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

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Expires = "Expires" ":" HTTP-dateAn example of its use isExpires: Thu, 01 Dec 1994 16:00:00 GMTNote: if a response includes a Cache-Control field with the maxagedirective (see section 14.9.3), that directive overrides theExpires field.HTTP/1.1 clients and caches MUST treat other invalid date formats,especially including the value "0", as in the past (i.e., "alreadyexpired").To mark a response as "already expired," an origin server sends anExpires date that is equal to the Date header value. (See the rulesfor expiration calculations in section 13.2.4.)Fielding, et al. Standards Track [Page 127]RFC 2616 HTTP/1.1 June 1999To mark a response as "never expires," an origin server sends anExpires date approximately one year from the time the response issent. HTTP/1.1 servers SHOULD NOT send Expires dates more than oneyear in the future.The presence of an Expires header field with a date value of sometime in the future on a response that otherwise would by default benon-cacheable indicates that the response is cacheable, unlessindicated otherwise by a Cache-Control header field (section 14.9).14.22 FromThe From request-header field, if given, SHOULD contain an Internete-mail address for the human user who controls the requesting useragent. The address SHOULD be machine-usable, as defined by "mailbox"in RFC 822 [9] as updated by RFC 1123 [8]:From = "From" ":" mailboxAn example is:
From: webmaster@w3.orgThis header field MAY be used for logging purposes and as a means foridentifying the source of invalid or unwanted requests. It SHOULD NOTbe used as an insecure form of access protection. The interpretationof this field is that the request is being performed on behalf of theperson given, who accepts responsibility for the method performed. Inparticular, robot agents SHOULD include this header so that theperson responsible for running the robot can be contacted if problemsoccur on the receiving end.The Internet e-mail address in this field MAY be separate from theInternet host which issued the request. For example, when a requestis passed through a proxy the original issuer's address SHOULD beused.The client SHOULD NOT send the From header field without the user'sapproval, as it might conflict with the user's privacy interests ortheir site's security policy. It is strongly recommended that theuser be able to disable, enable, and modify the value of this fieldat any time prior to a request.14.23 HostThe Host request-header field specifies the Internet host and portnumber of the resource being requested, as obtained from the originalURI given by the user or referring resource (generally an HTTP URL,Fielding, et al. Standards Track [Page 128]RFC 2616 HTTP/1.1 June 1999as described in section 3.2.2). The Host field value MUST representthe naming authority of the origin server or gateway given by theoriginal URL. This allows the origin server or gateway todifferentiate between internally-ambiguous URLs, such as the root "/"URL of a server for multiple host names on a single IP address.Host = "Host" ":" host [ ":" port ] ; Section 3.2.2A "host" without any trailing port information implies the defaultport for the service requested (e.g., "80" for an HTTP URL). Forexample, a request on the origin server for would properly include:GET /pub/WWW/ HTTP/1.1Host: www.w3.org
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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
Page 90 and 91: RFC 2616 HTTP/1.1 June 1999the time
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Page 94 and 95: match.In HTTP/1.1, a conditional re
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Page 100 and 101: Unless specifically constrained by
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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
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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
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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 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 182 and 183: Notes:1) Additional CRLFs may prece
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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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