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4Network Working Group                                   R. Fielding, Ed.
5Internet-Draft                                              Day Software
6Obsoletes: 2616 (if approved)                                  J. Gettys
7Intended status: Standards Track                    One Laptop per Child
8Expires: August 27, 2008                                        J. Mogul
9                                                                      HP
10                                                              H. Frystyk
11                                                               Microsoft
12                                                             L. Masinter
13                                                           Adobe Systems
14                                                                P. Leach
15                                                               Microsoft
16                                                          T. Berners-Lee
17                                                                 W3C/MIT
18                                                           Y. Lafon, Ed.
19                                                                     W3C
20                                                         J. Reschke, Ed.
21                                                              greenbytes
22                                                       February 24, 2008
23
24
25                  HTTP/1.1, part 2: Message Semantics
26                   draft-ietf-httpbis-p2-semantics-02
27
28Status of this Memo
29
30   By submitting this Internet-Draft, each author represents that any
31   applicable patent or other IPR claims of which he or she is aware
32   have been or will be disclosed, and any of which he or she becomes
33   aware will be disclosed, in accordance with Section 6 of BCP 79.
34
35   Internet-Drafts are working documents of the Internet Engineering
36   Task Force (IETF), its areas, and its working groups.  Note that
37   other groups may also distribute working documents as Internet-
38   Drafts.
39
40   Internet-Drafts are draft documents valid for a maximum of six months
41   and may be updated, replaced, or obsoleted by other documents at any
42   time.  It is inappropriate to use Internet-Drafts as reference
43   material or to cite them other than as "work in progress."
44
45   The list of current Internet-Drafts can be accessed at
46   http://www.ietf.org/ietf/1id-abstracts.txt.
47
48   The list of Internet-Draft Shadow Directories can be accessed at
49   http://www.ietf.org/shadow.html.
50
51   This Internet-Draft will expire on August 27, 2008.
52
53
54
55Fielding, et al.         Expires August 27, 2008                [Page 1]
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57Internet-Draft              HTTP/1.1, Part 2               February 2008
58
59
60Copyright Notice
61
62   Copyright (C) The IETF Trust (2008).
63
64Abstract
65
66   The Hypertext Transfer Protocol (HTTP) is an application-level
67   protocol for distributed, collaborative, hypermedia information
68   systems.  HTTP has been in use by the World Wide Web global
69   information initiative since 1990.  This document is Part 2 of the
70   seven-part specification that defines the protocol referred to as
71   "HTTP/1.1" and, taken together, obsoletes RFC 2616.  Part 2 defines
72   the semantics of HTTP messages as expressed by request methods,
73   request-header fields, response status codes, and response-header
74   fields.
75
76Editorial Note (To be removed by RFC Editor)
77
78   Discussion of this draft should take place on the HTTPBIS working
79   group mailing list (ietf-http-wg@w3.org).  The current issues list is
80   at <http://www.tools.ietf.org/wg/httpbis/trac/report/11> and related
81   documents (including fancy diffs) can be found at
82   <http://www.tools.ietf.org/wg/httpbis/>.
83
84   This draft incorporates those issue resolutions that were either
85   collected in the original RFC2616 errata list
86   (<http://purl.org/NET/http-errata>), or which were agreed upon on the
87   mailing list between October 2006 and November 2007 (as published in
88   "draft-lafon-rfc2616bis-03").
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111Fielding, et al.         Expires August 27, 2008                [Page 2]
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113Internet-Draft              HTTP/1.1, Part 2               February 2008
114
115
116Table of Contents
117
118   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  6
119     1.1.  Requirements . . . . . . . . . . . . . . . . . . . . . . .  6
120   2.  Notational Conventions and Generic Grammar . . . . . . . . . .  6
121   3.  Method . . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
122   4.  Request Header Fields  . . . . . . . . . . . . . . . . . . . .  8
123   5.  Status Code and Reason Phrase  . . . . . . . . . . . . . . . .  9
124   6.  Response Header Fields . . . . . . . . . . . . . . . . . . . . 11
125   7.  Entity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
126   8.  Method Definitions . . . . . . . . . . . . . . . . . . . . . . 12
127     8.1.  Safe and Idempotent Methods  . . . . . . . . . . . . . . . 12
128       8.1.1.  Safe Methods . . . . . . . . . . . . . . . . . . . . . 12
129       8.1.2.  Idempotent Methods . . . . . . . . . . . . . . . . . . 12
130     8.2.  OPTIONS  . . . . . . . . . . . . . . . . . . . . . . . . . 13
131     8.3.  GET  . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
132     8.4.  HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
133     8.5.  POST . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
134     8.6.  PUT  . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
135     8.7.  DELETE . . . . . . . . . . . . . . . . . . . . . . . . . . 17
136     8.8.  TRACE  . . . . . . . . . . . . . . . . . . . . . . . . . . 17
137     8.9.  CONNECT  . . . . . . . . . . . . . . . . . . . . . . . . . 18
138   9.  Status Code Definitions  . . . . . . . . . . . . . . . . . . . 18
139     9.1.  Informational 1xx  . . . . . . . . . . . . . . . . . . . . 18
140       9.1.1.  100 Continue . . . . . . . . . . . . . . . . . . . . . 18
141       9.1.2.  101 Switching Protocols  . . . . . . . . . . . . . . . 19
142     9.2.  Successful 2xx . . . . . . . . . . . . . . . . . . . . . . 19
143       9.2.1.  200 OK . . . . . . . . . . . . . . . . . . . . . . . . 19
144       9.2.2.  201 Created  . . . . . . . . . . . . . . . . . . . . . 19
145       9.2.3.  202 Accepted . . . . . . . . . . . . . . . . . . . . . 20
146       9.2.4.  203 Non-Authoritative Information  . . . . . . . . . . 20
147       9.2.5.  204 No Content . . . . . . . . . . . . . . . . . . . . 20
148       9.2.6.  205 Reset Content  . . . . . . . . . . . . . . . . . . 21
149       9.2.7.  206 Partial Content  . . . . . . . . . . . . . . . . . 21
150     9.3.  Redirection 3xx  . . . . . . . . . . . . . . . . . . . . . 21
151       9.3.1.  300 Multiple Choices . . . . . . . . . . . . . . . . . 21
152       9.3.2.  301 Moved Permanently  . . . . . . . . . . . . . . . . 22
153       9.3.3.  302 Found  . . . . . . . . . . . . . . . . . . . . . . 22
154       9.3.4.  303 See Other  . . . . . . . . . . . . . . . . . . . . 23
155       9.3.5.  304 Not Modified . . . . . . . . . . . . . . . . . . . 23
156       9.3.6.  305 Use Proxy  . . . . . . . . . . . . . . . . . . . . 23
157       9.3.7.  306 (Unused) . . . . . . . . . . . . . . . . . . . . . 24
158       9.3.8.  307 Temporary Redirect . . . . . . . . . . . . . . . . 24
159     9.4.  Client Error 4xx . . . . . . . . . . . . . . . . . . . . . 24
160       9.4.1.  400 Bad Request  . . . . . . . . . . . . . . . . . . . 25
161       9.4.2.  401 Unauthorized . . . . . . . . . . . . . . . . . . . 25
162       9.4.3.  402 Payment Required . . . . . . . . . . . . . . . . . 25
163       9.4.4.  403 Forbidden  . . . . . . . . . . . . . . . . . . . . 25
164
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172       9.4.5.  404 Not Found  . . . . . . . . . . . . . . . . . . . . 25
173       9.4.6.  405 Method Not Allowed . . . . . . . . . . . . . . . . 25
174       9.4.7.  406 Not Acceptable . . . . . . . . . . . . . . . . . . 25
175       9.4.8.  407 Proxy Authentication Required  . . . . . . . . . . 26
176       9.4.9.  408 Request Timeout  . . . . . . . . . . . . . . . . . 26
177       9.4.10. 409 Conflict . . . . . . . . . . . . . . . . . . . . . 26
178       9.4.11. 410 Gone . . . . . . . . . . . . . . . . . . . . . . . 27
179       9.4.12. 411 Length Required  . . . . . . . . . . . . . . . . . 27
180       9.4.13. 412 Precondition Failed  . . . . . . . . . . . . . . . 27
181       9.4.14. 413 Request Entity Too Large . . . . . . . . . . . . . 27
182       9.4.15. 414 Request-URI Too Long . . . . . . . . . . . . . . . 28
183       9.4.16. 415 Unsupported Media Type . . . . . . . . . . . . . . 28
184       9.4.17. 416 Requested Range Not Satisfiable  . . . . . . . . . 28
185       9.4.18. 417 Expectation Failed . . . . . . . . . . . . . . . . 28
186     9.5.  Server Error 5xx . . . . . . . . . . . . . . . . . . . . . 28
187       9.5.1.  500 Internal Server Error  . . . . . . . . . . . . . . 28
188       9.5.2.  501 Not Implemented  . . . . . . . . . . . . . . . . . 29
189       9.5.3.  502 Bad Gateway  . . . . . . . . . . . . . . . . . . . 29
190       9.5.4.  503 Service Unavailable  . . . . . . . . . . . . . . . 29
191       9.5.5.  504 Gateway Timeout  . . . . . . . . . . . . . . . . . 29
192       9.5.6.  505 HTTP Version Not Supported . . . . . . . . . . . . 29
193   10. Header Field Definitions . . . . . . . . . . . . . . . . . . . 30
194     10.1. Allow  . . . . . . . . . . . . . . . . . . . . . . . . . . 30
195     10.2. Expect . . . . . . . . . . . . . . . . . . . . . . . . . . 30
196     10.3. From . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
197     10.4. Location . . . . . . . . . . . . . . . . . . . . . . . . . 32
198     10.5. Max-Forwards . . . . . . . . . . . . . . . . . . . . . . . 33
199     10.6. Referer  . . . . . . . . . . . . . . . . . . . . . . . . . 33
200     10.7. Retry-After  . . . . . . . . . . . . . . . . . . . . . . . 34
201     10.8. Server . . . . . . . . . . . . . . . . . . . . . . . . . . 34
202     10.9. User-Agent . . . . . . . . . . . . . . . . . . . . . . . . 35
203   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 35
204   12. Security Considerations  . . . . . . . . . . . . . . . . . . . 35
205     12.1. Transfer of Sensitive Information  . . . . . . . . . . . . 35
206     12.2. Encoding Sensitive Information in URIs . . . . . . . . . . 36
207     12.3. Location Headers and Spoofing  . . . . . . . . . . . . . . 37
208   13. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 37
209   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 37
210     14.1. Normative References . . . . . . . . . . . . . . . . . . . 37
211     14.2. Informative References . . . . . . . . . . . . . . . . . . 38
212   Appendix A.  Compatibility with Previous Versions  . . . . . . . . 38
213     A.1.  Changes from RFC 2068  . . . . . . . . . . . . . . . . . . 38
214     A.2.  Changes from RFC 2616  . . . . . . . . . . . . . . . . . . 39
215   Appendix B.  Change Log (to be removed by RFC Editor before
216                publication)  . . . . . . . . . . . . . . . . . . . . 40
217     B.1.  Since RFC2616  . . . . . . . . . . . . . . . . . . . . . . 40
218     B.2.  Since draft-ietf-httpbis-p2-semantics-00 . . . . . . . . . 40
219     B.3.  Since draft-ietf-httpbis-p2-semantics-01 . . . . . . . . . 41
220
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225Internet-Draft              HTTP/1.1, Part 2               February 2008
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227
228   Index  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
229   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 45
230   Intellectual Property and Copyright Statements . . . . . . . . . . 48
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281Internet-Draft              HTTP/1.1, Part 2               February 2008
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283
2841.  Introduction
285
286   This document defines HTTP/1.1 request and response semantics.  Each
287   HTTP message, as defined in [Part1], is in the form of either a
288   request or a response.  An HTTP server listens on a connection for
289   HTTP requests and responds to each request, in the order received on
290   that connection, with one or more HTTP response messages.  This
291   document defines the commonly agreed upon semantics of the HTTP
292   uniform interface, the intentions defined by each request method, and
293   the various response messages that might be expected as a result of
294   applying that method for the requested resource.
295
296   This document is currently disorganized in order to minimize the
297   changes between drafts and enable reviewers to see the smaller errata
298   changes.  The next draft will reorganize the sections to better
299   reflect the content.  In particular, the sections will be ordered
300   according to the typical processing of an HTTP request message (after
301   message parsing): resource mapping, general header fields, methods,
302   request modifiers, response status, and resource metadata.  The
303   current mess reflects how widely dispersed these topics and
304   associated requirements had become in [RFC2616].
305
3061.1.  Requirements
307
308   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
309   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
310   document are to be interpreted as described in [RFC2119].
311
312   An implementation is not compliant if it fails to satisfy one or more
313   of the MUST or REQUIRED level requirements for the protocols it
314   implements.  An implementation that satisfies all the MUST or
315   REQUIRED level and all the SHOULD level requirements for its
316   protocols is said to be "unconditionally compliant"; one that
317   satisfies all the MUST level requirements but not all the SHOULD
318   level requirements for its protocols is said to be "conditionally
319   compliant."
320
321
3222.  Notational Conventions and Generic Grammar
323
324   This specification uses the ABNF syntax defined in Section 2.1 of
325   [Part1] and the core rules defined in Section 2.2 of [Part1]:
326   [[abnf.dep: ABNF syntax and basic rules will be adopted from RFC
327   5234, see <http://tools.ietf.org/wg/httpbis/trac/ticket/36>.]]
328
329     DIGIT         = <DIGIT, defined in [Part1], Section 2.2>
330
331
332
333
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339
340     comment       = <comment, defined in [Part1], Section 2.2>
341     quoted-string = <quoted-string, defined in [Part1], Section 2.2>
342     token         = <token, defined in [Part1], Section 2.2>
343
344   The ABNF rules below are defined in other parts:
345
346     absoluteURI   = <absoluteURI, defined in [Part1], Section 3.2.1>
347     fragment      = <fragment, defined in [Part1], Section 3.2.1>
348     Host          = <Host, defined in [Part1], Section 8.4>
349     HTTP-date     = <HTTP-date, defined in [Part1], Section 3.3.1>
350     product       = <product, defined in [Part1], Section 3.5>
351     relativeURI   = <relativeURI, defined in [Part1], Section 3.2.1>
352     TE            = <TE, defined in [Part1], Section 8.8>
353
354
355     Accept        = <Accept, defined in [Part3], Section 6.1>
356     Accept-Charset =
357                <Accept-Charset, defined in [Part3], Section 6.2>
358     Accept-Encoding =
359                <Accept-Encoding, defined in [Part3], Section 6.3>
360     Accept-Language =
361                <Accept-Language, defined in [Part3], Section 6.4>
362
363
364     ETag          = <ETag, defined in [Part4], Section 7.1>
365     If-Match      = <If-Match, defined in [Part4], Section 7.2>
366     If-Modified-Since =
367                <If-Modified-Since, defined in [Part4], Section 7.3>
368     If-None-Match = <If-None-Match, defined in [Part4], Section 7.4>
369     If-Unmodified-Since =
370                <If-Unmodified-Since, defined in [Part4], Section 7.5>
371
372
373     Accept-Ranges = <Accept-Ranges, defined in [Part5], Section 6.1>
374     If-Range      = <If-Range, defined in [Part5], Section 6.3>
375     Range         = <Range, defined in [Part5], Section 6.4>
376
377
378     Age           = <Age, defined in [Part6], Section 16.1>
379     Vary          = <Vary, defined in [Part6], Section 16.5>
380
381
382     Authorization = <Authorization, defined in [Part7], Section 4.1>
383     Proxy-Authenticate =
384                <Proxy-Authenticate, defined in [Part7], Section 4.2>
385     Proxy-Authorization =
386                <Proxy-Authorization, defined in [Part7], Section 4.3>
387     WWW-Authenticate =
388
389
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395
396                <WWW-Authenticate, defined in [Part7], Section 4.4>
397
398
3993.  Method
400
401   The Method token indicates the method to be performed on the resource
402   identified by the Request-URI.  The method is case-sensitive.
403
404     Method         = "OPTIONS"                ; Section 8.2
405                    | "GET"                    ; Section 8.3
406                    | "HEAD"                   ; Section 8.4
407                    | "POST"                   ; Section 8.5
408                    | "PUT"                    ; Section 8.6
409                    | "DELETE"                 ; Section 8.7
410                    | "TRACE"                  ; Section 8.8
411                    | "CONNECT"                ; Section 8.9
412                    | extension-method
413     extension-method = token
414
415   The list of methods allowed by a resource can be specified in an
416   Allow header field (Section 10.1).  The return code of the response
417   always notifies the client whether a method is currently allowed on a
418   resource, since the set of allowed methods can change dynamically.
419   An origin server SHOULD return the status code 405 (Method Not
420   Allowed) if the method is known by the origin server but not allowed
421   for the requested resource, and 501 (Not Implemented) if the method
422   is unrecognized or not implemented by the origin server.  The methods
423   GET and HEAD MUST be supported by all general-purpose servers.  All
424   other methods are OPTIONAL; however, if the above methods are
425   implemented, they MUST be implemented with the same semantics as
426   those specified in Section 8.
427
428
4294.  Request Header Fields
430
431   The request-header fields allow the client to pass additional
432   information about the request, and about the client itself, to the
433   server.  These fields act as request modifiers, with semantics
434   equivalent to the parameters on a programming language method
435   invocation.
436
437
438
439
440
441
442
443
444
445
446
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451
452     request-header = Accept                   ; [Part3], Section 6.1
453                    | Accept-Charset           ; [Part3], Section 6.2
454                    | Accept-Encoding          ; [Part3], Section 6.3
455                    | Accept-Language          ; [Part3], Section 6.4
456                    | Authorization            ; [Part7], Section 4.1
457                    | Expect                   ; Section 10.2
458                    | From                     ; Section 10.3
459                    | Host                     ; [Part1], Section 8.4
460                    | If-Match                 ; [Part4], Section 7.2
461                    | If-Modified-Since        ; [Part4], Section 7.3
462                    | If-None-Match            ; [Part4], Section 7.4
463                    | If-Range                 ; [Part5], Section 6.3
464                    | If-Unmodified-Since      ; [Part4], Section 7.5
465                    | Max-Forwards             ; Section 10.5
466                    | Proxy-Authorization      ; [Part7], Section 4.3
467                    | Range                    ; [Part5], Section 6.4
468                    | Referer                  ; Section 10.6
469                    | TE                       ; [Part1], Section 8.8
470                    | User-Agent               ; Section 10.9
471
472   Request-header field names can be extended reliably only in
473   combination with a change in the protocol version.  However, new or
474   experimental header fields MAY be given the semantics of request-
475   header fields if all parties in the communication recognize them to
476   be request-header fields.  Unrecognized header fields are treated as
477   entity-header fields.
478
479
4805.  Status Code and Reason Phrase
481
482   The Status-Code element is a 3-digit integer result code of the
483   attempt to understand and satisfy the request.  The status codes
484   listed below are defined in Section 9.  The Reason-Phrase is intended
485   to give a short textual description of the Status-Code.  The Status-
486   Code is intended for use by automata and the Reason-Phrase is
487   intended for the human user.  The client is not required to examine
488   or display the Reason-Phrase.
489
490   The individual values of the numeric status codes defined for
491   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
492   presented below.  The reason phrases listed here are only
493   recommendations -- they MAY be replaced by local equivalents without
494   affecting the protocol.
495
496
497
498
499
500
501
502
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507
508     Status-Code    =
509            "100"  ; Section 9.1.1: Continue
510          | "101"  ; Section 9.1.2: Switching Protocols
511          | "200"  ; Section 9.2.1: OK
512          | "201"  ; Section 9.2.2: Created
513          | "202"  ; Section 9.2.3: Accepted
514          | "203"  ; Section 9.2.4: Non-Authoritative Information
515          | "204"  ; Section 9.2.5: No Content
516          | "205"  ; Section 9.2.6: Reset Content
517          | "206"  ; Section 9.2.7: Partial Content
518          | "300"  ; Section 9.3.1: Multiple Choices
519          | "301"  ; Section 9.3.2: Moved Permanently
520          | "302"  ; Section 9.3.3: Found
521          | "303"  ; Section 9.3.4: See Other
522          | "304"  ; Section 9.3.5: Not Modified
523          | "305"  ; Section 9.3.6: Use Proxy
524          | "307"  ; Section 9.3.8: Temporary Redirect
525          | "400"  ; Section 9.4.1: Bad Request
526          | "401"  ; Section 9.4.2: Unauthorized
527          | "402"  ; Section 9.4.3: Payment Required
528          | "403"  ; Section 9.4.4: Forbidden
529          | "404"  ; Section 9.4.5: Not Found
530          | "405"  ; Section 9.4.6: Method Not Allowed
531          | "406"  ; Section 9.4.7: Not Acceptable
532          | "407"  ; Section 9.4.8: Proxy Authentication Required
533          | "408"  ; Section 9.4.9: Request Time-out
534          | "409"  ; Section 9.4.10: Conflict
535          | "410"  ; Section 9.4.11: Gone
536          | "411"  ; Section 9.4.12: Length Required
537          | "412"  ; Section 9.4.13: Precondition Failed
538          | "413"  ; Section 9.4.14: Request Entity Too Large
539          | "414"  ; Section 9.4.15: Request-URI Too Large
540          | "415"  ; Section 9.4.16: Unsupported Media Type
541          | "416"  ; Section 9.4.17: Requested range not satisfiable
542          | "417"  ; Section 9.4.18: Expectation Failed
543          | "500"  ; Section 9.5.1: Internal Server Error
544          | "501"  ; Section 9.5.2: Not Implemented
545          | "502"  ; Section 9.5.3: Bad Gateway
546          | "503"  ; Section 9.5.4: Service Unavailable
547          | "504"  ; Section 9.5.5: Gateway Time-out
548          | "505"  ; Section 9.5.6: HTTP Version not supported
549          | extension-code
550
551     extension-code = 3DIGIT
552     Reason-Phrase  = *<TEXT, excluding CR, LF>
553
554   HTTP status codes are extensible.  HTTP applications are not required
555   to understand the meaning of all registered status codes, though such
556
557
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563
564   understanding is obviously desirable.  However, applications MUST
565   understand the class of any status code, as indicated by the first
566   digit, and treat any unrecognized response as being equivalent to the
567   x00 status code of that class, with the exception that an
568   unrecognized response MUST NOT be cached.  For example, if an
569   unrecognized status code of 431 is received by the client, it can
570   safely assume that there was something wrong with its request and
571   treat the response as if it had received a 400 status code.  In such
572   cases, user agents SHOULD present to the user the entity returned
573   with the response, since that entity is likely to include human-
574   readable information which will explain the unusual status.
575
576
5776.  Response Header Fields
578
579   The response-header fields allow the server to pass additional
580   information about the response which cannot be placed in the Status-
581   Line.  These header fields give information about the server and
582   about further access to the resource identified by the Request-URI.
583
584     response-header = Accept-Ranges           ; [Part5], Section 6.1
585                     | Age                     ; [Part6], Section 16.1
586                     | ETag                    ; [Part4], Section 7.1
587                     | Location                ; Section 10.4
588                     | Proxy-Authenticate      ; [Part7], Section 4.2
589                     | Retry-After             ; Section 10.7
590                     | Server                  ; Section 10.8
591                     | Vary                    ; [Part6], Section 16.5
592                     | WWW-Authenticate        ; [Part7], Section 4.4
593
594   Response-header field names can be extended reliably only in
595   combination with a change in the protocol version.  However, new or
596   experimental header fields MAY be given the semantics of response-
597   header fields if all parties in the communication recognize them to
598   be response-header fields.  Unrecognized header fields are treated as
599   entity-header fields.
600
601
6027.  Entity
603
604   Request and Response messages MAY transfer an entity if not otherwise
605   restricted by the request method or response status code.  An entity
606   consists of entity-header fields and an entity-body, although some
607   responses will only include the entity-headers.  HTTP entity-body and
608   entity-header fields are defined in [Part3].
609
610   An entity-body is only present in a message when a message-body is
611   present, as described in Section 4.3 of [Part1].  The entity-body is
612
613
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619
620   obtained from the message-body by decoding any Transfer-Encoding that
621   might have been applied to ensure safe and proper transfer of the
622   message.
623
624
6258.  Method Definitions
626
627   The set of common methods for HTTP/1.1 is defined below.  Although
628   this set can be expanded, additional methods cannot be assumed to
629   share the same semantics for separately extended clients and servers.
630
6318.1.  Safe and Idempotent Methods
632
6338.1.1.  Safe Methods
634
635   Implementors should be aware that the software represents the user in
636   their interactions over the Internet, and should be careful to allow
637   the user to be aware of any actions they might take which may have an
638   unexpected significance to themselves or others.
639
640   In particular, the convention has been established that the GET and
641   HEAD methods SHOULD NOT have the significance of taking an action
642   other than retrieval.  These methods ought to be considered "safe".
643   This allows user agents to represent other methods, such as POST, PUT
644   and DELETE, in a special way, so that the user is made aware of the
645   fact that a possibly unsafe action is being requested.
646
647   Naturally, it is not possible to ensure that the server does not
648   generate side-effects as a result of performing a GET request; in
649   fact, some dynamic resources consider that a feature.  The important
650   distinction here is that the user did not request the side-effects,
651   so therefore cannot be held accountable for them.
652
6538.1.2.  Idempotent Methods
654
655   Methods can also have the property of "idempotence" in that (aside
656   from error or expiration issues) the side-effects of N > 0 identical
657   requests is the same as for a single request.  The methods GET, HEAD,
658   PUT and DELETE share this property.  Also, the methods OPTIONS and
659   TRACE SHOULD NOT have side effects, and so are inherently idempotent.
660
661   However, it is possible that a sequence of several requests is non-
662   idempotent, even if all of the methods executed in that sequence are
663   idempotent.  (A sequence is idempotent if a single execution of the
664   entire sequence always yields a result that is not changed by a
665   reexecution of all, or part, of that sequence.)  For example, a
666   sequence is non-idempotent if its result depends on a value that is
667   later modified in the same sequence.
668
669
670
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675
676   A sequence that never has side effects is idempotent, by definition
677   (provided that no concurrent operations are being executed on the
678   same set of resources).
679
6808.2.  OPTIONS
681
682   The OPTIONS method represents a request for information about the
683   communication options available on the request/response chain
684   identified by the Request-URI.  This method allows the client to
685   determine the options and/or requirements associated with a resource,
686   or the capabilities of a server, without implying a resource action
687   or initiating a resource retrieval.
688
689   Responses to this method are not cacheable.
690
691   If the OPTIONS request includes an entity-body (as indicated by the
692   presence of Content-Length or Transfer-Encoding), then the media type
693   MUST be indicated by a Content-Type field.  Although this
694   specification does not define any use for such a body, future
695   extensions to HTTP might use the OPTIONS body to make more detailed
696   queries on the server.  A server that does not support such an
697   extension MAY discard the request body.
698
699   If the Request-URI is an asterisk ("*"), the OPTIONS request is
700   intended to apply to the server in general rather than to a specific
701   resource.  Since a server's communication options typically depend on
702   the resource, the "*" request is only useful as a "ping" or "no-op"
703   type of method; it does nothing beyond allowing the client to test
704   the capabilities of the server.  For example, this can be used to
705   test a proxy for HTTP/1.1 compliance (or lack thereof).
706
707   If the Request-URI is not an asterisk, the OPTIONS request applies
708   only to the options that are available when communicating with that
709   resource.
710
711   A 200 response SHOULD include any header fields that indicate
712   optional features implemented by the server and applicable to that
713   resource (e.g., Allow), possibly including extensions not defined by
714   this specification.  The response body, if any, SHOULD also include
715   information about the communication options.  The format for such a
716   body is not defined by this specification, but might be defined by
717   future extensions to HTTP.  Content negotiation MAY be used to select
718   the appropriate response format.  If no response body is included,
719   the response MUST include a Content-Length field with a field-value
720   of "0".
721
722   The Max-Forwards request-header field MAY be used to target a
723   specific proxy in the request chain.  When a proxy receives an
724
725
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731
732   OPTIONS request on an absoluteURI for which request forwarding is
733   permitted, the proxy MUST check for a Max-Forwards field.  If the
734   Max-Forwards field-value is zero ("0"), the proxy MUST NOT forward
735   the message; instead, the proxy SHOULD respond with its own
736   communication options.  If the Max-Forwards field-value is an integer
737   greater than zero, the proxy MUST decrement the field-value when it
738   forwards the request.  If no Max-Forwards field is present in the
739   request, then the forwarded request MUST NOT include a Max-Forwards
740   field.
741
7428.3.  GET
743
744   The GET method means retrieve whatever information (in the form of an
745   entity) is identified by the Request-URI.  If the Request-URI refers
746   to a data-producing process, it is the produced data which shall be
747   returned as the entity in the response and not the source text of the
748   process, unless that text happens to be the output of the process.
749
750   The semantics of the GET method change to a "conditional GET" if the
751   request message includes an If-Modified-Since, If-Unmodified-Since,
752   If-Match, If-None-Match, or If-Range header field.  A conditional GET
753   method requests that the entity be transferred only under the
754   circumstances described by the conditional header field(s).  The
755   conditional GET method is intended to reduce unnecessary network
756   usage by allowing cached entities to be refreshed without requiring
757   multiple requests or transferring data already held by the client.
758
759   The semantics of the GET method change to a "partial GET" if the
760   request message includes a Range header field.  A partial GET
761   requests that only part of the entity be transferred, as described in
762   Section 6.4 of [Part5].  The partial GET method is intended to reduce
763   unnecessary network usage by allowing partially-retrieved entities to
764   be completed without transferring data already held by the client.
765
766   The response to a GET request is cacheable if and only if it meets
767   the requirements for HTTP caching described in [Part6].
768
769   See Section 12.2 for security considerations when used for forms.
770
7718.4.  HEAD
772
773   The HEAD method is identical to GET except that the server MUST NOT
774   return a message-body in the response.  The metainformation contained
775   in the HTTP headers in response to a HEAD request SHOULD be identical
776   to the information sent in response to a GET request.  This method
777   can be used for obtaining metainformation about the entity implied by
778   the request without transferring the entity-body itself.  This method
779   is often used for testing hypertext links for validity,
780
781
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787
788   accessibility, and recent modification.
789
790   The response to a HEAD request MAY be cacheable in the sense that the
791   information contained in the response MAY be used to update a
792   previously cached entity from that resource.  If the new field values
793   indicate that the cached entity differs from the current entity (as
794   would be indicated by a change in Content-Length, Content-MD5, ETag
795   or Last-Modified), then the cache MUST treat the cache entry as
796   stale.
797
7988.5.  POST
799
800   The POST method is used to request that the origin server accept the
801   entity enclosed in the request as data to be processed by the
802   resource identified by the Request-URI in the Request-Line.  POST is
803   designed to allow a uniform method to cover the following functions:
804
805   o  Annotation of existing resources;
806
807   o  Posting a message to a bulletin board, newsgroup, mailing list, or
808      similar group of articles;
809
810   o  Providing a block of data, such as the result of submitting a
811      form, to a data-handling process;
812
813   o  Extending a database through an append operation.
814
815   The actual function performed by the POST method is determined by the
816   server and is usually dependent on the Request-URI.
817
818   The action performed by the POST method might not result in a
819   resource that can be identified by a URI.  In this case, either 200
820   (OK) or 204 (No Content) is the appropriate response status,
821   depending on whether or not the response includes an entity that
822   describes the result.
823
824   If a resource has been created on the origin server, the response
825   SHOULD be 201 (Created) and contain an entity which describes the
826   status of the request and refers to the new resource, and a Location
827   header (see Section 10.4).
828
829   Responses to this method are not cacheable, unless the response
830   includes appropriate Cache-Control or Expires header fields.
831   However, the 303 (See Other) response can be used to direct the user
832   agent to retrieve a cacheable resource.
833
834
835
836
837
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843
8448.6.  PUT
845
846   The PUT method requests that the enclosed entity be stored under the
847   supplied Request-URI.  If the Request-URI refers to an already
848   existing resource, the enclosed entity SHOULD be considered as a
849   modified version of the one residing on the origin server.  If the
850   Request-URI does not point to an existing resource, and that URI is
851   capable of being defined as a new resource by the requesting user
852   agent, the origin server can create the resource with that URI.  If a
853   new resource is created at the Request-URI, the origin server MUST
854   inform the user agent via the 201 (Created) response.  If an existing
855   resource is modified, either the 200 (OK) or 204 (No Content)
856   response codes SHOULD be sent to indicate successful completion of
857   the request.  If the resource could not be created or modified with
858   the Request-URI, an appropriate error response SHOULD be given that
859   reflects the nature of the problem.  The recipient of the entity MUST
860   NOT ignore any Content-* (e.g.  Content-Range) headers that it does
861   not understand or implement and MUST return a 501 (Not Implemented)
862   response in such cases.
863
864   If the request passes through a cache and the Request-URI identifies
865   one or more currently cached entities, those entries SHOULD be
866   treated as stale.  Responses to this method are not cacheable.
867
868   The fundamental difference between the POST and PUT requests is
869   reflected in the different meaning of the Request-URI.  The URI in a
870   POST request identifies the resource that will handle the enclosed
871   entity.  That resource might be a data-accepting process, a gateway
872   to some other protocol, or a separate entity that accepts
873   annotations.  In contrast, the URI in a PUT request identifies the
874   entity enclosed with the request -- the user agent knows what URI is
875   intended and the server MUST NOT attempt to apply the request to some
876   other resource.  If the server desires that the request be applied to
877   a different URI, it MUST send a 301 (Moved Permanently) response; the
878   user agent MAY then make its own decision regarding whether or not to
879   redirect the request.
880
881   A single resource MAY be identified by many different URIs.  For
882   example, an article might have a URI for identifying "the current
883   version" which is separate from the URI identifying each particular
884   version.  In this case, a PUT request on a general URI might result
885   in several other URIs being defined by the origin server.
886
887   HTTP/1.1 does not define how a PUT method affects the state of an
888   origin server.
889
890   Unless otherwise specified for a particular entity-header, the
891   entity-headers in the PUT request SHOULD be applied to the resource
892
893
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899
900   created or modified by the PUT.
901
9028.7.  DELETE
903
904   The DELETE method requests that the origin server delete the resource
905   identified by the Request-URI.  This method MAY be overridden by
906   human intervention (or other means) on the origin server.  The client
907   cannot be guaranteed that the operation has been carried out, even if
908   the status code returned from the origin server indicates that the
909   action has been completed successfully.  However, the server SHOULD
910   NOT indicate success unless, at the time the response is given, it
911   intends to delete the resource or move it to an inaccessible
912   location.
913
914   A successful response SHOULD be 200 (OK) if the response includes an
915   entity describing the status, 202 (Accepted) if the action has not
916   yet been enacted, or 204 (No Content) if the action has been enacted
917   but the response does not include an entity.
918
919   If the request passes through a cache and the Request-URI identifies
920   one or more currently cached entities, those entries SHOULD be
921   treated as stale.  Responses to this method are not cacheable.
922
9238.8.  TRACE
924
925   The TRACE method is used to invoke a remote, application-layer loop-
926   back of the request message.  The final recipient of the request
927   SHOULD reflect the message received back to the client as the entity-
928   body of a 200 (OK) response.  The final recipient is either the
929   origin server or the first proxy or gateway to receive a Max-Forwards
930   value of zero (0) in the request (see Section 10.5).  A TRACE request
931   MUST NOT include an entity.
932
933   TRACE allows the client to see what is being received at the other
934   end of the request chain and use that data for testing or diagnostic
935   information.  The value of the Via header field (Section 8.9 of
936   [Part1]) is of particular interest, since it acts as a trace of the
937   request chain.  Use of the Max-Forwards header field allows the
938   client to limit the length of the request chain, which is useful for
939   testing a chain of proxies forwarding messages in an infinite loop.
940
941   If the request is valid, the response SHOULD contain the entire
942   request message in the entity-body, with a Content-Type of "message/
943   http".  Responses to this method MUST NOT be cached.
944
945
946
947
948
949
950
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954
955
9568.9.  CONNECT
957
958   This specification reserves the method name CONNECT for use with a
959   proxy that can dynamically switch to being a tunnel (e.g.  SSL
960   tunneling [Luo1998]).
961
962
9639.  Status Code Definitions
964
965   Each Status-Code is described below, including a description of which
966   method(s) it can follow and any metainformation required in the
967   response.
968
9699.1.  Informational 1xx
970
971   This class of status code indicates a provisional response,
972   consisting only of the Status-Line and optional headers, and is
973   terminated by an empty line.  There are no required headers for this
974   class of status code.  Since HTTP/1.0 did not define any 1xx status
975   codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client
976   except under experimental conditions.
977
978   A client MUST be prepared to accept one or more 1xx status responses
979   prior to a regular response, even if the client does not expect a 100
980   (Continue) status message.  Unexpected 1xx status responses MAY be
981   ignored by a user agent.
982
983   Proxies MUST forward 1xx responses, unless the connection between the
984   proxy and its client has been closed, or unless the proxy itself
985   requested the generation of the 1xx response.  (For example, if a
986   proxy adds a "Expect: 100-continue" field when it forwards a request,
987   then it need not forward the corresponding 100 (Continue)
988   response(s).)
989
9909.1.1.  100 Continue
991
992   The client SHOULD continue with its request.  This interim response
993   is used to inform the client that the initial part of the request has
994   been received and has not yet been rejected by the server.  The
995   client SHOULD continue by sending the remainder of the request or, if
996   the request has already been completed, ignore this response.  The
997   server MUST send a final response after the request has been
998   completed.  See Section 7.2.3 of [Part1] for detailed discussion of
999   the use and handling of this status code.
1000
1001
1002
1003
1004
1005
1006
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1010
1011
10129.1.2.  101 Switching Protocols
1013
1014   The server understands and is willing to comply with the client's
1015   request, via the Upgrade message header field (Section 6.4 of
1016   [Part5]), for a change in the application protocol being used on this
1017   connection.  The server will switch protocols to those defined by the
1018   response's Upgrade header field immediately after the empty line
1019   which terminates the 101 response.
1020
1021   The protocol SHOULD be switched only when it is advantageous to do
1022   so.  For example, switching to a newer version of HTTP is
1023   advantageous over older versions, and switching to a real-time,
1024   synchronous protocol might be advantageous when delivering resources
1025   that use such features.
1026
10279.2.  Successful 2xx
1028
1029   This class of status code indicates that the client's request was
1030   successfully received, understood, and accepted.
1031
10329.2.1.  200 OK
1033
1034   The request has succeeded.  The information returned with the
1035   response is dependent on the method used in the request, for example:
1036
1037   GET  an entity corresponding to the requested resource is sent in the
1038      response;
1039
1040   HEAD  the entity-header fields corresponding to the requested
1041      resource are sent in the response without any message-body;
1042
1043   POST  an entity describing or containing the result of the action;
1044
1045   TRACE  an entity containing the request message as received by the
1046      end server.
1047
10489.2.2.  201 Created
1049
1050   The request has been fulfilled and resulted in a new resource being
1051   created.  The newly created resource can be referenced by the URI(s)
1052   returned in the entity of the response, with the most specific URI
1053   for the resource given by a Location header field.  The response
1054   SHOULD include an entity containing a list of resource
1055   characteristics and location(s) from which the user or user agent can
1056   choose the one most appropriate.  The entity format is specified by
1057   the media type given in the Content-Type header field.  The origin
1058   server MUST create the resource before returning the 201 status code.
1059   If the action cannot be carried out immediately, the server SHOULD
1060
1061
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1067
1068   respond with 202 (Accepted) response instead.
1069
1070   A 201 response MAY contain an ETag response header field indicating
1071   the current value of the entity tag for the requested variant just
1072   created, see Section 7.1 of [Part4].
1073
10749.2.3.  202 Accepted
1075
1076   The request has been accepted for processing, but the processing has
1077   not been completed.  The request might or might not eventually be
1078   acted upon, as it might be disallowed when processing actually takes
1079   place.  There is no facility for re-sending a status code from an
1080   asynchronous operation such as this.
1081
1082   The 202 response is intentionally non-committal.  Its purpose is to
1083   allow a server to accept a request for some other process (perhaps a
1084   batch-oriented process that is only run once per day) without
1085   requiring that the user agent's connection to the server persist
1086   until the process is completed.  The entity returned with this
1087   response SHOULD include an indication of the request's current status
1088   and either a pointer to a status monitor or some estimate of when the
1089   user can expect the request to be fulfilled.
1090
10919.2.4.  203 Non-Authoritative Information
1092
1093   The returned metainformation in the entity-header is not the
1094   definitive set as available from the origin server, but is gathered
1095   from a local or a third-party copy.  The set presented MAY be a
1096   subset or superset of the original version.  For example, including
1097   local annotation information about the resource might result in a
1098   superset of the metainformation known by the origin server.  Use of
1099   this response code is not required and is only appropriate when the
1100   response would otherwise be 200 (OK).
1101
11029.2.5.  204 No Content
1103
1104   The server has fulfilled the request but does not need to return an
1105   entity-body, and might want to return updated metainformation.  The
1106   response MAY include new or updated metainformation in the form of
1107   entity-headers, which if present SHOULD be associated with the
1108   requested variant.
1109
1110   If the client is a user agent, it SHOULD NOT change its document view
1111   from that which caused the request to be sent.  This response is
1112   primarily intended to allow input for actions to take place without
1113   causing a change to the user agent's active document view, although
1114   any new or updated metainformation SHOULD be applied to the document
1115   currently in the user agent's active view.
1116
1117
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1123
1124   The 204 response MUST NOT include a message-body, and thus is always
1125   terminated by the first empty line after the header fields.
1126
11279.2.6.  205 Reset Content
1128
1129   The server has fulfilled the request and the user agent SHOULD reset
1130   the document view which caused the request to be sent.  This response
1131   is primarily intended to allow input for actions to take place via
1132   user input, followed by a clearing of the form in which the input is
1133   given so that the user can easily initiate another input action.  The
1134   response MUST NOT include an entity.
1135
11369.2.7.  206 Partial Content
1137
1138   The server has fulfilled the partial GET request for the resource and
1139   the enclosed entity is a partial representation as defined in
1140   [Part5].
1141
11429.3.  Redirection 3xx
1143
1144   This class of status code indicates that further action needs to be
1145   taken by the user agent in order to fulfill the request.  The action
1146   required MAY be carried out by the user agent without interaction
1147   with the user if and only if the method used in the second request is
1148   GET or HEAD.  A client SHOULD detect infinite redirection loops,
1149   since such loops generate network traffic for each redirection.
1150
1151      Note: previous versions of this specification recommended a
1152      maximum of five redirections.  Content developers should be aware
1153      that there might be clients that implement such a fixed
1154      limitation.
1155
11569.3.1.  300 Multiple Choices
1157
1158   The requested resource corresponds to any one of a set of
1159   representations, each with its own specific location, and agent-
1160   driven negotiation information (Section 5 of [Part3]) is being
1161   provided so that the user (or user agent) can select a preferred
1162   representation and redirect its request to that location.
1163
1164   Unless it was a HEAD request, the response SHOULD include an entity
1165   containing a list of resource characteristics and location(s) from
1166   which the user or user agent can choose the one most appropriate.
1167   The entity format is specified by the media type given in the
1168   Content-Type header field.  Depending upon the format and the
1169   capabilities of the user agent, selection of the most appropriate
1170   choice MAY be performed automatically.  However, this specification
1171   does not define any standard for such automatic selection.
1172
1173
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1179
1180   If the server has a preferred choice of representation, it SHOULD
1181   include the specific URI for that representation in the Location
1182   field; user agents MAY use the Location field value for automatic
1183   redirection.  This response is cacheable unless indicated otherwise.
1184
11859.3.2.  301 Moved Permanently
1186
1187   The requested resource has been assigned a new permanent URI and any
1188   future references to this resource SHOULD use one of the returned
1189   URIs.  Clients with link editing capabilities ought to automatically
1190   re-link references to the Request-URI to one or more of the new
1191   references returned by the server, where possible.  This response is
1192   cacheable unless indicated otherwise.
1193
1194   The new permanent URI SHOULD be given by the Location field in the
1195   response.  Unless the request method was HEAD, the entity of the
1196   response SHOULD contain a short hypertext note with a hyperlink to
1197   the new URI(s).
1198
1199   If the 301 status code is received in response to a request method
1200   that is known to be "safe", as defined in Section 8.1.1, then the
1201   request MAY be automatically redirected by the user agent without
1202   confirmation.  Otherwise, the user agent MUST NOT automatically
1203   redirect the request unless it can be confirmed by the user, since
1204   this might change the conditions under which the request was issued.
1205
1206      Note: When automatically redirecting a POST request after
1207      receiving a 301 status code, some existing HTTP/1.0 user agents
1208      will erroneously change it into a GET request.
1209
12109.3.3.  302 Found
1211
1212   The requested resource resides temporarily under a different URI.
1213   Since the redirection might be altered on occasion, the client SHOULD
1214   continue to use the Request-URI for future requests.  This response
1215   is only cacheable if indicated by a Cache-Control or Expires header
1216   field.
1217
1218   The temporary URI SHOULD be given by the Location field in the
1219   response.  Unless the request method was HEAD, the entity of the
1220   response SHOULD contain a short hypertext note with a hyperlink to
1221   the new URI(s).
1222
1223   If the 302 status code is received in response to a request method
1224   that is known to be "safe", as defined in Section 8.1.1, then the
1225   request MAY be automatically redirected by the user agent without
1226   confirmation.  Otherwise, the user agent MUST NOT automatically
1227   redirect the request unless it can be confirmed by the user, since
1228
1229
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1235
1236   this might change the conditions under which the request was issued.
1237
1238      Note: [RFC1945] and [RFC2068] specify that the client is not
1239      allowed to change the method on the redirected request.  However,
1240      most existing user agent implementations treat 302 as if it were a
1241      303 response, performing a GET on the Location field-value
1242      regardless of the original request method.  The status codes 303
1243      and 307 have been added for servers that wish to make
1244      unambiguously clear which kind of reaction is expected of the
1245      client.
1246
12479.3.4.  303 See Other
1248
1249   The response to the request can be found under a different URI and
1250   SHOULD be retrieved using a GET method on that resource.  This method
1251   exists primarily to allow the output of a POST-activated script to
1252   redirect the user agent to a selected resource.  The new URI is not a
1253   substitute reference for the originally requested resource.  The 303
1254   response MUST NOT be cached, but the response to the second
1255   (redirected) request might be cacheable.
1256
1257   The different URI SHOULD be given by the Location field in the
1258   response.  Unless the request method was HEAD, the entity of the
1259   response SHOULD contain a short hypertext note with a hyperlink to
1260   the new URI(s).
1261
1262      Note: Many pre-HTTP/1.1 user agents do not understand the 303
1263      status.  When interoperability with such clients is a concern, the
1264      302 status code may be used instead, since most user agents react
1265      to a 302 response as described here for 303.
1266
12679.3.5.  304 Not Modified
1268
1269   The response to the request has not been modified since the
1270   conditions indicated by the client's conditional GET request, as
1271   defined in [Part4].
1272
12739.3.6.  305 Use Proxy
1274
1275   The requested resource MUST be accessed through the proxy given by
1276   the Location field.  The Location field gives the URI of the proxy.
1277   The recipient is expected to repeat this single request via the
1278   proxy. 305 responses MUST only be generated by origin servers.
1279
1280      Note: [RFC2068] was not clear that 305 was intended to redirect a
1281      single request, and to be generated by origin servers only.  Not
1282      observing these limitations has significant security consequences.
1283
1284
1285
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1291
12929.3.7.  306 (Unused)
1293
1294   The 306 status code was used in a previous version of the
1295   specification, is no longer used, and the code is reserved.
1296
12979.3.8.  307 Temporary Redirect
1298
1299   The requested resource resides temporarily under a different URI.
1300   Since the redirection MAY be altered on occasion, the client SHOULD
1301   continue to use the Request-URI for future requests.  This response
1302   is only cacheable if indicated by a Cache-Control or Expires header
1303   field.
1304
1305   The temporary URI SHOULD be given by the Location field in the
1306   response.  Unless the request method was HEAD, the entity of the
1307   response SHOULD contain a short hypertext note with a hyperlink to
1308   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1309   understand the 307 status.  Therefore, the note SHOULD contain the
1310   information necessary for a user to repeat the original request on
1311   the new URI.
1312
1313   If the 307 status code is received in response to a request method
1314   that is known to be "safe", as defined in Section 8.1.1, then the
1315   request MAY be automatically redirected by the user agent without
1316   confirmation.  Otherwise, the user agent MUST NOT automatically
1317   redirect the request unless it can be confirmed by the user, since
1318   this might change the conditions under which the request was issued.
1319
13209.4.  Client Error 4xx
1321
1322   The 4xx class of status code is intended for cases in which the
1323   client seems to have erred.  Except when responding to a HEAD
1324   request, the server SHOULD include an entity containing an
1325   explanation of the error situation, and whether it is a temporary or
1326   permanent condition.  These status codes are applicable to any
1327   request method.  User agents SHOULD display any included entity to
1328   the user.
1329
1330   If the client is sending data, a server implementation using TCP
1331   SHOULD be careful to ensure that the client acknowledges receipt of
1332   the packet(s) containing the response, before the server closes the
1333   input connection.  If the client continues sending data to the server
1334   after the close, the server's TCP stack will send a reset packet to
1335   the client, which may erase the client's unacknowledged input buffers
1336   before they can be read and interpreted by the HTTP application.
1337
1338
1339
1340
1341
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1347
13489.4.1.  400 Bad Request
1349
1350   The request could not be understood by the server due to malformed
1351   syntax.  The client SHOULD NOT repeat the request without
1352   modifications.
1353
13549.4.2.  401 Unauthorized
1355
1356   The request requires user authentication (see [Part7]).
1357
13589.4.3.  402 Payment Required
1359
1360   This code is reserved for future use.
1361
13629.4.4.  403 Forbidden
1363
1364   The server understood the request, but is refusing to fulfill it.
1365   Authorization will not help and the request SHOULD NOT be repeated.
1366   If the request method was not HEAD and the server wishes to make
1367   public why the request has not been fulfilled, it SHOULD describe the
1368   reason for the refusal in the entity.  If the server does not wish to
1369   make this information available to the client, the status code 404
1370   (Not Found) can be used instead.
1371
13729.4.5.  404 Not Found
1373
1374   The server has not found anything matching the Request-URI.  No
1375   indication is given of whether the condition is temporary or
1376   permanent.  The 410 (Gone) status code SHOULD be used if the server
1377   knows, through some internally configurable mechanism, that an old
1378   resource is permanently unavailable and has no forwarding address.
1379   This status code is commonly used when the server does not wish to
1380   reveal exactly why the request has been refused, or when no other
1381   response is applicable.
1382
13839.4.6.  405 Method Not Allowed
1384
1385   The method specified in the Request-Line is not allowed for the
1386   resource identified by the Request-URI.  The response MUST include an
1387   Allow header containing a list of valid methods for the requested
1388   resource.
1389
13909.4.7.  406 Not Acceptable
1391
1392   The resource identified by the request is only capable of generating
1393   response entities which have content characteristics not acceptable
1394   according to the accept headers sent in the request.
1395
1396
1397
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1403
1404   Unless it was a HEAD request, the response SHOULD include an entity
1405   containing a list of available entity characteristics and location(s)
1406   from which the user or user agent can choose the one most
1407   appropriate.  The entity format is specified by the media type given
1408   in the Content-Type header field.  Depending upon the format and the
1409   capabilities of the user agent, selection of the most appropriate
1410   choice MAY be performed automatically.  However, this specification
1411   does not define any standard for such automatic selection.
1412
1413      Note: HTTP/1.1 servers are allowed to return responses which are
1414      not acceptable according to the accept headers sent in the
1415      request.  In some cases, this may even be preferable to sending a
1416      406 response.  User agents are encouraged to inspect the headers
1417      of an incoming response to determine if it is acceptable.
1418
1419   If the response could be unacceptable, a user agent SHOULD
1420   temporarily stop receipt of more data and query the user for a
1421   decision on further actions.
1422
14239.4.8.  407 Proxy Authentication Required
1424
1425   This code is similar to 401 (Unauthorized), but indicates that the
1426   client must first authenticate itself with the proxy (see [Part7]).
1427
14289.4.9.  408 Request Timeout
1429
1430   The client did not produce a request within the time that the server
1431   was prepared to wait.  The client MAY repeat the request without
1432   modifications at any later time.
1433
14349.4.10.  409 Conflict
1435
1436   The request could not be completed due to a conflict with the current
1437   state of the resource.  This code is only allowed in situations where
1438   it is expected that the user might be able to resolve the conflict
1439   and resubmit the request.  The response body SHOULD include enough
1440   information for the user to recognize the source of the conflict.
1441   Ideally, the response entity would include enough information for the
1442   user or user agent to fix the problem; however, that might not be
1443   possible and is not required.
1444
1445   Conflicts are most likely to occur in response to a PUT request.  For
1446   example, if versioning were being used and the entity being PUT
1447   included changes to a resource which conflict with those made by an
1448   earlier (third-party) request, the server might use the 409 response
1449   to indicate that it can't complete the request.  In this case, the
1450   response entity would likely contain a list of the differences
1451   between the two versions in a format defined by the response Content-
1452
1453
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1459
1460   Type.
1461
14629.4.11.  410 Gone
1463
1464   The requested resource is no longer available at the server and no
1465   forwarding address is known.  This condition is expected to be
1466   considered permanent.  Clients with link editing capabilities SHOULD
1467   delete references to the Request-URI after user approval.  If the
1468   server does not know, or has no facility to determine, whether or not
1469   the condition is permanent, the status code 404 (Not Found) SHOULD be
1470   used instead.  This response is cacheable unless indicated otherwise.
1471
1472   The 410 response is primarily intended to assist the task of web
1473   maintenance by notifying the recipient that the resource is
1474   intentionally unavailable and that the server owners desire that
1475   remote links to that resource be removed.  Such an event is common
1476   for limited-time, promotional services and for resources belonging to
1477   individuals no longer working at the server's site.  It is not
1478   necessary to mark all permanently unavailable resources as "gone" or
1479   to keep the mark for any length of time -- that is left to the
1480   discretion of the server owner.
1481
14829.4.12.  411 Length Required
1483
1484   The server refuses to accept the request without a defined Content-
1485   Length.  The client MAY repeat the request if it adds a valid
1486   Content-Length header field containing the length of the message-body
1487   in the request message.
1488
14899.4.13.  412 Precondition Failed
1490
1491   The precondition given in one or more of the request-header fields
1492   evaluated to false when it was tested on the server, as defined in
1493   [Part4].
1494
14959.4.14.  413 Request Entity Too Large
1496
1497   The server is refusing to process a request because the request
1498   entity is larger than the server is willing or able to process.  The
1499   server MAY close the connection to prevent the client from continuing
1500   the request.
1501
1502   If the condition is temporary, the server SHOULD include a Retry-
1503   After header field to indicate that it is temporary and after what
1504   time the client MAY try again.
1505
1506
1507
1508
1509
1510
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1514
1515
15169.4.15.  414 Request-URI Too Long
1517
1518   The server is refusing to service the request because the Request-URI
1519   is longer than the server is willing to interpret.  This rare
1520   condition is only likely to occur when a client has improperly
1521   converted a POST request to a GET request with long query
1522   information, when the client has descended into a URI "black hole" of
1523   redirection (e.g., a redirected URI prefix that points to a suffix of
1524   itself), or when the server is under attack by a client attempting to
1525   exploit security holes present in some servers using fixed-length
1526   buffers for reading or manipulating the Request-URI.
1527
15289.4.16.  415 Unsupported Media Type
1529
1530   The server is refusing to service the request because the entity of
1531   the request is in a format not supported by the requested resource
1532   for the requested method.
1533
15349.4.17.  416 Requested Range Not Satisfiable
1535
1536   The request included a Range request-header field (Section 6.4 of
1537   [Part5]) and none of the range-specifier values in this field overlap
1538   the current extent of the selected resource.
1539
15409.4.18.  417 Expectation Failed
1541
1542   The expectation given in an Expect request-header field (see
1543   Section 10.2) could not be met by this server, or, if the server is a
1544   proxy, the server has unambiguous evidence that the request could not
1545   be met by the next-hop server.
1546
15479.5.  Server Error 5xx
1548
1549   Response status codes beginning with the digit "5" indicate cases in
1550   which the server is aware that it has erred or is incapable of
1551   performing the request.  Except when responding to a HEAD request,
1552   the server SHOULD include an entity containing an explanation of the
1553   error situation, and whether it is a temporary or permanent
1554   condition.  User agents SHOULD display any included entity to the
1555   user.  These response codes are applicable to any request method.
1556
15579.5.1.  500 Internal Server Error
1558
1559   The server encountered an unexpected condition which prevented it
1560   from fulfilling the request.
1561
1562
1563
1564
1565
1566
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1570
1571
15729.5.2.  501 Not Implemented
1573
1574   The server does not support the functionality required to fulfill the
1575   request.  This is the appropriate response when the server does not
1576   recognize the request method and is not capable of supporting it for
1577   any resource.
1578
15799.5.3.  502 Bad Gateway
1580
1581   The server, while acting as a gateway or proxy, received an invalid
1582   response from the upstream server it accessed in attempting to
1583   fulfill the request.
1584
15859.5.4.  503 Service Unavailable
1586
1587   The server is currently unable to handle the request due to a
1588   temporary overloading or maintenance of the server.  The implication
1589   is that this is a temporary condition which will be alleviated after
1590   some delay.  If known, the length of the delay MAY be indicated in a
1591   Retry-After header.  If no Retry-After is given, the client SHOULD
1592   handle the response as it would for a 500 response.
1593
1594      Note: The existence of the 503 status code does not imply that a
1595      server must use it when becoming overloaded.  Some servers may
1596      wish to simply refuse the connection.
1597
15989.5.5.  504 Gateway Timeout
1599
1600   The server, while acting as a gateway or proxy, did not receive a
1601   timely response from the upstream server specified by the URI (e.g.
1602   HTTP, FTP, LDAP) or some other auxiliary server (e.g.  DNS) it needed
1603   to access in attempting to complete the request.
1604
1605      Note: Note to implementors: some deployed proxies are known to
1606      return 400 or 500 when DNS lookups time out.
1607
16089.5.6.  505 HTTP Version Not Supported
1609
1610   The server does not support, or refuses to support, the protocol
1611   version that was used in the request message.  The server is
1612   indicating that it is unable or unwilling to complete the request
1613   using the same major version as the client, as described in Section
1614   3.1 of [Part1], other than with this error message.  The response
1615   SHOULD contain an entity describing why that version is not supported
1616   and what other protocols are supported by that server.
1617
1618
1619
1620
1621
1622
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1626
1627
162810.  Header Field Definitions
1629
1630   This section defines the syntax and semantics of HTTP/1.1 header
1631   fields related to request and response semantics.
1632
1633   For entity-header fields, both sender and recipient refer to either
1634   the client or the server, depending on who sends and who receives the
1635   entity.
1636
163710.1.  Allow
1638
1639   The Allow entity-header field lists the set of methods supported by
1640   the resource identified by the Request-URI.  The purpose of this
1641   field is strictly to inform the recipient of valid methods associated
1642   with the resource.  An Allow header field MUST be present in a 405
1643   (Method Not Allowed) response.
1644
1645     Allow   = "Allow" ":" #Method
1646
1647   Example of use:
1648
1649          Allow: GET, HEAD, PUT
1650
1651   This field cannot prevent a client from trying other methods.
1652   However, the indications given by the Allow header field value SHOULD
1653   be followed.  The actual set of allowed methods is defined by the
1654   origin server at the time of each request.
1655
1656   The Allow header field MAY be provided with a PUT request to
1657   recommend the methods to be supported by the new or modified
1658   resource.  The server is not required to support these methods and
1659   SHOULD include an Allow header in the response giving the actual
1660   supported methods.
1661
1662   A proxy MUST NOT modify the Allow header field even if it does not
1663   understand all the methods specified, since the user agent might have
1664   other means of communicating with the origin server.
1665
166610.2.  Expect
1667
1668   The Expect request-header field is used to indicate that particular
1669   server behaviors are required by the client.
1670
1671     Expect       =  "Expect" ":" 1#expectation
1672
1673     expectation  =  "100-continue" | expectation-extension
1674     expectation-extension =  token [ "=" ( token | quoted-string )
1675                              *expect-params ]
1676
1677
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1682
1683
1684     expect-params =  ";" token [ "=" ( token | quoted-string ) ]
1685
1686   A server that does not understand or is unable to comply with any of
1687   the expectation values in the Expect field of a request MUST respond
1688   with appropriate error status.  The server MUST respond with a 417
1689   (Expectation Failed) status if any of the expectations cannot be met
1690   or, if there are other problems with the request, some other 4xx
1691   status.
1692
1693   This header field is defined with extensible syntax to allow for
1694   future extensions.  If a server receives a request containing an
1695   Expect field that includes an expectation-extension that it does not
1696   support, it MUST respond with a 417 (Expectation Failed) status.
1697
1698   Comparison of expectation values is case-insensitive for unquoted
1699   tokens (including the 100-continue token), and is case-sensitive for
1700   quoted-string expectation-extensions.
1701
1702   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST
1703   return a 417 (Expectation Failed) status if it receives a request
1704   with an expectation that it cannot meet.  However, the Expect
1705   request-header itself is end-to-end; it MUST be forwarded if the
1706   request is forwarded.
1707
1708   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1709   Expect header.
1710
1711   See Section 7.2.3 of [Part1] for the use of the 100 (Continue)
1712   status.
1713
171410.3.  From
1715
1716   The From request-header field, if given, SHOULD contain an Internet
1717   e-mail address for the human user who controls the requesting user
1718   agent.  The address SHOULD be machine-usable, as defined by "mailbox"
1719   in Section 3.4 of [RFC2822]:
1720
1721     From    = "From" ":" mailbox
1722
1723     mailbox = <mailbox, defined in [RFC2822], Section 3.4>
1724
1725   An example is:
1726
1727       From: webmaster@example.org
1728
1729   This header field MAY be used for logging purposes and as a means for
1730   identifying the source of invalid or unwanted requests.  It SHOULD
1731   NOT be used as an insecure form of access protection.  The
1732
1733
1734
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1738
1739
1740   interpretation of this field is that the request is being performed
1741   on behalf of the person given, who accepts responsibility for the
1742   method performed.  In particular, robot agents SHOULD include this
1743   header so that the person responsible for running the robot can be
1744   contacted if problems occur on the receiving end.
1745
1746   The Internet e-mail address in this field MAY be separate from the
1747   Internet host which issued the request.  For example, when a request
1748   is passed through a proxy the original issuer's address SHOULD be
1749   used.
1750
1751   The client SHOULD NOT send the From header field without the user's
1752   approval, as it might conflict with the user's privacy interests or
1753   their site's security policy.  It is strongly recommended that the
1754   user be able to disable, enable, and modify the value of this field
1755   at any time prior to a request.
1756
175710.4.  Location
1758
1759   The Location response-header field is used to redirect the recipient
1760   to a location other than the Request-URI for completion of the
1761   request or identification of a new resource.  For 201 (Created)
1762   responses, the Location is that of the new resource which was created
1763   by the request.  For 3xx responses, the location SHOULD indicate the
1764   server's preferred URI for automatic redirection to the resource.
1765   The field value consists of a single absolute URI.
1766
1767     Location       = "Location" ":" absoluteURI [ "#" fragment ]
1768
1769   An example is:
1770
1771       Location: http://www.example.org/pub/WWW/People.html
1772
1773      Note: The Content-Location header field (Section 6.7 of [Part3])
1774      differs from Location in that the Content-Location identifies the
1775      original location of the entity enclosed in the request.  It is
1776      therefore possible for a response to contain header fields for
1777      both Location and Content-Location.
1778
1779   There are circumstances in which a fragment identifier in a Location
1780   URL would not be appropriate:
1781
1782   o  With a 201 Created response, because in this usage the Location
1783      header specifies the URL for the entire created resource.
1784
1785   o  With a 300 Multiple Choices, since the choice decision is intended
1786      to be made on resource characteristics and not fragment
1787      characteristics.
1788
1789
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1794
1795
1796   o  With 305 Use Proxy.
1797
179810.5.  Max-Forwards
1799
1800   The Max-Forwards request-header field provides a mechanism with the
1801   TRACE (Section 8.8) and OPTIONS (Section 8.2) methods to limit the
1802   number of proxies or gateways that can forward the request to the
1803   next inbound server.  This can be useful when the client is
1804   attempting to trace a request chain which appears to be failing or
1805   looping in mid-chain.
1806
1807     Max-Forwards   = "Max-Forwards" ":" 1*DIGIT
1808
1809   The Max-Forwards value is a decimal integer indicating the remaining
1810   number of times this request message may be forwarded.
1811
1812   Each proxy or gateway recipient of a TRACE or OPTIONS request
1813   containing a Max-Forwards header field MUST check and update its
1814   value prior to forwarding the request.  If the received value is zero
1815   (0), the recipient MUST NOT forward the request; instead, it MUST
1816   respond as the final recipient.  If the received Max-Forwards value
1817   is greater than zero, then the forwarded message MUST contain an
1818   updated Max-Forwards field with a value decremented by one (1).
1819
1820   The Max-Forwards header field MAY be ignored for all other methods
1821   defined by this specification and for any extension methods for which
1822   it is not explicitly referred to as part of that method definition.
1823
182410.6.  Referer
1825
1826   The Referer[sic] request-header field allows the client to specify,
1827   for the server's benefit, the address (URI) of the resource from
1828   which the Request-URI was obtained (the "referrer", although the
1829   header field is misspelled.)  The Referer request-header allows a
1830   server to generate lists of back-links to resources for interest,
1831   logging, optimized caching, etc.  It also allows obsolete or mistyped
1832   links to be traced for maintenance.  The Referer field MUST NOT be
1833   sent if the Request-URI was obtained from a source that does not have
1834   its own URI, such as input from the user keyboard.
1835
1836     Referer        = "Referer" ":" ( absoluteURI | relativeURI )
1837
1838   Example:
1839
1840       Referer: http://www.example.org/hypertext/Overview.html
1841
1842   If the field value is a relative URI, it SHOULD be interpreted
1843   relative to the Request-URI.  The URI MUST NOT include a fragment.
1844
1845
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1850
1851
1852   See Section 12.2 for security considerations.
1853
185410.7.  Retry-After
1855
1856   The Retry-After response-header field can be used with a 503 (Service
1857   Unavailable) response to indicate how long the service is expected to
1858   be unavailable to the requesting client.  This field MAY also be used
1859   with any 3xx (Redirection) response to indicate the minimum time the
1860   user-agent is asked wait before issuing the redirected request.  The
1861   value of this field can be either an HTTP-date or an integer number
1862   of seconds (in decimal) after the time of the response.
1863
1864     Retry-After   = "Retry-After" ":" ( HTTP-date | delta-seconds )
1865
1866   Time spans are non-negative decimal integers, representing time in
1867   seconds.
1868
1869     delta-seconds  = 1*DIGIT
1870
1871   Two examples of its use are
1872
1873       Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
1874       Retry-After: 120
1875
1876   In the latter example, the delay is 2 minutes.
1877
187810.8.  Server
1879
1880   The Server response-header field contains information about the
1881   software used by the origin server to handle the request.  The field
1882   can contain multiple product tokens (Section 3.5 of [Part1]) and
1883   comments identifying the server and any significant subproducts.  The
1884   product tokens are listed in order of their significance for
1885   identifying the application.
1886
1887     Server         = "Server" ":" 1*( product | comment )
1888
1889   Example:
1890
1891       Server: CERN/3.0 libwww/2.17
1892
1893   If the response is being forwarded through a proxy, the proxy
1894   application MUST NOT modify the Server response-header.  Instead, it
1895   MUST include a Via field (as described in Section 8.9 of [Part1]).
1896
1897      Note: Revealing the specific software version of the server might
1898      allow the server machine to become more vulnerable to attacks
1899      against software that is known to contain security holes.  Server
1900
1901
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1906
1907
1908      implementors are encouraged to make this field a configurable
1909      option.
1910
191110.9.  User-Agent
1912
1913   The User-Agent request-header field contains information about the
1914   user agent originating the request.  This is for statistical
1915   purposes, the tracing of protocol violations, and automated
1916   recognition of user agents for the sake of tailoring responses to
1917   avoid particular user agent limitations.  User agents SHOULD include
1918   this field with requests.  The field can contain multiple product
1919   tokens (Section 3.5 of [Part1]) and comments identifying the agent
1920   and any subproducts which form a significant part of the user agent.
1921   By convention, the product tokens are listed in order of their
1922   significance for identifying the application.
1923
1924     User-Agent     = "User-Agent" ":" 1*( product | comment )
1925
1926   Example:
1927
1928       User-Agent: CERN-LineMode/2.15 libwww/2.17b3
1929
1930
193111.  IANA Considerations
1932
1933   [[anchor1: TBD.]]
1934
1935
193612.  Security Considerations
1937
1938   This section is meant to inform application developers, information
1939   providers, and users of the security limitations in HTTP/1.1 as
1940   described by this document.  The discussion does not include
1941   definitive solutions to the problems revealed, though it does make
1942   some suggestions for reducing security risks.
1943
194412.1.  Transfer of Sensitive Information
1945
1946   Like any generic data transfer protocol, HTTP cannot regulate the
1947   content of the data that is transferred, nor is there any a priori
1948   method of determining the sensitivity of any particular piece of
1949   information within the context of any given request.  Therefore,
1950   applications SHOULD supply as much control over this information as
1951   possible to the provider of that information.  Four header fields are
1952   worth special mention in this context: Server, Via, Referer and From.
1953
1954   Revealing the specific software version of the server might allow the
1955   server machine to become more vulnerable to attacks against software
1956
1957
1958
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1962
1963
1964   that is known to contain security holes.  Implementors SHOULD make
1965   the Server header field a configurable option.
1966
1967   Proxies which serve as a portal through a network firewall SHOULD
1968   take special precautions regarding the transfer of header information
1969   that identifies the hosts behind the firewall.  In particular, they
1970   SHOULD remove, or replace with sanitized versions, any Via fields
1971   generated behind the firewall.
1972
1973   The Referer header allows reading patterns to be studied and reverse
1974   links drawn.  Although it can be very useful, its power can be abused
1975   if user details are not separated from the information contained in
1976   the Referer.  Even when the personal information has been removed,
1977   the Referer header might indicate a private document's URI whose
1978   publication would be inappropriate.
1979
1980   The information sent in the From field might conflict with the user's
1981   privacy interests or their site's security policy, and hence it
1982   SHOULD NOT be transmitted without the user being able to disable,
1983   enable, and modify the contents of the field.  The user MUST be able
1984   to set the contents of this field within a user preference or
1985   application defaults configuration.
1986
1987   We suggest, though do not require, that a convenient toggle interface
1988   be provided for the user to enable or disable the sending of From and
1989   Referer information.
1990
1991   The User-Agent (Section 10.9) or Server (Section 10.8) header fields
1992   can sometimes be used to determine that a specific client or server
1993   have a particular security hole which might be exploited.
1994   Unfortunately, this same information is often used for other valuable
1995   purposes for which HTTP currently has no better mechanism.
1996
199712.2.  Encoding Sensitive Information in URIs
1998
1999   Because the source of a link might be private information or might
2000   reveal an otherwise private information source, it is strongly
2001   recommended that the user be able to select whether or not the
2002   Referer field is sent.  For example, a browser client could have a
2003   toggle switch for browsing openly/anonymously, which would
2004   respectively enable/disable the sending of Referer and From
2005   information.
2006
2007   Clients SHOULD NOT include a Referer header field in a (non-secure)
2008   HTTP request if the referring page was transferred with a secure
2009   protocol.
2010
2011   Authors of services should not use GET-based forms for the submission
2012
2013
2014
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2018
2019
2020   of sensitive data because that data will be encoded in the Request-
2021   URI.  Many existing servers, proxies, and user agents log or display
2022   the Request-URI in places where it might be visible to third parties.
2023   Such services can use POST-based form submission instead.
2024
202512.3.  Location Headers and Spoofing
2026
2027   If a single server supports multiple organizations that do not trust
2028   one another, then it MUST check the values of Location and Content-
2029   Location headers in responses that are generated under control of
2030   said organizations to make sure that they do not attempt to
2031   invalidate resources over which they have no authority.
2032
2033
203413.  Acknowledgments
2035
2036
203714.  References
2038
203914.1.  Normative References
2040
2041   [Part1]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
2042              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
2043              and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections,
2044              and Message Parsing", draft-ietf-httpbis-p1-messaging-02
2045              (work in progress), February 2008.
2046
2047   [Part3]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
2048              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
2049              and J. Reschke, Ed., "HTTP/1.1, part 3: Message Payload
2050              and Content Negotiation", draft-ietf-httpbis-p3-payload-02
2051              (work in progress), February 2008.
2052
2053   [Part4]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
2054              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
2055              and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional
2056              Requests", draft-ietf-httpbis-p4-conditional-02 (work in
2057              progress), February 2008.
2058
2059   [Part5]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
2060              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
2061              and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and
2062              Partial Responses", draft-ietf-httpbis-p5-range-02 (work
2063              in progress), February 2008.
2064
2065   [Part6]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
2066              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
2067              and J. Reschke, Ed., "HTTP/1.1, part 6: Caching",
2068
2069
2070
2071Fielding, et al.         Expires August 27, 2008               [Page 37]
2072
2073Internet-Draft              HTTP/1.1, Part 2               February 2008
2074
2075
2076              draft-ietf-httpbis-p6-cache-02 (work in progress),
2077              February 2008.
2078
2079   [Part7]    Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
2080              Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
2081              and J. Reschke, Ed., "HTTP/1.1, part 7: Authentication",
2082              draft-ietf-httpbis-p7-auth-02 (work in progress),
2083              February 2008.
2084
2085   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
2086              Requirement Levels", BCP 14, RFC 2119, March 1997.
2087
208814.2.  Informative References
2089
2090   [Luo1998]  Luotonen, A., "Tunneling TCP based protocols through Web
2091              proxy servers", draft-luotonen-web-proxy-tunneling-01
2092              (work in progress), August 1998.
2093
2094   [RFC1945]  Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext
2095              Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996.
2096
2097   [RFC2068]  Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T.
2098              Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
2099              RFC 2068, January 1997.
2100
2101   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
2102              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
2103              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
2104
2105   [RFC2822]  Resnick, P., "Internet Message Format", RFC 2822,
2106              April 2001.
2107
2108
2109Appendix A.  Compatibility with Previous Versions
2110
2111A.1.  Changes from RFC 2068
2112
2113   Clarified which error code should be used for inbound server failures
2114   (e.g.  DNS failures).  (Section 9.5.5).
2115
2116   201 (Created) had a race that required an Etag be sent when a
2117   resource is first created.  (Section 9.2.2).
2118
2119   Rewrite of message transmission requirements to make it much harder
2120   for implementors to get it wrong, as the consequences of errors here
2121   can have significant impact on the Internet, and to deal with the
2122   following problems:
2123
2124
2125
2126
2127Fielding, et al.         Expires August 27, 2008               [Page 38]
2128
2129Internet-Draft              HTTP/1.1, Part 2               February 2008
2130
2131
2132   1.  Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
2133       this was incorrectly placing a requirement on the behavior of an
2134       implementation of a future version of HTTP/1.x
2135
2136   2.  Made it clear that user-agents should retry requests, not
2137       "clients" in general.
2138
2139   3.  Converted requirements for clients to ignore unexpected 100
2140       (Continue) responses, and for proxies to forward 100 responses,
2141       into a general requirement for 1xx responses.
2142
2143   4.  Modified some TCP-specific language, to make it clearer that non-
2144       TCP transports are possible for HTTP.
2145
2146   5.  Require that the origin server MUST NOT wait for the request body
2147       before it sends a required 100 (Continue) response.
2148
2149   6.  Allow, rather than require, a server to omit 100 (Continue) if it
2150       has already seen some of the request body.
2151
2152   7.  Allow servers to defend against denial-of-service attacks and
2153       broken clients.
2154
2155   This change adds the Expect header and 417 status code.
2156
2157   Clean up confusion between 403 and 404 responses.  (Section 9.4.4,
2158   9.4.5, and 9.4.11)
2159
2160   The PATCH, LINK, UNLINK methods were defined but not commonly
2161   implemented in previous versions of this specification.  See
2162   [RFC2068].
2163
2164A.2.  Changes from RFC 2616
2165
2166   Clarify definition of POST.  (Section 8.5)
2167
2168   Failed to consider that there are many other request methods that are
2169   safe to automatically redirect, and further that the user agent is
2170   able to make that determination based on the request method
2171   semantics.  (Sections 9.3.2, 9.3.3 and 9.3.8 )
2172
2173   Correct syntax of Location header to allow fragment, as referred
2174   symbol wasn't what was expected, and add some clarifications as to
2175   when it would not be appropriate.  (Section 10.4)
2176
2177   In the description of the Server header, the Via field was described
2178   as a SHOULD.  The requirement was and is stated correctly in the
2179   description of the Via header in Section 8.9 of [Part1].
2180
2181
2182
2183Fielding, et al.         Expires August 27, 2008               [Page 39]
2184
2185Internet-Draft              HTTP/1.1, Part 2               February 2008
2186
2187
2188   (Section 10.8)
2189
2190
2191Appendix B.  Change Log (to be removed by RFC Editor before publication)
2192
2193B.1.  Since RFC2616
2194
2195   Extracted relevant partitions from [RFC2616].
2196
2197B.2.  Since draft-ietf-httpbis-p2-semantics-00
2198
2199   Closed issues:
2200
2201   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/5>: "Via is a
2202      MUST" (<http://purl.org/NET/http-errata#via-must>)
2203
2204   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/6>: "Fragments
2205      allowed in Location"
2206      (<http://purl.org/NET/http-errata#location-fragments>)
2207
2208   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/10>: "Safe
2209      Methods vs Redirection"
2210      (<http://purl.org/NET/http-errata#saferedirect>)
2211
2212   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/17>: "Revise
2213      description of the POST method"
2214      (<http://purl.org/NET/http-errata#post>)
2215
2216   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35>: "Normative
2217      and Informative references"
2218
2219   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/42>: "RFC2606
2220      Compliance"
2221
2222   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/65>:
2223      "Informative references"
2224
2225   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/84>: "Redundant
2226      cross-references"
2227
2228   Other changes:
2229
2230   o  Move definitions of 304 and 412 condition codes to [Part4]
2231
2232
2233
2234
2235
2236
2237
2238
2239Fielding, et al.         Expires August 27, 2008               [Page 40]
2240
2241Internet-Draft              HTTP/1.1, Part 2               February 2008
2242
2243
2244B.3.  Since draft-ietf-httpbis-p2-semantics-01
2245
2246   Closed issues:
2247
2248   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/21>: "PUT side
2249      effects"
2250
2251   o  <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/91>: "Duplicate
2252      Host header requirements"
2253
2254   Ongoing work on ABNF conversion
2255   (<http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36>):
2256
2257   o  Move "Product Tokens" section (back) into Part 1, as "token" is
2258      used in the definition of the Upgrade header.
2259
2260   o  Add explicit references to BNF syntax and rules imported from
2261      other parts of the specification.
2262
2263   o  Copy definition of delta-seconds from Part6 instead of referencing
2264      it.
2265
2266
2267Index
2268
2269   1
2270      100 Continue (status code)  18
2271      101 Switching Protocols (status code)  19
2272
2273   2
2274      200 OK (status code)  19
2275      201 Created (status code)  19
2276      202 Accepted (status code)  20
2277      203 Non-Authoritative Information (status code)  20
2278      204 No Content (status code)  20
2279      205 Reset Content (status code)  21
2280      206 Partial Content (status code)  21
2281
2282   3
2283      300 Multiple Choices (status code)  21
2284      301 Moved Permanently (status code)  22
2285      302 Found (status code)  22
2286      303 See Other (status code)  23
2287      304 Not Modified (status code)  23
2288      305 Use Proxy (status code)  23
2289      306 (Unused) (status code)  24
2290      307 Temporary Redirect (status code)  24
2291
2292
2293
2294
2295Fielding, et al.         Expires August 27, 2008               [Page 41]
2296
2297Internet-Draft              HTTP/1.1, Part 2               February 2008
2298
2299
2300   4
2301      400 Bad Request (status code)  25
2302      401 Unauthorized (status code)  25
2303      402 Payment Required (status code)  25
2304      403 Forbidden (status code)  25
2305      404 Not Found (status code)  25
2306      405 Method Not Allowed (status code)  25
2307      406 Not Acceptable (status code)  25
2308      407 Proxy Authentication Required (status code)  26
2309      408 Request Timeout (status code)  26
2310      409 Conflict (status code)  26
2311      410 Gone (status code)  27
2312      411 Length Required (status code)  27
2313      412 Precondition Failed (status code)  27
2314      413 Request Entity Too Large (status code)  27
2315      414 Request-URI Too Long (status code)  28
2316      415 Unsupported Media Type (status code)  28
2317      416 Requested Range Not Satisfiable (status code)  28
2318      417 Expectation Failed (status code)  28
2319
2320   5
2321      500 Internal Server Error (status code)  28
2322      501 Not Implemented (status code)  29
2323      502 Bad Gateway (status code)  29
2324      503 Service Unavailable (status code)  29
2325      504 Gateway Timeout (status code)  29
2326      505 HTTP Version Not Supported (status code)  29
2327
2328   A
2329      Allow header  30
2330
2331   C
2332      CONNECT method  18
2333
2334   D
2335      DELETE method  17
2336
2337   E
2338      Expect header  30
2339
2340   F
2341      From header  31
2342
2343   G
2344      GET method  14
2345      Grammar
2346         Allow  30
2347         delta-seconds  34
2348
2349
2350
2351Fielding, et al.         Expires August 27, 2008               [Page 42]
2352
2353Internet-Draft              HTTP/1.1, Part 2               February 2008
2354
2355
2356         Expect  30
2357         expect-params  30
2358         expectation  30
2359         expectation-extension  30
2360         extension-code  10
2361         extension-method  8
2362         From  31
2363         Location  32
2364         Max-Forwards  33
2365         Method  8
2366         Reason-Phrase  10
2367         Referer  33
2368         request-header  9
2369         response-header  11
2370         Retry-After  34
2371         Server  34
2372         Status-Code  10
2373         User-Agent  35
2374
2375   H
2376      HEAD method  14
2377      Headers
2378         Allow  30
2379         Expect  30
2380         From  31
2381         Location  32
2382         Max-Forwards  33
2383         Referer  33
2384         Retry-After  34
2385         Server  34
2386         User-Agent  35
2387
2388   L
2389      LINK method  39
2390      Location header  32
2391
2392   M
2393      Max-Forwards header  33
2394      Methods
2395         CONNECT  18
2396         DELETE  17
2397         GET  14
2398         HEAD  14
2399         LINK  39
2400         OPTIONS  13
2401         PATCH  39
2402         POST  15
2403         PUT  16
2404
2405
2406
2407Fielding, et al.         Expires August 27, 2008               [Page 43]
2408
2409Internet-Draft              HTTP/1.1, Part 2               February 2008
2410
2411
2412         TRACE  17
2413         UNLINK  39
2414
2415   O
2416      OPTIONS method  13
2417
2418   P
2419      PATCH method  39
2420      POST method  15
2421      PUT method  16
2422
2423   R
2424      Referer header  33
2425      Retry-After header  34
2426
2427   S
2428      Server header  34
2429      Status Codes
2430         100 Continue  18
2431         101 Switching Protocols  19
2432         200 OK  19
2433         201 Created  19
2434         202 Accepted  20
2435         203 Non-Authoritative Information  20
2436         204 No Content  20
2437         205 Reset Content  21
2438         206 Partial Content  21
2439         300 Multiple Choices  21
2440         301 Moved Permanently  22
2441         302 Found  22
2442         303 See Other  23
2443         304 Not Modified  23
2444         305 Use Proxy  23
2445         306 (Unused)  24
2446         307 Temporary Redirect  24
2447         400 Bad Request  25
2448         401 Unauthorized  25
2449         402 Payment Required  25
2450         403 Forbidden  25
2451         404 Not Found  25
2452         405 Method Not Allowed  25
2453         406 Not Acceptable  25
2454         407 Proxy Authentication Required  26
2455         408 Request Timeout  26
2456         409 Conflict  26
2457         410 Gone  27
2458         411 Length Required  27
2459         412 Precondition Failed  27
2460
2461
2462
2463Fielding, et al.         Expires August 27, 2008               [Page 44]
2464
2465Internet-Draft              HTTP/1.1, Part 2               February 2008
2466
2467
2468         413 Request Entity Too Large  27
2469         414 Request-URI Too Long  28
2470         415 Unsupported Media Type  28
2471         416 Requested Range Not Satisfiable  28
2472         417 Expectation Failed  28
2473         500 Internal Server Error  28
2474         501 Not Implemented  29
2475         502 Bad Gateway  29
2476         503 Service Unavailable  29
2477         504 Gateway Timeout  29
2478         505 HTTP Version Not Supported  29
2479
2480   T
2481      TRACE method  17
2482
2483   U
2484      UNLINK method  39
2485      User-Agent header  35
2486
2487
2488Authors' Addresses
2489
2490   Roy T. Fielding (editor)
2491   Day Software
2492   23 Corporate Plaza DR, Suite 280
2493   Newport Beach, CA  92660
2494   USA
2495
2496   Phone: +1-949-706-5300
2497   Fax:   +1-949-706-5305
2498   Email: fielding@gbiv.com
2499   URI:   http://roy.gbiv.com/
2500
2501
2502   Jim Gettys
2503   One Laptop per Child
2504   21 Oak Knoll Road
2505   Carlisle, MA  01741
2506   USA
2507
2508   Email: jg@laptop.org
2509   URI:   http://www.laptop.org/
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519Fielding, et al.         Expires August 27, 2008               [Page 45]
2520
2521Internet-Draft              HTTP/1.1, Part 2               February 2008
2522
2523
2524   Jeffrey C. Mogul
2525   Hewlett-Packard Company
2526   HP Labs, Large Scale Systems Group
2527   1501 Page Mill Road, MS 1177
2528   Palo Alto, CA  94304
2529   USA
2530
2531   Email: JeffMogul@acm.org
2532
2533
2534   Henrik Frystyk Nielsen
2535   Microsoft Corporation
2536   1 Microsoft Way
2537   Redmond, WA  98052
2538   USA
2539
2540   Email: henrikn@microsoft.com
2541
2542
2543   Larry Masinter
2544   Adobe Systems, Incorporated
2545   345 Park Ave
2546   San Jose, CA  95110
2547   USA
2548
2549   Email: LMM@acm.org
2550   URI:   http://larry.masinter.net/
2551
2552
2553   Paul J. Leach
2554   Microsoft Corporation
2555   1 Microsoft Way
2556   Redmond, WA  98052
2557
2558   Email: paulle@microsoft.com
2559
2560
2561   Tim Berners-Lee
2562   World Wide Web Consortium
2563   MIT Computer Science and Artificial Intelligence Laboratory
2564   The Stata Center, Building 32
2565   32 Vassar Street
2566   Cambridge, MA  02139
2567   USA
2568
2569   Email: timbl@w3.org
2570   URI:   http://www.w3.org/People/Berners-Lee/
2571
2572
2573
2574
2575Fielding, et al.         Expires August 27, 2008               [Page 46]
2576
2577Internet-Draft              HTTP/1.1, Part 2               February 2008
2578
2579
2580   Yves Lafon (editor)
2581   World Wide Web Consortium
2582   W3C / ERCIM
2583   2004, rte des Lucioles
2584   Sophia-Antipolis, AM  06902
2585   France
2586
2587   Email: ylafon@w3.org
2588   URI:   http://www.raubacapeu.net/people/yves/
2589
2590
2591   Julian F. Reschke (editor)
2592   greenbytes GmbH
2593   Hafenweg 16
2594   Muenster, NW  48155
2595   Germany
2596
2597   Phone: +49 251 2807760
2598   Fax:   +49 251 2807761
2599   Email: julian.reschke@greenbytes.de
2600   URI:   http://greenbytes.de/tech/webdav/
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631Fielding, et al.         Expires August 27, 2008               [Page 47]
2632
2633Internet-Draft              HTTP/1.1, Part 2               February 2008
2634
2635
2636Full Copyright Statement
2637
2638   Copyright (C) The IETF Trust (2008).
2639
2640   This document is subject to the rights, licenses and restrictions
2641   contained in BCP 78, and except as set forth therein, the authors
2642   retain all their rights.
2643
2644   This document and the information contained herein are provided on an
2645   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
2646   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
2647   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
2648   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
2649   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
2650   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
2651
2652
2653Intellectual Property
2654
2655   The IETF takes no position regarding the validity or scope of any
2656   Intellectual Property Rights or other rights that might be claimed to
2657   pertain to the implementation or use of the technology described in
2658   this document or the extent to which any license under such rights
2659   might or might not be available; nor does it represent that it has
2660   made any independent effort to identify any such rights.  Information
2661   on the procedures with respect to rights in RFC documents can be
2662   found in BCP 78 and BCP 79.
2663
2664   Copies of IPR disclosures made to the IETF Secretariat and any
2665   assurances of licenses to be made available, or the result of an
2666   attempt made to obtain a general license or permission for the use of
2667   such proprietary rights by implementers or users of this
2668   specification can be obtained from the IETF on-line IPR repository at
2669   http://www.ietf.org/ipr.
2670
2671   The IETF invites any interested party to bring to its attention any
2672   copyrights, patents or patent applications, or other proprietary
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2674   this standard.  Please address the information to the IETF at
2675   ietf-ipr@ietf.org.
2676
2677
2678Acknowledgment
2679
2680   Funding for the RFC Editor function is provided by the IETF
2681   Administrative Support Activity (IASA).
2682
2683
2684
2685
2686
2687Fielding, et al.         Expires August 27, 2008               [Page 48]
2688
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