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

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SHOULD NOT, by default, forward the names and ports of hosts withinthe firewall region. This information SHOULD only be propagated ifexplicitly enabled. If not enabled, the received-by host of any hostbehind the firewall SHOULD be replaced by an appropriate pseudonymfor that host.For organizations that have strong privacy requirements for hidinginternal structures, a proxy MAY combine an ordered subsequence ofVia header field entries with identical received-protocol values intoa single such entry. For example,Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucycould be collapsed toVia: 1.0 ricky, 1.1 mertz, 1.0 lucyFielding, et al. Standards Track [Page 147]RFC 2616 HTTP/1.1 June 1999Applications SHOULD NOT combine multiple entries unless they are allunder the same organizational control and the hosts have already beenreplaced by pseudonyms. Applications MUST NOT combine entries whichhave different received-protocol values.14.46 WarningThe Warning general-header field is used to carry additionalinformation about the status or transformation of a message whichmight not be reflected in the message. This information is typicallyused to warn about a possible lack of semantic transparency fromcaching operations or transformations applied to the entity body ofthe message.Warning headers are sent with responses using:Warning= "Warning" ":" 1#warning-valuewarning-value = warn-code SP warn-agent SP warn-text[SP warn-date]warn-code = 3DIGITwarn-agent = ( host [ ":" port ] ) | pseudonym
; the name or pseudonym of the server adding; the Warning header, for use in debuggingwarn-text = quoted-stringwarn-date = A response MAY carry more than one Warning header.The warn-text SHOULD be in a natural language and character set thatis most likely to be intelligible to the human user receiving theresponse. This decision MAY be based on any available knowledge, suchas the location of the cache or user, the Accept-Language field in arequest, the Content-Language field in a response, etc. The defaultlanguage is English and the default character set is ISO-8859-1.If a character set other than ISO-8859-1 is used, it MUST be encodedin the warn-text using the method described in RFC 2047 [14].Warning headers can in general be applied to any message, howeversome specific warn-codes are specific to caches and can only beapplied to response messages. New Warning headers SHOULD be addedafter any existing Warning headers. A cache MUST NOT delete anyWarning header that it received with a message. However, if a cachesuccessfully validates a cache entry, it SHOULD remove any Warningheaders previously attached to that entry except as specified forFielding, et al. Standards Track [Page 148]RFC 2616 HTTP/1.1 June 1999specific Warning codes. It MUST then add any Warning headers receivedin the validating response. In other words, Warning headers are thosethat would be attached to the most recent relevant response.When multiple Warning headers are attached to a response, the useragent ought to inform the user of as many of them as possible, in theorder that they appear in the response. If it is not possible toinform the user of all of the warnings, the user agent SHOULD followthese heuristics:- Warnings that appear early in the response take priority overthose appearing later in the response.- Warnings in the user's preferred character set take priorityover warnings in other character sets but with identical warncodesand warn-agents.Systems that generate multiple Warning headers SHOULD order them with
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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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Page 114 and 115: Note: If the request does not inclu
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Page 120 and 121: - Restrictions on what may be store
Page 122 and 123: improve privacy in some cases, we c
Page 124 and 125: Fielding, et al. Standards Track [P
Page 126 and 127: must-revalidateBecause a cache MAY
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Page 132 and 133: 14.14 Content-LocationThe Content-L
Page 134 and 135: Note: while the definition of Conte
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Page 138 and 139: Some origin server implementations
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Page 142 and 143: A client MUST include a Host header
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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 154 and 155: Content) instead of 200 (OK).- The
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Page 172 and 173: The HTTP protocol has evolved consi
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Page 178 and 179: University of California, IrvineIrv
Page 182 and 183: Notes:1) Additional CRLFs may prece
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Page 188 and 189: - understand any valid response in
Page 190 and 191: CREATE had a race that required an
Page 192 and 193: also needed to be a general header,
Page 194: Fielding, et al. Standards Track [P
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Network Working Group R. Fielding Request for Comments: 2616 ...

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