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

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MAY require that behavior be consistent with the directives.Pragma = "Pragma" ":" 1#pragma-directivepragma-directive = "no-cache" | extension-pragmaextension-pragma = token [ "=" ( token | quoted-string ) ]When the no-cache directive is present in a request message, anapplication SHOULD forward the request toward the origin server evenif it has a cached copy of what is being requested. This pragmadirective has the same semantics as the no-cache cache-directive (seesection 14.9) and is defined here for backward compatibility withHTTP/1.0. Clients SHOULD include both header fields when a no-cacherequest is sent to a server not known to be HTTP/1.1 compliant.Fielding, et al. Standards Track [Page 136]RFC 2616 HTTP/1.1 June 1999Pragma directives MUST be passed through by a proxy or gatewayapplication, regardless of their significance to that application,since the directives might be applicable to all recipients along therequest/response chain. It is not possible to specify a pragma for aspecific recipient; however, any pragma directive not relevant to arecipient SHOULD be ignored by that recipient.HTTP/1.1 caches SHOULD treat "Pragma: no-cache" as if the client hadsent "Cache-Control: no-cache". No new Pragma directives will bedefined in HTTP.Note: because the meaning of "Pragma: no-cache as a responseheader field is not actually specified, it does not provide areliable replacement for "Cache-Control: no-cache" in a response14.33 Proxy-AuthenticateThe Proxy-Authenticate response-header field MUST be included as partof a 407 (Proxy Authentication Required) response. The field valueconsists of a challenge that indicates the authentication scheme andparameters applicable to the proxy for this Request-URI.Proxy-Authenticate = "Proxy-Authenticate" ":" 1#challengeThe HTTP access authentication process is described in "HTTPAuthentication: Basic and Digest Access Authentication" [43]. UnlikeWWW-Authenticate, the Proxy-Authenticate header field applies only to
the current connection and SHOULD NOT be passed on to downstreamclients. However, an intermediate proxy might need to obtain its owncredentials by requesting them from the downstream client, which insome circumstances will appear as if the proxy is forwarding theProxy-Authenticate header field.14.34 Proxy-AuthorizationThe Proxy-Authorization request-header field allows the client toidentify itself (or its user) to a proxy which requiresauthentication. The Proxy-Authorization field value consists ofcredentials containing the authentication information of the useragent for the proxy and/or realm of the resource being requested.Proxy-Authorization= "Proxy-Authorization" ":" credentialsThe HTTP access authentication process is described in "HTTPAuthentication: Basic and Digest Access Authentication" [43] . UnlikeAuthorization, the Proxy-Authorization header field applies only tothe next outbound proxy that demanded authentication using the Proxy-Authenticate field. When multiple proxies are used in a chain, theFielding, et al. Standards Track [Page 137]RFC 2616 HTTP/1.1 June 1999Proxy-Authorization header field is consumed by the first outboundproxy that was expecting to receive credentials. A proxy MAY relaythe credentials from the client request to the next proxy if that isthe mechanism by which the proxies cooperatively authenticate a givenrequest.14.35 Range14.35.1 Byte RangesSince all HTTP entities are represented in HTTP messages as sequencesof bytes, the concept of a byte range is meaningful for any HTTPentity. (However, not all clients and servers need to support byterangeoperations.)Byte range specifications in HTTP apply to the sequence of bytes inthe entity-body (not necessarily the same as the message-body).A byte range operation MAY specify a single range of bytes, or a setof ranges within a single entity.ranges-specifier = byte-ranges-specifier
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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
Page 100 and 101: Unless specifically constrained by
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Page 104 and 105: warn-code 1xx, which are deleted ev
Page 106 and 107: for the associated entity, its enti
Page 108 and 109: - DELETE- POSTIn order to prevent d
Page 110 and 111: The Accept request-header field can
Page 112 and 113: image/jpeg = 0.5text/html;level=2 =
Page 114 and 115: Note: If the request does not inclu
Page 116 and 117: Accept-Ranges: bytesbut are not req
Page 118 and 119: containing an Authorization field,
Page 120 and 121: - Restrictions on what may be store
Page 122 and 123: improve privacy in some cases, we c
Page 126 and 127: must-revalidateBecause a cache MAY
Page 128 and 129: understand.For example, consider a
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Page 132 and 133: 14.14 Content-LocationThe Content-L
Page 134 and 135: Note: while the definition of Conte
Page 136 and 137: server SHOULD return them in the or
Page 138 and 139: Some origin server implementations
Page 140 and 141: Expires = "Expires" ":" HTTP-dateAn
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
Page 152 and 153: yte-ranges-specifier = bytes-unit "
Page 154 and 155: Content) instead of 200 (OK).- The
Page 156 and 157: The TE request-header field indicat
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Page 162 and 163: SHOULD NOT, by default, forward the
Page 164 and 165: this user agent behavior in mind.Re
Page 166 and 167: designers and implementors be parti
Page 168 and 169: strongly correlated to the membersh
Page 170 and 171: serious security considerations. Co
Page 172 and 173: The HTTP protocol has evolved consi
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Page 176 and 177: Implementation and Analysis", RFC 1
Page 178 and 179: University of California, IrvineIrv
Page 182 and 183: Notes:1) Additional CRLFs may prece
Page 184 and 185: full compliance with the MIME proto
Page 186 and 187: ead chunk-size and CRLF}read entity
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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