idnits 2.17.1 draft-ietf-httpbis-p2-semantics-06.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** The document seems to lack a License Notice according IETF Trust Provisions of 28 Dec 2009, Section 6.b.i or Provisions of 12 Sep 2009 Section 6.b -- however, there's a paragraph with a matching beginning. Boilerplate error? (You're using the IETF Trust Provisions' Section 6.b License Notice from 12 Feb 2009 rather than one of the newer Notices. See https://trustee.ietf.org/license-info/.) Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The draft header indicates that this document updates RFC2817, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year (Using the creation date from RFC2817, updated by this document, for RFC5378 checks: 1998-11-18) -- The document seems to contain a disclaimer for pre-RFC5378 work, and may have content which was first submitted before 10 November 2008. The disclaimer is necessary when there are original authors that you have been unable to contact, or if some do not wish to grant the BCP78 rights to the IETF Trust. If you are able to get all authors (current and original) to grant those rights, you can and should remove the disclaimer; otherwise, the disclaimer is needed and you can ignore this comment. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (March 9, 2009) is 5520 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-26) exists of draft-ietf-httpbis-p1-messaging-06 == Outdated reference: A later version (-20) exists of draft-ietf-httpbis-p3-payload-06 == Outdated reference: A later version (-26) exists of draft-ietf-httpbis-p4-conditional-06 == Outdated reference: A later version (-26) exists of draft-ietf-httpbis-p5-range-06 == Outdated reference: A later version (-26) exists of draft-ietf-httpbis-p6-cache-06 == Outdated reference: A later version (-26) exists of draft-ietf-httpbis-p7-auth-06 -- Obsolete informational reference (is this intentional?): RFC 2068 (Obsoleted by RFC 2616) -- Obsolete informational reference (is this intentional?): RFC 2616 (Obsoleted by RFC 7230, RFC 7231, RFC 7232, RFC 7233, RFC 7234, RFC 7235) -- Obsolete informational reference (is this intentional?): RFC 5226 (Obsoleted by RFC 8126) Summary: 1 error (**), 0 flaws (~~), 7 warnings (==), 6 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 HTTPbis Working Group R. Fielding, Ed. 3 Internet-Draft Day Software 4 Obsoletes: 2616 (if approved) J. Gettys 5 Updates: 2817 (if approved) One Laptop per Child 6 Intended status: Standards Track J. Mogul 7 Expires: September 10, 2009 HP 8 H. Frystyk 9 Microsoft 10 L. Masinter 11 Adobe Systems 12 P. Leach 13 Microsoft 14 T. Berners-Lee 15 W3C/MIT 16 Y. Lafon, Ed. 17 W3C 18 J. Reschke, Ed. 19 greenbytes 20 March 9, 2009 22 HTTP/1.1, part 2: Message Semantics 23 draft-ietf-httpbis-p2-semantics-06 25 Status of this Memo 27 This Internet-Draft is submitted to IETF in full conformance with the 28 provisions of BCP 78 and BCP 79. This document may contain material 29 from IETF Documents or IETF Contributions published or made publicly 30 available before November 10, 2008. The person(s) controlling the 31 copyright in some of this material may not have granted the IETF 32 Trust the right to allow modifications of such material outside the 33 IETF Standards Process. Without obtaining an adequate license from 34 the person(s) controlling the copyright in such materials, this 35 document may not be modified outside the IETF Standards Process, and 36 derivative works of it may not be created outside the IETF Standards 37 Process, except to format it for publication as an RFC or to 38 translate it into languages other than English. 40 Internet-Drafts are working documents of the Internet Engineering 41 Task Force (IETF), its areas, and its working groups. Note that 42 other groups may also distribute working documents as Internet- 43 Drafts. 45 Internet-Drafts are draft documents valid for a maximum of six months 46 and may be updated, replaced, or obsoleted by other documents at any 47 time. It is inappropriate to use Internet-Drafts as reference 48 material or to cite them other than as "work in progress." 49 The list of current Internet-Drafts can be accessed at 50 http://www.ietf.org/ietf/1id-abstracts.txt. 52 The list of Internet-Draft Shadow Directories can be accessed at 53 http://www.ietf.org/shadow.html. 55 This Internet-Draft will expire on September 10, 2009. 57 Copyright Notice 59 Copyright (c) 2009 IETF Trust and the persons identified as the 60 document authors. All rights reserved. 62 This document is subject to BCP 78 and the IETF Trust's Legal 63 Provisions Relating to IETF Documents in effect on the date of 64 publication of this document (http://trustee.ietf.org/license-info). 65 Please review these documents carefully, as they describe your rights 66 and restrictions with respect to this document. 68 Abstract 70 The Hypertext Transfer Protocol (HTTP) is an application-level 71 protocol for distributed, collaborative, hypermedia information 72 systems. HTTP has been in use by the World Wide Web global 73 information initiative since 1990. This document is Part 2 of the 74 seven-part specification that defines the protocol referred to as 75 "HTTP/1.1" and, taken together, obsoletes RFC 2616. Part 2 defines 76 the semantics of HTTP messages as expressed by request methods, 77 request-header fields, response status codes, and response-header 78 fields. 80 Editorial Note (To be removed by RFC Editor) 82 Discussion of this draft should take place on the HTTPBIS working 83 group mailing list (ietf-http-wg@w3.org). The current issues list is 84 at and related 85 documents (including fancy diffs) can be found at 86 . 88 The changes in this draft are summarized in Appendix C.7. 90 Table of Contents 92 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6 93 1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 6 94 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 6 95 1.2.1. Core Rules . . . . . . . . . . . . . . . . . . . . . . 7 96 1.2.2. ABNF Rules defined in other Parts of the 97 Specification . . . . . . . . . . . . . . . . . . . . 7 98 2. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 99 2.1. Method Registry . . . . . . . . . . . . . . . . . . . . . 8 100 3. Request Header Fields . . . . . . . . . . . . . . . . . . . . 9 101 4. Status Code and Reason Phrase . . . . . . . . . . . . . . . . 10 102 4.1. Status Code Registry . . . . . . . . . . . . . . . . . . . 12 103 5. Response Header Fields . . . . . . . . . . . . . . . . . . . . 12 104 6. Entity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 105 7. Method Definitions . . . . . . . . . . . . . . . . . . . . . . 13 106 7.1. Safe and Idempotent Methods . . . . . . . . . . . . . . . 13 107 7.1.1. Safe Methods . . . . . . . . . . . . . . . . . . . . . 13 108 7.1.2. Idempotent Methods . . . . . . . . . . . . . . . . . . 14 109 7.2. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 14 110 7.3. GET . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 111 7.4. HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 112 7.5. POST . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 113 7.6. PUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 114 7.7. DELETE . . . . . . . . . . . . . . . . . . . . . . . . . . 18 115 7.8. TRACE . . . . . . . . . . . . . . . . . . . . . . . . . . 18 116 7.9. CONNECT . . . . . . . . . . . . . . . . . . . . . . . . . 19 117 8. Status Code Definitions . . . . . . . . . . . . . . . . . . . 19 118 8.1. Informational 1xx . . . . . . . . . . . . . . . . . . . . 19 119 8.1.1. 100 Continue . . . . . . . . . . . . . . . . . . . . . 20 120 8.1.2. 101 Switching Protocols . . . . . . . . . . . . . . . 20 121 8.2. Successful 2xx . . . . . . . . . . . . . . . . . . . . . . 20 122 8.2.1. 200 OK . . . . . . . . . . . . . . . . . . . . . . . . 20 123 8.2.2. 201 Created . . . . . . . . . . . . . . . . . . . . . 21 124 8.2.3. 202 Accepted . . . . . . . . . . . . . . . . . . . . . 21 125 8.2.4. 203 Non-Authoritative Information . . . . . . . . . . 21 126 8.2.5. 204 No Content . . . . . . . . . . . . . . . . . . . . 22 127 8.2.6. 205 Reset Content . . . . . . . . . . . . . . . . . . 22 128 8.2.7. 206 Partial Content . . . . . . . . . . . . . . . . . 22 129 8.3. Redirection 3xx . . . . . . . . . . . . . . . . . . . . . 22 130 8.3.1. 300 Multiple Choices . . . . . . . . . . . . . . . . . 23 131 8.3.2. 301 Moved Permanently . . . . . . . . . . . . . . . . 23 132 8.3.3. 302 Found . . . . . . . . . . . . . . . . . . . . . . 24 133 8.3.4. 303 See Other . . . . . . . . . . . . . . . . . . . . 24 134 8.3.5. 304 Not Modified . . . . . . . . . . . . . . . . . . . 25 135 8.3.6. 305 Use Proxy . . . . . . . . . . . . . . . . . . . . 25 136 8.3.7. 306 (Unused) . . . . . . . . . . . . . . . . . . . . . 25 137 8.3.8. 307 Temporary Redirect . . . . . . . . . . . . . . . . 25 139 8.4. Client Error 4xx . . . . . . . . . . . . . . . . . . . . . 26 140 8.4.1. 400 Bad Request . . . . . . . . . . . . . . . . . . . 26 141 8.4.2. 401 Unauthorized . . . . . . . . . . . . . . . . . . . 26 142 8.4.3. 402 Payment Required . . . . . . . . . . . . . . . . . 26 143 8.4.4. 403 Forbidden . . . . . . . . . . . . . . . . . . . . 26 144 8.4.5. 404 Not Found . . . . . . . . . . . . . . . . . . . . 27 145 8.4.6. 405 Method Not Allowed . . . . . . . . . . . . . . . . 27 146 8.4.7. 406 Not Acceptable . . . . . . . . . . . . . . . . . . 27 147 8.4.8. 407 Proxy Authentication Required . . . . . . . . . . 27 148 8.4.9. 408 Request Timeout . . . . . . . . . . . . . . . . . 28 149 8.4.10. 409 Conflict . . . . . . . . . . . . . . . . . . . . . 28 150 8.4.11. 410 Gone . . . . . . . . . . . . . . . . . . . . . . . 28 151 8.4.12. 411 Length Required . . . . . . . . . . . . . . . . . 29 152 8.4.13. 412 Precondition Failed . . . . . . . . . . . . . . . 29 153 8.4.14. 413 Request Entity Too Large . . . . . . . . . . . . . 29 154 8.4.15. 414 URI Too Long . . . . . . . . . . . . . . . . . . . 29 155 8.4.16. 415 Unsupported Media Type . . . . . . . . . . . . . . 29 156 8.4.17. 416 Requested Range Not Satisfiable . . . . . . . . . 29 157 8.4.18. 417 Expectation Failed . . . . . . . . . . . . . . . . 30 158 8.5. Server Error 5xx . . . . . . . . . . . . . . . . . . . . . 30 159 8.5.1. 500 Internal Server Error . . . . . . . . . . . . . . 30 160 8.5.2. 501 Not Implemented . . . . . . . . . . . . . . . . . 30 161 8.5.3. 502 Bad Gateway . . . . . . . . . . . . . . . . . . . 30 162 8.5.4. 503 Service Unavailable . . . . . . . . . . . . . . . 30 163 8.5.5. 504 Gateway Timeout . . . . . . . . . . . . . . . . . 31 164 8.5.6. 505 HTTP Version Not Supported . . . . . . . . . . . . 31 165 9. Header Field Definitions . . . . . . . . . . . . . . . . . . . 31 166 9.1. Allow . . . . . . . . . . . . . . . . . . . . . . . . . . 31 167 9.2. Expect . . . . . . . . . . . . . . . . . . . . . . . . . . 32 168 9.3. From . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 169 9.4. Location . . . . . . . . . . . . . . . . . . . . . . . . . 33 170 9.5. Max-Forwards . . . . . . . . . . . . . . . . . . . . . . . 34 171 9.6. Referer . . . . . . . . . . . . . . . . . . . . . . . . . 35 172 9.7. Retry-After . . . . . . . . . . . . . . . . . . . . . . . 35 173 9.8. Server . . . . . . . . . . . . . . . . . . . . . . . . . . 36 174 9.9. User-Agent . . . . . . . . . . . . . . . . . . . . . . . . 36 175 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 176 10.1. Method Registry . . . . . . . . . . . . . . . . . . . . . 37 177 10.2. Status Code Registry . . . . . . . . . . . . . . . . . . . 37 178 10.3. Message Header Registration . . . . . . . . . . . . . . . 39 179 11. Security Considerations . . . . . . . . . . . . . . . . . . . 39 180 11.1. Transfer of Sensitive Information . . . . . . . . . . . . 39 181 11.2. Encoding Sensitive Information in URIs . . . . . . . . . . 40 182 11.3. Location Headers and Spoofing . . . . . . . . . . . . . . 41 183 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 41 184 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 41 185 13.1. Normative References . . . . . . . . . . . . . . . . . . . 41 186 13.2. Informative References . . . . . . . . . . . . . . . . . . 42 188 Appendix A. Compatibility with Previous Versions . . . . . . . . 42 189 A.1. Changes from RFC 2068 . . . . . . . . . . . . . . . . . . 42 190 A.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 43 191 Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 44 192 Appendix C. Change Log (to be removed by RFC Editor before 193 publication) . . . . . . . . . . . . . . . . . . . . 47 194 C.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 47 195 C.2. Since draft-ietf-httpbis-p2-semantics-00 . . . . . . . . . 47 196 C.3. Since draft-ietf-httpbis-p2-semantics-01 . . . . . . . . . 47 197 C.4. Since draft-ietf-httpbis-p2-semantics-02 . . . . . . . . . 48 198 C.5. Since draft-ietf-httpbis-p2-semantics-03 . . . . . . . . . 49 199 C.6. Since draft-ietf-httpbis-p2-semantics-04 . . . . . . . . . 49 200 C.7. Since draft-ietf-httpbis-p2-semantics-05 . . . . . . . . . 49 201 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 202 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 54 204 1. Introduction 206 This document defines HTTP/1.1 request and response semantics. Each 207 HTTP message, as defined in [Part1], is in the form of either a 208 request or a response. An HTTP server listens on a connection for 209 HTTP requests and responds to each request, in the order received on 210 that connection, with one or more HTTP response messages. This 211 document defines the commonly agreed upon semantics of the HTTP 212 uniform interface, the intentions defined by each request method, and 213 the various response messages that might be expected as a result of 214 applying that method for the requested resource. 216 This document is currently disorganized in order to minimize the 217 changes between drafts and enable reviewers to see the smaller errata 218 changes. The next draft will reorganize the sections to better 219 reflect the content. In particular, the sections will be ordered 220 according to the typical processing of an HTTP request message (after 221 message parsing): resource mapping, general header fields, methods, 222 request modifiers, response status, and resource metadata. The 223 current mess reflects how widely dispersed these topics and 224 associated requirements had become in [RFC2616]. 226 1.1. Requirements 228 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 229 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 230 document are to be interpreted as described in [RFC2119]. 232 An implementation is not compliant if it fails to satisfy one or more 233 of the MUST or REQUIRED level requirements for the protocols it 234 implements. An implementation that satisfies all the MUST or 235 REQUIRED level and all the SHOULD level requirements for its 236 protocols is said to be "unconditionally compliant"; one that 237 satisfies all the MUST level requirements but not all the SHOULD 238 level requirements for its protocols is said to be "conditionally 239 compliant." 241 1.2. Syntax Notation 243 This specification uses the ABNF syntax defined in Section 1.2 of 244 [Part1] (which extends the syntax defined in [RFC5234] with a list 245 rule). Appendix B shows the collected ABNF, with the list rule 246 expanded. 248 The following core rules are included by reference, as defined in 249 [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF 250 (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), 251 HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any 8-bit 252 sequence of data), SP (space), VCHAR (any visible USASCII character), 253 and WSP (whitespace). 255 1.2.1. Core Rules 257 The core rules below are defined in Section 1.2.2 of [Part1]: 259 comment = 260 quoted-string = 261 token = 262 OWS = 263 RWS = 264 obs-text = 266 1.2.2. ABNF Rules defined in other Parts of the Specification 268 The ABNF rules below are defined in other parts: 270 absolute-URI = 271 fragment = 272 Host = 273 HTTP-date = 274 partial-URI = 275 product = 276 TE = 278 Accept = 279 Accept-Charset = 280 281 Accept-Encoding = 282 283 Accept-Language = 284 286 ETag = 287 If-Match = 288 If-Modified-Since = 289 290 If-None-Match = 291 If-Unmodified-Since = 292 294 Accept-Ranges = 295 If-Range = 296 Range = 297 Age = 298 Vary = 300 Authorization = 301 Proxy-Authenticate = 302 303 Proxy-Authorization = 304 305 WWW-Authenticate = 306 308 2. Method 310 The Method token indicates the method to be performed on the resource 311 identified by the request-target. The method is case-sensitive. 313 Method = %x4F.50.54.49.4F.4E.53 ; "OPTIONS", Section 7.2 314 / %x47.45.54 ; "GET", Section 7.3 315 / %x48.45.41.44 ; "HEAD", Section 7.4 316 / %x50.4F.53.54 ; "POST", Section 7.5 317 / %x50.55.54 ; "PUT", Section 7.6 318 / %x44.45.4C.45.54.45 ; "DELETE", Section 7.7 319 / %x54.52.41.43.45 ; "TRACE", Section 7.8 320 / %x43.4F.4E.4E.45.43.54 ; "CONNECT", Section 7.9 321 / extension-method 322 extension-method = token 324 The list of methods allowed by a resource can be specified in an 325 Allow header field (Section 9.1). The return code of the response 326 always notifies the client whether a method is currently allowed on a 327 resource, since the set of allowed methods can change dynamically. 328 An origin server SHOULD return the status code 405 (Method Not 329 Allowed) if the method is known by the origin server but not allowed 330 for the requested resource, and 501 (Not Implemented) if the method 331 is unrecognized or not implemented by the origin server. The methods 332 GET and HEAD MUST be supported by all general-purpose servers. All 333 other methods are OPTIONAL; however, if the above methods are 334 implemented, they MUST be implemented with the same semantics as 335 those specified in Section 7. 337 2.1. Method Registry 339 The HTTP Method Registry defines the name space for the Method token 340 in the Request line of an HTTP request. 342 Registrations MUST include the following fields: 344 o Method Name (see Section 2) 346 o Safe ("yes" or "no", see Section 7.1.1) 348 o Pointer to specification text 350 Values to be added to this name space are subject to IETF review 351 ([RFC5226], Section 4.1). Any document registering new method names 352 should be traceable through statuses of either 'Obsoletes' or 353 'Updates' to this document. 355 The registry itself is maintained at 356 . 358 3. Request Header Fields 360 The request-header fields allow the client to pass additional 361 information about the request, and about the client itself, to the 362 server. These fields act as request modifiers, with semantics 363 equivalent to the parameters on a programming language method 364 invocation. 366 request-header = Accept ; [Part3], Section 5.1 367 / Accept-Charset ; [Part3], Section 5.2 368 / Accept-Encoding ; [Part3], Section 5.3 369 / Accept-Language ; [Part3], Section 5.4 370 / Authorization ; [Part7], Section 3.1 371 / Expect ; Section 9.2 372 / From ; Section 9.3 373 / Host ; [Part1], Section 8.4 374 / If-Match ; [Part4], Section 6.2 375 / If-Modified-Since ; [Part4], Section 6.3 376 / If-None-Match ; [Part4], Section 6.4 377 / If-Range ; [Part5], Section 5.3 378 / If-Unmodified-Since ; [Part4], Section 6.5 379 / Max-Forwards ; Section 9.5 380 / Proxy-Authorization ; [Part7], Section 3.3 381 / Range ; [Part5], Section 5.4 382 / Referer ; Section 9.6 383 / TE ; [Part1], Section 8.8 384 / User-Agent ; Section 9.9 386 Request-header field names can be extended reliably only in 387 combination with a change in the protocol version. However, new or 388 experimental header fields MAY be given the semantics of request- 389 header fields if all parties in the communication recognize them to 390 be request-header fields. Unrecognized header fields are treated as 391 entity-header fields. 393 4. Status Code and Reason Phrase 395 The Status-Code element is a 3-digit integer result code of the 396 attempt to understand and satisfy the request. The status codes 397 listed below are defined in Section 8. The Reason-Phrase is intended 398 to give a short textual description of the Status-Code. The Status- 399 Code is intended for use by automata and the Reason-Phrase is 400 intended for the human user. The client is not required to examine 401 or display the Reason-Phrase. 403 The individual values of the numeric status codes defined for 404 HTTP/1.1, and an example set of corresponding Reason-Phrase's, are 405 presented below. The reason phrases listed here are only 406 recommendations -- they MAY be replaced by local equivalents without 407 affecting the protocol. 409 Status-Code = 410 "100" ; Section 8.1.1: Continue 411 / "101" ; Section 8.1.2: Switching Protocols 412 / "200" ; Section 8.2.1: OK 413 / "201" ; Section 8.2.2: Created 414 / "202" ; Section 8.2.3: Accepted 415 / "203" ; Section 8.2.4: Non-Authoritative Information 416 / "204" ; Section 8.2.5: No Content 417 / "205" ; Section 8.2.6: Reset Content 418 / "206" ; Section 8.2.7: Partial Content 419 / "300" ; Section 8.3.1: Multiple Choices 420 / "301" ; Section 8.3.2: Moved Permanently 421 / "302" ; Section 8.3.3: Found 422 / "303" ; Section 8.3.4: See Other 423 / "304" ; Section 8.3.5: Not Modified 424 / "305" ; Section 8.3.6: Use Proxy 425 / "307" ; Section 8.3.8: Temporary Redirect 426 / "400" ; Section 8.4.1: Bad Request 427 / "401" ; Section 8.4.2: Unauthorized 428 / "402" ; Section 8.4.3: Payment Required 429 / "403" ; Section 8.4.4: Forbidden 430 / "404" ; Section 8.4.5: Not Found 431 / "405" ; Section 8.4.6: Method Not Allowed 432 / "406" ; Section 8.4.7: Not Acceptable 433 / "407" ; Section 8.4.8: Proxy Authentication Required 434 / "408" ; Section 8.4.9: Request Time-out 435 / "409" ; Section 8.4.10: Conflict 436 / "410" ; Section 8.4.11: Gone 437 / "411" ; Section 8.4.12: Length Required 438 / "412" ; Section 8.4.13: Precondition Failed 439 / "413" ; Section 8.4.14: Request Entity Too Large 440 / "414" ; Section 8.4.15: URI Too Long 441 / "415" ; Section 8.4.16: Unsupported Media Type 442 / "416" ; Section 8.4.17: Requested range not satisfiable 443 / "417" ; Section 8.4.18: Expectation Failed 444 / "500" ; Section 8.5.1: Internal Server Error 445 / "501" ; Section 8.5.2: Not Implemented 446 / "502" ; Section 8.5.3: Bad Gateway 447 / "503" ; Section 8.5.4: Service Unavailable 448 / "504" ; Section 8.5.5: Gateway Time-out 449 / "505" ; Section 8.5.6: HTTP Version not supported 450 / extension-code 452 extension-code = 3DIGIT 453 Reason-Phrase = *( WSP / VCHAR / obs-text ) 455 HTTP status codes are extensible. HTTP applications are not required 456 to understand the meaning of all registered status codes, though such 457 understanding is obviously desirable. However, applications MUST 458 understand the class of any status code, as indicated by the first 459 digit, and treat any unrecognized response as being equivalent to the 460 x00 status code of that class, with the exception that an 461 unrecognized response MUST NOT be cached. For example, if an 462 unrecognized status code of 431 is received by the client, it can 463 safely assume that there was something wrong with its request and 464 treat the response as if it had received a 400 status code. In such 465 cases, user agents SHOULD present to the user the entity returned 466 with the response, since that entity is likely to include human- 467 readable information which will explain the unusual status. 469 4.1. Status Code Registry 471 The HTTP Status Code Registry defines the name space for the Status- 472 Code token in the Status line of an HTTP response. 474 Values to be added to this name space are subject to IETF review 475 ([RFC5226], Section 4.1). Any document registering new status codes 476 should be traceable through statuses of either 'Obsoletes' or 477 'Updates' to this document. 479 The registry itself is maintained at 480 . 482 5. Response Header Fields 484 The response-header fields allow the server to pass additional 485 information about the response which cannot be placed in the Status- 486 Line. These header fields give information about the server and 487 about further access to the resource identified by the request- 488 target. 490 response-header = Accept-Ranges ; [Part5], Section 5.1 491 / Age ; [Part6], Section 3.1 492 / Allow ; Section 9.1 493 / ETag ; [Part4], Section 6.1 494 / Location ; Section 9.4 495 / Proxy-Authenticate ; [Part7], Section 3.2 496 / Retry-After ; Section 9.7 497 / Server ; Section 9.8 498 / Vary ; [Part6], Section 3.5 499 / WWW-Authenticate ; [Part7], Section 3.4 501 Response-header field names can be extended reliably only in 502 combination with a change in the protocol version. However, new or 503 experimental header fields MAY be given the semantics of response- 504 header fields if all parties in the communication recognize them to 505 be response-header fields. Unrecognized header fields are treated as 506 entity-header fields. 508 6. Entity 510 Request and Response messages MAY transfer an entity if not otherwise 511 restricted by the request method or response status code. An entity 512 consists of entity-header fields and an entity-body, although some 513 responses will only include the entity-headers. HTTP entity-body and 514 entity-header fields are defined in [Part3]. 516 An entity-body is only present in a message when a message-body is 517 present, as described in Section 4.3 of [Part1]. The entity-body is 518 obtained from the message-body by decoding any Transfer-Encoding that 519 might have been applied to ensure safe and proper transfer of the 520 message. 522 7. Method Definitions 524 The set of common methods for HTTP/1.1 is defined below. Although 525 this set can be expanded, additional methods cannot be assumed to 526 share the same semantics for separately extended clients and servers. 528 7.1. Safe and Idempotent Methods 530 7.1.1. Safe Methods 532 Implementors should be aware that the software represents the user in 533 their interactions over the Internet, and should be careful to allow 534 the user to be aware of any actions they might take which may have an 535 unexpected significance to themselves or others. 537 In particular, the convention has been established that the GET and 538 HEAD methods SHOULD NOT have the significance of taking an action 539 other than retrieval. These methods ought to be considered "safe". 540 This allows user agents to represent other methods, such as POST, PUT 541 and DELETE, in a special way, so that the user is made aware of the 542 fact that a possibly unsafe action is being requested. 544 Naturally, it is not possible to ensure that the server does not 545 generate side-effects as a result of performing a GET request; in 546 fact, some dynamic resources consider that a feature. The important 547 distinction here is that the user did not request the side-effects, 548 so therefore cannot be held accountable for them. 550 7.1.2. Idempotent Methods 552 Methods can also have the property of "idempotence" in that (aside 553 from error or expiration issues) the side-effects of N > 0 identical 554 requests is the same as for a single request. The methods GET, HEAD, 555 PUT and DELETE share this property. Also, the methods OPTIONS and 556 TRACE SHOULD NOT have side effects, and so are inherently idempotent. 558 However, it is possible that a sequence of several requests is non- 559 idempotent, even if all of the methods executed in that sequence are 560 idempotent. (A sequence is idempotent if a single execution of the 561 entire sequence always yields a result that is not changed by a 562 reexecution of all, or part, of that sequence.) For example, a 563 sequence is non-idempotent if its result depends on a value that is 564 later modified in the same sequence. 566 A sequence that never has side effects is idempotent, by definition 567 (provided that no concurrent operations are being executed on the 568 same set of resources). 570 7.2. OPTIONS 572 The OPTIONS method represents a request for information about the 573 communication options available on the request/response chain 574 identified by the request-target. This method allows the client to 575 determine the options and/or requirements associated with a resource, 576 or the capabilities of a server, without implying a resource action 577 or initiating a resource retrieval. 579 Responses to this method are not cacheable. 581 If the OPTIONS request includes an entity-body (as indicated by the 582 presence of Content-Length or Transfer-Encoding), then the media type 583 MUST be indicated by a Content-Type field. Although this 584 specification does not define any use for such a body, future 585 extensions to HTTP might use the OPTIONS body to make more detailed 586 queries on the server. 588 If the request-target is an asterisk ("*"), the OPTIONS request is 589 intended to apply to the server in general rather than to a specific 590 resource. Since a server's communication options typically depend on 591 the resource, the "*" request is only useful as a "ping" or "no-op" 592 type of method; it does nothing beyond allowing the client to test 593 the capabilities of the server. For example, this can be used to 594 test a proxy for HTTP/1.1 compliance (or lack thereof). 596 If the request-target is not an asterisk, the OPTIONS request applies 597 only to the options that are available when communicating with that 598 resource. 600 A 200 response SHOULD include any header fields that indicate 601 optional features implemented by the server and applicable to that 602 resource (e.g., Allow), possibly including extensions not defined by 603 this specification. The response body, if any, SHOULD also include 604 information about the communication options. The format for such a 605 body is not defined by this specification, but might be defined by 606 future extensions to HTTP. Content negotiation MAY be used to select 607 the appropriate response format. If no response body is included, 608 the response MUST include a Content-Length field with a field-value 609 of "0". 611 The Max-Forwards request-header field MAY be used to target a 612 specific proxy in the request chain. When a proxy receives an 613 OPTIONS request on an absolute-URI for which request forwarding is 614 permitted, the proxy MUST check for a Max-Forwards field. If the 615 Max-Forwards field-value is zero ("0"), the proxy MUST NOT forward 616 the message; instead, the proxy SHOULD respond with its own 617 communication options. If the Max-Forwards field-value is an integer 618 greater than zero, the proxy MUST decrement the field-value when it 619 forwards the request. If no Max-Forwards field is present in the 620 request, then the forwarded request MUST NOT include a Max-Forwards 621 field. 623 7.3. GET 625 The GET method means retrieve whatever information (in the form of an 626 entity) is identified by the request-target. If the request-target 627 refers to a data-producing process, it is the produced data which 628 shall be returned as the entity in the response and not the source 629 text of the process, unless that text happens to be the output of the 630 process. 632 The semantics of the GET method change to a "conditional GET" if the 633 request message includes an If-Modified-Since, If-Unmodified-Since, 634 If-Match, If-None-Match, or If-Range header field. A conditional GET 635 method requests that the entity be transferred only under the 636 circumstances described by the conditional header field(s). The 637 conditional GET method is intended to reduce unnecessary network 638 usage by allowing cached entities to be refreshed without requiring 639 multiple requests or transferring data already held by the client. 641 The semantics of the GET method change to a "partial GET" if the 642 request message includes a Range header field. A partial GET 643 requests that only part of the entity be transferred, as described in 644 Section 5.4 of [Part5]. The partial GET method is intended to reduce 645 unnecessary network usage by allowing partially-retrieved entities to 646 be completed without transferring data already held by the client. 648 The response to a GET request is cacheable if and only if it meets 649 the requirements for HTTP caching described in [Part6]. 651 See Section 11.2 for security considerations when used for forms. 653 7.4. HEAD 655 The HEAD method is identical to GET except that the server MUST NOT 656 return a message-body in the response. The metainformation contained 657 in the HTTP headers in response to a HEAD request SHOULD be identical 658 to the information sent in response to a GET request. This method 659 can be used for obtaining metainformation about the entity implied by 660 the request without transferring the entity-body itself. This method 661 is often used for testing hypertext links for validity, 662 accessibility, and recent modification. 664 The response to a HEAD request MAY be cacheable in the sense that the 665 information contained in the response MAY be used to update a 666 previously cached entity from that resource. If the new field values 667 indicate that the cached entity differs from the current entity (as 668 would be indicated by a change in Content-Length, Content-MD5, ETag 669 or Last-Modified), then the cache MUST treat the cache entry as 670 stale. 672 7.5. POST 674 The POST method is used to request that the origin server accept the 675 entity enclosed in the request as data to be processed by the 676 resource identified by the request-target in the Request-Line. POST 677 is designed to allow a uniform method to cover the following 678 functions: 680 o Annotation of existing resources; 682 o Posting a message to a bulletin board, newsgroup, mailing list, or 683 similar group of articles; 685 o Providing a block of data, such as the result of submitting a 686 form, to a data-handling process; 688 o Extending a database through an append operation. 690 The actual function performed by the POST method is determined by the 691 server and is usually dependent on the request-target. 693 The action performed by the POST method might not result in a 694 resource that can be identified by a URI. In this case, either 200 695 (OK) or 204 (No Content) is the appropriate response status, 696 depending on whether or not the response includes an entity that 697 describes the result. 699 If a resource has been created on the origin server, the response 700 SHOULD be 201 (Created) and contain an entity which describes the 701 status of the request and refers to the new resource, and a Location 702 header (see Section 9.4). 704 Responses to this method are not cacheable, unless the response 705 includes appropriate Cache-Control or Expires header fields. 706 However, the 303 (See Other) response can be used to direct the user 707 agent to retrieve a cacheable resource. 709 7.6. PUT 711 The PUT method requests that the enclosed entity be stored at the 712 supplied request-target. If the request-target refers to an already 713 existing resource, the enclosed entity SHOULD be considered as a 714 modified version of the one residing on the origin server. If the 715 request-target does not point to an existing resource, and that URI 716 is capable of being defined as a new resource by the requesting user 717 agent, the origin server can create the resource with that URI. If a 718 new resource is created at the request-target, the origin server MUST 719 inform the user agent via the 201 (Created) response. If an existing 720 resource is modified, either the 200 (OK) or 204 (No Content) 721 response codes SHOULD be sent to indicate successful completion of 722 the request. If the resource could not be created or modified with 723 the request-target, an appropriate error response SHOULD be given 724 that reflects the nature of the problem. The recipient of the entity 725 MUST NOT ignore any Content-* headers (headers starting with the 726 prefix 'Content-') that it does not understand or implement and MUST 727 return a 501 (Not Implemented) response in such cases. 729 If the request passes through a cache and the request-target 730 identifies one or more currently cached entities, those entries 731 SHOULD be treated as stale. Responses to this method are not 732 cacheable. 734 The fundamental difference between the POST and PUT requests is 735 reflected in the different meaning of the request-target. The URI in 736 a POST request identifies the resource that will handle the enclosed 737 entity. That resource might be a data-accepting process, a gateway 738 to some other protocol, or a separate entity that accepts 739 annotations. In contrast, the URI in a PUT request identifies the 740 entity enclosed with the request -- the user agent knows what URI is 741 intended and the server MUST NOT attempt to apply the request to some 742 other resource. If the server desires that the request be applied to 743 a different URI, it MUST send a 301 (Moved Permanently) response; the 744 user agent MAY then make its own decision regarding whether or not to 745 redirect the request. 747 A single resource MAY be identified by many different URIs. For 748 example, an article might have a URI for identifying "the current 749 version" which is separate from the URI identifying each particular 750 version. In this case, a PUT request on a general URI might result 751 in several other URIs being defined by the origin server. 753 HTTP/1.1 does not define how a PUT method affects the state of an 754 origin server. 756 Unless otherwise specified for a particular entity-header, the 757 entity-headers in the PUT request SHOULD be applied to the resource 758 created or modified by the PUT. 760 7.7. DELETE 762 The DELETE method requests that the origin server delete the resource 763 identified by the request-target. This method MAY be overridden by 764 human intervention (or other means) on the origin server. The client 765 cannot be guaranteed that the operation has been carried out, even if 766 the status code returned from the origin server indicates that the 767 action has been completed successfully. However, the server SHOULD 768 NOT indicate success unless, at the time the response is given, it 769 intends to delete the resource or move it to an inaccessible 770 location. 772 A successful response SHOULD be 200 (OK) if the response includes an 773 entity describing the status, 202 (Accepted) if the action has not 774 yet been enacted, or 204 (No Content) if the action has been enacted 775 but the response does not include an entity. 777 If the request passes through a cache and the request-target 778 identifies one or more currently cached entities, those entries 779 SHOULD be treated as stale. Responses to this method are not 780 cacheable. 782 7.8. TRACE 784 The TRACE method is used to invoke a remote, application-layer loop- 785 back of the request message. The final recipient of the request 786 SHOULD reflect the message received back to the client as the entity- 787 body of a 200 (OK) response. The final recipient is either the 788 origin server or the first proxy or gateway to receive a Max-Forwards 789 value of zero (0) in the request (see Section 9.5). A TRACE request 790 MUST NOT include an entity. 792 TRACE allows the client to see what is being received at the other 793 end of the request chain and use that data for testing or diagnostic 794 information. The value of the Via header field (Section 8.9 of 795 [Part1]) is of particular interest, since it acts as a trace of the 796 request chain. Use of the Max-Forwards header field allows the 797 client to limit the length of the request chain, which is useful for 798 testing a chain of proxies forwarding messages in an infinite loop. 800 If the request is valid, the response SHOULD contain the entire 801 request message in the entity-body, with a Content-Type of "message/ 802 http" (see Section 9.3.1 of [Part1]). Responses to this method MUST 803 NOT be cached. 805 7.9. CONNECT 807 This specification reserves the method name CONNECT for use with a 808 proxy that can dynamically switch to being a tunnel (e.g. SSL 809 tunneling [RFC2817]). 811 8. Status Code Definitions 813 Each Status-Code is described below, including a description of which 814 method(s) it can follow and any metainformation required in the 815 response. 817 8.1. Informational 1xx 819 This class of status code indicates a provisional response, 820 consisting only of the Status-Line and optional headers, and is 821 terminated by an empty line. There are no required headers for this 822 class of status code. Since HTTP/1.0 did not define any 1xx status 823 codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client 824 except under experimental conditions. 826 A client MUST be prepared to accept one or more 1xx status responses 827 prior to a regular response, even if the client does not expect a 100 828 (Continue) status message. Unexpected 1xx status responses MAY be 829 ignored by a user agent. 831 Proxies MUST forward 1xx responses, unless the connection between the 832 proxy and its client has been closed, or unless the proxy itself 833 requested the generation of the 1xx response. (For example, if a 834 proxy adds a "Expect: 100-continue" field when it forwards a request, 835 then it need not forward the corresponding 100 (Continue) 836 response(s).) 838 8.1.1. 100 Continue 840 The client SHOULD continue with its request. This interim response 841 is used to inform the client that the initial part of the request has 842 been received and has not yet been rejected by the server. The 843 client SHOULD continue by sending the remainder of the request or, if 844 the request has already been completed, ignore this response. The 845 server MUST send a final response after the request has been 846 completed. See Section 7.2.3 of [Part1] for detailed discussion of 847 the use and handling of this status code. 849 8.1.2. 101 Switching Protocols 851 The server understands and is willing to comply with the client's 852 request, via the Upgrade message header field (Section 5.4 of 853 [Part5]), for a change in the application protocol being used on this 854 connection. The server will switch protocols to those defined by the 855 response's Upgrade header field immediately after the empty line 856 which terminates the 101 response. 858 The protocol SHOULD be switched only when it is advantageous to do 859 so. For example, switching to a newer version of HTTP is 860 advantageous over older versions, and switching to a real-time, 861 synchronous protocol might be advantageous when delivering resources 862 that use such features. 864 8.2. Successful 2xx 866 This class of status code indicates that the client's request was 867 successfully received, understood, and accepted. 869 8.2.1. 200 OK 871 The request has succeeded. The information returned with the 872 response is dependent on the method used in the request, for example: 874 GET an entity corresponding to the requested resource is sent in the 875 response; 877 HEAD the entity-header fields corresponding to the requested 878 resource are sent in the response without any message-body; 880 POST an entity describing or containing the result of the action; 882 TRACE an entity containing the request message as received by the 883 end server. 885 8.2.2. 201 Created 887 The request has been fulfilled and resulted in a new resource being 888 created. The newly created resource can be referenced by the URI(s) 889 returned in the entity of the response, with the most specific URI 890 for the resource given by a Location header field. The response 891 SHOULD include an entity containing a list of resource 892 characteristics and location(s) from which the user or user agent can 893 choose the one most appropriate. The entity format is specified by 894 the media type given in the Content-Type header field. The origin 895 server MUST create the resource before returning the 201 status code. 896 If the action cannot be carried out immediately, the server SHOULD 897 respond with 202 (Accepted) response instead. 899 A 201 response MAY contain an ETag response header field indicating 900 the current value of the entity tag for the requested variant just 901 created, see Section 6.1 of [Part4]. 903 8.2.3. 202 Accepted 905 The request has been accepted for processing, but the processing has 906 not been completed. The request might or might not eventually be 907 acted upon, as it might be disallowed when processing actually takes 908 place. There is no facility for re-sending a status code from an 909 asynchronous operation such as this. 911 The 202 response is intentionally non-committal. Its purpose is to 912 allow a server to accept a request for some other process (perhaps a 913 batch-oriented process that is only run once per day) without 914 requiring that the user agent's connection to the server persist 915 until the process is completed. The entity returned with this 916 response SHOULD include an indication of the request's current status 917 and either a pointer to a status monitor or some estimate of when the 918 user can expect the request to be fulfilled. 920 8.2.4. 203 Non-Authoritative Information 922 The returned metainformation in the entity-header is not the 923 definitive set as available from the origin server, but is gathered 924 from a local or a third-party copy. The set presented MAY be a 925 subset or superset of the original version. For example, including 926 local annotation information about the resource might result in a 927 superset of the metainformation known by the origin server. Use of 928 this response code is not required and is only appropriate when the 929 response would otherwise be 200 (OK). 931 8.2.5. 204 No Content 933 The server has fulfilled the request but does not need to return an 934 entity-body, and might want to return updated metainformation. The 935 response MAY include new or updated metainformation in the form of 936 entity-headers, which if present SHOULD be associated with the 937 requested variant. 939 If the client is a user agent, it SHOULD NOT change its document view 940 from that which caused the request to be sent. This response is 941 primarily intended to allow input for actions to take place without 942 causing a change to the user agent's active document view, although 943 any new or updated metainformation SHOULD be applied to the document 944 currently in the user agent's active view. 946 The 204 response MUST NOT include a message-body, and thus is always 947 terminated by the first empty line after the header fields. 949 8.2.6. 205 Reset Content 951 The server has fulfilled the request and the user agent SHOULD reset 952 the document view which caused the request to be sent. This response 953 is primarily intended to allow input for actions to take place via 954 user input, followed by a clearing of the form in which the input is 955 given so that the user can easily initiate another input action. The 956 response MUST NOT include an entity. 958 8.2.7. 206 Partial Content 960 The server has fulfilled the partial GET request for the resource and 961 the enclosed entity is a partial representation as defined in 962 [Part5]. 964 8.3. Redirection 3xx 966 This class of status code indicates that further action needs to be 967 taken by the user agent in order to fulfill the request. The action 968 required MAY be carried out by the user agent without interaction 969 with the user if and only if the method used in the second request is 970 GET or HEAD. A client SHOULD detect infinite redirection loops, 971 since such loops generate network traffic for each redirection. 973 Note: previous versions of this specification recommended a 974 maximum of five redirections. Content developers should be aware 975 that there might be clients that implement such a fixed 976 limitation. 978 8.3.1. 300 Multiple Choices 980 The requested resource corresponds to any one of a set of 981 representations, each with its own specific location, and agent- 982 driven negotiation information (Section 4 of [Part3]) is being 983 provided so that the user (or user agent) can select a preferred 984 representation and redirect its request to that location. 986 Unless it was a HEAD request, the response SHOULD include an entity 987 containing a list of resource characteristics and location(s) from 988 which the user or user agent can choose the one most appropriate. 989 The entity format is specified by the media type given in the 990 Content-Type header field. Depending upon the format and the 991 capabilities of the user agent, selection of the most appropriate 992 choice MAY be performed automatically. However, this specification 993 does not define any standard for such automatic selection. 995 If the server has a preferred choice of representation, it SHOULD 996 include the specific URI for that representation in the Location 997 field; user agents MAY use the Location field value for automatic 998 redirection. This response is cacheable unless indicated otherwise. 1000 8.3.2. 301 Moved Permanently 1002 The requested resource has been assigned a new permanent URI and any 1003 future references to this resource SHOULD use one of the returned 1004 URIs. Clients with link editing capabilities ought to automatically 1005 re-link references to the request-target to one or more of the new 1006 references returned by the server, where possible. This response is 1007 cacheable unless indicated otherwise. 1009 The new permanent URI SHOULD be given by the Location field in the 1010 response. Unless the request method was HEAD, the entity of the 1011 response SHOULD contain a short hypertext note with a hyperlink to 1012 the new URI(s). 1014 If the 301 status code is received in response to a request method 1015 that is known to be "safe", as defined in Section 7.1.1, then the 1016 request MAY be automatically redirected by the user agent without 1017 confirmation. Otherwise, the user agent MUST NOT automatically 1018 redirect the request unless it can be confirmed by the user, since 1019 this might change the conditions under which the request was issued. 1021 Note: When automatically redirecting a POST request after 1022 receiving a 301 status code, some existing HTTP/1.0 user agents 1023 will erroneously change it into a GET request. 1025 8.3.3. 302 Found 1027 The requested resource resides temporarily under a different URI. 1028 Since the redirection might be altered on occasion, the client SHOULD 1029 continue to use the request-target for future requests. This 1030 response is only cacheable if indicated by a Cache-Control or Expires 1031 header field. 1033 The temporary URI SHOULD be given by the Location field in the 1034 response. Unless the request method was HEAD, the entity of the 1035 response SHOULD contain a short hypertext note with a hyperlink to 1036 the new URI(s). 1038 If the 302 status code is received in response to a request method 1039 that is known to be "safe", as defined in Section 7.1.1, then the 1040 request MAY be automatically redirected by the user agent without 1041 confirmation. Otherwise, the user agent MUST NOT automatically 1042 redirect the request unless it can be confirmed by the user, since 1043 this might change the conditions under which the request was issued. 1045 Note: [RFC1945] and [RFC2068] specify that the client is not 1046 allowed to change the method on the redirected request. However, 1047 most existing user agent implementations treat 302 as if it were a 1048 303 response, performing a GET on the Location field-value 1049 regardless of the original request method. The status codes 303 1050 and 307 have been added for servers that wish to make 1051 unambiguously clear which kind of reaction is expected of the 1052 client. 1054 8.3.4. 303 See Other 1056 The server directs the user agent to a different resource, indicated 1057 by a URI in the Location header field, that provides an indirect 1058 response to the original request. The user agent MAY perform a GET 1059 request on the URI in the Location field in order to obtain a 1060 representation corresponding to the response, be redirected again, or 1061 end with an error status. The Location URI is not a substitute 1062 reference for the originally requested resource. 1064 The 303 status is generally applicable to any HTTP method. It is 1065 primarily used to allow the output of a POST action to redirect the 1066 user agent to a selected resource, since doing so provides the 1067 information corresponding to the POST response in a form that can be 1068 separately identified, bookmarked, and cached independent of the 1069 original request. 1071 A 303 response to a GET request indicates that the requested resource 1072 does not have a representation of its own that can be transferred by 1073 the server over HTTP. The Location URI indicates a resource that is 1074 descriptive of the requested resource such that the follow-on 1075 representation may be useful without implying that it adequately 1076 represents the previously requested resource. Note that answers to 1077 the questions of what can be represented, what representations are 1078 adequate, and what might be a useful description are outside the 1079 scope of HTTP and thus entirely determined by the resource owner(s). 1081 A 303 response SHOULD NOT be cached unless it is indicated as 1082 cacheable by Cache-Control or Expires header fields. Except for 1083 responses to a HEAD request, the entity of a 303 response SHOULD 1084 contain a short hypertext note with a hyperlink to the Location URI. 1086 8.3.5. 304 Not Modified 1088 The response to the request has not been modified since the 1089 conditions indicated by the client's conditional GET request, as 1090 defined in [Part4]. 1092 8.3.6. 305 Use Proxy 1094 The 305 status was defined in a previous version of this 1095 specification (see Appendix A.2), and is now deprecated. 1097 8.3.7. 306 (Unused) 1099 The 306 status code was used in a previous version of the 1100 specification, is no longer used, and the code is reserved. 1102 8.3.8. 307 Temporary Redirect 1104 The requested resource resides temporarily under a different URI. 1105 Since the redirection MAY be altered on occasion, the client SHOULD 1106 continue to use the request-target for future requests. This 1107 response is only cacheable if indicated by a Cache-Control or Expires 1108 header field. 1110 The temporary URI SHOULD be given by the Location field in the 1111 response. Unless the request method was HEAD, the entity of the 1112 response SHOULD contain a short hypertext note with a hyperlink to 1113 the new URI(s) , since many pre-HTTP/1.1 user agents do not 1114 understand the 307 status. Therefore, the note SHOULD contain the 1115 information necessary for a user to repeat the original request on 1116 the new URI. 1118 If the 307 status code is received in response to a request method 1119 that is known to be "safe", as defined in Section 7.1.1, then the 1120 request MAY be automatically redirected by the user agent without 1121 confirmation. Otherwise, the user agent MUST NOT automatically 1122 redirect the request unless it can be confirmed by the user, since 1123 this might change the conditions under which the request was issued. 1125 8.4. Client Error 4xx 1127 The 4xx class of status code is intended for cases in which the 1128 client seems to have erred. Except when responding to a HEAD 1129 request, the server SHOULD include an entity containing an 1130 explanation of the error situation, and whether it is a temporary or 1131 permanent condition. These status codes are applicable to any 1132 request method. User agents SHOULD display any included entity to 1133 the user. 1135 If the client is sending data, a server implementation using TCP 1136 SHOULD be careful to ensure that the client acknowledges receipt of 1137 the packet(s) containing the response, before the server closes the 1138 input connection. If the client continues sending data to the server 1139 after the close, the server's TCP stack will send a reset packet to 1140 the client, which may erase the client's unacknowledged input buffers 1141 before they can be read and interpreted by the HTTP application. 1143 8.4.1. 400 Bad Request 1145 The request could not be understood by the server due to malformed 1146 syntax. The client SHOULD NOT repeat the request without 1147 modifications. 1149 8.4.2. 401 Unauthorized 1151 The request requires user authentication (see [Part7]). 1153 8.4.3. 402 Payment Required 1155 This code is reserved for future use. 1157 8.4.4. 403 Forbidden 1159 The server understood the request, but is refusing to fulfill it. 1160 Authorization will not help and the request SHOULD NOT be repeated. 1161 If the request method was not HEAD and the server wishes to make 1162 public why the request has not been fulfilled, it SHOULD describe the 1163 reason for the refusal in the entity. If the server does not wish to 1164 make this information available to the client, the status code 404 1165 (Not Found) can be used instead. 1167 8.4.5. 404 Not Found 1169 The server has not found anything matching the request-target. No 1170 indication is given of whether the condition is temporary or 1171 permanent. The 410 (Gone) status code SHOULD be used if the server 1172 knows, through some internally configurable mechanism, that an old 1173 resource is permanently unavailable and has no forwarding address. 1174 This status code is commonly used when the server does not wish to 1175 reveal exactly why the request has been refused, or when no other 1176 response is applicable. 1178 8.4.6. 405 Method Not Allowed 1180 The method specified in the Request-Line is not allowed for the 1181 resource identified by the request-target. The response MUST include 1182 an Allow header containing a list of valid methods for the requested 1183 resource. 1185 8.4.7. 406 Not Acceptable 1187 The resource identified by the request is only capable of generating 1188 response entities which have content characteristics not acceptable 1189 according to the accept headers sent in the request. 1191 Unless it was a HEAD request, the response SHOULD include an entity 1192 containing a list of available entity characteristics and location(s) 1193 from which the user or user agent can choose the one most 1194 appropriate. The entity format is specified by the media type given 1195 in the Content-Type header field. Depending upon the format and the 1196 capabilities of the user agent, selection of the most appropriate 1197 choice MAY be performed automatically. However, this specification 1198 does not define any standard for such automatic selection. 1200 Note: HTTP/1.1 servers are allowed to return responses which are 1201 not acceptable according to the accept headers sent in the 1202 request. In some cases, this may even be preferable to sending a 1203 406 response. User agents are encouraged to inspect the headers 1204 of an incoming response to determine if it is acceptable. 1206 If the response could be unacceptable, a user agent SHOULD 1207 temporarily stop receipt of more data and query the user for a 1208 decision on further actions. 1210 8.4.8. 407 Proxy Authentication Required 1212 This code is similar to 401 (Unauthorized), but indicates that the 1213 client must first authenticate itself with the proxy (see [Part7]). 1215 8.4.9. 408 Request Timeout 1217 The client did not produce a request within the time that the server 1218 was prepared to wait. The client MAY repeat the request without 1219 modifications at any later time. 1221 8.4.10. 409 Conflict 1223 The request could not be completed due to a conflict with the current 1224 state of the resource. This code is only allowed in situations where 1225 it is expected that the user might be able to resolve the conflict 1226 and resubmit the request. The response body SHOULD include enough 1227 information for the user to recognize the source of the conflict. 1228 Ideally, the response entity would include enough information for the 1229 user or user agent to fix the problem; however, that might not be 1230 possible and is not required. 1232 Conflicts are most likely to occur in response to a PUT request. For 1233 example, if versioning were being used and the entity being PUT 1234 included changes to a resource which conflict with those made by an 1235 earlier (third-party) request, the server might use the 409 response 1236 to indicate that it can't complete the request. In this case, the 1237 response entity would likely contain a list of the differences 1238 between the two versions in a format defined by the response Content- 1239 Type. 1241 8.4.11. 410 Gone 1243 The requested resource is no longer available at the server and no 1244 forwarding address is known. This condition is expected to be 1245 considered permanent. Clients with link editing capabilities SHOULD 1246 delete references to the request-target after user approval. If the 1247 server does not know, or has no facility to determine, whether or not 1248 the condition is permanent, the status code 404 (Not Found) SHOULD be 1249 used instead. This response is cacheable unless indicated otherwise. 1251 The 410 response is primarily intended to assist the task of web 1252 maintenance by notifying the recipient that the resource is 1253 intentionally unavailable and that the server owners desire that 1254 remote links to that resource be removed. Such an event is common 1255 for limited-time, promotional services and for resources belonging to 1256 individuals no longer working at the server's site. It is not 1257 necessary to mark all permanently unavailable resources as "gone" or 1258 to keep the mark for any length of time -- that is left to the 1259 discretion of the server owner. 1261 8.4.12. 411 Length Required 1263 The server refuses to accept the request without a defined Content- 1264 Length. The client MAY repeat the request if it adds a valid 1265 Content-Length header field containing the length of the message-body 1266 in the request message. 1268 8.4.13. 412 Precondition Failed 1270 The precondition given in one or more of the request-header fields 1271 evaluated to false when it was tested on the server, as defined in 1272 [Part4]. 1274 8.4.14. 413 Request Entity Too Large 1276 The server is refusing to process a request because the request 1277 entity is larger than the server is willing or able to process. The 1278 server MAY close the connection to prevent the client from continuing 1279 the request. 1281 If the condition is temporary, the server SHOULD include a Retry- 1282 After header field to indicate that it is temporary and after what 1283 time the client MAY try again. 1285 8.4.15. 414 URI Too Long 1287 The server is refusing to service the request because the request- 1288 target is longer than the server is willing to interpret. This rare 1289 condition is only likely to occur when a client has improperly 1290 converted a POST request to a GET request with long query 1291 information, when the client has descended into a URI "black hole" of 1292 redirection (e.g., a redirected URI prefix that points to a suffix of 1293 itself), or when the server is under attack by a client attempting to 1294 exploit security holes present in some servers using fixed-length 1295 buffers for reading or manipulating the request-target. 1297 8.4.16. 415 Unsupported Media Type 1299 The server is refusing to service the request because the entity of 1300 the request is in a format not supported by the requested resource 1301 for the requested method. 1303 8.4.17. 416 Requested Range Not Satisfiable 1305 The request included a Range request-header field (Section 5.4 of 1306 [Part5]) and none of the range-specifier values in this field overlap 1307 the current extent of the selected resource. 1309 8.4.18. 417 Expectation Failed 1311 The expectation given in an Expect request-header field (see 1312 Section 9.2) could not be met by this server, or, if the server is a 1313 proxy, the server has unambiguous evidence that the request could not 1314 be met by the next-hop server. 1316 8.5. Server Error 5xx 1318 Response status codes beginning with the digit "5" indicate cases in 1319 which the server is aware that it has erred or is incapable of 1320 performing the request. Except when responding to a HEAD request, 1321 the server SHOULD include an entity containing an explanation of the 1322 error situation, and whether it is a temporary or permanent 1323 condition. User agents SHOULD display any included entity to the 1324 user. These response codes are applicable to any request method. 1326 8.5.1. 500 Internal Server Error 1328 The server encountered an unexpected condition which prevented it 1329 from fulfilling the request. 1331 8.5.2. 501 Not Implemented 1333 The server does not support the functionality required to fulfill the 1334 request. This is the appropriate response when the server does not 1335 recognize the request method and is not capable of supporting it for 1336 any resource. 1338 8.5.3. 502 Bad Gateway 1340 The server, while acting as a gateway or proxy, received an invalid 1341 response from the upstream server it accessed in attempting to 1342 fulfill the request. 1344 8.5.4. 503 Service Unavailable 1346 The server is currently unable to handle the request due to a 1347 temporary overloading or maintenance of the server. The implication 1348 is that this is a temporary condition which will be alleviated after 1349 some delay. If known, the length of the delay MAY be indicated in a 1350 Retry-After header. If no Retry-After is given, the client SHOULD 1351 handle the response as it would for a 500 response. 1353 Note: The existence of the 503 status code does not imply that a 1354 server must use it when becoming overloaded. Some servers may 1355 wish to simply refuse the connection. 1357 8.5.5. 504 Gateway Timeout 1359 The server, while acting as a gateway or proxy, did not receive a 1360 timely response from the upstream server specified by the URI (e.g. 1361 HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed 1362 to access in attempting to complete the request. 1364 Note: Note to implementors: some deployed proxies are known to 1365 return 400 or 500 when DNS lookups time out. 1367 8.5.6. 505 HTTP Version Not Supported 1369 The server does not support, or refuses to support, the protocol 1370 version that was used in the request message. The server is 1371 indicating that it is unable or unwilling to complete the request 1372 using the same major version as the client, as described in Section 1373 3.1 of [Part1], other than with this error message. The response 1374 SHOULD contain an entity describing why that version is not supported 1375 and what other protocols are supported by that server. 1377 9. Header Field Definitions 1379 This section defines the syntax and semantics of HTTP/1.1 header 1380 fields related to request and response semantics. 1382 For entity-header fields, both sender and recipient refer to either 1383 the client or the server, depending on who sends and who receives the 1384 entity. 1386 9.1. Allow 1388 The response-header field "Allow" lists the set of methods advertised 1389 as supported by the resource identified by the request-target. The 1390 purpose of this field is strictly to inform the recipient of valid 1391 methods associated with the resource. An Allow header field MUST be 1392 present in a 405 (Method Not Allowed) response. 1394 Allow = "Allow" ":" OWS Allow-v 1395 Allow-v = #Method 1397 Example of use: 1399 Allow: GET, HEAD, PUT 1401 The actual set of allowed methods is defined by the origin server at 1402 the time of each request. 1404 A proxy MUST NOT modify the Allow header field even if it does not 1405 understand all the methods specified, since the user agent might have 1406 other means of communicating with the origin server. 1408 9.2. Expect 1410 The request-header field "Expect" is used to indicate that particular 1411 server behaviors are required by the client. 1413 Expect = "Expect" ":" OWS Expect-v 1414 Expect-v = 1#expectation 1416 expectation = "100-continue" / expectation-extension 1417 expectation-extension = token [ "=" ( token / quoted-string ) 1418 *expect-params ] 1419 expect-params = ";" token [ "=" ( token / quoted-string ) ] 1421 A server that does not understand or is unable to comply with any of 1422 the expectation values in the Expect field of a request MUST respond 1423 with appropriate error status. The server MUST respond with a 417 1424 (Expectation Failed) status if any of the expectations cannot be met 1425 or, if there are other problems with the request, some other 4xx 1426 status. 1428 This header field is defined with extensible syntax to allow for 1429 future extensions. If a server receives a request containing an 1430 Expect field that includes an expectation-extension that it does not 1431 support, it MUST respond with a 417 (Expectation Failed) status. 1433 Comparison of expectation values is case-insensitive for unquoted 1434 tokens (including the 100-continue token), and is case-sensitive for 1435 quoted-string expectation-extensions. 1437 The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST 1438 return a 417 (Expectation Failed) status if it receives a request 1439 with an expectation that it cannot meet. However, the Expect 1440 request-header itself is end-to-end; it MUST be forwarded if the 1441 request is forwarded. 1443 Many older HTTP/1.0 and HTTP/1.1 applications do not understand the 1444 Expect header. 1446 See Section 7.2.3 of [Part1] for the use of the 100 (Continue) 1447 status. 1449 9.3. From 1451 The request-header field "From", if given, SHOULD contain an Internet 1452 e-mail address for the human user who controls the requesting user 1453 agent. The address SHOULD be machine-usable, as defined by "mailbox" 1454 in Section 3.4 of [RFC5322]: 1456 From = "From" ":" OWS From-v 1457 From-v = mailbox 1459 mailbox = 1461 An example is: 1463 From: webmaster@example.org 1465 This header field MAY be used for logging purposes and as a means for 1466 identifying the source of invalid or unwanted requests. It SHOULD 1467 NOT be used as an insecure form of access protection. The 1468 interpretation of this field is that the request is being performed 1469 on behalf of the person given, who accepts responsibility for the 1470 method performed. In particular, robot agents SHOULD include this 1471 header so that the person responsible for running the robot can be 1472 contacted if problems occur on the receiving end. 1474 The Internet e-mail address in this field MAY be separate from the 1475 Internet host which issued the request. For example, when a request 1476 is passed through a proxy the original issuer's address SHOULD be 1477 used. 1479 The client SHOULD NOT send the From header field without the user's 1480 approval, as it might conflict with the user's privacy interests or 1481 their site's security policy. It is strongly recommended that the 1482 user be able to disable, enable, and modify the value of this field 1483 at any time prior to a request. 1485 9.4. Location 1487 The response-header field "Location" is used for the identification 1488 of a new resource or to redirect the recipient to a location other 1489 than the request-target for completion of the request. For 201 1490 (Created) responses, the Location is that of the new resource which 1491 was created by the request. For 3xx responses, the location SHOULD 1492 indicate the server's preferred URI for automatic redirection to the 1493 resource. The field value consists of a single absolute URI. 1495 Location = "Location" ":" OWS Location-v 1496 Location-v = absolute-URI [ "#" fragment ] 1498 An example is: 1500 Location: http://www.example.org/pub/WWW/People.html 1502 Note: The Content-Location header field (Section 5.7 of [Part3]) 1503 differs from Location in that the Content-Location identifies the 1504 original location of the entity enclosed in the response. It is 1505 therefore possible for a response to contain header fields for 1506 both Location and Content-Location. 1508 There are circumstances in which a fragment identifier in a Location 1509 URL would not be appropriate: 1511 o With a 201 Created response, because in this usage the Location 1512 header specifies the URL for the entire created resource. 1514 o With a 300 Multiple Choices, since the choice decision is intended 1515 to be made on resource characteristics and not fragment 1516 characteristics. 1518 o With 305 Use Proxy. 1520 9.5. Max-Forwards 1522 The request-header "Max-Forwards" field provides a mechanism with the 1523 TRACE (Section 7.8) and OPTIONS (Section 7.2) methods to limit the 1524 number of proxies or gateways that can forward the request to the 1525 next inbound server. This can be useful when the client is 1526 attempting to trace a request chain which appears to be failing or 1527 looping in mid-chain. 1529 Max-Forwards = "Max-Forwards" ":" OWS Max-Forwards-v 1530 Max-Forwards-v = 1*DIGIT 1532 The Max-Forwards value is a decimal integer indicating the remaining 1533 number of times this request message may be forwarded. 1535 Each proxy or gateway recipient of a TRACE or OPTIONS request 1536 containing a Max-Forwards header field MUST check and update its 1537 value prior to forwarding the request. If the received value is zero 1538 (0), the recipient MUST NOT forward the request; instead, it MUST 1539 respond as the final recipient. If the received Max-Forwards value 1540 is greater than zero, then the forwarded message MUST contain an 1541 updated Max-Forwards field with a value decremented by one (1). 1543 The Max-Forwards header field MAY be ignored for all other methods 1544 defined by this specification and for any extension methods for which 1545 it is not explicitly referred to as part of that method definition. 1547 9.6. Referer 1549 The request-header field "Referer" [sic] allows the client to 1550 specify, for the server's benefit, the address (URI) of the resource 1551 from which the request-target was obtained (the "referrer", although 1552 the header field is misspelled.) The Referer request-header allows a 1553 server to generate lists of back-links to resources for interest, 1554 logging, optimized caching, etc. It also allows obsolete or mistyped 1555 links to be traced for maintenance. The Referer field MUST NOT be 1556 sent if the request-target was obtained from a source that does not 1557 have its own URI, such as input from the user keyboard. 1559 Referer = "Referer" ":" OWS Referer-v 1560 Referer-v = absolute-URI / partial-URI 1562 Example: 1564 Referer: http://www.example.org/hypertext/Overview.html 1566 If the field value is a relative URI, it SHOULD be interpreted 1567 relative to the request-target. The URI MUST NOT include a fragment. 1568 See Section 11.2 for security considerations. 1570 9.7. Retry-After 1572 The response-header "Retry-After" field can be used with a 503 1573 (Service Unavailable) response to indicate how long the service is 1574 expected to be unavailable to the requesting client. This field MAY 1575 also be used with any 3xx (Redirection) response to indicate the 1576 minimum time the user-agent is asked wait before issuing the 1577 redirected request. The value of this field can be either an HTTP- 1578 date or an integer number of seconds (in decimal) after the time of 1579 the response. 1581 Retry-After = "Retry-After" ":" OWS Retry-After-v 1582 Retry-After-v = HTTP-date / delta-seconds 1584 Time spans are non-negative decimal integers, representing time in 1585 seconds. 1587 delta-seconds = 1*DIGIT 1589 Two examples of its use are 1591 Retry-After: Fri, 31 Dec 1999 23:59:59 GMT 1592 Retry-After: 120 1594 In the latter example, the delay is 2 minutes. 1596 9.8. Server 1598 The response-header field "Server" contains information about the 1599 software used by the origin server to handle the request. The field 1600 can contain multiple product tokens (Section 3.4 of [Part1]) and 1601 comments identifying the server and any significant subproducts. The 1602 product tokens are listed in order of their significance for 1603 identifying the application. 1605 Server = "Server" ":" OWS Server-v 1606 Server-v = product 1607 *( RWS ( product / comment ) ) 1609 Example: 1611 Server: CERN/3.0 libwww/2.17 1613 If the response is being forwarded through a proxy, the proxy 1614 application MUST NOT modify the Server response-header. Instead, it 1615 MUST include a Via field (as described in Section 8.9 of [Part1]). 1617 Note: Revealing the specific software version of the server might 1618 allow the server machine to become more vulnerable to attacks 1619 against software that is known to contain security holes. Server 1620 implementors are encouraged to make this field a configurable 1621 option. 1623 9.9. User-Agent 1625 The request-header field "User-Agent" contains information about the 1626 user agent originating the request. This is for statistical 1627 purposes, the tracing of protocol violations, and automated 1628 recognition of user agents for the sake of tailoring responses to 1629 avoid particular user agent limitations. User agents SHOULD include 1630 this field with requests. The field can contain multiple product 1631 tokens (Section 3.4 of [Part1]) and comments identifying the agent 1632 and any subproducts which form a significant part of the user agent. 1633 By convention, the product tokens are listed in order of their 1634 significance for identifying the application. 1636 User-Agent = "User-Agent" ":" OWS User-Agent-v 1637 User-Agent-v = product 1638 *( RWS ( product / comment ) ) 1640 Example: 1642 User-Agent: CERN-LineMode/2.15 libwww/2.17b3 1644 10. IANA Considerations 1646 10.1. Method Registry 1648 The registration procedure for HTTP Methods is defined by Section 2.1 1649 of this document. 1651 The HTTP Method Registry located at 1652 should be populated 1653 with the registrations below: 1655 +---------+------+-------------+ 1656 | Method | Safe | Reference | 1657 +---------+------+-------------+ 1658 | CONNECT | no | Section 7.9 | 1659 | DELETE | no | Section 7.7 | 1660 | GET | yes | Section 7.3 | 1661 | HEAD | yes | Section 7.4 | 1662 | OPTIONS | yes | Section 7.2 | 1663 | POST | no | Section 7.5 | 1664 | PUT | no | Section 7.6 | 1665 | TRACE | yes | Section 7.8 | 1666 +---------+------+-------------+ 1668 10.2. Status Code Registry 1670 The registration procedure for HTTP Status Codes -- previously 1671 defined in Section 7.1 of [RFC2817] -- is now defined by Section 4.1 1672 of this document. 1674 The HTTP Status Code Registry located at 1675 should be updated 1676 with the registrations below: 1678 +-------+---------------------------------+----------------+ 1679 | Value | Description | Reference | 1680 +-------+---------------------------------+----------------+ 1681 | 100 | Continue | Section 8.1.1 | 1682 | 101 | Switching Protocols | Section 8.1.2 | 1683 | 200 | OK | Section 8.2.1 | 1684 | 201 | Created | Section 8.2.2 | 1685 | 202 | Accepted | Section 8.2.3 | 1686 | 203 | Non-Authoritative Information | Section 8.2.4 | 1687 | 204 | No Content | Section 8.2.5 | 1688 | 205 | Reset Content | Section 8.2.6 | 1689 | 206 | Partial Content | Section 8.2.7 | 1690 | 300 | Multiple Choices | Section 8.3.1 | 1691 | 301 | Moved Permanently | Section 8.3.2 | 1692 | 302 | Found | Section 8.3.3 | 1693 | 303 | See Other | Section 8.3.4 | 1694 | 304 | Not Modified | Section 8.3.5 | 1695 | 305 | Use Proxy | Section 8.3.6 | 1696 | 306 | (Unused) | Section 8.3.7 | 1697 | 307 | Temporary Redirect | Section 8.3.8 | 1698 | 400 | Bad Request | Section 8.4.1 | 1699 | 401 | Unauthorized | Section 8.4.2 | 1700 | 402 | Payment Required | Section 8.4.3 | 1701 | 403 | Forbidden | Section 8.4.4 | 1702 | 404 | Not Found | Section 8.4.5 | 1703 | 405 | Method Not Allowed | Section 8.4.6 | 1704 | 406 | Not Acceptable | Section 8.4.7 | 1705 | 407 | Proxy Authentication Required | Section 8.4.8 | 1706 | 408 | Request Timeout | Section 8.4.9 | 1707 | 409 | Conflict | Section 8.4.10 | 1708 | 410 | Gone | Section 8.4.11 | 1709 | 411 | Length Required | Section 8.4.12 | 1710 | 412 | Precondition Failed | Section 8.4.13 | 1711 | 413 | Request Entity Too Large | Section 8.4.14 | 1712 | 414 | URI Too Long | Section 8.4.15 | 1713 | 415 | Unsupported Media Type | Section 8.4.16 | 1714 | 416 | Requested Range Not Satisfiable | Section 8.4.17 | 1715 | 417 | Expectation Failed | Section 8.4.18 | 1716 | 500 | Internal Server Error | Section 8.5.1 | 1717 | 501 | Not Implemented | Section 8.5.2 | 1718 | 502 | Bad Gateway | Section 8.5.3 | 1719 | 503 | Service Unavailable | Section 8.5.4 | 1720 | 504 | Gateway Timeout | Section 8.5.5 | 1721 | 505 | HTTP Version Not Supported | Section 8.5.6 | 1722 +-------+---------------------------------+----------------+ 1724 10.3. Message Header Registration 1726 The Message Header Registry located at should be 1728 updated with the permanent registrations below (see [RFC3864]): 1730 +-------------------+----------+----------+-------------+ 1731 | Header Field Name | Protocol | Status | Reference | 1732 +-------------------+----------+----------+-------------+ 1733 | Allow | http | standard | Section 9.1 | 1734 | Expect | http | standard | Section 9.2 | 1735 | From | http | standard | Section 9.3 | 1736 | Location | http | standard | Section 9.4 | 1737 | Max-Forwards | http | standard | Section 9.5 | 1738 | Referer | http | standard | Section 9.6 | 1739 | Retry-After | http | standard | Section 9.7 | 1740 | Server | http | standard | Section 9.8 | 1741 | User-Agent | http | standard | Section 9.9 | 1742 +-------------------+----------+----------+-------------+ 1744 The change controller is: "IETF (iesg@ietf.org) - Internet 1745 Engineering Task Force". 1747 11. Security Considerations 1749 This section is meant to inform application developers, information 1750 providers, and users of the security limitations in HTTP/1.1 as 1751 described by this document. The discussion does not include 1752 definitive solutions to the problems revealed, though it does make 1753 some suggestions for reducing security risks. 1755 11.1. Transfer of Sensitive Information 1757 Like any generic data transfer protocol, HTTP cannot regulate the 1758 content of the data that is transferred, nor is there any a priori 1759 method of determining the sensitivity of any particular piece of 1760 information within the context of any given request. Therefore, 1761 applications SHOULD supply as much control over this information as 1762 possible to the provider of that information. Four header fields are 1763 worth special mention in this context: Server, Via, Referer and From. 1765 Revealing the specific software version of the server might allow the 1766 server machine to become more vulnerable to attacks against software 1767 that is known to contain security holes. Implementors SHOULD make 1768 the Server header field a configurable option. 1770 Proxies which serve as a portal through a network firewall SHOULD 1771 take special precautions regarding the transfer of header information 1772 that identifies the hosts behind the firewall. In particular, they 1773 SHOULD remove, or replace with sanitized versions, any Via fields 1774 generated behind the firewall. 1776 The Referer header allows reading patterns to be studied and reverse 1777 links drawn. Although it can be very useful, its power can be abused 1778 if user details are not separated from the information contained in 1779 the Referer. Even when the personal information has been removed, 1780 the Referer header might indicate a private document's URI whose 1781 publication would be inappropriate. 1783 The information sent in the From field might conflict with the user's 1784 privacy interests or their site's security policy, and hence it 1785 SHOULD NOT be transmitted without the user being able to disable, 1786 enable, and modify the contents of the field. The user MUST be able 1787 to set the contents of this field within a user preference or 1788 application defaults configuration. 1790 We suggest, though do not require, that a convenient toggle interface 1791 be provided for the user to enable or disable the sending of From and 1792 Referer information. 1794 The User-Agent (Section 9.9) or Server (Section 9.8) header fields 1795 can sometimes be used to determine that a specific client or server 1796 have a particular security hole which might be exploited. 1797 Unfortunately, this same information is often used for other valuable 1798 purposes for which HTTP currently has no better mechanism. 1800 11.2. Encoding Sensitive Information in URIs 1802 Because the source of a link might be private information or might 1803 reveal an otherwise private information source, it is strongly 1804 recommended that the user be able to select whether or not the 1805 Referer field is sent. For example, a browser client could have a 1806 toggle switch for browsing openly/anonymously, which would 1807 respectively enable/disable the sending of Referer and From 1808 information. 1810 Clients SHOULD NOT include a Referer header field in a (non-secure) 1811 HTTP request if the referring page was transferred with a secure 1812 protocol. 1814 Authors of services should not use GET-based forms for the submission 1815 of sensitive data because that data will be encoded in the Request- 1816 target. Many existing servers, proxies, and user agents log or 1817 display the Request-target in places where it might be visible to 1818 third parties. Such services can use POST-based form submission 1819 instead. 1821 11.3. Location Headers and Spoofing 1823 If a single server supports multiple organizations that do not trust 1824 one another, then it MUST check the values of Location and Content- 1825 Location headers in responses that are generated under control of 1826 said organizations to make sure that they do not attempt to 1827 invalidate resources over which they have no authority. 1829 12. Acknowledgments 1831 13. References 1833 13.1. Normative References 1835 [Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., 1836 Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., 1837 and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections, 1838 and Message Parsing", draft-ietf-httpbis-p1-messaging-06 1839 (work in progress), March 2009. 1841 [Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., 1842 Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., 1843 and J. Reschke, Ed., "HTTP/1.1, part 3: Message Payload 1844 and Content Negotiation", draft-ietf-httpbis-p3-payload-06 1845 (work in progress), March 2009. 1847 [Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., 1848 Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., 1849 and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional 1850 Requests", draft-ietf-httpbis-p4-conditional-06 (work in 1851 progress), March 2009. 1853 [Part5] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., 1854 Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., 1855 and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and 1856 Partial Responses", draft-ietf-httpbis-p5-range-06 (work 1857 in progress), March 2009. 1859 [Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., 1860 Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., 1861 and J. Reschke, Ed., "HTTP/1.1, part 6: Caching", 1862 draft-ietf-httpbis-p6-cache-06 (work in progress), 1863 March 2009. 1865 [Part7] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., 1866 Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., 1867 and J. Reschke, Ed., "HTTP/1.1, part 7: Authentication", 1868 draft-ietf-httpbis-p7-auth-06 (work in progress), 1869 March 2009. 1871 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1872 Requirement Levels", BCP 14, RFC 2119, March 1997. 1874 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 1875 Specifications: ABNF", STD 68, RFC 5234, January 2008. 1877 13.2. Informative References 1879 [RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext 1880 Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996. 1882 [RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T. 1883 Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", 1884 RFC 2068, January 1997. 1886 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 1887 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 1888 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 1890 [RFC2817] Khare, R. and S. Lawrence, "Upgrading to TLS Within 1891 HTTP/1.1", RFC 2817, May 2000. 1893 [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration 1894 Procedures for Message Header Fields", BCP 90, RFC 3864, 1895 September 2004. 1897 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1898 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1899 May 2008. 1901 [RFC5322] Resnick, P., "Internet Message Format", RFC 5322, 1902 October 2008. 1904 Appendix A. Compatibility with Previous Versions 1906 A.1. Changes from RFC 2068 1908 Clarified which error code should be used for inbound server failures 1909 (e.g. DNS failures). (Section 8.5.5). 1911 201 (Created) had a race that required an Etag be sent when a 1912 resource is first created. (Section 8.2.2). 1914 Rewrite of message transmission requirements to make it much harder 1915 for implementors to get it wrong, as the consequences of errors here 1916 can have significant impact on the Internet, and to deal with the 1917 following problems: 1919 1. Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where 1920 this was incorrectly placing a requirement on the behavior of an 1921 implementation of a future version of HTTP/1.x 1923 2. Made it clear that user-agents should retry requests, not 1924 "clients" in general. 1926 3. Converted requirements for clients to ignore unexpected 100 1927 (Continue) responses, and for proxies to forward 100 responses, 1928 into a general requirement for 1xx responses. 1930 4. Modified some TCP-specific language, to make it clearer that non- 1931 TCP transports are possible for HTTP. 1933 5. Require that the origin server MUST NOT wait for the request body 1934 before it sends a required 100 (Continue) response. 1936 6. Allow, rather than require, a server to omit 100 (Continue) if it 1937 has already seen some of the request body. 1939 7. Allow servers to defend against denial-of-service attacks and 1940 broken clients. 1942 This change adds the Expect header and 417 status code. 1944 Clean up confusion between 403 and 404 responses. (Section 8.4.4, 1945 8.4.5, and 8.4.11) 1947 The PATCH, LINK, UNLINK methods were defined but not commonly 1948 implemented in previous versions of this specification. See Section 1949 19.6.1 of [RFC2068]. 1951 A.2. Changes from RFC 2616 1953 This document takes over the Status Code Registry, previously defined 1954 in Section 7.1 of [RFC2817]. (Section 4.1) 1956 Clarify definition of POST. (Section 7.5) 1958 Failed to consider that there are many other request methods that are 1959 safe to automatically redirect, and further that the user agent is 1960 able to make that determination based on the request method 1961 semantics. (Sections 8.3.2, 8.3.3 and 8.3.8) 1963 Deprecate 305 Use Proxy status code, because user agents did not 1964 implement it. It used to indicate that the requested resource must 1965 be accessed through the proxy given by the Location field. The 1966 Location field gave the URI of the proxy. The recipient was expected 1967 to repeat this single request via the proxy. (Section 8.3.6) 1969 Reclassify Allow header as response header, removing the option to 1970 specify it in a PUT request. Relax the server requirement on the 1971 contents of the Allow header and remove requirement on clients to 1972 always trust the header value. (Section 9.1) 1974 Correct syntax of Location header to allow fragment, as referred 1975 symbol wasn't what was expected, and add some clarifications as to 1976 when it would not be appropriate. (Section 9.4) 1978 In the description of the Server header, the Via field was described 1979 as a SHOULD. The requirement was and is stated correctly in the 1980 description of the Via header in Section 8.9 of [Part1]. 1981 (Section 9.8) 1983 Appendix B. Collected ABNF 1985 Accept = 1986 Accept-Charset = 1987 Accept-Encoding = 1988 Accept-Language = 1989 Accept-Ranges = 1990 Age = 1991 Allow = "Allow:" OWS Allow-v 1992 Allow-v = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ] 1993 Authorization = 1995 ETag = 1996 Expect = "Expect:" OWS Expect-v 1997 Expect-v = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] ) 1999 From = "From:" OWS From-v 2000 From-v = mailbox 2002 HTTP-date = 2003 Host = 2005 If-Match = 2006 If-Modified-Since = 2007 2008 If-None-Match = 2009 If-Range = 2010 If-Unmodified-Since = 2011 2013 Location = "Location:" OWS Location-v 2014 Location-v = absolute-URI [ "#" fragment ] 2016 Max-Forwards = "Max-Forwards:" OWS Max-Forwards-v 2017 Max-Forwards-v = 1*DIGIT 2018 Method = %x4F.50.54.49.4F.4E.53 / %x47.45.54 / %x48.45.41.44 / 2019 %x50.4F.54 / %x50.55.54 / %x44.45.4C.45.54.45 / %x54.52.41.43.45 / 2020 %x43.4E.4E.45.43.54 / extension-method 2022 OWS = 2024 Proxy-Authenticate = 2025 2026 Proxy-Authorization = 2027 2029 RWS = 2030 Range = 2031 Reason-Phrase = *( WSP / VCHAR / obs-text ) 2032 Referer = "Referer:" OWS Referer-v 2033 Referer-v = absolute-URI / partial-URI 2034 Retry-After = "Retry-After:" OWS Retry-After-v 2035 Retry-After-v = HTTP-date / delta-seconds 2037 Server = "Server:" OWS Server-v 2038 Server-v = product *( RWS ( product / comment ) ) 2039 Status-Code = "100" / "101" / "200" / "201" / "202" / "203" / "204" / 2040 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" / 2041 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" / 2042 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" / 2043 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" / 2044 "505" / extension-code 2046 TE = 2048 User-Agent = "User-Agent:" OWS User-Agent-v 2049 User-Agent-v = product *( RWS ( product / comment ) ) 2051 Vary = 2052 WWW-Authenticate = 2053 2055 absolute-URI = 2057 comment = 2059 delta-seconds = 1*DIGIT 2061 expect-params = ";" token [ "=" ( token / quoted-string ) ] 2062 expectation = "100-continue" / expectation-extension 2063 expectation-extension = token [ "=" ( token / quoted-string ) 2064 *expect-params ] 2065 extension-code = 3DIGIT 2066 extension-method = token 2068 fragment = 2070 mailbox = 2072 obs-text = 2074 partial-URI = 2075 product = 2077 quoted-string = 2079 request-header = Accept / Accept-Charset / Accept-Encoding / 2080 Accept-Language / Authorization / Expect / From / Host / If-Match / 2081 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since / 2082 Max-Forwards / Proxy-Authorization / Range / Referer / TE / 2083 User-Agent 2084 response-header = Accept-Ranges / Age / Allow / ETag / Location / 2085 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate 2087 token = 2089 ABNF diagnostics: 2091 ; Reason-Phrase defined but not used 2092 ; Status-Code defined but not used 2093 ; request-header defined but not used 2094 ; response-header defined but not used 2096 Appendix C. Change Log (to be removed by RFC Editor before publication) 2098 C.1. Since RFC2616 2100 Extracted relevant partitions from [RFC2616]. 2102 C.2. Since draft-ietf-httpbis-p2-semantics-00 2104 Closed issues: 2106 o : "Via is a MUST" 2107 () 2109 o : "Fragments 2110 allowed in Location" 2111 () 2113 o : "Safe Methods 2114 vs Redirection" () 2116 o : "Revise 2117 description of the POST method" 2118 () 2120 o : "Normative and 2121 Informative references" 2123 o : "RFC2606 2124 Compliance" 2126 o : "Informative 2127 references" 2129 o : "Redundant 2130 cross-references" 2132 Other changes: 2134 o Move definitions of 304 and 412 condition codes to [Part4] 2136 C.3. Since draft-ietf-httpbis-p2-semantics-01 2138 Closed issues: 2140 o : "PUT side 2141 effects" 2143 o : "Duplicate Host 2144 header requirements" 2146 Ongoing work on ABNF conversion 2147 (): 2149 o Move "Product Tokens" section (back) into Part 1, as "token" is 2150 used in the definition of the Upgrade header. 2152 o Add explicit references to BNF syntax and rules imported from 2153 other parts of the specification. 2155 o Copy definition of delta-seconds from Part6 instead of referencing 2156 it. 2158 C.4. Since draft-ietf-httpbis-p2-semantics-02 2160 Closed issues: 2162 o : "Requiring 2163 Allow in 405 responses" 2165 o : "Status Code 2166 Registry" 2168 o : "Redirection 2169 vs. Location" 2171 o : "Cacheability 2172 of 303 response" 2174 o : "305 Use Proxy" 2176 o : 2177 "Classification for Allow header" 2179 o : "PUT - 'store 2180 under' vs 'store at'" 2182 Ongoing work on IANA Message Header Registration 2183 (): 2185 o Reference RFC 3984, and update header registrations for headers 2186 defined in this document. 2188 Ongoing work on ABNF conversion 2189 (): 2191 o Replace string literals when the string really is case-sensitive 2192 (method). 2194 C.5. Since draft-ietf-httpbis-p2-semantics-03 2196 Closed issues: 2198 o : "OPTIONS 2199 request bodies" 2201 o : "Description 2202 of CONNECT should refer to RFC2817" 2204 o : "Location 2205 Content-Location reference request/response mixup" 2207 Ongoing work on Method Registry 2208 (): 2210 o Added initial proposal for registration process, plus initial 2211 content (non-HTTP/1.1 methods to be added by a separate 2212 specification). 2214 C.6. Since draft-ietf-httpbis-p2-semantics-04 2216 Closed issues: 2218 o : "Content-*" 2220 o : "RFC 2822 is 2221 updated by RFC 5322" 2223 Ongoing work on ABNF conversion 2224 (): 2226 o Use "/" instead of "|" for alternatives. 2228 o Introduce new ABNF rules for "bad" whitespace ("BWS"), optional 2229 whitespace ("OWS") and required whitespace ("RWS"). 2231 o Rewrite ABNFs to spell out whitespace rules, factor out header 2232 value format definitions. 2234 C.7. Since draft-ietf-httpbis-p2-semantics-05 2236 Closed issues: 2238 o : "Reason-Phrase 2239 BNF" 2241 Final work on ABNF conversion 2242 (): 2244 o Add appendix containing collected and expanded ABNF, reorganize 2245 ABNF introduction. 2247 Index 2249 1 2250 100 Continue (status code) 20 2251 101 Switching Protocols (status code) 20 2253 2 2254 200 OK (status code) 20 2255 201 Created (status code) 21 2256 202 Accepted (status code) 21 2257 203 Non-Authoritative Information (status code) 21 2258 204 No Content (status code) 22 2259 205 Reset Content (status code) 22 2260 206 Partial Content (status code) 22 2262 3 2263 300 Multiple Choices (status code) 23 2264 301 Moved Permanently (status code) 23 2265 302 Found (status code) 24 2266 303 See Other (status code) 24 2267 304 Not Modified (status code) 25 2268 305 Use Proxy (status code) 25 2269 306 (Unused) (status code) 25 2270 307 Temporary Redirect (status code) 25 2272 4 2273 400 Bad Request (status code) 26 2274 401 Unauthorized (status code) 26 2275 402 Payment Required (status code) 26 2276 403 Forbidden (status code) 26 2277 404 Not Found (status code) 27 2278 405 Method Not Allowed (status code) 27 2279 406 Not Acceptable (status code) 27 2280 407 Proxy Authentication Required (status code) 27 2281 408 Request Timeout (status code) 28 2282 409 Conflict (status code) 28 2283 410 Gone (status code) 28 2284 411 Length Required (status code) 29 2285 412 Precondition Failed (status code) 29 2286 413 Request Entity Too Large (status code) 29 2287 414 URI Too Long (status code) 29 2288 415 Unsupported Media Type (status code) 29 2289 416 Requested Range Not Satisfiable (status code) 29 2290 417 Expectation Failed (status code) 30 2292 5 2293 500 Internal Server Error (status code) 30 2294 501 Not Implemented (status code) 30 2295 502 Bad Gateway (status code) 30 2296 503 Service Unavailable (status code) 30 2297 504 Gateway Timeout (status code) 31 2298 505 HTTP Version Not Supported (status code) 31 2300 A 2301 Allow header 31 2303 C 2304 CONNECT method 19 2306 D 2307 DELETE method 18 2309 E 2310 Expect header 32 2312 F 2313 From header 33 2315 G 2316 GET method 15 2317 Grammar 2318 Allow 31 2319 Allow-v 31 2320 delta-seconds 35 2321 Expect 32 2322 expect-params 32 2323 Expect-v 32 2324 expectation 32 2325 expectation-extension 32 2326 extension-code 11 2327 extension-method 8 2328 From 33 2329 From-v 33 2330 Location 33 2331 Location-v 33 2332 Max-Forwards 34 2333 Max-Forwards-v 34 2334 Method 8 2335 Reason-Phrase 11 2336 Referer 35 2337 Referer-v 35 2338 request-header 9 2339 response-header 12 2340 Retry-After 35 2341 Retry-After-v 35 2342 Server 36 2343 Server-v 36 2344 Status-Code 11 2345 User-Agent 36 2346 User-Agent-v 36 2348 H 2349 HEAD method 16 2350 Headers 2351 Allow 31 2352 Expect 32 2353 From 33 2354 Location 33 2355 Max-Forwards 34 2356 Referer 35 2357 Retry-After 35 2358 Server 36 2359 User-Agent 36 2361 I 2362 Idempotent Methods 14 2364 L 2365 LINK method 43 2366 Location header 33 2368 M 2369 Max-Forwards header 34 2370 Methods 2371 CONNECT 19 2372 DELETE 18 2373 GET 15 2374 HEAD 16 2375 LINK 43 2376 OPTIONS 14 2377 PATCH 43 2378 POST 16 2379 PUT 17 2380 TRACE 18 2381 UNLINK 43 2383 O 2384 OPTIONS method 14 2386 P 2387 PATCH method 43 2388 POST method 16 2389 PUT method 17 2391 R 2392 Referer header 35 2393 Retry-After header 35 2395 S 2396 Safe Methods 13 2397 Server header 36 2398 Status Codes 2399 100 Continue 20 2400 101 Switching Protocols 20 2401 200 OK 20 2402 201 Created 21 2403 202 Accepted 21 2404 203 Non-Authoritative Information 21 2405 204 No Content 22 2406 205 Reset Content 22 2407 206 Partial Content 22 2408 300 Multiple Choices 23 2409 301 Moved Permanently 23 2410 302 Found 24 2411 303 See Other 24 2412 304 Not Modified 25 2413 305 Use Proxy 25 2414 306 (Unused) 25 2415 307 Temporary Redirect 25 2416 400 Bad Request 26 2417 401 Unauthorized 26 2418 402 Payment Required 26 2419 403 Forbidden 26 2420 404 Not Found 27 2421 405 Method Not Allowed 27 2422 406 Not Acceptable 27 2423 407 Proxy Authentication Required 27 2424 408 Request Timeout 28 2425 409 Conflict 28 2426 410 Gone 28 2427 411 Length Required 29 2428 412 Precondition Failed 29 2429 413 Request Entity Too Large 29 2430 414 URI Too Long 29 2431 415 Unsupported Media Type 29 2432 416 Requested Range Not Satisfiable 29 2433 417 Expectation Failed 30 2434 500 Internal Server Error 30 2435 501 Not Implemented 30 2436 502 Bad Gateway 30 2437 503 Service Unavailable 30 2438 504 Gateway Timeout 31 2439 505 HTTP Version Not Supported 31 2441 T 2442 TRACE method 18 2444 U 2445 UNLINK method 43 2446 User-Agent header 36 2448 Authors' Addresses 2450 Roy T. Fielding (editor) 2451 Day Software 2452 23 Corporate Plaza DR, Suite 280 2453 Newport Beach, CA 92660 2454 USA 2456 Phone: +1-949-706-5300 2457 Fax: +1-949-706-5305 2458 Email: fielding@gbiv.com 2459 URI: http://roy.gbiv.com/ 2461 Jim Gettys 2462 One Laptop per Child 2463 21 Oak Knoll Road 2464 Carlisle, MA 01741 2465 USA 2467 Email: jg@laptop.org 2468 URI: http://www.laptop.org/ 2469 Jeffrey C. Mogul 2470 Hewlett-Packard Company 2471 HP Labs, Large Scale Systems Group 2472 1501 Page Mill Road, MS 1177 2473 Palo Alto, CA 94304 2474 USA 2476 Email: JeffMogul@acm.org 2478 Henrik Frystyk Nielsen 2479 Microsoft Corporation 2480 1 Microsoft Way 2481 Redmond, WA 98052 2482 USA 2484 Email: henrikn@microsoft.com 2486 Larry Masinter 2487 Adobe Systems, Incorporated 2488 345 Park Ave 2489 San Jose, CA 95110 2490 USA 2492 Email: LMM@acm.org 2493 URI: http://larry.masinter.net/ 2495 Paul J. Leach 2496 Microsoft Corporation 2497 1 Microsoft Way 2498 Redmond, WA 98052 2500 Email: paulle@microsoft.com 2502 Tim Berners-Lee 2503 World Wide Web Consortium 2504 MIT Computer Science and Artificial Intelligence Laboratory 2505 The Stata Center, Building 32 2506 32 Vassar Street 2507 Cambridge, MA 02139 2508 USA 2510 Email: timbl@w3.org 2511 URI: http://www.w3.org/People/Berners-Lee/ 2512 Yves Lafon (editor) 2513 World Wide Web Consortium 2514 W3C / ERCIM 2515 2004, rte des Lucioles 2516 Sophia-Antipolis, AM 06902 2517 France 2519 Email: ylafon@w3.org 2520 URI: http://www.raubacapeu.net/people/yves/ 2522 Julian F. Reschke (editor) 2523 greenbytes GmbH 2524 Hafenweg 16 2525 Muenster, NW 48155 2526 Germany 2528 Phone: +49 251 2807760 2529 Fax: +49 251 2807761 2530 Email: julian.reschke@greenbytes.de 2531 URI: http://greenbytes.de/tech/webdav/