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

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this user agent behavior in mind.Requirements for the behavior of caches with respect to Warnings arestated in section 13.1.2.This is a list of the currently-defined warn-codes, each with arecommended warn-text in English, and a description of its meaning.110 Response is staleMUST be included whenever the returned response is stale.111 Revalidation failedMUST be included if a cache returns a stale response because anattempt to revalidate the response failed, due to an inability toreach the server.112 Disconnected operationSHOULD be included if the cache is intentionally disconnected fromthe rest of the network for a period of time.113 Heuristic expirationMUST be included if the cache heuristically chose a freshnesslifetime greater than 24 hours and the response's age is greaterthan 24 hours.199 Miscellaneous warningThe warning text MAY include arbitrary information to be presentedto a human user, or logged. A system receiving this warning MUSTNOT take any automated action, besides presenting the warning tothe user.Fielding, et al. Standards Track [Page 149]RFC 2616 HTTP/1.1 June 1999214 Transformation appliedMUST be added by an intermediate cache or proxy if it applies anytransformation changing the content-coding (as specified in theContent-Encoding header) or media-type (as specified in theContent-Type header) of the response, or the entity-body of theresponse, unless this Warning code already appears in the response.299 Miscellaneous persistent warningThe warning text MAY include arbitrary information to be presentedto a human user, or logged. A system receiving this warning MUSTNOT take any automated action.If an implementation sends a message with one or more Warning headers
whose version is HTTP/1.0 or lower, then the sender MUST include ineach warning-value a warn-date that matches the date in the response.If an implementation receives a message with a warning-value thatincludes a warn-date, and that warn-date is different from the Datevalue in the response, then that warning-value MUST be deleted fromthe message before storing, forwarding, or using it. (This preventsbad consequences of naive caching of Warning header fields.) If allof the warning-values are deleted for this reason, the Warning headerMUST be deleted as well.14.47 WWW-AuthenticateThe WWW-Authenticate response-header field MUST be included in 401(Unauthorized) response messages. The field value consists of atleast one challenge that indicates the authentication scheme(s) andparameters applicable to the Request-URI.WWW-Authenticate = "WWW-Authenticate" ":" 1#challengeThe HTTP access authentication process is described in "HTTPAuthentication: Basic and Digest Access Authentication" [43]. Useragents are advised to take special care in parsing the WWW-Authenticate field value as it might contain more than one challenge,or if more than one WWW-Authenticate header field is provided, thecontents of a challenge itself can contain a comma-separated list ofauthentication parameters.15 Security ConsiderationsThis section is meant to inform application developers, informationproviders, and users of the security limitations in HTTP/1.1 asdescribed by this document. The discussion does not includedefinitive solutions to the problems revealed, though it does makesome suggestions for reducing security risks.Fielding, et al. Standards Track [Page 150]RFC 2616 HTTP/1.1 June 199915.1 Personal InformationHTTP clients are often privy to large amounts of personal information(e.g. the user's name, location, mail address, passwords, encryptionkeys, etc.), and SHOULD be very careful to prevent unintentionalleakage of this information via the HTTP protocol to other sources.We very strongly recommend that a convenient interface be providedfor the user to control dissemination of such information, and that
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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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Page 122 and 123: improve privacy in some cases, we c
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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 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 178 and 179: University of California, IrvineIrv
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,
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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