Network Working Group R. Fielding Request for Comments: 2616 ...

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is not desirable and is discouraged for future encodings. Theiruse here is representative of historical practice, not gooddesign. For compatibility with previous implementations of HTTP,applications SHOULD consider "x-gzip" and "x-compress" to beequivalent to "gzip" and "compress" respectively.deflateThe "zlib" format defined in RFC 1950 [31] in combination withthe "deflate" compression mechanism described in RFC 1951 [29].Fielding, et al. Standards Track [Page 23]RFC 2616 HTTP/1.1 June 1999identityThe default (identity) encoding; the use of no transformationwhatsoever. This content-coding is used only in the Accept-Encoding header, and SHOULD NOT be used in the Content-Encodingheader.New content-coding value tokens SHOULD be registered; to allowinteroperability between clients and servers, specifications of thecontent coding algorithms needed to implement a new value SHOULD bepublicly available and adequate for independent implementation, andconform to the purpose of content coding defined in this section.3.6 Transfer CodingsTransfer-coding values are used to indicate an encodingtransformation that has been, can be, or may need to be applied to anentity-body in order to ensure "safe transport" through the network.This differs from a content coding in that the transfer-coding is aproperty of the message, not of the original entity.transfer-coding= "chunked" | transfer-extensiontransfer-extension = token *( ";" parameter )Parameters are in the form of attribute/value pairs.parameterattributevalue= attribute "=" value= token= token | quoted-stringAll transfer-coding values are case-insensitive. HTTP/1.1 usestransfer-coding values in the TE header field (section 14.39) and in
the Transfer-Encoding header field (section 14.41).Whenever a transfer-coding is applied to a message-body, the set oftransfer-codings MUST include "chunked", unless the message isterminated by closing the connection. When the "chunked" transfercodingis used, it MUST be the last transfer-coding applied to themessage-body. The "chunked" transfer-coding MUST NOT be applied morethan once to a message-body. These rules allow the recipient todetermine the transfer-length of the message (section 4.4).Transfer-codings are analogous to the Content-Transfer-Encodingvalues of MIME [7], which were designed to enable safe transport ofbinary data over a 7-bit transport service. However, safe transporthas a different focus for an 8bit-clean transfer protocol. In HTTP,the only unsafe characteristic of message-bodies is the difficulty indetermining the exact body length (section 7.2.2), or the desire toencrypt data over a shared transport.Fielding, et al. Standards Track [Page 24]RFC 2616 HTTP/1.1 June 1999The Internet Assigned Numbers Authority (IANA) acts as a registry fortransfer-coding value tokens. Initially, the registry contains thefollowing tokens: "chunked" (section 3.6.1), "identity" (section3.6.2), "gzip" (section 3.5), "compress" (section 3.5), and "deflate"(section 3.5).New transfer-coding value tokens SHOULD be registered in the same wayas new content-coding value tokens (section 3.5).A server which receives an entity-body with a transfer-coding it doesnot understand SHOULD return 501 (Unimplemented), and close theconnection. A server MUST NOT send transfer-codings to an HTTP/1.0client.3.6.1 Chunked Transfer CodingThe chunked encoding modifies the body of a message in order totransfer it as a series of chunks, each with its own size indicator,followed by an OPTIONAL trailer containing entity-header fields. Thisallows dynamically produced content to be transferred along with theinformation necessary for the recipient to verify that it hasreceived the full message.Chunked-Body = *chunklast-chunktrailer
Page 2: eferred to as "HTTP/1.1", and is an
Page 5 and 6: 12.1 Server-driven Negotiation ....
Page 7 and 8: 14.40 Trailer .....................
Page 9 and 10: 1.2 RequirementsThe key words "MUST
Page 12 and 13: Fielding, et al. Standards Track [P
Page 14 and 15: equest chain ----------------------
Page 16 and 17: Elements separated by a bar ("|") a
Page 18 and 19: HTTP/1.1 header field values can be
Page 20 and 21: An application that sends a request
Page 22 and 23: 3.2.3 URI ComparisonWhen comparing
Page 28 and 29: CRLFchunk = chunk-size [ chunk-exte
Page 30 and 31: When in canonical form, media subty
Page 32 and 33: 3.9 Quality ValuesHTTP content nego
Page 34 and 35: RFC 2616 HTTP/1.1 June 1999HTTP/1.1
Page 36 and 37: message-body = entity-body| Transfe
Page 38 and 39: in advance.Messages MUST NOT includ
Page 40 and 41: equested resource, and 501 (Not Imp
Page 42 and 43: names) MUST use the following rules
Page 44 and 45: values for the first digit:- 1xx: I
Page 48 and 49: how the transfer-length of a messag
Page 50 and 51: connection-token close.If either th
Page 52 and 53: idempotent (see section 9.1.2). Non
Page 54 and 55: compatibility with RFC 2068, a serv
Page 56 and 57: If at any point an error status is
Page 58 and 59: optional features implemented by th
Page 60 and 61: - Extending a database through an a
Page 62 and 63: intervention (or other means) on th
Page 64 and 65: 10.1.2 101 Switching ProtocolsThe s
Page 66 and 67: esponse MAY include new or updated
Page 70 and 71: The response MUST include the follo
Page 72 and 73: If the client is sending data, a se
Page 74 and 75: If the response could be unacceptab
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10.4.15 414 Request-URI Too LongThe
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10.5.5 504 Gateway TimeoutThe serve
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Fielding, et al. Standards Track [P
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Caching would be useless if it did
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Warning (but without removing any e
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If the user has overridden the basi
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in the past. This means that the re
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RFC 2616 HTTP/1.1 June 1999the time
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simple:response_is_fresh = (freshne
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match.In HTTP/1.1, a conditional re
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validators or strong validators. Cl
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- MAY send a weak entity tag instea
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Unless specifically constrained by
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warn-code 1xx, which are deleted ev
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for the associated entity, its enti
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- DELETE- POSTIn order to prevent d
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The Accept request-header field can
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image/jpeg = 0.5text/html;level=2 =
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Note: If the request does not inclu
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Accept-Ranges: bytesbut are not req
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containing an Authorization field,
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- Restrictions on what may be store
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improve privacy in some cases, we c
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must-revalidateBecause a cache MAY
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understand.For example, consider a
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new coding is known to be acceptabl
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14.14 Content-LocationThe Content-L
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Note: while the definition of Conte
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server SHOULD return them in the or
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Some origin server implementations
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Expires = "Expires" ":" HTTP-dateAn
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A client MUST include a Host header
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een modified since the date given b
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RFC 2616 HTTP/1.1 June 1999If none
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14.29 Last-ModifiedThe Last-Modifie
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MAY require that behavior be consis
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yte-ranges-specifier = bytes-unit "
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Content) instead of 200 (OK).- The
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The TE request-header field indicat
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a cache cannot determine from the r
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SHOULD NOT, by default, forward the
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this user agent behavior in mind.Re
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designers and implementors be parti
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strongly correlated to the membersh
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serious security considerations. Co
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The HTTP protocol has evolved consi
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Protocol -- HTTP/1.0", RFC 1945, Ma
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Implementation and Analysis", RFC 1
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University of California, IrvineIrv
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Notes:1) Additional CRLFs may prece
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full compliance with the MIME proto
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ead chunk-size and CRLF}read entity
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- understand any valid response in
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CREATE had a race that required an
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also needed to be a general header,
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