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

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full compliance with the MIME protocol (as defined in RFC 2045[7]).Proxies/gateways are responsible for ensuring full compliance (wherepossible) when exporting HTTP messages to strict MIME environments.MIME-Version = "MIME-Version" ":" 1*DIGIT "." 1*DIGITMIME version "1.0" is the default for use in HTTP/1.1. However,HTTP/1.1 message parsing and semantics are defined by this documentand not the MIME specification.19.4.2 Conversion to Canonical FormRFC 2045 [7] requires that an Internet mail entity be converted tocanonical form prior to being transferred, as described in section 4of RFC 2049 [48]. Section 3.7.1 of this document describes the formsallowed for subtypes of the "text" media type when transmitted overHTTP. RFC 2046 requires that content with a type of "text" representline breaks as CRLF and forbids the use of CR or LF outside of lineFielding, et al. Standards Track [Page 167]RFC 2616 HTTP/1.1 June 1999break sequences. HTTP allows CRLF, bare CR, and bare LF to indicate aline break within text content when a message is transmitted overHTTP.Where it is possible, a proxy or gateway from HTTP to a strict MIMEenvironment SHOULD translate all line breaks within the text mediatypes described in section 3.7.1 of this document to the RFC 2049canonical form of CRLF. Note, however, that this might be complicatedby the presence of a Content-Encoding and by the fact that HTTPallows the use of some character sets which do not use octets 13 and10 to represent CR and LF, as is the case for some multi-bytecharacter sets.Implementors should note that conversion will break any cryptographicchecksums applied to the original content unless the original contentis already in canonical form. Therefore, the canonical form isrecommended for any content that uses such checksums in HTTP.19.4.3 Conversion of Date FormatsHTTP/1.1 uses a restricted set of date formats (section 3.3.1) tosimplify the process of date comparison. Proxies and gateways fromother protocols SHOULD ensure that any Date header field present in amessage conforms to one of the HTTP/1.1 formats and rewrite the dateif necessary.
19.4.4 Introduction of Content-EncodingRFC 2045 does not include any concept equivalent to HTTP/1.1'sContent-Encoding header field. Since this acts as a modifier on themedia type, proxies and gateways from HTTP to MIME-compliantprotocols MUST either change the value of the Content-Type headerfield or decode the entity-body before forwarding the message. (Someexperimental applications of Content-Type for Internet mail have useda media-type parameter of ";conversions=" to performa function equivalent to Content-Encoding. However, this parameter isnot part of RFC 2045.)19.4.5 No Content-Transfer-EncodingHTTP does not use the Content-Transfer-Encoding (CTE) field of RFC2045. Proxies and gateways from MIME-compliant protocols to HTTP MUSTremove any non-identity CTE ("quoted-printable" or "base64") encodingprior to delivering the response message to an HTTP client.Proxies and gateways from HTTP to MIME-compliant protocols areresponsible for ensuring that the message is in the correct formatand encoding for safe transport on that protocol, where "safeFielding, et al. Standards Track [Page 168]RFC 2616 HTTP/1.1 June 1999transport" is defined by the limitations of the protocol being used.Such a proxy or gateway SHOULD label the data with an appropriateContent-Transfer-Encoding if doing so will improve the likelihood ofsafe transport over the destination protocol.19.4.6 Introduction of Transfer-EncodingHTTP/1.1 introduces the Transfer-Encoding header field (section14.41). Proxies/gateways MUST remove any transfer-coding prior toforwarding a message via a MIME-compliant protocol.A process for decoding the "chunked" transfer-coding (section 3.6)can be represented in pseudo-code as:length := 0read chunk-size, chunk-extension (if any) and CRLFwhile (chunk-size > 0) {read chunk-data and CRLFappend chunk-data to entity-bodylength := length + chunk-size
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eferred to as "HTTP/1.1", and is an
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12.1 Server-driven Negotiation ....
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14.40 Trailer .....................
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1.2 RequirementsThe key words "MUST
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Fielding, et al. Standards Track [P
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equest chain ----------------------
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Elements separated by a bar ("|") a
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HTTP/1.1 header field values can be
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An application that sends a request
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3.2.3 URI ComparisonWhen comparing
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is not desirable and is discouraged
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CRLFchunk = chunk-size [ chunk-exte
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When in canonical form, media subty
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3.9 Quality ValuesHTTP content nego
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RFC 2616 HTTP/1.1 June 1999HTTP/1.1
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message-body = entity-body| Transfe
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in advance.Messages MUST NOT includ
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equested resource, and 501 (Not Imp
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names) MUST use the following rules
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values for the first digit:- 1xx: I
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how the transfer-length of a messag
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connection-token close.If either th
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idempotent (see section 9.1.2). Non
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compatibility with RFC 2068, a serv
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If at any point an error status is
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optional features implemented by th
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- Extending a database through an a
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intervention (or other means) on th
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10.1.2 101 Switching ProtocolsThe s
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esponse MAY include new or updated
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The response MUST include the follo
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If the client is sending data, a se
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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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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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Page 146 and 147: RFC 2616 HTTP/1.1 June 1999If none
Page 148 and 149: 14.29 Last-ModifiedThe Last-Modifie
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Page 172 and 173: The HTTP protocol has evolved consi
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Page 182 and 183: Notes:1) Additional CRLFs may prece
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Page 190 and 191: CREATE had a race that required an
Page 192 and 193: also needed to be a general header,
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