests    on a target resource MAY combine those responses into a larger    continuous range if they share the same strong validator.     If the most recent response is an incomplete 200 (OK) response, then    the header fields of that response are used for any combined response    and replace those of the matching stored responses.     If the most recent response is a 206 (Partial Content) response and    at least one of the matching stored responses is a 200 (OK), then the    combined response header fields consist of the most recent 200    response's header fields.  If all of the matching stored responses    are 206 responses, then the stored response with the most recent    header fields is used as the source of header fields for the combined    response, except that the client MUST use other header fields    provided in the new response, aside from Content-Range, to replace    all instances of the corresponding header fields in the stored    response.      The combined response message body consists of the union of partial    content ranges in the new response and each of the selected    responses.  If the union consists of the entire range of the    representation, then the client MUST process the combined response as    if it were a complete 200 (OK) response, including a Content-Length    header field that reflects the complete length.  Otherwise, the    client MUST process the set of continuous ranges as one of the    following: an incomplete 200 (OK) response if the combined response    is a prefix of the 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.  

The 416 (Range Not Satisfiable) status code indicates that none of    the ranges in the request's Range header field ([Section 3.1](about:blank#section-3.1)) overlap    the current extent of the selected resource or that the set of ranges    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 current length of the selected representation.  When this status    code is generated in response to a byte-range request, the sender    SHOULD generate a Content-Range header field specifying the current    length of the selected representation ([Section 4.2](about:blank#section-4.2)).     For example:       HTTP/1.1 416 Range Not Satisfiable      Date: Fri, 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 the entire selected       representation in a 200 (OK) response.  That is partly because       most clients are prepared to receive a 200 (OK) to complete the       task (albeit less efficiently) and partly because clients might       not stop making an invalid partial request until they have       received a complete representation.  Thus, clients cannot depend       on receiving a 416 (Range Not Satisfiable) response even when it       is most appropriate.   

The "HTTP Range Unit Registry" defines the namespace for the range    unit names and refers to their corresponding specifications.  The    registry has been created and is now maintained at    <[http://www.iana.org/assignments/http-parameters](http://www.iana.org/assignments/http-parameters)>.  

Registration of an HTTP Range Unit MUST include the following fields:     o  Name     o  Description     o  Pointer to specification text     Values to be added to this namespace require IETF Review (see    [[RFC5226], Section 4.1](https://tools.ietf.org/html/rfc5226#section-4.1)).  

The initial range unit registry contains the registrations below:     +-------------+---------------------------------------+-------------+    | Range Unit  | Description                           | Reference   |    | Name        |                                       |             |    +-------------+---------------------------------------+-------------+    | bytes       | a range of octets                     | [Section 2.1](about:blank#section-2.1) |    | none        | reserved as keyword, indicating no    | [Section 2.3](about:blank#section-2.3) |    |             | ranges are supported                  |             |    +-------------+---------------------------------------+-------------+     The change controller is: "IETF (iesg@ietf.org) - Internet    Engineering Task Force".   

The "Hypertext Transfer Protocol (HTTP) Status Code Registry" located    at <[http://www.iana.org/assignments/http-status-codes](http://www.iana.org/assignments/http-status-codes)> has been    updated to include the registrations below:     +-------+-----------------------+-------------+    | Value | Description           | Reference   |    +-------+-----------------------+-------------+    | 206   | Partial Content       | [Section 4.1](about:blank#section-4.1) |    | 416   | Range Not Satisfiable | [Section 4.4](about:blank#section-4.4) |    +-------+-----------------------+-------------+  

HTTP header fields are registered within the "Message Headers"    registry maintained at    <[http://www.iana.org/assignments/message-headers/](http://www.iana.org/assignments/message-headers/)>.     This document defines the following HTTP header fields, so their    associated registry entries have been updated according to the    permanent registrations below (see [[BCP90](about:blank#ref-BCP90)]):     +-------------------+----------+----------+-------------+    | Header Field Name | Protocol | Status   | Reference   |    +-------------------+----------+----------+-------------+    | Accept-Ranges     | http     | standard | [Section 2.3](about:blank#section-2.3) |    | Content-Range     | http     | standard | [Section 4.2](about:blank#section-4.2) |    | If-Range          | http     | standard | [Section 3.2](about:blank#section-3.2) |    | Range             | http     | standard | [Section 3.1](about:blank#section-3.1) |    +-------------------+----------+----------+-------------+     The change controller is: "IETF (iesg@ietf.org) - Internet    Engineering Task Force".  

IANA maintains the registry of Internet media types [[BCP13](about:blank#ref-BCP13)] at    <[http://www.iana.org/assignments/media-types](http://www.iana.org/assignments/media-types)>.     This document serves as the specification for the Internet media type    "multipart/byteranges".  The following has been registered with IANA.   

Type name:  multipart     Subtype name:  byteranges     Required parameters:  boundary     Optional parameters:  N/A     Encoding considerations:  only "7bit", "8bit", or "binary" are       permitted     Security considerations:  see [Section 6](about:blank#section-6)     Interoperability considerations:  N/A     Published specification:  This specification (see [Appendix A](about:blank#appendix-A)).     Applications that use this media type:  HTTP components supporting       multiple ranges in a single request.     Fragment identifier considerations:  N/A     Additional information:        Deprecated alias names for this type:  N/A        Magic number(s):  N/A        File extension(s):  N/A        Macintosh file type code(s):  N/A     Person and email address to contact for further information:  See       Authors' Addresses section.     Intended usage:  COMMON     Restrictions on usage:  N/A     Author:  See Authors' Addresses section.     Change controller:  IESG   

This section is meant to inform developers, information providers,    and users of known security concerns specific to the HTTP range    request mechanisms.  More general security considerations are    addressed in HTTP messaging [[RFC7230](https://tools.ietf.org/html/rfc7230)] and semantics [[RFC7231](https://tools.ietf.org/html/rfc7231)].  

Unconstrained multiple range requests are susceptible to denial-of-    service attacks because the effort required to request many    overlapping ranges of the same data is 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 ranges are requested out of order for no    apparent reason.  Multipart range requests are not designed to    support random access.  

[[RFC2046]()]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail               Extensions (MIME) Part Two: Media Types", [RFC 2046](https://tools.ietf.org/html/rfc2046),               November 1996.     [[RFC2119]()]  Bradner, S., "Key words for use in RFCs to Indicate               Requirement Levels", [BCP 14](https://tools.ietf.org/html/bcp14), [RFC 2119](https://tools.ietf.org/html/rfc2119), March 1997.     [[RFC5234]()]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax               Specifications: ABNF", STD 68, [RFC 5234](https://tools.ietf.org/html/rfc5234), January 2008.     [[RFC7230]()]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer               Protocol (HTTP/1.1): Message Syntax and Routing",               [RFC 7230](https://tools.ietf.org/html/rfc7230), June 2014.     [[RFC7231]()]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer               Protocol (HTTP/1.1): Semantics and Content", [RFC 7231](https://tools.ietf.org/html/rfc7231),               June 2014.     [[RFC7232]()]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer               Protocol (HTTP/1.1): Conditional Requests", [RFC 7232](https://tools.ietf.org/html/rfc7232),               June 2014.     [[RFC7234]()]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,               Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",               [RFC 7234](https://tools.ietf.org/html/rfc7234), June 2014.  

[[BCP13]()]    Freed, N., Klensin, J., and T. Hansen, "Media Type               Specifications and Registration Procedures", [BCP 13](https://tools.ietf.org/html/bcp13),               [RFC 6838](https://tools.ietf.org/html/rfc6838), January 2013.     [[BCP90]()]    Klyne, G., Nottingham, M., and J. Mogul, "Registration               Procedures for Message Header Fields", [BCP 90](https://tools.ietf.org/html/bcp90), [RFC 3864](https://tools.ietf.org/html/rfc3864),               September 2004.     [[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](https://tools.ietf.org/html/rfc2616), June 1999.     [[RFC5226]()]  Narten, T. and H. Alvestrand, "Guidelines for Writing an               IANA Considerations Section in RFCs", [BCP 26](https://tools.ietf.org/html/bcp26), [RFC 5226](https://tools.ietf.org/html/rfc5226),               May 2008.   

When a 206 (Partial Content) response message includes the content of    multiple ranges, they are transmitted as body parts in a multipart    message body ([[RFC2046], Section 5.1](https://tools.ietf.org/html/rfc2046#section-5.1)) with the media type of    "multipart/byteranges".     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.     Implementation Notes:     1.  Additional CRLFs might precede the first boundary string in the        body.     2.  Although [[RFC2046](https://tools.ietf.org/html/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 that used a media type of multipart/        x-byteranges, which is almost (but not quite) compatible with        this type.     Despite the 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--   

Servers are given more leeway in how they respond to a range request,    in order to mitigate abuse by malicious (or just greedy) clients.    ([Section 3.1](about:blank#section-3.1))     A weak validator cannot be used in a 206 response.  ([Section 4.1](about:blank#section-4.1))     The Content-Range header field only has meaning when the status code    explicitly defines its use.  ([Section 4.2](about:blank#section-4.2))     This specification introduces a Range Unit Registry.  ([Section 5.1](about:blank#section-5.1))     multipart/byteranges can consist of a single part.  (Appendix A)  

The following core rules are included by reference, as defined in    [Appendix B.1 of [RFC5234]](https://tools.ietf.org/html/rfc5234#appendix-B.1): 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 [[RFC7230](https://tools.ietf.org/html/rfc7230)]:       OWS        = <OWS, see [[RFC7230], Section 3.2.3](https://tools.ietf.org/html/rfc7230#section-3.2.3)>      token      = <token, see [[RFC7230], Section 3.2.6](https://tools.ietf.org/html/rfc7230#section-3.2.6)>     The rules below are defined in other parts:       HTTP-date  = <HTTP-date, see [[RFC7231], Section 7.1.1.1](https://tools.ietf.org/html/rfc7231#section-7.1.1.1)>      entity-tag = <entity-tag, see [[RFC7232], Section 2.3](https://tools.ietf.org/html/rfc7232#section-2.3)>   

In the collected ABNF below, list rules are expanded as per [Section](https://tools.ietf.org/html/rfc7230#section-1.2) [1.2 of [RFC7230]](https://tools.ietf.org/html/rfc7230#section-1.2).     Accept-Ranges = acceptable-ranges     Content-Range = byte-content-range / other-content-range     HTTP-date = <HTTP-date, see [[RFC7231], Section 7.1.1.1](https://tools.ietf.org/html/rfc7231#section-7.1.1.1)>     If-Range = entity-tag / HTTP-date     OWS = <OWS, see [[RFC7230], Section 3.2.3](https://tools.ietf.org/html/rfc7230#section-3.2.3)>     Range = byte-ranges-specifier / other-ranges-specifier     acceptable-ranges = ( \*( "," OWS ) range-unit \*( OWS "," [ OWS     range-unit ] ) ) / "none"     byte-content-range = bytes-unit SP ( byte-range-resp /     unsatisfied-range )    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, see [[RFC7232], Section 2.3](https://tools.ietf.org/html/rfc7232#section-2.3)>     first-byte-pos = 1\*DIGIT     last-byte-pos = 1\*DIGIT     other-content-range = other-range-unit SP other-range-resp    other-range-resp = \*CHAR    other-range-set = 1\*VCHAR    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, see [[RFC7230], Section 3.2.6](https://tools.ietf.org/html/rfc7230#section-3.2.6)>     unsatisfied-range = "\*/" complete-length  Index     2       206 Partial Content (status code)  10     4       416 Range Not Satisfiable (status code)  15     A       Accept-Ranges header field  7     C       Content-Range header field  12     G       Grammar          Accept-Ranges  7          acceptable-ranges  7          byte-content-range  12          byte-range  12          byte-range-resp  12          byte-range-set  5          byte-range-spec  5          byte-ranges-specifier  5          bytes-unit  5          complete-length  12          Content-Range  12          first-byte-pos  5          If-Range  9          last-byte-pos  5          other-content-range  12          other-range-resp  12          other-range-unit  5, 7          Range  8          range-unit  5          ranges-specifier  5          suffix-byte-range-spec  6          suffix-length  6          unsatisfied-range  12      I       If-Range header field  9     M       Media Type          multipart/byteranges  18, 21          multipart/x-byteranges  19       multipart/byteranges Media Type  18, 21       multipart/x-byteranges Media Type  21     R       Range header field  8  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/](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/](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/](http://greenbytes.de/tech/webdav/)   Fielding, et al.             Standards Track                   [Page 25]