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2 HTTP Working Group R. Fielding, Ed.
3 Internet-Draft Adobe
4 Obsoletes: 7230 (if approved) M. Nottingham, Ed.
5 Intended status: Standards Track Fastly
6 Expires: January 9, 2020 J. Reschke, Ed.
7 greenbytes
8 July 8, 2019
10 HTTP/1.1 Messaging
11 draft-ietf-httpbis-messaging-05
13 Abstract
15 The Hypertext Transfer Protocol (HTTP) is a stateless application-
16 level protocol for distributed, collaborative, hypertext information
17 systems. This document specifies the HTTP/1.1 message syntax,
18 message parsing, connection management, and related security
19 concerns.
21 This document obsoletes portions of RFC 7230.
23 Editorial Note
25 This note is to be removed before publishing as an RFC.
27 Discussion of this draft takes place on the HTTP working group
28 mailing list (ietf-http-wg@w3.org), which is archived at
29 .
31 Working Group information can be found at ;
32 source code and issues list for this draft can be found at
33 .
35 The changes in this draft are summarized in Appendix D.6.
37 Status of This Memo
39 This Internet-Draft is submitted in full conformance with the
40 provisions of BCP 78 and BCP 79.
42 Internet-Drafts are working documents of the Internet Engineering
43 Task Force (IETF). Note that other groups may also distribute
44 working documents as Internet-Drafts. The list of current Internet-
45 Drafts is at https://datatracker.ietf.org/drafts/current/.
47 Internet-Drafts are draft documents valid for a maximum of six months
48 and may be updated, replaced, or obsoleted by other documents at any
49 time. It is inappropriate to use Internet-Drafts as reference
50 material or to cite them other than as "work in progress."
52 This Internet-Draft will expire on January 9, 2020.
54 Copyright Notice
56 Copyright (c) 2019 IETF Trust and the persons identified as the
57 document authors. All rights reserved.
59 This document is subject to BCP 78 and the IETF Trust's Legal
60 Provisions Relating to IETF Documents
61 (https://trustee.ietf.org/license-info) in effect on the date of
62 publication of this document. Please review these documents
63 carefully, as they describe your rights and restrictions with respect
64 to this document. Code Components extracted from this document must
65 include Simplified BSD License text as described in Section 4.e of
66 the Trust Legal Provisions and are provided without warranty as
67 described in the Simplified BSD License.
69 This document may contain material from IETF Documents or IETF
70 Contributions published or made publicly available before November
71 10, 2008. The person(s) controlling the copyright in some of this
72 material may not have granted the IETF Trust the right to allow
73 modifications of such material outside the IETF Standards Process.
74 Without obtaining an adequate license from the person(s) controlling
75 the copyright in such materials, this document may not be modified
76 outside the IETF Standards Process, and derivative works of it may
77 not be created outside the IETF Standards Process, except to format
78 it for publication as an RFC or to translate it into languages other
79 than English.
81 Table of Contents
83 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
84 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 5
85 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 5
86 2. Message . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
87 2.1. Message Format . . . . . . . . . . . . . . . . . . . . . 6
88 2.2. HTTP Version . . . . . . . . . . . . . . . . . . . . . . 7
89 2.3. Message Parsing . . . . . . . . . . . . . . . . . . . . . 8
90 3. Request Line . . . . . . . . . . . . . . . . . . . . . . . . 9
91 3.1. Method . . . . . . . . . . . . . . . . . . . . . . . . . 9
92 3.2. Request Target . . . . . . . . . . . . . . . . . . . . . 10
93 3.2.1. origin-form . . . . . . . . . . . . . . . . . . . . . 10
94 3.2.2. absolute-form . . . . . . . . . . . . . . . . . . . . 11
95 3.2.3. authority-form . . . . . . . . . . . . . . . . . . . 11
96 3.2.4. asterisk-form . . . . . . . . . . . . . . . . . . . . 12
98 3.3. Effective Request URI . . . . . . . . . . . . . . . . . . 12
99 4. Status Line . . . . . . . . . . . . . . . . . . . . . . . . . 14
100 5. Header Fields . . . . . . . . . . . . . . . . . . . . . . . . 15
101 5.1. Header Field Parsing . . . . . . . . . . . . . . . . . . 15
102 5.2. Obsolete Line Folding . . . . . . . . . . . . . . . . . . 16
103 6. Message Body . . . . . . . . . . . . . . . . . . . . . . . . 17
104 6.1. Transfer-Encoding . . . . . . . . . . . . . . . . . . . . 17
105 6.2. Content-Length . . . . . . . . . . . . . . . . . . . . . 19
106 6.3. Message Body Length . . . . . . . . . . . . . . . . . . . 19
107 7. Transfer Codings . . . . . . . . . . . . . . . . . . . . . . 21
108 7.1. Chunked Transfer Coding . . . . . . . . . . . . . . . . . 22
109 7.1.1. Chunk Extensions . . . . . . . . . . . . . . . . . . 23
110 7.1.2. Chunked Trailer Part . . . . . . . . . . . . . . . . 24
111 7.1.3. Decoding Chunked . . . . . . . . . . . . . . . . . . 25
112 7.2. Transfer Codings for Compression . . . . . . . . . . . . 25
113 7.3. Transfer Coding Registry . . . . . . . . . . . . . . . . 26
114 7.4. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
115 8. Handling Incomplete Messages . . . . . . . . . . . . . . . . 27
116 9. Connection Management . . . . . . . . . . . . . . . . . . . . 28
117 9.1. Connection . . . . . . . . . . . . . . . . . . . . . . . 29
118 9.2. Establishment . . . . . . . . . . . . . . . . . . . . . . 30
119 9.3. Associating a Response to a Request . . . . . . . . . . . 30
120 9.4. Persistence . . . . . . . . . . . . . . . . . . . . . . . 31
121 9.4.1. Retrying Requests . . . . . . . . . . . . . . . . . . 32
122 9.4.2. Pipelining . . . . . . . . . . . . . . . . . . . . . 32
123 9.5. Concurrency . . . . . . . . . . . . . . . . . . . . . . . 33
124 9.6. Failures and Timeouts . . . . . . . . . . . . . . . . . . 33
125 9.7. Tear-down . . . . . . . . . . . . . . . . . . . . . . . . 34
126 9.8. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 35
127 9.8.1. Upgrade Protocol Names . . . . . . . . . . . . . . . 37
128 9.8.2. Upgrade Token Registry . . . . . . . . . . . . . . . 38
129 10. Enclosing Messages as Data . . . . . . . . . . . . . . . . . 38
130 10.1. Media Type message/http . . . . . . . . . . . . . . . . 38
131 10.2. Media Type application/http . . . . . . . . . . . . . . 40
132 11. Security Considerations . . . . . . . . . . . . . . . . . . . 41
133 11.1. Response Splitting . . . . . . . . . . . . . . . . . . . 41
134 11.2. Request Smuggling . . . . . . . . . . . . . . . . . . . 42
135 11.3. Message Integrity . . . . . . . . . . . . . . . . . . . 42
136 11.4. Message Confidentiality . . . . . . . . . . . . . . . . 43
137 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 43
138 12.1. Header Field Registration . . . . . . . . . . . . . . . 43
139 12.2. Media Type Registration . . . . . . . . . . . . . . . . 43
140 12.3. Transfer Coding Registration . . . . . . . . . . . . . . 43
141 12.4. Upgrade Token Registration . . . . . . . . . . . . . . . 43
142 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 44
143 13.1. Normative References . . . . . . . . . . . . . . . . . . 44
144 13.2. Informative References . . . . . . . . . . . . . . . . . 45
145 Appendix A. Collected ABNF . . . . . . . . . . . . . . . . . . . 47
146 Appendix B. Differences between HTTP and MIME . . . . . . . . . 48
147 B.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 49
148 B.2. Conversion to Canonical Form . . . . . . . . . . . . . . 49
149 B.3. Conversion of Date Formats . . . . . . . . . . . . . . . 49
150 B.4. Conversion of Content-Encoding . . . . . . . . . . . . . 50
151 B.5. Conversion of Content-Transfer-Encoding . . . . . . . . . 50
152 B.6. MHTML and Line Length Limitations . . . . . . . . . . . . 50
153 Appendix C. HTTP Version History . . . . . . . . . . . . . . . . 50
154 C.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 51
155 C.1.1. Multihomed Web Servers . . . . . . . . . . . . . . . 51
156 C.1.2. Keep-Alive Connections . . . . . . . . . . . . . . . 52
157 C.1.3. Introduction of Transfer-Encoding . . . . . . . . . . 52
158 C.2. Changes from RFC 7230 . . . . . . . . . . . . . . . . . . 52
159 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 53
160 D.1. Between RFC7230 and draft 00 . . . . . . . . . . . . . . 53
161 D.2. Since draft-ietf-httpbis-messaging-00 . . . . . . . . . . 53
162 D.3. Since draft-ietf-httpbis-messaging-01 . . . . . . . . . . 54
163 D.4. Since draft-ietf-httpbis-messaging-02 . . . . . . . . . . 54
164 D.5. Since draft-ietf-httpbis-messaging-03 . . . . . . . . . . 55
165 D.6. Since draft-ietf-httpbis-messaging-04 . . . . . . . . . . 55
166 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
167 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 57
168 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 57
170 1. Introduction
172 The Hypertext Transfer Protocol (HTTP) is a stateless application-
173 level request/response protocol that uses extensible semantics and
174 self-descriptive messages for flexible interaction with network-based
175 hypertext information systems. HTTP is defined by a series of
176 documents that collectively form the HTTP/1.1 specification:
178 o "HTTP Semantics" [Semantics]
180 o "HTTP Caching" [Caching]
182 o "HTTP/1.1 Messaging" (this document)
184 This document defines HTTP/1.1 message syntax and framing
185 requirements and their associated connection management. Our goal is
186 to define all of the mechanisms necessary for HTTP/1.1 message
187 handling that are independent of message semantics, thereby defining
188 the complete set of requirements for message parsers and message-
189 forwarding intermediaries.
191 This document obsoletes the portions of RFC 7230 related to HTTP/1.1
192 messaging and connection management, with the changes being
193 summarized in Appendix C.2. The other parts of RFC 7230 are
194 obsoleted by "HTTP Semantics" [Semantics].
196 1.1. Requirements Notation
198 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
199 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
200 document are to be interpreted as described in [RFC2119].
202 Conformance criteria and considerations regarding error handling are
203 defined in Section 3 of [Semantics].
205 1.2. Syntax Notation
207 This specification uses the Augmented Backus-Naur Form (ABNF)
208 notation of [RFC5234], extended with the notation for case-
209 sensitivity in strings defined in [RFC7405].
211 It also uses a list extension, defined in Section 11 of [Semantics],
212 that allows for compact definition of comma-separated lists using a
213 '#' operator (similar to how the '*' operator indicates repetition).
214 Appendix A shows the collected grammar with all list operators
215 expanded to standard ABNF notation.
217 As a convention, ABNF rule names prefixed with "obs-" denote
218 "obsolete" grammar rules that appear for historical reasons.
220 The following core rules are included by reference, as defined in
221 [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF
222 (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),
223 HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line
224 feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any
225 visible [USASCII] character).
227 The rules below are defined in [Semantics]:
229 BWS =
230 OWS =
231 RWS =
232 absolute-URI =
233 absolute-path =
234 authority =
235 comment =
236 field-name =
237 field-value =
238 obs-text =
239 port =
240 query =
241 quoted-string =
242 token =
243 uri-host =
245 2. Message
247 2.1. Message Format
249 All HTTP/1.1 messages consist of a start-line followed by a sequence
250 of octets in a format similar to the Internet Message Format
251 [RFC5322]: zero or more header fields (collectively referred to as
252 the "headers" or the "header section"), an empty line indicating the
253 end of the header section, and an optional message body.
255 HTTP-message = start-line
256 *( header-field CRLF )
257 CRLF
258 [ message-body ]
260 An HTTP message can be either a request from client to server or a
261 response from server to client. Syntactically, the two types of
262 message differ only in the start-line, which is either a request-line
263 (for requests) or a status-line (for responses), and in the algorithm
264 for determining the length of the message body (Section 6).
266 start-line = request-line / status-line
268 In theory, a client could receive requests and a server could receive
269 responses, distinguishing them by their different start-line formats.
270 In practice, servers are implemented to only expect a request (a
271 response is interpreted as an unknown or invalid request method) and
272 clients are implemented to only expect a response.
274 Although HTTP makes use of some protocol elements similar to the
275 Multipurpose Internet Mail Extensions (MIME) [RFC2045], see
276 Appendix B for the differences between HTTP and MIME messages.
278 2.2. HTTP Version
280 HTTP uses a "." numbering scheme to indicate versions
281 of the protocol. This specification defines version "1.1".
282 Section 3.5 of [Semantics] specifies the semantics of HTTP version
283 numbers.
285 The version of an HTTP/1.x message is indicated by an HTTP-version
286 field in the start-line. HTTP-version is case-sensitive.
288 HTTP-version = HTTP-name "/" DIGIT "." DIGIT
289 HTTP-name = %s"HTTP"
291 When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [RFC1945]
292 or a recipient whose version is unknown, the HTTP/1.1 message is
293 constructed such that it can be interpreted as a valid HTTP/1.0
294 message if all of the newer features are ignored. This specification
295 places recipient-version requirements on some new features so that a
296 conformant sender will only use compatible features until it has
297 determined, through configuration or the receipt of a message, that
298 the recipient supports HTTP/1.1.
300 Intermediaries that process HTTP messages (i.e., all intermediaries
301 other than those acting as tunnels) MUST send their own HTTP-version
302 in forwarded messages. In other words, they are not allowed to
303 blindly forward the start-line without ensuring that the protocol
304 version in that message matches a version to which that intermediary
305 is conformant for both the receiving and sending of messages.
306 Forwarding an HTTP message without rewriting the HTTP-version might
307 result in communication errors when downstream recipients use the
308 message sender's version to determine what features are safe to use
309 for later communication with that sender.
311 A server MAY send an HTTP/1.0 response to an HTTP/1.1 request if it
312 is known or suspected that the client incorrectly implements the HTTP
313 specification and is incapable of correctly processing later version
314 responses, such as when a client fails to parse the version number
315 correctly or when an intermediary is known to blindly forward the
316 HTTP-version even when it doesn't conform to the given minor version
317 of the protocol. Such protocol downgrades SHOULD NOT be performed
318 unless triggered by specific client attributes, such as when one or
319 more of the request header fields (e.g., User-Agent) uniquely match
320 the values sent by a client known to be in error.
322 2.3. Message Parsing
324 The normal procedure for parsing an HTTP message is to read the
325 start-line into a structure, read each header field into a hash table
326 by field name until the empty line, and then use the parsed data to
327 determine if a message body is expected. If a message body has been
328 indicated, then it is read as a stream until an amount of octets
329 equal to the message body length is read or the connection is closed.
331 A recipient MUST parse an HTTP message as a sequence of octets in an
332 encoding that is a superset of US-ASCII [USASCII]. Parsing an HTTP
333 message as a stream of Unicode characters, without regard for the
334 specific encoding, creates security vulnerabilities due to the
335 varying ways that string processing libraries handle invalid
336 multibyte character sequences that contain the octet LF (%x0A).
337 String-based parsers can only be safely used within protocol elements
338 after the element has been extracted from the message, such as within
339 a header field-value after message parsing has delineated the
340 individual fields.
342 Although the line terminator for the start-line and header fields is
343 the sequence CRLF, a recipient MAY recognize a single LF as a line
344 terminator and ignore any preceding CR.
346 Older HTTP/1.0 user agent implementations might send an extra CRLF
347 after a POST request as a workaround for some early server
348 applications that failed to read message body content that was not
349 terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface
350 or follow a request with an extra CRLF. If terminating the request
351 message body with a line-ending is desired, then the user agent MUST
352 count the terminating CRLF octets as part of the message body length.
354 In the interest of robustness, a server that is expecting to receive
355 and parse a request-line SHOULD ignore at least one empty line (CRLF)
356 received prior to the request-line.
358 A sender MUST NOT send whitespace between the start-line and the
359 first header field. A recipient that receives whitespace between the
360 start-line and the first header field MUST either reject the message
361 as invalid or consume each whitespace-preceded line without further
362 processing of it (i.e., ignore the entire line, along with any
363 subsequent lines preceded by whitespace, until a properly formed
364 header field is received or the header section is terminated).
366 The presence of such whitespace in a request might be an attempt to
367 trick a server into ignoring that field or processing the line after
368 it as a new request, either of which might result in a security
369 vulnerability if other implementations within the request chain
370 interpret the same message differently. Likewise, the presence of
371 such whitespace in a response might be ignored by some clients or
372 cause others to cease parsing.
374 When a server listening only for HTTP request messages, or processing
375 what appears from the start-line to be an HTTP request message,
376 receives a sequence of octets that does not match the HTTP-message
377 grammar aside from the robustness exceptions listed above, the server
378 SHOULD respond with a 400 (Bad Request) response.
380 3. Request Line
382 A request-line begins with a method token, followed by a single space
383 (SP), the request-target, another single space (SP), the protocol
384 version, and ends with CRLF.
386 request-line = method SP request-target SP HTTP-version CRLF
388 Although the request-line grammar rule requires that each of the
389 component elements be separated by a single SP octet, recipients MAY
390 instead parse on whitespace-delimited word boundaries and, aside from
391 the CRLF terminator, treat any form of whitespace as the SP separator
392 while ignoring preceding or trailing whitespace; such whitespace
393 includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
394 (%x0C), or bare CR. However, lenient parsing can result in request
395 smuggling security vulnerabilities if there are multiple recipients
396 of the message and each has its own unique interpretation of
397 robustness (see Section 11.2).
399 HTTP does not place a predefined limit on the length of a request-
400 line, as described in Section 3 of [Semantics]. A server that
401 receives a method longer than any that it implements SHOULD respond
402 with a 501 (Not Implemented) status code. A server that receives a
403 request-target longer than any URI it wishes to parse MUST respond
404 with a 414 (URI Too Long) status code (see Section 9.5.15 of
405 [Semantics]).
407 Various ad hoc limitations on request-line length are found in
408 practice. It is RECOMMENDED that all HTTP senders and recipients
409 support, at a minimum, request-line lengths of 8000 octets.
411 3.1. Method
413 The method token indicates the request method to be performed on the
414 target resource. The request method is case-sensitive.
416 method = token
418 The request methods defined by this specification can be found in
419 Section 7 of [Semantics], along with information regarding the HTTP
420 method registry and considerations for defining new methods.
422 3.2. Request Target
424 The request-target identifies the target resource upon which to apply
425 the request. The client derives a request-target from its desired
426 target URI. There are four distinct formats for the request-target,
427 depending on both the method being requested and whether the request
428 is to a proxy.
430 request-target = origin-form
431 / absolute-form
432 / authority-form
433 / asterisk-form
435 No whitespace is allowed in the request-target. Unfortunately, some
436 user agents fail to properly encode or exclude whitespace found in
437 hypertext references, resulting in those disallowed characters being
438 sent as the request-target in a malformed request-line.
440 Recipients of an invalid request-line SHOULD respond with either a
441 400 (Bad Request) error or a 301 (Moved Permanently) redirect with
442 the request-target properly encoded. A recipient SHOULD NOT attempt
443 to autocorrect and then process the request without a redirect, since
444 the invalid request-line might be deliberately crafted to bypass
445 security filters along the request chain.
447 3.2.1. origin-form
449 The most common form of request-target is the origin-form.
451 origin-form = absolute-path [ "?" query ]
453 When making a request directly to an origin server, other than a
454 CONNECT or server-wide OPTIONS request (as detailed below), a client
455 MUST send only the absolute path and query components of the target
456 URI as the request-target. If the target URI's path component is
457 empty, the client MUST send "/" as the path within the origin-form of
458 request-target. A Host header field is also sent, as defined in
459 Section 5.4 of [Semantics].
461 For example, a client wishing to retrieve a representation of the
462 resource identified as
464 http://www.example.org/where?q=now
466 directly from the origin server would open (or reuse) a TCP
467 connection to port 80 of the host "www.example.org" and send the
468 lines:
470 GET /where?q=now HTTP/1.1
471 Host: www.example.org
473 followed by the remainder of the request message.
475 3.2.2. absolute-form
477 When making a request to a proxy, other than a CONNECT or server-wide
478 OPTIONS request (as detailed below), a client MUST send the target
479 URI in absolute-form as the request-target.
481 absolute-form = absolute-URI
483 The proxy is requested to either service that request from a valid
484 cache, if possible, or make the same request on the client's behalf
485 to either the next inbound proxy server or directly to the origin
486 server indicated by the request-target. Requirements on such
487 "forwarding" of messages are defined in Section 5.5 of [Semantics].
489 An example absolute-form of request-line would be:
491 GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
493 To allow for transition to the absolute-form for all requests in some
494 future version of HTTP, a server MUST accept the absolute-form in
495 requests, even though HTTP/1.1 clients will only send them in
496 requests to proxies.
498 3.2.3. authority-form
500 The authority-form of request-target is only used for CONNECT
501 requests (Section 7.3.6 of [Semantics]).
503 authority-form = authority
505 When making a CONNECT request to establish a tunnel through one or
506 more proxies, a client MUST send only the target URI's authority
507 component (excluding any userinfo and its "@" delimiter) as the
508 request-target. For example,
510 CONNECT www.example.com:80 HTTP/1.1
512 3.2.4. asterisk-form
514 The asterisk-form of request-target is only used for a server-wide
515 OPTIONS request (Section 7.3.7 of [Semantics]).
517 asterisk-form = "*"
519 When a client wishes to request OPTIONS for the server as a whole, as
520 opposed to a specific named resource of that server, the client MUST
521 send only "*" (%x2A) as the request-target. For example,
523 OPTIONS * HTTP/1.1
525 If a proxy receives an OPTIONS request with an absolute-form of
526 request-target in which the URI has an empty path and no query
527 component, then the last proxy on the request chain MUST send a
528 request-target of "*" when it forwards the request to the indicated
529 origin server.
531 For example, the request
533 OPTIONS http://www.example.org:8001 HTTP/1.1
535 would be forwarded by the final proxy as
537 OPTIONS * HTTP/1.1
538 Host: www.example.org:8001
540 after connecting to port 8001 of host "www.example.org".
542 3.3. Effective Request URI
544 Since the request-target often contains only part of the user agent's
545 target URI, a server reconstructs the intended target as an effective
546 request URI to properly service the request (Section 5.3 of
547 [Semantics]).
549 If the request-target is in absolute-form, the effective request URI
550 is the same as the request-target. Otherwise, the effective request
551 URI is constructed as follows:
553 If the server's configuration (or outbound gateway) provides a
554 fixed URI scheme, that scheme is used for the effective request
555 URI. Otherwise, if the request is received over a TLS-secured TCP
556 connection, the effective request URI's scheme is "https"; if not,
557 the scheme is "http".
559 If the server's configuration (or outbound gateway) provides a
560 fixed URI authority component, that authority is used for the
561 effective request URI. If not, then if the request-target is in
562 authority-form, the effective request URI's authority component is
563 the same as the request-target. If not, then if a Host header
564 field is supplied with a non-empty field-value, the authority
565 component is the same as the Host field-value. Otherwise, the
566 authority component is assigned the default name configured for
567 the server and, if the connection's incoming TCP port number
568 differs from the default port for the effective request URI's
569 scheme, then a colon (":") and the incoming port number (in
570 decimal form) are appended to the authority component.
572 If the request-target is in authority-form or asterisk-form, the
573 effective request URI's combined path and query component is
574 empty. Otherwise, the combined path and query component is the
575 same as the request-target.
577 The components of the effective request URI, once determined as
578 above, can be combined into absolute-URI form by concatenating the
579 scheme, "://", authority, and combined path and query component.
581 Example 1: the following message received over an insecure TCP
582 connection
584 GET /pub/WWW/TheProject.html HTTP/1.1
585 Host: www.example.org:8080
587 has an effective request URI of
589 http://www.example.org:8080/pub/WWW/TheProject.html
591 Example 2: the following message received over a TLS-secured TCP
592 connection
594 OPTIONS * HTTP/1.1
595 Host: www.example.org
597 has an effective request URI of
599 https://www.example.org
601 Recipients of an HTTP/1.0 request that lacks a Host header field
602 might need to use heuristics (e.g., examination of the URI path for
603 something unique to a particular host) in order to guess the
604 effective request URI's authority component.
606 4. Status Line
608 The first line of a response message is the status-line, consisting
609 of the protocol version, a space (SP), the status code, another
610 space, an OPTIONAL textual phrase describing the status code, and
611 ending with CRLF.
613 status-line = HTTP-version SP status-code SP [reason-phrase] CRLF
615 Although the status-line grammar rule requires that each of the
616 component elements be separated by a single SP octet, recipients MAY
617 instead parse on whitespace-delimited word boundaries and, aside from
618 the line terminator, treat any form of whitespace as the SP separator
619 while ignoring preceding or trailing whitespace; such whitespace
620 includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
621 (%x0C), or bare CR. However, lenient parsing can result in response
622 splitting security vulnerabilities if there are multiple recipients
623 of the message and each has its own unique interpretation of
624 robustness (see Section 11.1).
626 The status-code element is a 3-digit integer code describing the
627 result of the server's attempt to understand and satisfy the client's
628 corresponding request. The rest of the response message is to be
629 interpreted in light of the semantics defined for that status code.
630 See Section 9 of [Semantics] for information about the semantics of
631 status codes, including the classes of status code (indicated by the
632 first digit), the status codes defined by this specification,
633 considerations for the definition of new status codes, and the IANA
634 registry.
636 status-code = 3DIGIT
638 The reason-phrase element exists for the sole purpose of providing a
639 textual description associated with the numeric status code, mostly
640 out of deference to earlier Internet application protocols that were
641 more frequently used with interactive text clients.
643 reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
645 A client SHOULD ignore the reason-phrase content because it is not a
646 reliable channel for information (it might be translated for a given
647 locale, overwritten by intermediaries, or discarded when the message
648 is forwarded via other versions of HTTP). A server MUST send the
649 space that separates status-code from the reason-phrase even when the
650 reason-phrase is absent (i.e., the status-line would end with the
651 three octets SP CR LF).
653 5. Header Fields
655 Each header field consists of a case-insensitive field name followed
656 by a colon (":"), optional leading whitespace, the field value, and
657 optional trailing whitespace.
659 header-field = field-name ":" OWS field-value OWS
661 Most HTTP field names and the rules for parsing within field values
662 are defined in Section 4 of [Semantics]. This section covers the
663 generic syntax for header field inclusion within, and extraction
664 from, HTTP/1.1 messages. In addition, the following header fields
665 are defined by this document because they are specific to HTTP/1.1
666 message processing:
668 +-------------------+----------+---------------+
669 | Header Field Name | Status | Reference |
670 +-------------------+----------+---------------+
671 | Connection | standard | Section 9.1 |
672 | MIME-Version | standard | Appendix B.1 |
673 | TE | standard | Section 7.4 |
674 | Transfer-Encoding | standard | Section 6.1 |
675 | Upgrade | standard | Section 9.8 |
676 +-------------------+----------+---------------+
678 Table 1
680 Furthermore, the field name "Close" is reserved, since using that
681 name as an HTTP header field might conflict with the "close"
682 connection option of the Connection header field (Section 9.1).
684 +-------------------+----------+----------+------------+
685 | Header Field Name | Protocol | Status | Reference |
686 +-------------------+----------+----------+------------+
687 | Close | http | reserved | Section 5 |
688 +-------------------+----------+----------+------------+
690 5.1. Header Field Parsing
692 Messages are parsed using a generic algorithm, independent of the
693 individual header field names. The contents within a given field
694 value are not parsed until a later stage of message interpretation
695 (usually after the message's entire header section has been
696 processed).
698 No whitespace is allowed between the header field-name and colon. In
699 the past, differences in the handling of such whitespace have led to
700 security vulnerabilities in request routing and response handling. A
701 server MUST reject any received request message that contains
702 whitespace between a header field-name and colon with a response
703 status code of 400 (Bad Request). A proxy MUST remove any such
704 whitespace from a response message before forwarding the message
705 downstream.
707 A field value might be preceded and/or followed by optional
708 whitespace (OWS); a single SP preceding the field-value is preferred
709 for consistent readability by humans. The field value does not
710 include any leading or trailing whitespace: OWS occurring before the
711 first non-whitespace octet of the field value or after the last non-
712 whitespace octet of the field value ought to be excluded by parsers
713 when extracting the field value from a header field.
715 5.2. Obsolete Line Folding
717 Historically, HTTP header field values could be extended over
718 multiple lines by preceding each extra line with at least one space
719 or horizontal tab (obs-fold). This specification deprecates such
720 line folding except within the message/http media type
721 (Section 10.1).
723 obs-fold = OWS CRLF RWS
724 ; obsolete line folding
726 A sender MUST NOT generate a message that includes line folding
727 (i.e., that has any field-value that contains a match to the obs-fold
728 rule) unless the message is intended for packaging within the
729 message/http media type.
731 A server that receives an obs-fold in a request message that is not
732 within a message/http container MUST either reject the message by
733 sending a 400 (Bad Request), preferably with a representation
734 explaining that obsolete line folding is unacceptable, or replace
735 each received obs-fold with one or more SP octets prior to
736 interpreting the field value or forwarding the message downstream.
738 A proxy or gateway that receives an obs-fold in a response message
739 that is not within a message/http container MUST either discard the
740 message and replace it with a 502 (Bad Gateway) response, preferably
741 with a representation explaining that unacceptable line folding was
742 received, or replace each received obs-fold with one or more SP
743 octets prior to interpreting the field value or forwarding the
744 message downstream.
746 A user agent that receives an obs-fold in a response message that is
747 not within a message/http container MUST replace each received obs-
748 fold with one or more SP octets prior to interpreting the field
749 value.
751 6. Message Body
753 The message body (if any) of an HTTP message is used to carry the
754 payload body of that request or response. The message body is
755 identical to the payload body unless a transfer coding has been
756 applied, as described in Section 6.1.
758 message-body = *OCTET
760 The rules for when a message body is allowed in a message differ for
761 requests and responses.
763 The presence of a message body in a request is signaled by a Content-
764 Length or Transfer-Encoding header field. Request message framing is
765 independent of method semantics, even if the method does not define
766 any use for a message body.
768 The presence of a message body in a response depends on both the
769 request method to which it is responding and the response status code
770 (Section 4). Responses to the HEAD request method (Section 7.3.2 of
771 [Semantics]) never include a message body because the associated
772 response header fields (e.g., Transfer-Encoding, Content-Length,
773 etc.), if present, indicate only what their values would have been if
774 the request method had been GET (Section 7.3.1 of [Semantics]). 2xx
775 (Successful) responses to a CONNECT request method (Section 7.3.6 of
776 [Semantics]) switch to tunnel mode instead of having a message body.
777 All 1xx (Informational), 204 (No Content), and 304 (Not Modified)
778 responses do not include a message body. All other responses do
779 include a message body, although the body might be of zero length.
781 6.1. Transfer-Encoding
783 The Transfer-Encoding header field lists the transfer coding names
784 corresponding to the sequence of transfer codings that have been (or
785 will be) applied to the payload body in order to form the message
786 body. Transfer codings are defined in Section 7.
788 Transfer-Encoding = 1#transfer-coding
790 Transfer-Encoding is analogous to the Content-Transfer-Encoding field
791 of MIME, which was designed to enable safe transport of binary data
792 over a 7-bit transport service ([RFC2045], Section 6). However, safe
793 transport has a different focus for an 8bit-clean transfer protocol.
794 In HTTP's case, Transfer-Encoding is primarily intended to accurately
795 delimit a dynamically generated payload and to distinguish payload
796 encodings that are only applied for transport efficiency or security
797 from those that are characteristics of the selected resource.
799 A recipient MUST be able to parse the chunked transfer coding
800 (Section 7.1) because it plays a crucial role in framing messages
801 when the payload body size is not known in advance. A sender MUST
802 NOT apply chunked more than once to a message body (i.e., chunking an
803 already chunked message is not allowed). If any transfer coding
804 other than chunked is applied to a request payload body, the sender
805 MUST apply chunked as the final transfer coding to ensure that the
806 message is properly framed. If any transfer coding other than
807 chunked is applied to a response payload body, the sender MUST either
808 apply chunked as the final transfer coding or terminate the message
809 by closing the connection.
811 For example,
813 Transfer-Encoding: gzip, chunked
815 indicates that the payload body has been compressed using the gzip
816 coding and then chunked using the chunked coding while forming the
817 message body.
819 Unlike Content-Encoding (Section 6.1.2 of [Semantics]), Transfer-
820 Encoding is a property of the message, not of the representation, and
821 any recipient along the request/response chain MAY decode the
822 received transfer coding(s) or apply additional transfer coding(s) to
823 the message body, assuming that corresponding changes are made to the
824 Transfer-Encoding field-value. Additional information about the
825 encoding parameters can be provided by other header fields not
826 defined by this specification.
828 Transfer-Encoding MAY be sent in a response to a HEAD request or in a
829 304 (Not Modified) response (Section 9.4.5 of [Semantics]) to a GET
830 request, neither of which includes a message body, to indicate that
831 the origin server would have applied a transfer coding to the message
832 body if the request had been an unconditional GET. This indication
833 is not required, however, because any recipient on the response chain
834 (including the origin server) can remove transfer codings when they
835 are not needed.
837 A server MUST NOT send a Transfer-Encoding header field in any
838 response with a status code of 1xx (Informational) or 204 (No
839 Content). A server MUST NOT send a Transfer-Encoding header field in
840 any 2xx (Successful) response to a CONNECT request (Section 7.3.6 of
841 [Semantics]).
843 Transfer-Encoding was added in HTTP/1.1. It is generally assumed
844 that implementations advertising only HTTP/1.0 support will not
845 understand how to process a transfer-encoded payload. A client MUST
846 NOT send a request containing Transfer-Encoding unless it knows the
847 server will handle HTTP/1.1 (or later) requests; such knowledge might
848 be in the form of specific user configuration or by remembering the
849 version of a prior received response. A server MUST NOT send a
850 response containing Transfer-Encoding unless the corresponding
851 request indicates HTTP/1.1 (or later).
853 A server that receives a request message with a transfer coding it
854 does not understand SHOULD respond with 501 (Not Implemented).
856 6.2. Content-Length
858 When a message does not have a Transfer-Encoding header field, a
859 Content-Length header field can provide the anticipated size, as a
860 decimal number of octets, for a potential payload body. For messages
861 that do include a payload body, the Content-Length field-value
862 provides the framing information necessary for determining where the
863 body (and message) ends. For messages that do not include a payload
864 body, the Content-Length indicates the size of the selected
865 representation (Section 6.2.4 of [Semantics]).
867 Note: HTTP's use of Content-Length for message framing differs
868 significantly from the same field's use in MIME, where it is an
869 optional field used only within the "message/external-body" media-
870 type.
872 6.3. Message Body Length
874 The length of a message body is determined by one of the following
875 (in order of precedence):
877 1. Any response to a HEAD request and any response with a 1xx
878 (Informational), 204 (No Content), or 304 (Not Modified) status
879 code is always terminated by the first empty line after the
880 header fields, regardless of the header fields present in the
881 message, and thus cannot contain a message body.
883 2. Any 2xx (Successful) response to a CONNECT request implies that
884 the connection will become a tunnel immediately after the empty
885 line that concludes the header fields. A client MUST ignore any
886 Content-Length or Transfer-Encoding header fields received in
887 such a message.
889 3. If a Transfer-Encoding header field is present and the chunked
890 transfer coding (Section 7.1) is the final encoding, the message
891 body length is determined by reading and decoding the chunked
892 data until the transfer coding indicates the data is complete.
894 If a Transfer-Encoding header field is present in a response and
895 the chunked transfer coding is not the final encoding, the
896 message body length is determined by reading the connection until
897 it is closed by the server. If a Transfer-Encoding header field
898 is present in a request and the chunked transfer coding is not
899 the final encoding, the message body length cannot be determined
900 reliably; the server MUST respond with the 400 (Bad Request)
901 status code and then close the connection.
903 If a message is received with both a Transfer-Encoding and a
904 Content-Length header field, the Transfer-Encoding overrides the
905 Content-Length. Such a message might indicate an attempt to
906 perform request smuggling (Section 11.2) or response splitting
907 (Section 11.1) and ought to be handled as an error. A sender
908 MUST remove the received Content-Length field prior to forwarding
909 such a message downstream.
911 4. If a message is received without Transfer-Encoding and with
912 either multiple Content-Length header fields having differing
913 field-values or a single Content-Length header field having an
914 invalid value, then the message framing is invalid and the
915 recipient MUST treat it as an unrecoverable error. If this is a
916 request message, the server MUST respond with a 400 (Bad Request)
917 status code and then close the connection. If this is a response
918 message received by a proxy, the proxy MUST close the connection
919 to the server, discard the received response, and send a 502 (Bad
920 Gateway) response to the client. If this is a response message
921 received by a user agent, the user agent MUST close the
922 connection to the server and discard the received response.
924 5. If a valid Content-Length header field is present without
925 Transfer-Encoding, its decimal value defines the expected message
926 body length in octets. If the sender closes the connection or
927 the recipient times out before the indicated number of octets are
928 received, the recipient MUST consider the message to be
929 incomplete and close the connection.
931 6. If this is a request message and none of the above are true, then
932 the message body length is zero (no message body is present).
934 7. Otherwise, this is a response message without a declared message
935 body length, so the message body length is determined by the
936 number of octets received prior to the server closing the
937 connection.
939 Since there is no way to distinguish a successfully completed, close-
940 delimited message from a partially received message interrupted by
941 network failure, a server SHOULD generate encoding or length-
942 delimited messages whenever possible. The close-delimiting feature
943 exists primarily for backwards compatibility with HTTP/1.0.
945 A server MAY reject a request that contains a message body but not a
946 Content-Length by responding with 411 (Length Required).
948 Unless a transfer coding other than chunked has been applied, a
949 client that sends a request containing a message body SHOULD use a
950 valid Content-Length header field if the message body length is known
951 in advance, rather than the chunked transfer coding, since some
952 existing services respond to chunked with a 411 (Length Required)
953 status code even though they understand the chunked transfer coding.
954 This is typically because such services are implemented via a gateway
955 that requires a content-length in advance of being called and the
956 server is unable or unwilling to buffer the entire request before
957 processing.
959 A user agent that sends a request containing a message body MUST send
960 a valid Content-Length header field if it does not know the server
961 will handle HTTP/1.1 (or later) requests; such knowledge can be in
962 the form of specific user configuration or by remembering the version
963 of a prior received response.
965 If the final response to the last request on a connection has been
966 completely received and there remains additional data to read, a user
967 agent MAY discard the remaining data or attempt to determine if that
968 data belongs as part of the prior response body, which might be the
969 case if the prior message's Content-Length value is incorrect. A
970 client MUST NOT process, cache, or forward such extra data as a
971 separate response, since such behavior would be vulnerable to cache
972 poisoning.
974 7. Transfer Codings
976 Transfer coding names are used to indicate an encoding transformation
977 that has been, can be, or might need to be applied to a payload body
978 in order to ensure "safe transport" through the network. This
979 differs from a content coding in that the transfer coding is a
980 property of the message rather than a property of the representation
981 that is being transferred.
983 transfer-coding = token *( OWS ";" OWS transfer-parameter )
985 Parameters are in the form of a name=value pair.
987 transfer-parameter = token BWS "=" BWS ( token / quoted-string )
989 All transfer-coding names are case-insensitive and ought to be
990 registered within the HTTP Transfer Coding registry, as defined in
991 Section 7.3. They are used in the TE (Section 7.4) and Transfer-
992 Encoding (Section 6.1) header fields.
994 +------------+------------------------------------------+-----------+
995 | Name | Description | Reference |
996 +------------+------------------------------------------+-----------+
997 | chunked | Transfer in a series of chunks | Section |
998 | | | 7.1 |
999 | compress | UNIX "compress" data format [Welch] | Section |
1000 | | | 7.2 |
1001 | deflate | "deflate" compressed data ([RFC1951]) | Section |
1002 | | inside the "zlib" data format | 7.2 |
1003 | | ([RFC1950]) | |
1004 | gzip | GZIP file format [RFC1952] | Section |
1005 | | | 7.2 |
1006 | trailers | (reserved) | Section 7 |
1007 | x-compress | Deprecated (alias for compress) | Section |
1008 | | | 7.2 |
1009 | x-gzip | Deprecated (alias for gzip) | Section |
1010 | | | 7.2 |
1011 +------------+------------------------------------------+-----------+
1013 Table 2
1015 Note: the coding name "trailers" is reserved because it would
1016 clash with the use of the keyword "trailers" in the TE header
1017 field (Section 7.4).
1019 7.1. Chunked Transfer Coding
1021 The chunked transfer coding wraps the payload body in order to
1022 transfer it as a series of chunks, each with its own size indicator,
1023 followed by an OPTIONAL trailer containing header fields. Chunked
1024 enables content streams of unknown size to be transferred as a
1025 sequence of length-delimited buffers, which enables the sender to
1026 retain connection persistence and the recipient to know when it has
1027 received the entire message.
1029 chunked-body = *chunk
1030 last-chunk
1031 trailer-part
1032 CRLF
1034 chunk = chunk-size [ chunk-ext ] CRLF
1035 chunk-data CRLF
1036 chunk-size = 1*HEXDIG
1037 last-chunk = 1*("0") [ chunk-ext ] CRLF
1039 chunk-data = 1*OCTET ; a sequence of chunk-size octets
1041 The chunk-size field is a string of hex digits indicating the size of
1042 the chunk-data in octets. The chunked transfer coding is complete
1043 when a chunk with a chunk-size of zero is received, possibly followed
1044 by a trailer, and finally terminated by an empty line.
1046 A recipient MUST be able to parse and decode the chunked transfer
1047 coding.
1049 The chunked encoding does not define any parameters. Their presence
1050 SHOULD be treated as an error.
1052 7.1.1. Chunk Extensions
1054 The chunked encoding allows each chunk to include zero or more chunk
1055 extensions, immediately following the chunk-size, for the sake of
1056 supplying per-chunk metadata (such as a signature or hash), mid-
1057 message control information, or randomization of message body size.
1059 chunk-ext = *( BWS ";" BWS chunk-ext-name
1060 [ BWS "=" BWS chunk-ext-val ] )
1062 chunk-ext-name = token
1063 chunk-ext-val = token / quoted-string
1065 The chunked encoding is specific to each connection and is likely to
1066 be removed or recoded by each recipient (including intermediaries)
1067 before any higher-level application would have a chance to inspect
1068 the extensions. Hence, use of chunk extensions is generally limited
1069 to specialized HTTP services such as "long polling" (where client and
1070 server can have shared expectations regarding the use of chunk
1071 extensions) or for padding within an end-to-end secured connection.
1073 A recipient MUST ignore unrecognized chunk extensions. A server
1074 ought to limit the total length of chunk extensions received in a
1075 request to an amount reasonable for the services provided, in the
1076 same way that it applies length limitations and timeouts for other
1077 parts of a message, and generate an appropriate 4xx (Client Error)
1078 response if that amount is exceeded.
1080 7.1.2. Chunked Trailer Part
1082 A trailer allows the sender to include additional fields at the end
1083 of a chunked message in order to supply metadata that might be
1084 dynamically generated while the message body is sent, such as a
1085 message integrity check, digital signature, or post-processing
1086 status. The trailer fields are identical to header fields, except
1087 they are sent in a chunked trailer instead of the message's header
1088 section.
1090 trailer-part = *( header-field CRLF )
1092 A sender MUST NOT generate a trailer that contains a field necessary
1093 for message framing (e.g., Transfer-Encoding and Content-Length),
1094 routing (e.g., Host), request modifiers (e.g., controls and
1095 conditionals in Section 8 of [Semantics]), authentication (e.g., see
1096 Section 8.5 of [Semantics] and [RFC6265]), response control data
1097 (e.g., see Section 10.1 of [Semantics]), or determining how to
1098 process the payload (e.g., Content-Encoding, Content-Type, Content-
1099 Range, and Trailer).
1101 When a chunked message containing a non-empty trailer is received,
1102 the recipient MAY process the fields (aside from those forbidden
1103 above) as if they were appended to the message's header section. A
1104 recipient MUST ignore (or consider as an error) any fields that are
1105 forbidden to be sent in a trailer, since processing them as if they
1106 were present in the header section might bypass external security
1107 filters.
1109 Unless the request includes a TE header field indicating "trailers"
1110 is acceptable, as described in Section 7.4, a server SHOULD NOT
1111 generate trailer fields that it believes are necessary for the user
1112 agent to receive. Without a TE containing "trailers", the server
1113 ought to assume that the trailer fields might be silently discarded
1114 along the path to the user agent. This requirement allows
1115 intermediaries to forward a de-chunked message to an HTTP/1.0
1116 recipient without buffering the entire response.
1118 When a message includes a message body encoded with the chunked
1119 transfer coding and the sender desires to send metadata in the form
1120 of trailer fields at the end of the message, the sender SHOULD
1121 generate a Trailer header field before the message body to indicate
1122 which fields will be present in the trailers. This allows the
1123 recipient to prepare for receipt of that metadata before it starts
1124 processing the body, which is useful if the message is being streamed
1125 and the recipient wishes to confirm an integrity check on the fly.
1127 7.1.3. Decoding Chunked
1129 A process for decoding the chunked transfer coding can be represented
1130 in pseudo-code as:
1132 length := 0
1133 read chunk-size, chunk-ext (if any), and CRLF
1134 while (chunk-size > 0) {
1135 read chunk-data and CRLF
1136 append chunk-data to decoded-body
1137 length := length + chunk-size
1138 read chunk-size, chunk-ext (if any), and CRLF
1139 }
1140 read trailer field
1141 while (trailer field is not empty) {
1142 if (trailer field is allowed to be sent in a trailer) {
1143 append trailer field to existing header fields
1144 }
1145 read trailer-field
1146 }
1147 Content-Length := length
1148 Remove "chunked" from Transfer-Encoding
1149 Remove Trailer from existing header fields
1151 7.2. Transfer Codings for Compression
1153 The following transfer coding names for compression are defined by
1154 the same algorithm as their corresponding content coding:
1156 compress (and x-compress)
1157 See Section 6.1.2.1 of [Semantics].
1159 deflate
1160 See Section 6.1.2.2 of [Semantics].
1162 gzip (and x-gzip)
1163 See Section 6.1.2.3 of [Semantics].
1165 The compression codings do not define any parameters. Their presence
1166 SHOULD be treated as an error.
1168 7.3. Transfer Coding Registry
1170 The "HTTP Transfer Coding Registry" defines the namespace for
1171 transfer coding names. It is maintained at
1172 .
1174 Registrations MUST include the following fields:
1176 o Name
1178 o Description
1180 o Pointer to specification text
1182 Names of transfer codings MUST NOT overlap with names of content
1183 codings (Section 6.1.2 of [Semantics]) unless the encoding
1184 transformation is identical, as is the case for the compression
1185 codings defined in Section 7.2.
1187 The TE header field (Section 7.4) uses a pseudo parameter named "q"
1188 as rank value when multiple transfer codings are acceptable. Future
1189 registrations of transfer codings SHOULD NOT define parameters called
1190 "q" (case-insensitively) in order to avoid ambiguities.
1192 Values to be added to this namespace require IETF Review (see
1193 Section 4.8 of [RFC8126]), and MUST conform to the purpose of
1194 transfer coding defined in this specification.
1196 Use of program names for the identification of encoding formats is
1197 not desirable and is discouraged for future encodings.
1199 7.4. TE
1201 The "TE" header field in a request indicates what transfer codings,
1202 besides chunked, the client is willing to accept in response, and
1203 whether or not the client is willing to accept trailer fields in a
1204 chunked transfer coding.
1206 The TE field-value consists of a comma-separated list of transfer
1207 coding names, each allowing for optional parameters (as described in
1208 Section 7), and/or the keyword "trailers". A client MUST NOT send
1209 the chunked transfer coding name in TE; chunked is always acceptable
1210 for HTTP/1.1 recipients.
1212 TE = #t-codings
1213 t-codings = "trailers" / ( transfer-coding [ t-ranking ] )
1214 t-ranking = OWS ";" OWS "q=" rank
1215 rank = ( "0" [ "." 0*3DIGIT ] )
1216 / ( "1" [ "." 0*3("0") ] )
1218 Three examples of TE use are below.
1220 TE: deflate
1221 TE:
1222 TE: trailers, deflate;q=0.5
1224 The presence of the keyword "trailers" indicates that the client is
1225 willing to accept trailer fields in a chunked transfer coding, as
1226 defined in Section 7.1.2, on behalf of itself and any downstream
1227 clients. For requests from an intermediary, this implies that
1228 either: (a) all downstream clients are willing to accept trailer
1229 fields in the forwarded response; or, (b) the intermediary will
1230 attempt to buffer the response on behalf of downstream recipients.
1231 Note that HTTP/1.1 does not define any means to limit the size of a
1232 chunked response such that an intermediary can be assured of
1233 buffering the entire response.
1235 When multiple transfer codings are acceptable, the client MAY rank
1236 the codings by preference using a case-insensitive "q" parameter
1237 (similar to the qvalues used in content negotiation fields,
1238 Section 8.4.1 of [Semantics]). The rank value is a real number in
1239 the range 0 through 1, where 0.001 is the least preferred and 1 is
1240 the most preferred; a value of 0 means "not acceptable".
1242 If the TE field-value is empty or if no TE field is present, the only
1243 acceptable transfer coding is chunked. A message with no transfer
1244 coding is always acceptable.
1246 Since the TE header field only applies to the immediate connection, a
1247 sender of TE MUST also send a "TE" connection option within the
1248 Connection header field (Section 9.1) in order to prevent the TE
1249 field from being forwarded by intermediaries that do not support its
1250 semantics.
1252 8. Handling Incomplete Messages
1254 A server that receives an incomplete request message, usually due to
1255 a canceled request or a triggered timeout exception, MAY send an
1256 error response prior to closing the connection.
1258 A client that receives an incomplete response message, which can
1259 occur when a connection is closed prematurely or when decoding a
1260 supposedly chunked transfer coding fails, MUST record the message as
1261 incomplete. Cache requirements for incomplete responses are defined
1262 in Section 3 of [Caching].
1264 If a response terminates in the middle of the header section (before
1265 the empty line is received) and the status code might rely on header
1266 fields to convey the full meaning of the response, then the client
1267 cannot assume that meaning has been conveyed; the client might need
1268 to repeat the request in order to determine what action to take next.
1270 A message body that uses the chunked transfer coding is incomplete if
1271 the zero-sized chunk that terminates the encoding has not been
1272 received. A message that uses a valid Content-Length is incomplete
1273 if the size of the message body received (in octets) is less than the
1274 value given by Content-Length. A response that has neither chunked
1275 transfer coding nor Content-Length is terminated by closure of the
1276 connection and, thus, is considered complete regardless of the number
1277 of message body octets received, provided that the header section was
1278 received intact.
1280 9. Connection Management
1282 HTTP messaging is independent of the underlying transport- or
1283 session-layer connection protocol(s). HTTP only presumes a reliable
1284 transport with in-order delivery of requests and the corresponding
1285 in-order delivery of responses. The mapping of HTTP request and
1286 response structures onto the data units of an underlying transport
1287 protocol is outside the scope of this specification.
1289 As described in Section 5.2 of [Semantics], the specific connection
1290 protocols to be used for an HTTP interaction are determined by client
1291 configuration and the target URI. For example, the "http" URI scheme
1292 (Section 2.5.1 of [Semantics]) indicates a default connection of TCP
1293 over IP, with a default TCP port of 80, but the client might be
1294 configured to use a proxy via some other connection, port, or
1295 protocol.
1297 HTTP implementations are expected to engage in connection management,
1298 which includes maintaining the state of current connections,
1299 establishing a new connection or reusing an existing connection,
1300 processing messages received on a connection, detecting connection
1301 failures, and closing each connection. Most clients maintain
1302 multiple connections in parallel, including more than one connection
1303 per server endpoint. Most servers are designed to maintain thousands
1304 of concurrent connections, while controlling request queues to enable
1305 fair use and detect denial-of-service attacks.
1307 9.1. Connection
1309 The "Connection" header field allows the sender to indicate desired
1310 control options for the current connection. In order to avoid
1311 confusing downstream recipients, a proxy or gateway MUST remove or
1312 replace any received connection options before forwarding the
1313 message.
1315 When a header field aside from Connection is used to supply control
1316 information for or about the current connection, the sender MUST list
1317 the corresponding field-name within the Connection header field. A
1318 proxy or gateway MUST parse a received Connection header field before
1319 a message is forwarded and, for each connection-option in this field,
1320 remove any header field(s) from the message with the same name as the
1321 connection-option, and then remove the Connection header field itself
1322 (or replace it with the intermediary's own connection options for the
1323 forwarded message).
1325 Hence, the Connection header field provides a declarative way of
1326 distinguishing header fields that are only intended for the immediate
1327 recipient ("hop-by-hop") from those fields that are intended for all
1328 recipients on the chain ("end-to-end"), enabling the message to be
1329 self-descriptive and allowing future connection-specific extensions
1330 to be deployed without fear that they will be blindly forwarded by
1331 older intermediaries.
1333 The Connection header field's value has the following grammar:
1335 Connection = 1#connection-option
1336 connection-option = token
1338 Connection options are case-insensitive.
1340 A sender MUST NOT send a connection option corresponding to a header
1341 field that is intended for all recipients of the payload. For
1342 example, Cache-Control is never appropriate as a connection option
1343 (Section 5.2 of [Caching]).
1345 The connection options do not always correspond to a header field
1346 present in the message, since a connection-specific header field
1347 might not be needed if there are no parameters associated with a
1348 connection option. In contrast, a connection-specific header field
1349 that is received without a corresponding connection option usually
1350 indicates that the field has been improperly forwarded by an
1351 intermediary and ought to be ignored by the recipient.
1353 When defining new connection options, specification authors ought to
1354 survey existing header field names and ensure that the new connection
1355 option does not share the same name as an already deployed header
1356 field. Defining a new connection option essentially reserves that
1357 potential field-name for carrying additional information related to
1358 the connection option, since it would be unwise for senders to use
1359 that field-name for anything else.
1361 The "close" connection option is defined for a sender to signal that
1362 this connection will be closed after completion of the response. For
1363 example,
1365 Connection: close
1367 in either the request or the response header fields indicates that
1368 the sender is going to close the connection after the current
1369 request/response is complete (Section 9.7).
1371 A client that does not support persistent connections MUST send the
1372 "close" connection option in every request message.
1374 A server that does not support persistent connections MUST send the
1375 "close" connection option in every response message that does not
1376 have a 1xx (Informational) status code.
1378 9.2. Establishment
1380 It is beyond the scope of this specification to describe how
1381 connections are established via various transport- or session-layer
1382 protocols. Each connection applies to only one transport link.
1384 9.3. Associating a Response to a Request
1386 HTTP/1.1 does not include a request identifier for associating a
1387 given request message with its corresponding one or more response
1388 messages. Hence, it relies on the order of response arrival to
1389 correspond exactly to the order in which requests are made on the
1390 same connection. More than one response message per request only
1391 occurs when one or more informational responses (1xx, see Section 9.2
1392 of [Semantics]) precede a final response to the same request.
1394 A client that has more than one outstanding request on a connection
1395 MUST maintain a list of outstanding requests in the order sent and
1396 MUST associate each received response message on that connection to
1397 the highest ordered request that has not yet received a final (non-
1398 1xx) response.
1400 If an HTTP/1.1 client receives data on a connection that doesn't have
1401 any outstanding requests, it MUST NOT consider them to be a response
1402 to a not-yet-issued request; it SHOULD close the connection, since
1403 message delimitation is now ambiguous, unless the data consists only
1404 of one or more CRLF (which can be discarded, as per Section 2.3).
1406 9.4. Persistence
1408 HTTP/1.1 defaults to the use of "persistent connections", allowing
1409 multiple requests and responses to be carried over a single
1410 connection. The "close" connection option is used to signal that a
1411 connection will not persist after the current request/response. HTTP
1412 implementations SHOULD support persistent connections.
1414 A recipient determines whether a connection is persistent or not
1415 based on the most recently received message's protocol version and
1416 Connection header field (if any):
1418 o If the "close" connection option is present, the connection will
1419 not persist after the current response; else,
1421 o If the received protocol is HTTP/1.1 (or later), the connection
1422 will persist after the current response; else,
1424 o If the received protocol is HTTP/1.0, the "keep-alive" connection
1425 option is present, either the recipient is not a proxy or the
1426 message is a response, and the recipient wishes to honor the
1427 HTTP/1.0 "keep-alive" mechanism, the connection will persist after
1428 the current response; otherwise,
1430 o The connection will close after the current response.
1432 A client MAY send additional requests on a persistent connection
1433 until it sends or receives a "close" connection option or receives an
1434 HTTP/1.0 response without a "keep-alive" connection option.
1436 In order to remain persistent, all messages on a connection need to
1437 have a self-defined message length (i.e., one not defined by closure
1438 of the connection), as described in Section 6. A server MUST read
1439 the entire request message body or close the connection after sending
1440 its response, since otherwise the remaining data on a persistent
1441 connection would be misinterpreted as the next request. Likewise, a
1442 client MUST read the entire response message body if it intends to
1443 reuse the same connection for a subsequent request.
1445 A proxy server MUST NOT maintain a persistent connection with an
1446 HTTP/1.0 client (see Section 19.7.1 of [RFC2068] for information and
1447 discussion of the problems with the Keep-Alive header field
1448 implemented by many HTTP/1.0 clients).
1450 See Appendix C.1.2 for more information on backwards compatibility
1451 with HTTP/1.0 clients.
1453 9.4.1. Retrying Requests
1455 Connections can be closed at any time, with or without intention.
1456 Implementations ought to anticipate the need to recover from
1457 asynchronous close events.
1459 When an inbound connection is closed prematurely, a client MAY open a
1460 new connection and automatically retransmit an aborted sequence of
1461 requests if all of those requests have idempotent methods
1462 (Section 7.2.2 of [Semantics]).
1464 9.4.2. Pipelining
1466 A client that supports persistent connections MAY "pipeline" its
1467 requests (i.e., send multiple requests without waiting for each
1468 response). A server MAY process a sequence of pipelined requests in
1469 parallel if they all have safe methods (Section 7.2.1 of
1470 [Semantics]), but it MUST send the corresponding responses in the
1471 same order that the requests were received.
1473 A client that pipelines requests SHOULD retry unanswered requests if
1474 the connection closes before it receives all of the corresponding
1475 responses. When retrying pipelined requests after a failed
1476 connection (a connection not explicitly closed by the server in its
1477 last complete response), a client MUST NOT pipeline immediately after
1478 connection establishment, since the first remaining request in the
1479 prior pipeline might have caused an error response that can be lost
1480 again if multiple requests are sent on a prematurely closed
1481 connection (see the TCP reset problem described in Section 9.7).
1483 Idempotent methods (Section 7.2.2 of [Semantics]) are significant to
1484 pipelining because they can be automatically retried after a
1485 connection failure. A user agent SHOULD NOT pipeline requests after
1486 a non-idempotent method, until the final response status code for
1487 that method has been received, unless the user agent has a means to
1488 detect and recover from partial failure conditions involving the
1489 pipelined sequence.
1491 An intermediary that receives pipelined requests MAY pipeline those
1492 requests when forwarding them inbound, since it can rely on the
1493 outbound user agent(s) to determine what requests can be safely
1494 pipelined. If the inbound connection fails before receiving a
1495 response, the pipelining intermediary MAY attempt to retry a sequence
1496 of requests that have yet to receive a response if the requests all
1497 have idempotent methods; otherwise, the pipelining intermediary
1498 SHOULD forward any received responses and then close the
1499 corresponding outbound connection(s) so that the outbound user
1500 agent(s) can recover accordingly.
1502 9.5. Concurrency
1504 A client ought to limit the number of simultaneous open connections
1505 that it maintains to a given server.
1507 Previous revisions of HTTP gave a specific number of connections as a
1508 ceiling, but this was found to be impractical for many applications.
1509 As a result, this specification does not mandate a particular maximum
1510 number of connections but, instead, encourages clients to be
1511 conservative when opening multiple connections.
1513 Multiple connections are typically used to avoid the "head-of-line
1514 blocking" problem, wherein a request that takes significant server-
1515 side processing and/or has a large payload blocks subsequent requests
1516 on the same connection. However, each connection consumes server
1517 resources. Furthermore, using multiple connections can cause
1518 undesirable side effects in congested networks.
1520 Note that a server might reject traffic that it deems abusive or
1521 characteristic of a denial-of-service attack, such as an excessive
1522 number of open connections from a single client.
1524 9.6. Failures and Timeouts
1526 Servers will usually have some timeout value beyond which they will
1527 no longer maintain an inactive connection. Proxy servers might make
1528 this a higher value since it is likely that the client will be making
1529 more connections through the same proxy server. The use of
1530 persistent connections places no requirements on the length (or
1531 existence) of this timeout for either the client or the server.
1533 A client or server that wishes to time out SHOULD issue a graceful
1534 close on the connection. Implementations SHOULD constantly monitor
1535 open connections for a received closure signal and respond to it as
1536 appropriate, since prompt closure of both sides of a connection
1537 enables allocated system resources to be reclaimed.
1539 A client, server, or proxy MAY close the transport connection at any
1540 time. For example, a client might have started to send a new request
1541 at the same time that the server has decided to close the "idle"
1542 connection. From the server's point of view, the connection is being
1543 closed while it was idle, but from the client's point of view, a
1544 request is in progress.
1546 A server SHOULD sustain persistent connections, when possible, and
1547 allow the underlying transport's flow-control mechanisms to resolve
1548 temporary overloads, rather than terminate connections with the
1549 expectation that clients will retry. The latter technique can
1550 exacerbate network congestion.
1552 A client sending a message body SHOULD monitor the network connection
1553 for an error response while it is transmitting the request. If the
1554 client sees a response that indicates the server does not wish to
1555 receive the message body and is closing the connection, the client
1556 SHOULD immediately cease transmitting the body and close its side of
1557 the connection.
1559 9.7. Tear-down
1561 The Connection header field (Section 9.1) provides a "close"
1562 connection option that a sender SHOULD send when it wishes to close
1563 the connection after the current request/response pair.
1565 A client that sends a "close" connection option MUST NOT send further
1566 requests on that connection (after the one containing "close") and
1567 MUST close the connection after reading the final response message
1568 corresponding to this request.
1570 A server that receives a "close" connection option MUST initiate a
1571 close of the connection (see below) after it sends the final response
1572 to the request that contained "close". The server SHOULD send a
1573 "close" connection option in its final response on that connection.
1574 The server MUST NOT process any further requests received on that
1575 connection.
1577 A server that sends a "close" connection option MUST initiate a close
1578 of the connection (see below) after it sends the response containing
1579 "close". The server MUST NOT process any further requests received
1580 on that connection.
1582 A client that receives a "close" connection option MUST cease sending
1583 requests on that connection and close the connection after reading
1584 the response message containing the "close"; if additional pipelined
1585 requests had been sent on the connection, the client SHOULD NOT
1586 assume that they will be processed by the server.
1588 If a server performs an immediate close of a TCP connection, there is
1589 a significant risk that the client will not be able to read the last
1590 HTTP response. If the server receives additional data from the
1591 client on a fully closed connection, such as another request that was
1592 sent by the client before receiving the server's response, the
1593 server's TCP stack will send a reset packet to the client;
1594 unfortunately, the reset packet might erase the client's
1595 unacknowledged input buffers before they can be read and interpreted
1596 by the client's HTTP parser.
1598 To avoid the TCP reset problem, servers typically close a connection
1599 in stages. First, the server performs a half-close by closing only
1600 the write side of the read/write connection. The server then
1601 continues to read from the connection until it receives a
1602 corresponding close by the client, or until the server is reasonably
1603 certain that its own TCP stack has received the client's
1604 acknowledgement of the packet(s) containing the server's last
1605 response. Finally, the server fully closes the connection.
1607 It is unknown whether the reset problem is exclusive to TCP or might
1608 also be found in other transport connection protocols.
1610 9.8. Upgrade
1612 The "Upgrade" header field is intended to provide a simple mechanism
1613 for transitioning from HTTP/1.1 to some other protocol on the same
1614 connection.
1616 A client MAY send a list of protocol names in the Upgrade header
1617 field of a request to invite the server to switch to one or more of
1618 the named protocols, in order of descending preference, before
1619 sending the final response. A server MAY ignore a received Upgrade
1620 header field if it wishes to continue using the current protocol on
1621 that connection. Upgrade cannot be used to insist on a protocol
1622 change.
1624 Upgrade = 1#protocol
1626 protocol = protocol-name ["/" protocol-version]
1627 protocol-name = token
1628 protocol-version = token
1630 Although protocol names are registered with a preferred case,
1631 recipients SHOULD use case-insensitive comparison when matching each
1632 protocol-name to supported protocols.
1634 A server that sends a 101 (Switching Protocols) response MUST send an
1635 Upgrade header field to indicate the new protocol(s) to which the
1636 connection is being switched; if multiple protocol layers are being
1637 switched, the sender MUST list the protocols in layer-ascending
1638 order. A server MUST NOT switch to a protocol that was not indicated
1639 by the client in the corresponding request's Upgrade header field. A
1640 server MAY choose to ignore the order of preference indicated by the
1641 client and select the new protocol(s) based on other factors, such as
1642 the nature of the request or the current load on the server.
1644 A server that sends a 426 (Upgrade Required) response MUST send an
1645 Upgrade header field to indicate the acceptable protocols, in order
1646 of descending preference.
1648 A server MAY send an Upgrade header field in any other response to
1649 advertise that it implements support for upgrading to the listed
1650 protocols, in order of descending preference, when appropriate for a
1651 future request.
1653 The following is a hypothetical example sent by a client:
1655 GET /hello.txt HTTP/1.1
1656 Host: www.example.com
1657 Connection: upgrade
1658 Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
1660 The capabilities and nature of the application-level communication
1661 after the protocol change is entirely dependent upon the new
1662 protocol(s) chosen. However, immediately after sending the 101
1663 (Switching Protocols) response, the server is expected to continue
1664 responding to the original request as if it had received its
1665 equivalent within the new protocol (i.e., the server still has an
1666 outstanding request to satisfy after the protocol has been changed,
1667 and is expected to do so without requiring the request to be
1668 repeated).
1670 For example, if the Upgrade header field is received in a GET request
1671 and the server decides to switch protocols, it first responds with a
1672 101 (Switching Protocols) message in HTTP/1.1 and then immediately
1673 follows that with the new protocol's equivalent of a response to a
1674 GET on the target resource. This allows a connection to be upgraded
1675 to protocols with the same semantics as HTTP without the latency cost
1676 of an additional round trip. A server MUST NOT switch protocols
1677 unless the received message semantics can be honored by the new
1678 protocol; an OPTIONS request can be honored by any protocol.
1680 The following is an example response to the above hypothetical
1681 request:
1683 HTTP/1.1 101 Switching Protocols
1684 Connection: upgrade
1685 Upgrade: HTTP/2.0
1687 [... data stream switches to HTTP/2.0 with an appropriate response
1688 (as defined by new protocol) to the "GET /hello.txt" request ...]
1690 When Upgrade is sent, the sender MUST also send a Connection header
1691 field (Section 9.1) that contains an "upgrade" connection option, in
1692 order to prevent Upgrade from being accidentally forwarded by
1693 intermediaries that might not implement the listed protocols. A
1694 server MUST ignore an Upgrade header field that is received in an
1695 HTTP/1.0 request.
1697 A client cannot begin using an upgraded protocol on the connection
1698 until it has completely sent the request message (i.e., the client
1699 can't change the protocol it is sending in the middle of a message).
1700 If a server receives both an Upgrade and an Expect header field with
1701 the "100-continue" expectation (Section 8.1.1 of [Semantics]), the
1702 server MUST send a 100 (Continue) response before sending a 101
1703 (Switching Protocols) response.
1705 The Upgrade header field only applies to switching protocols on top
1706 of the existing connection; it cannot be used to switch the
1707 underlying connection (transport) protocol, nor to switch the
1708 existing communication to a different connection. For those
1709 purposes, it is more appropriate to use a 3xx (Redirection) response
1710 (Section 9.4 of [Semantics]).
1712 9.8.1. Upgrade Protocol Names
1714 This specification only defines the protocol name "HTTP" for use by
1715 the family of Hypertext Transfer Protocols, as defined by the HTTP
1716 version rules of Section 3.5 of [Semantics] and future updates to
1717 this specification. Additional protocol names ought to be registered
1718 using the registration procedure defined in Section 9.8.2.
1720 +------+-------------------+--------------------+-------------------+
1721 | Name | Description | Expected Version | Reference |
1722 | | | Tokens | |
1723 +------+-------------------+--------------------+-------------------+
1724 | HTTP | Hypertext | any DIGIT.DIGIT | Section 3.5 of |
1725 | | Transfer Protocol | (e.g, "2.0") | [Semantics] |
1726 +------+-------------------+--------------------+-------------------+
1728 9.8.2. Upgrade Token Registry
1730 The "Hypertext Transfer Protocol (HTTP) Upgrade Token Registry"
1731 defines the namespace for protocol-name tokens used to identify
1732 protocols in the Upgrade header field. The registry is maintained at
1733 .
1735 Each registered protocol name is associated with contact information
1736 and an optional set of specifications that details how the connection
1737 will be processed after it has been upgraded.
1739 Registrations happen on a "First Come First Served" basis (see
1740 Section 4.4 of [RFC8126]) and are subject to the following rules:
1742 1. A protocol-name token, once registered, stays registered forever.
1744 2. A protocol-name token is case-insensitive and registered with the
1745 preferred case to be generated by senders.
1747 3. The registration MUST name a responsible party for the
1748 registration.
1750 4. The registration MUST name a point of contact.
1752 5. The registration MAY name a set of specifications associated with
1753 that token. Such specifications need not be publicly available.
1755 6. The registration SHOULD name a set of expected "protocol-version"
1756 tokens associated with that token at the time of registration.
1758 7. The responsible party MAY change the registration at any time.
1759 The IANA will keep a record of all such changes, and make them
1760 available upon request.
1762 8. The IESG MAY reassign responsibility for a protocol token. This
1763 will normally only be used in the case when a responsible party
1764 cannot be contacted.
1766 10. Enclosing Messages as Data
1768 10.1. Media Type message/http
1770 The message/http media type can be used to enclose a single HTTP
1771 request or response message, provided that it obeys the MIME
1772 restrictions for all "message" types regarding line length and
1773 encodings.
1775 Type name: message
1776 Subtype name: http
1778 Required parameters: N/A
1780 Optional parameters: version, msgtype
1782 version: The HTTP-version number of the enclosed message (e.g.,
1783 "1.1"). If not present, the version can be determined from the
1784 first line of the body.
1786 msgtype: The message type -- "request" or "response". If not
1787 present, the type can be determined from the first line of the
1788 body.
1790 Encoding considerations: only "7bit", "8bit", or "binary" are
1791 permitted
1793 Security considerations: see Section 11
1795 Interoperability considerations: N/A
1797 Published specification: This specification (see Section 10.1).
1799 Applications that use this media type: N/A
1801 Fragment identifier considerations: N/A
1803 Additional information:
1805 Magic number(s): N/A
1807 Deprecated alias names for this type: N/A
1809 File extension(s): N/A
1811 Macintosh file type code(s): N/A
1813 Person and email address to contact for further information:
1814 See Authors' Addresses section.
1816 Intended usage: COMMON
1818 Restrictions on usage: N/A
1820 Author: See Authors' Addresses section.
1822 Change controller: IESG
1824 10.2. Media Type application/http
1826 The application/http media type can be used to enclose a pipeline of
1827 one or more HTTP request or response messages (not intermixed).
1829 Type name: application
1831 Subtype name: http
1833 Required parameters: N/A
1835 Optional parameters: version, msgtype
1837 version: The HTTP-version number of the enclosed messages (e.g.,
1838 "1.1"). If not present, the version can be determined from the
1839 first line of the body.
1841 msgtype: The message type -- "request" or "response". If not
1842 present, the type can be determined from the first line of the
1843 body.
1845 Encoding considerations: HTTP messages enclosed by this type are in
1846 "binary" format; use of an appropriate Content-Transfer-Encoding
1847 is required when transmitted via email.
1849 Security considerations: see Section 11
1851 Interoperability considerations: N/A
1853 Published specification: This specification (see Section 10.2).
1855 Applications that use this media type: N/A
1857 Fragment identifier considerations: N/A
1859 Additional information:
1861 Deprecated alias names for this type: N/A
1863 Magic number(s): N/A
1865 File extension(s): N/A
1867 Macintosh file type code(s): N/A
1869 Person and email address to contact for further information:
1870 See Authors' Addresses section.
1872 Intended usage: COMMON
1874 Restrictions on usage: N/A
1876 Author: See Authors' Addresses section.
1878 Change controller: IESG
1880 11. Security Considerations
1882 This section is meant to inform developers, information providers,
1883 and users of known security considerations relevant to HTTP message
1884 syntax, parsing, and routing. Security considerations about HTTP
1885 semantics and payloads are addressed in [Semantics].
1887 11.1. Response Splitting
1889 Response splitting (a.k.a, CRLF injection) is a common technique,
1890 used in various attacks on Web usage, that exploits the line-based
1891 nature of HTTP message framing and the ordered association of
1892 requests to responses on persistent connections [Klein]. This
1893 technique can be particularly damaging when the requests pass through
1894 a shared cache.
1896 Response splitting exploits a vulnerability in servers (usually
1897 within an application server) where an attacker can send encoded data
1898 within some parameter of the request that is later decoded and echoed
1899 within any of the response header fields of the response. If the
1900 decoded data is crafted to look like the response has ended and a
1901 subsequent response has begun, the response has been split and the
1902 content within the apparent second response is controlled by the
1903 attacker. The attacker can then make any other request on the same
1904 persistent connection and trick the recipients (including
1905 intermediaries) into believing that the second half of the split is
1906 an authoritative answer to the second request.
1908 For example, a parameter within the request-target might be read by
1909 an application server and reused within a redirect, resulting in the
1910 same parameter being echoed in the Location header field of the
1911 response. If the parameter is decoded by the application and not
1912 properly encoded when placed in the response field, the attacker can
1913 send encoded CRLF octets and other content that will make the
1914 application's single response look like two or more responses.
1916 A common defense against response splitting is to filter requests for
1917 data that looks like encoded CR and LF (e.g., "%0D" and "%0A").
1918 However, that assumes the application server is only performing URI
1919 decoding, rather than more obscure data transformations like charset
1920 transcoding, XML entity translation, base64 decoding, sprintf
1921 reformatting, etc. A more effective mitigation is to prevent
1922 anything other than the server's core protocol libraries from sending
1923 a CR or LF within the header section, which means restricting the
1924 output of header fields to APIs that filter for bad octets and not
1925 allowing application servers to write directly to the protocol
1926 stream.
1928 11.2. Request Smuggling
1930 Request smuggling ([Linhart]) is a technique that exploits
1931 differences in protocol parsing among various recipients to hide
1932 additional requests (which might otherwise be blocked or disabled by
1933 policy) within an apparently harmless request. Like response
1934 splitting, request smuggling can lead to a variety of attacks on HTTP
1935 usage.
1937 This specification has introduced new requirements on request
1938 parsing, particularly with regard to message framing in Section 6.3,
1939 to reduce the effectiveness of request smuggling.
1941 11.3. Message Integrity
1943 HTTP does not define a specific mechanism for ensuring message
1944 integrity, instead relying on the error-detection ability of
1945 underlying transport protocols and the use of length or chunk-
1946 delimited framing to detect completeness. Additional integrity
1947 mechanisms, such as hash functions or digital signatures applied to
1948 the content, can be selectively added to messages via extensible
1949 metadata header fields. Historically, the lack of a single integrity
1950 mechanism has been justified by the informal nature of most HTTP
1951 communication. However, the prevalence of HTTP as an information
1952 access mechanism has resulted in its increasing use within
1953 environments where verification of message integrity is crucial.
1955 User agents are encouraged to implement configurable means for
1956 detecting and reporting failures of message integrity such that those
1957 means can be enabled within environments for which integrity is
1958 necessary. For example, a browser being used to view medical history
1959 or drug interaction information needs to indicate to the user when
1960 such information is detected by the protocol to be incomplete,
1961 expired, or corrupted during transfer. Such mechanisms might be
1962 selectively enabled via user agent extensions or the presence of
1963 message integrity metadata in a response. At a minimum, user agents
1964 ought to provide some indication that allows a user to distinguish
1965 between a complete and incomplete response message (Section 8) when
1966 such verification is desired.
1968 11.4. Message Confidentiality
1970 HTTP relies on underlying transport protocols to provide message
1971 confidentiality when that is desired. HTTP has been specifically
1972 designed to be independent of the transport protocol, such that it
1973 can be used over many different forms of encrypted connection, with
1974 the selection of such transports being identified by the choice of
1975 URI scheme or within user agent configuration.
1977 The "https" scheme can be used to identify resources that require a
1978 confidential connection, as described in Section 2.5.2 of
1979 [Semantics].
1981 12. IANA Considerations
1983 The change controller for the following registrations is: "IETF
1984 (iesg@ietf.org) - Internet Engineering Task Force".
1986 12.1. Header Field Registration
1988 Please update the "Hypertext Transfer Protocol (HTTP) Header Field
1989 Registry" registry at
1990 with the header field names listed in the two tables of Section 5.
1992 12.2. Media Type Registration
1994 Please update the "Media Types" registry at
1995 with the registration
1996 information in Section 10.1 and Section 10.2 for the media types
1997 "message/http" and "application/http", respectively.
1999 12.3. Transfer Coding Registration
2001 Please update the "HTTP Transfer Coding Registry" at
2002 with the
2003 registration procedure of Section 7.3 and the content coding names
2004 summarized in the table of Section 7.
2006 12.4. Upgrade Token Registration
2008 Please update the "Hypertext Transfer Protocol (HTTP) Upgrade Token
2009 Registry" at
2010 with the registration procedure of Section 9.8.2 and the upgrade
2011 token names summarized in the table of Section 9.8.1.
2013 13. References
2015 13.1. Normative References
2017 [Caching] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
2018 Ed., "HTTP Caching", draft-ietf-httpbis-cache-05 (work in
2019 progress), July 2019.
2021 [RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Format
2022 Specification version 3.3", RFC 1950,
2023 DOI 10.17487/RFC1950, May 1996,
2024 .
2026 [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
2027 version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996,
2028 .
2030 [RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and G.
2031 Randers-Pehrson, "GZIP file format specification version
2032 4.3", RFC 1952, DOI 10.17487/RFC1952, May 1996,
2033 .
2035 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
2036 Requirement Levels", BCP 14, RFC 2119,
2037 DOI 10.17487/RFC2119, March 1997,
2038 .
2040 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
2041 Resource Identifier (URI): Generic Syntax", STD 66,
2042 RFC 3986, DOI 10.17487/RFC3986, January 2005,
2043 .
2045 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
2046 Specifications: ABNF", STD 68, RFC 5234,
2047 DOI 10.17487/RFC5234, January 2008,
2048 .
2050 [RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
2051 RFC 7405, DOI 10.17487/RFC7405, December 2014,
2052 .
2054 [Semantics]
2055 Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
2056 Ed., "HTTP Semantics", draft-ietf-httpbis-semantics-05
2057 (work in progress), July 2019.
2059 [USASCII] American National Standards Institute, "Coded Character
2060 Set -- 7-bit American Standard Code for Information
2061 Interchange", ANSI X3.4, 1986.
2063 [Welch] Welch, T., "A Technique for High-Performance Data
2064 Compression", IEEE Computer 17(6), June 1984.
2066 13.2. Informative References
2068 [Err4667] RFC Errata, Erratum ID 4667, RFC 7230,
2069 .
2071 [Klein] Klein, A., "Divide and Conquer - HTTP Response Splitting,
2072 Web Cache Poisoning Attacks, and Related Topics", March
2073 2004, .
2076 [Linhart] Linhart, C., Klein, A., Heled, R., and S. Orrin, "HTTP
2077 Request Smuggling", June 2005,
2078 .
2080 [RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext
2081 Transfer Protocol -- HTTP/1.0", RFC 1945,
2082 DOI 10.17487/RFC1945, May 1996,
2083 .
2085 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2086 Extensions (MIME) Part One: Format of Internet Message
2087 Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
2088 .
2090 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2091 Extensions (MIME) Part Two: Media Types", RFC 2046,
2092 DOI 10.17487/RFC2046, November 1996,
2093 .
2095 [RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2096 Extensions (MIME) Part Five: Conformance Criteria and
2097 Examples", RFC 2049, DOI 10.17487/RFC2049, November 1996,
2098 .
2100 [RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T.
2101 Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
2102 RFC 2068, DOI 10.17487/RFC2068, January 1997,
2103 .
2105 [RFC2557] Palme, F., Hopmann, A., Shelness, N., and E. Stefferud,
2106 "MIME Encapsulation of Aggregate Documents, such as HTML
2107 (MHTML)", RFC 2557, DOI 10.17487/RFC2557, March 1999,
2108 .
2110 [RFC5322] Resnick, P., "Internet Message Format", RFC 5322,
2111 DOI 10.17487/RFC5322, October 2008,
2112 .
2114 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
2115 DOI 10.17487/RFC6265, April 2011,
2116 .
2118 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
2119 Protocol (HTTP/1.1): Message Syntax and Routing",
2120 RFC 7230, DOI 10.17487/RFC7230, June 2014,
2121 .
2123 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
2124 Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
2125 DOI 10.17487/RFC7231, June 2014,
2126 .
2128 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
2129 Writing an IANA Considerations Section in RFCs", BCP 26,
2130 RFC 8126, DOI 10.17487/RFC8126, June 2017,
2131 .
2133 Appendix A. Collected ABNF
2135 In the collected ABNF below, list rules are expanded as per
2136 Section 11 of [Semantics].
2138 BWS =
2140 Connection = [ connection-option ] *( OWS "," OWS [ connection-option
2141 ] )
2143 HTTP-message = start-line *( header-field CRLF ) CRLF [ message-body
2144 ]
2145 HTTP-name = %x48.54.54.50 ; HTTP
2146 HTTP-version = HTTP-name "/" DIGIT "." DIGIT
2148 OWS =
2150 RWS =
2152 TE = [ t-codings ] *( OWS "," OWS [ t-codings ] )
2153 Transfer-Encoding = [ transfer-coding ] *( OWS "," OWS [
2154 transfer-coding ] )
2156 Upgrade = [ protocol ] *( OWS "," OWS [ protocol ] )
2158 absolute-URI =
2159 absolute-form = absolute-URI
2160 absolute-path =
2161 asterisk-form = "*"
2162 authority =
2163 authority-form = authority
2165 chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
2166 chunk-data = 1*OCTET
2167 chunk-ext = *( BWS ";" BWS chunk-ext-name [ BWS "=" BWS chunk-ext-val
2168 ] )
2169 chunk-ext-name = token
2170 chunk-ext-val = token / quoted-string
2171 chunk-size = 1*HEXDIG
2172 chunked-body = *chunk last-chunk trailer-part CRLF
2173 comment =
2174 connection-option = token
2176 field-name =
2177 field-value =
2179 header-field = field-name ":" OWS field-value OWS
2180 last-chunk = 1*"0" [ chunk-ext ] CRLF
2182 message-body = *OCTET
2183 method = token
2185 obs-fold = OWS CRLF RWS
2186 obs-text =
2187 origin-form = absolute-path [ "?" query ]
2189 port =
2190 protocol = protocol-name [ "/" protocol-version ]
2191 protocol-name = token
2192 protocol-version = token
2194 query =
2195 quoted-string =
2197 rank = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] )
2198 reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
2199 request-line = method SP request-target SP HTTP-version CRLF
2200 request-target = origin-form / absolute-form / authority-form /
2201 asterisk-form
2203 start-line = request-line / status-line
2204 status-code = 3DIGIT
2205 status-line = HTTP-version SP status-code SP [ reason-phrase ] CRLF
2207 t-codings = "trailers" / ( transfer-coding [ t-ranking ] )
2208 t-ranking = OWS ";" OWS "q=" rank
2209 token =
2210 trailer-part = *( header-field CRLF )
2211 transfer-coding = token *( OWS ";" OWS transfer-parameter )
2212 transfer-parameter = token BWS "=" BWS ( token / quoted-string )
2214 uri-host =
2216 Appendix B. Differences between HTTP and MIME
2218 HTTP/1.1 uses many of the constructs defined for the Internet Message
2219 Format [RFC5322] and the Multipurpose Internet Mail Extensions (MIME)
2220 [RFC2045] to allow a message body to be transmitted in an open
2221 variety of representations and with extensible header fields.
2222 However, RFC 2045 is focused only on email; applications of HTTP have
2223 many characteristics that differ from email; hence, HTTP has features
2224 that differ from MIME. These differences were carefully chosen to
2225 optimize performance over binary connections, to allow greater
2226 freedom in the use of new media types, to make date comparisons
2227 easier, and to acknowledge the practice of some early HTTP servers
2228 and clients.
2230 This appendix describes specific areas where HTTP differs from MIME.
2231 Proxies and gateways to and from strict MIME environments need to be
2232 aware of these differences and provide the appropriate conversions
2233 where necessary.
2235 B.1. MIME-Version
2237 HTTP is not a MIME-compliant protocol. However, messages can include
2238 a single MIME-Version header field to indicate what version of the
2239 MIME protocol was used to construct the message. Use of the MIME-
2240 Version header field indicates that the message is in full
2241 conformance with the MIME protocol (as defined in [RFC2045]).
2242 Senders are responsible for ensuring full conformance (where
2243 possible) when exporting HTTP messages to strict MIME environments.
2245 B.2. Conversion to Canonical Form
2247 MIME requires that an Internet mail body part be converted to
2248 canonical form prior to being transferred, as described in Section 4
2249 of [RFC2049]. Section 6.1.1.2 of [Semantics] describes the forms
2250 allowed for subtypes of the "text" media type when transmitted over
2251 HTTP. [RFC2046] requires that content with a type of "text"
2252 represent line breaks as CRLF and forbids the use of CR or LF outside
2253 of line break sequences. HTTP allows CRLF, bare CR, and bare LF to
2254 indicate a line break within text content.
2256 A proxy or gateway from HTTP to a strict MIME environment ought to
2257 translate all line breaks within text media types to the RFC 2049
2258 canonical form of CRLF. Note, however, this might be complicated by
2259 the presence of a Content-Encoding and by the fact that HTTP allows
2260 the use of some charsets that do not use octets 13 and 10 to
2261 represent CR and LF, respectively.
2263 Conversion will break any cryptographic checksums applied to the
2264 original content unless the original content is already in canonical
2265 form. Therefore, the canonical form is recommended for any content
2266 that uses such checksums in HTTP.
2268 B.3. Conversion of Date Formats
2270 HTTP/1.1 uses a restricted set of date formats (Section 10.1.1.1 of
2271 [Semantics]) to simplify the process of date comparison. Proxies and
2272 gateways from other protocols ought to ensure that any Date header
2273 field present in a message conforms to one of the HTTP/1.1 formats
2274 and rewrite the date if necessary.
2276 B.4. Conversion of Content-Encoding
2278 MIME does not include any concept equivalent to HTTP/1.1's Content-
2279 Encoding header field. Since this acts as a modifier on the media
2280 type, proxies and gateways from HTTP to MIME-compliant protocols
2281 ought to either change the value of the Content-Type header field or
2282 decode the representation before forwarding the message. (Some
2283 experimental applications of Content-Type for Internet mail have used
2284 a media-type parameter of ";conversions=" to perform
2285 a function equivalent to Content-Encoding. However, this parameter
2286 is not part of the MIME standards).
2288 B.5. Conversion of Content-Transfer-Encoding
2290 HTTP does not use the Content-Transfer-Encoding field of MIME.
2291 Proxies and gateways from MIME-compliant protocols to HTTP need to
2292 remove any Content-Transfer-Encoding prior to delivering the response
2293 message to an HTTP client.
2295 Proxies and gateways from HTTP to MIME-compliant protocols are
2296 responsible for ensuring that the message is in the correct format
2297 and encoding for safe transport on that protocol, where "safe
2298 transport" is defined by the limitations of the protocol being used.
2299 Such a proxy or gateway ought to transform and label the data with an
2300 appropriate Content-Transfer-Encoding if doing so will improve the
2301 likelihood of safe transport over the destination protocol.
2303 B.6. MHTML and Line Length Limitations
2305 HTTP implementations that share code with MHTML [RFC2557]
2306 implementations need to be aware of MIME line length limitations.
2307 Since HTTP does not have this limitation, HTTP does not fold long
2308 lines. MHTML messages being transported by HTTP follow all
2309 conventions of MHTML, including line length limitations and folding,
2310 canonicalization, etc., since HTTP transfers message-bodies as
2311 payload and, aside from the "multipart/byteranges" type
2312 (Section 6.3.4 of [Semantics]), does not interpret the content or any
2313 MIME header lines that might be contained therein.
2315 Appendix C. HTTP Version History
2317 HTTP has been in use since 1990. The first version, later referred
2318 to as HTTP/0.9, was a simple protocol for hypertext data transfer
2319 across the Internet, using only a single request method (GET) and no
2320 metadata. HTTP/1.0, as defined by [RFC1945], added a range of
2321 request methods and MIME-like messaging, allowing for metadata to be
2322 transferred and modifiers placed on the request/response semantics.
2323 However, HTTP/1.0 did not sufficiently take into consideration the
2324 effects of hierarchical proxies, caching, the need for persistent
2325 connections, or name-based virtual hosts. The proliferation of
2326 incompletely implemented applications calling themselves "HTTP/1.0"
2327 further necessitated a protocol version change in order for two
2328 communicating applications to determine each other's true
2329 capabilities.
2331 HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent
2332 requirements that enable reliable implementations, adding only those
2333 features that can either be safely ignored by an HTTP/1.0 recipient
2334 or only be sent when communicating with a party advertising
2335 conformance with HTTP/1.1.
2337 HTTP/1.1 has been designed to make supporting previous versions easy.
2338 A general-purpose HTTP/1.1 server ought to be able to understand any
2339 valid request in the format of HTTP/1.0, responding appropriately
2340 with an HTTP/1.1 message that only uses features understood (or
2341 safely ignored) by HTTP/1.0 clients. Likewise, an HTTP/1.1 client
2342 can be expected to understand any valid HTTP/1.0 response.
2344 Since HTTP/0.9 did not support header fields in a request, there is
2345 no mechanism for it to support name-based virtual hosts (selection of
2346 resource by inspection of the Host header field). Any server that
2347 implements name-based virtual hosts ought to disable support for
2348 HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact,
2349 badly constructed HTTP/1.x requests caused by a client failing to
2350 properly encode the request-target.
2352 C.1. Changes from HTTP/1.0
2354 This section summarizes major differences between versions HTTP/1.0
2355 and HTTP/1.1.
2357 C.1.1. Multihomed Web Servers
2359 The requirements that clients and servers support the Host header
2360 field (Section 5.4 of [Semantics]), report an error if it is missing
2361 from an HTTP/1.1 request, and accept absolute URIs (Section 3.2) are
2362 among the most important changes defined by HTTP/1.1.
2364 Older HTTP/1.0 clients assumed a one-to-one relationship of IP
2365 addresses and servers; there was no other established mechanism for
2366 distinguishing the intended server of a request than the IP address
2367 to which that request was directed. The Host header field was
2368 introduced during the development of HTTP/1.1 and, though it was
2369 quickly implemented by most HTTP/1.0 browsers, additional
2370 requirements were placed on all HTTP/1.1 requests in order to ensure
2371 complete adoption. At the time of this writing, most HTTP-based
2372 services are dependent upon the Host header field for targeting
2373 requests.
2375 C.1.2. Keep-Alive Connections
2377 In HTTP/1.0, each connection is established by the client prior to
2378 the request and closed by the server after sending the response.
2379 However, some implementations implement the explicitly negotiated
2380 ("Keep-Alive") version of persistent connections described in
2381 Section 19.7.1 of [RFC2068].
2383 Some clients and servers might wish to be compatible with these
2384 previous approaches to persistent connections, by explicitly
2385 negotiating for them with a "Connection: keep-alive" request header
2386 field. However, some experimental implementations of HTTP/1.0
2387 persistent connections are faulty; for example, if an HTTP/1.0 proxy
2388 server doesn't understand Connection, it will erroneously forward
2389 that header field to the next inbound server, which would result in a
2390 hung connection.
2392 One attempted solution was the introduction of a Proxy-Connection
2393 header field, targeted specifically at proxies. In practice, this
2394 was also unworkable, because proxies are often deployed in multiple
2395 layers, bringing about the same problem discussed above.
2397 As a result, clients are encouraged not to send the Proxy-Connection
2398 header field in any requests.
2400 Clients are also encouraged to consider the use of Connection: keep-
2401 alive in requests carefully; while they can enable persistent
2402 connections with HTTP/1.0 servers, clients using them will need to
2403 monitor the connection for "hung" requests (which indicate that the
2404 client ought stop sending the header field), and this mechanism ought
2405 not be used by clients at all when a proxy is being used.
2407 C.1.3. Introduction of Transfer-Encoding
2409 HTTP/1.1 introduces the Transfer-Encoding header field (Section 6.1).
2410 Transfer codings need to be decoded prior to forwarding an HTTP
2411 message over a MIME-compliant protocol.
2413 C.2. Changes from RFC 7230
2415 Most of the sections introducing HTTP's design goals, history,
2416 architecture, conformance criteria, protocol versioning, URIs,
2417 message routing, and header field values have been moved to
2418 [Semantics]. This document has been reduced to just the messaging
2419 syntax and connection management requirements specific to HTTP/1.1.
2421 Furthermore:
2423 In the ABNF for chunked extensions, re-introduce (bad) whitespace
2424 around ";" and "=". Whitespace was removed in [RFC7230], but later
2425 this change was found to break existing implementations (see
2426 [Err4667]). (Section 7.1.1)
2428 Disallow transfer coding parameters called "q" in order to avoid
2429 conflicts with the use of ranks in the TE header field.
2430 (Section 7.3)
2432 Appendix D. Change Log
2434 This section is to be removed before publishing as an RFC.
2436 D.1. Between RFC7230 and draft 00
2438 The changes were purely editorial:
2440 o Change boilerplate and abstract to indicate the "draft" status,
2441 and update references to ancestor specifications.
2443 o Adjust historical notes.
2445 o Update links to sibling specifications.
2447 o Replace sections listing changes from RFC 2616 by new empty
2448 sections referring to RFC 723x.
2450 o Remove acknowledgements specific to RFC 723x.
2452 o Move "Acknowledgements" to the very end and make them unnumbered.
2454 D.2. Since draft-ietf-httpbis-messaging-00
2456 The changes in this draft are editorial, with respect to HTTP as a
2457 whole, to move all core HTTP semantics into [Semantics]:
2459 o Moved introduction, architecture, conformance, and ABNF extensions
2460 from RFC 7230 (Messaging) to semantics [Semantics].
2462 o Moved discussion of MIME differences from RFC 7231 (Semantics) to
2463 Appendix B since they mostly cover transforming 1.1 messages.
2465 o Moved all extensibility tips, registration procedures, and
2466 registry tables from the IANA considerations to normative
2467 sections, reducing the IANA considerations to just instructions
2468 that will be removed prior to publication as an RFC.
2470 D.3. Since draft-ietf-httpbis-messaging-01
2472 o Cite RFC 8126 instead of RFC 5226 ()
2475 o Resolved erratum 4779, no change needed here
2476 (,
2477 )
2479 o In Section 7, fixed prose claiming transfer parameters allow bare
2480 names (,
2481 )
2483 o Resolved erratum 4225, no change needed here
2484 (,
2485 )
2487 o Replace "response code" with "response status code"
2488 (,
2489 )
2491 o In Section 9.4, clarify statement about HTTP/1.0 keep-alive
2492 (,
2493 )
2495 o In Section 7.1.1, re-introduce (bad) whitespace around ";" and "="
2496 (,
2497 , )
2500 o In Section 7.3, state that transfer codings should not use
2501 parameters named "q" (, )
2504 o In Section 7, mark coding name "trailers" as reserved in the IANA
2505 registry ()
2507 D.4. Since draft-ietf-httpbis-messaging-02
2509 o In Section 4, explain why the reason phrase should be ignored by
2510 clients ().
2512 o Add Section 9.3 to explain how request/response correlation is
2513 performed ()
2515 D.5. Since draft-ietf-httpbis-messaging-03
2517 o In Section 9.3, caution against treating data on a connection as
2518 part of a not-yet-issued request ()
2521 o In Section 7, remove the predefined codings from the ABNF and make
2522 it generic instead ()
2525 o Use RFC 7405 ABNF notation for case-sensitive string constants
2526 ()
2528 D.6. Since draft-ietf-httpbis-messaging-04
2530 o In Section 9.8, clarify that protocol-name is to be matched case-
2531 insensitively ()
2533 o In Section 5.2, add leading optional whitespace to obs-fold ABNF
2534 (,
2535 )
2537 o In Section 4, add clarifications about empty reason phrases
2538 ()
2540 o Move discussion of retries from Section 9.4.1 into [Semantics]
2541 ()
2543 Index
2545 A
2546 absolute-form (of request-target) 11
2547 application/http Media Type 40
2548 asterisk-form (of request-target) 12
2549 authority-form (of request-target) 11
2551 C
2552 Connection header field 29, 34
2553 Content-Length header field 19
2554 Content-Transfer-Encoding header field 50
2555 chunked (Coding Format) 17, 19
2556 chunked (transfer coding) 22
2557 close 29, 34
2558 compress (transfer coding) 25
2560 D
2561 deflate (transfer coding) 25
2563 E
2564 effective request URI 12
2566 G
2567 Grammar
2568 absolute-form 10-11
2569 ALPHA 5
2570 asterisk-form 10, 12
2571 authority-form 10-11
2572 chunk 23
2573 chunk-data 23
2574 chunk-ext 23
2575 chunk-ext-name 23
2576 chunk-ext-val 23
2577 chunk-size 23
2578 chunked-body 23
2579 Connection 29
2580 connection-option 29
2581 CR 5
2582 CRLF 5
2583 CTL 5
2584 DIGIT 5
2585 DQUOTE 5
2586 field-name 15
2587 field-value 15
2588 header-field 15, 24
2589 HEXDIG 5
2590 HTAB 5
2591 HTTP-message 6
2592 HTTP-name 7
2593 HTTP-version 7
2594 last-chunk 23
2595 LF 5
2596 message-body 17
2597 method 9
2598 obs-fold 16
2599 OCTET 5
2600 origin-form 10
2601 rank 27
2602 reason-phrase 14
2603 request-line 9
2604 request-target 10
2605 SP 5
2606 start-line 6
2607 status-code 14
2608 status-line 14
2609 t-codings 27
2610 t-ranking 27
2611 TE 27
2612 trailer-part 23-24
2613 transfer-coding 21
2614 Transfer-Encoding 17
2615 transfer-parameter 22
2616 Upgrade 35
2617 VCHAR 5
2618 gzip (transfer coding) 25
2620 H
2621 header field 6
2622 header section 6
2623 headers 6
2625 M
2626 MIME-Version header field 49
2627 Media Type
2628 application/http 40
2629 message/http 38
2630 message/http Media Type 38
2631 method 9
2633 O
2634 origin-form (of request-target) 10
2636 R
2637 request-target 10
2639 T
2640 TE header field 26
2641 Transfer-Encoding header field 17
2643 U
2644 Upgrade header field 35
2646 X
2647 x-compress (transfer coding) 25
2648 x-gzip (transfer coding) 25
2650 Acknowledgments
2652 See Appendix "Acknowledgments" of [Semantics].
2654 Authors' Addresses
2655 Roy T. Fielding (editor)
2656 Adobe
2657 345 Park Ave
2658 San Jose, CA 95110
2659 USA
2661 EMail: fielding@gbiv.com
2662 URI: https://roy.gbiv.com/
2664 Mark Nottingham (editor)
2665 Fastly
2667 EMail: mnot@mnot.net
2668 URI: https://www.mnot.net/
2670 Julian F. Reschke (editor)
2671 greenbytes GmbH
2672 Hafenweg 16
2673 Muenster, NW 48155
2674 Germany
2676 EMail: julian.reschke@greenbytes.de
2677 URI: https://greenbytes.de/tech/webdav/