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

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compatibility with RFC 2068, a server MAY send a 100 (Continue)status in response to an HTTP/1.1 PUT or POST request that doesnot include an Expect request-header field with the "100-continue" expectation. This exception, the purpose of which isto minimize any client processing delays associated with anundeclared wait for 100 (Continue) status, applies only toHTTP/1.1 requests, and not to requests with any other HTTPversionvalue.- An origin server MAY omit a 100 (Continue) response if it hasalready received some or all of the request body for thecorresponding request.- An origin server that sends a 100 (Continue) response MUSTultimately send a final status code, once the request body isreceived and processed, unless it terminates the transportconnection prematurely.- If an origin server receives a request that does not include anExpect request-header field with the "100-continue" expectation,the request includes a request body, and the server respondswith a final status code before reading the entire request bodyfrom the transport connection, then the server SHOULD NOT closethe transport connection until it has read the entire request,or until the client closes the connection. Otherwise, the clientmight not reliably receive the response message. However, thisrequirement is not be construed as preventing a server fromdefending itself against denial-of-service attacks, or frombadly broken client implementations.Requirements for HTTP/1.1 proxies:- If a proxy receives a request that includes an Expect requestheaderfield with the "100-continue" expectation, and the proxyeither knows that the next-hop server complies with HTTP/1.1 orhigher, or does not know the HTTP version of the next-hopserver, it MUST forward the request, including the Expect headerfield.Fielding, et al. Standards Track [Page 49]RFC 2616 HTTP/1.1 June 1999- If the proxy knows that the version of the next-hop server isHTTP/1.0 or lower, it MUST NOT forward the request, and it MUSTrespond with a 417 (Expectation Failed) status.
- Proxies SHOULD maintain a cache recording the HTTP versionnumbers received from recently-referenced next-hop servers.- A proxy MUST NOT forward a 100 (Continue) response if therequest message was received from an HTTP/1.0 (or earlier)client and did not include an Expect request-header field withthe "100-continue" expectation. This requirement overrides thegeneral rule for forwarding of 1xx responses (see section 10.1).8.2.4 Client Behavior if Server Prematurely Closes ConnectionIf an HTTP/1.1 client sends a request which includes a request body,but which does not include an Expect request-header field with the"100-continue" expectation, and if the client is not directlyconnected to an HTTP/1.1 origin server, and if the client sees theconnection close before receiving any status from the server, theclient SHOULD retry the request. If the client does retry thisrequest, it MAY use the following "binary exponential backoff"algorithm to be assured of obtaining a reliable response:1. Initiate a new connection to the server2. Transmit the request-headers3. Initialize a variable R to the estimated round-trip time to theserver (e.g., based on the time it took to establish theconnection), or to a constant value of 5 seconds if the roundtriptime is not available.4. Compute T = R * (2**N), where N is the number of previousretries of this request.5. Wait either for an error response from the server, or for Tseconds (whichever comes first)6. If no error response is received, after T seconds transmit thebody of the request.7. If client sees that the connection is closed prematurely,repeat from step 1 until the request is accepted, an errorresponse is received, or the user becomes impatient andterminates the retry process.Fielding, et al. Standards Track [Page 50]RFC 2616 HTTP/1.1 June 1999
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eferred to as "HTTP/1.1", and is an
Page 5 and 6: 12.1 Server-driven Negotiation ....
Page 7 and 8: 14.40 Trailer .....................
Page 9 and 10: 1.2 RequirementsThe key words "MUST
Page 12 and 13: Fielding, et al. Standards Track [P
Page 14 and 15: equest chain ----------------------
Page 16 and 17: Elements separated by a bar ("|") a
Page 18 and 19: HTTP/1.1 header field values can be
Page 20 and 21: An application that sends a request
Page 22 and 23: 3.2.3 URI ComparisonWhen comparing
Page 26 and 27: is not desirable and is discouraged
Page 28 and 29: CRLFchunk = chunk-size [ chunk-exte
Page 30 and 31: When in canonical form, media subty
Page 32 and 33: 3.9 Quality ValuesHTTP content nego
Page 34 and 35: RFC 2616 HTTP/1.1 June 1999HTTP/1.1
Page 36 and 37: message-body = entity-body| Transfe
Page 38 and 39: in advance.Messages MUST NOT includ
Page 40 and 41: equested resource, and 501 (Not Imp
Page 42 and 43: names) MUST use the following rules
Page 44 and 45: values for the first digit:- 1xx: I
Page 48 and 49: how the transfer-length of a messag
Page 50 and 51: connection-token close.If either th
Page 52 and 53: idempotent (see section 9.1.2). Non
Page 56 and 57: If at any point an error status is
Page 58 and 59: optional features implemented by th
Page 60 and 61: - Extending a database through an a
Page 62 and 63: intervention (or other means) on th
Page 64 and 65: 10.1.2 101 Switching ProtocolsThe s
Page 66 and 67: esponse MAY include new or updated
Page 70 and 71: The response MUST include the follo
Page 72 and 73: If the client is sending data, a se
Page 74 and 75: If the response could be unacceptab
Page 76 and 77: 10.4.15 414 Request-URI Too LongThe
Page 78 and 79: 10.5.5 504 Gateway TimeoutThe serve
Page 82 and 83: Caching would be useless if it did
Page 84 and 85: Warning (but without removing any e
Page 86 and 87: If the user has overridden the basi
Page 88 and 89: 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
Page 96 and 97: validators or strong validators. Cl
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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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Fielding, et al. Standards Track [P
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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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Note: while the definition of Conte
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server SHOULD return them in the or
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Some origin server implementations
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Expires = "Expires" ":" HTTP-dateAn
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A client MUST include a Host header
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een modified since the date given b
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RFC 2616 HTTP/1.1 June 1999If none
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14.29 Last-ModifiedThe Last-Modifie
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MAY require that behavior be consis
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yte-ranges-specifier = bytes-unit "
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Content) instead of 200 (OK).- The
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The TE request-header field indicat
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a cache cannot determine from the r
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SHOULD NOT, by default, forward the
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this user agent behavior in mind.Re
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designers and implementors be parti
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strongly correlated to the membersh
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serious security considerations. Co
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The HTTP protocol has evolved consi
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Protocol -- HTTP/1.0", RFC 1945, Ma
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Implementation and Analysis", RFC 1
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University of California, IrvineIrv
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Notes:1) Additional CRLFs may prece
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full compliance with the MIME proto
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ead chunk-size and CRLF}read entity
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- understand any valid response in
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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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