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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 3, 2019 J. Reschke, Ed.
7 greenbytes
8 July 2, 2018
10 HTTP/1.1 Messaging
11 draft-ietf-httpbis-messaging-02
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.3.
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 3, 2019.
54 Copyright Notice
56 Copyright (c) 2018 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 . . . . . . . . . . . . . . . . . . . . . . 6
89 2.3. Message Parsing . . . . . . . . . . . . . . . . . . . . . 7
90 3. Request Line . . . . . . . . . . . . . . . . . . . . . . . . 8
91 3.1. Method . . . . . . . . . . . . . . . . . . . . . . . . . 9
92 3.2. Request Target . . . . . . . . . . . . . . . . . . . . . 9
93 3.2.1. origin-form . . . . . . . . . . . . . . . . . . . . . 10
94 3.2.2. absolute-form . . . . . . . . . . . . . . . . . . . . 10
95 3.2.3. authority-form . . . . . . . . . . . . . . . . . . . 11
96 3.2.4. asterisk-form . . . . . . . . . . . . . . . . . . . . 11
98 3.3. Effective Request URI . . . . . . . . . . . . . . . . . . 12
99 4. Status Line . . . . . . . . . . . . . . . . . . . . . . . . . 13
100 5. Header Fields . . . . . . . . . . . . . . . . . . . . . . . . 14
101 5.1. Field Parsing . . . . . . . . . . . . . . . . . . . . . . 15
102 5.2. Obsolete Line Folding . . . . . . . . . . . . . . . . . . 15
103 6. Message Body . . . . . . . . . . . . . . . . . . . . . . . . 16
104 6.1. Transfer-Encoding . . . . . . . . . . . . . . . . . . . . 17
105 6.2. Content-Length . . . . . . . . . . . . . . . . . . . . . 18
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 . . . . . . . . . . . . . . . . 23
111 7.1.3. Decoding Chunked . . . . . . . . . . . . . . . . . . 24
112 7.2. Transfer Codings for Compression . . . . . . . . . . . . 25
113 7.3. Transfer Coding Registry . . . . . . . . . . . . . . . . 25
114 7.4. TE . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
115 8. Handling Incomplete Messages . . . . . . . . . . . . . . . . 27
116 9. Connection Management . . . . . . . . . . . . . . . . . . . . 28
117 9.1. Connection . . . . . . . . . . . . . . . . . . . . . . . 28
118 9.2. Establishment . . . . . . . . . . . . . . . . . . . . . . 30
119 9.3. Persistence . . . . . . . . . . . . . . . . . . . . . . . 30
120 9.3.1. Retrying Requests . . . . . . . . . . . . . . . . . . 31
121 9.3.2. Pipelining . . . . . . . . . . . . . . . . . . . . . 31
122 9.4. Concurrency . . . . . . . . . . . . . . . . . . . . . . . 32
123 9.5. Failures and Timeouts . . . . . . . . . . . . . . . . . . 33
124 9.6. Tear-down . . . . . . . . . . . . . . . . . . . . . . . . 33
125 9.7. Upgrade . . . . . . . . . . . . . . . . . . . . . . . . . 34
126 9.7.1. Upgrade Protocol Names . . . . . . . . . . . . . . . 36
127 9.7.2. Upgrade Token Registry . . . . . . . . . . . . . . . 37
128 10. Enclosing Messages as Data . . . . . . . . . . . . . . . . . 37
129 10.1. Media Type message/http . . . . . . . . . . . . . . . . 38
130 10.2. Media Type application/http . . . . . . . . . . . . . . 39
131 11. Security Considerations . . . . . . . . . . . . . . . . . . . 40
132 11.1. Response Splitting . . . . . . . . . . . . . . . . . . . 40
133 11.2. Request Smuggling . . . . . . . . . . . . . . . . . . . 41
134 11.3. Message Integrity . . . . . . . . . . . . . . . . . . . 41
135 11.4. Message Confidentiality . . . . . . . . . . . . . . . . 42
136 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42
137 12.1. Header Field Registration . . . . . . . . . . . . . . . 42
138 12.2. Media Type Registration . . . . . . . . . . . . . . . . 42
139 12.3. Transfer Coding Registration . . . . . . . . . . . . . . 42
140 12.4. Upgrade Token Registration . . . . . . . . . . . . . . . 43
141 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 43
142 13.1. Normative References . . . . . . . . . . . . . . . . . . 43
143 13.2. Informative References . . . . . . . . . . . . . . . . . 44
144 Appendix A. Collected ABNF . . . . . . . . . . . . . . . . . . . 46
145 Appendix B. Differences between HTTP and MIME . . . . . . . . . 47
146 B.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 48
147 B.2. Conversion to Canonical Form . . . . . . . . . . . . . . 48
148 B.3. Conversion of Date Formats . . . . . . . . . . . . . . . 48
149 B.4. Conversion of Content-Encoding . . . . . . . . . . . . . 49
150 B.5. Conversion of Content-Transfer-Encoding . . . . . . . . . 49
151 B.6. MHTML and Line Length Limitations . . . . . . . . . . . . 49
152 Appendix C. HTTP Version History . . . . . . . . . . . . . . . . 49
153 C.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 50
154 C.1.1. Multihomed Web Servers . . . . . . . . . . . . . . . 50
155 C.1.2. Keep-Alive Connections . . . . . . . . . . . . . . . 51
156 C.1.3. Introduction of Transfer-Encoding . . . . . . . . . . 51
157 C.2. Changes from RFC 7230 . . . . . . . . . . . . . . . . . . 52
158 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 52
159 D.1. Between RFC7230 and draft 00 . . . . . . . . . . . . . . 52
160 D.2. Since draft-ietf-httpbis-messaging-00 . . . . . . . . . . 52
161 D.3. Since draft-ietf-httpbis-messaging-01 . . . . . . . . . . 53
162 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
163 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 56
164 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 56
166 1. Introduction
168 The Hypertext Transfer Protocol (HTTP) is a stateless application-
169 level request/response protocol that uses extensible semantics and
170 self-descriptive messages for flexible interaction with network-based
171 hypertext information systems. HTTP is defined by a series of
172 documents that collectively form the HTTP/1.1 specification:
174 o "HTTP Semantics" [Semantics]
176 o "HTTP Caching" [Caching]
178 o "HTTP/1.1 Messaging" (this document)
180 This document defines HTTP/1.1 message syntax and framing
181 requirements and their associated connection management. Our goal is
182 to define all of the mechanisms necessary for HTTP/1.1 message
183 handling that are independent of message semantics, thereby defining
184 the complete set of requirements for message parsers and message-
185 forwarding intermediaries.
187 This document obsoletes the portions of RFC 7230 related to HTTP/1.1
188 messaging and connection management, with the changes being
189 summarized in Appendix C.2. The other parts of RFC 7230 are
190 obsoleted by "HTTP Semantics" [Semantics].
192 1.1. Requirements Notation
194 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
195 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
196 document are to be interpreted as described in [RFC2119].
198 Conformance criteria and considerations regarding error handling are
199 defined in Section 3 of [Semantics].
201 1.2. Syntax Notation
203 This specification uses the Augmented Backus-Naur Form (ABNF)
204 notation of [RFC5234] with a list extension, defined in Section 11 of
205 [Semantics], that allows for compact definition of comma-separated
206 lists using a '#' operator (similar to how the '*' operator indicates
207 repetition). Appendix A shows the collected grammar with all list
208 operators expanded to standard ABNF notation.
210 As a convention, ABNF rule names prefixed with "obs-" denote
211 "obsolete" grammar rules that appear for historical reasons.
213 The following core rules are included by reference, as defined in
214 [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF
215 (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),
216 HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line
217 feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any
218 visible [USASCII] character).
220 The rules below are defined in [Semantics]:
222 BWS =
223 OWS =
224 RWS =
225 absolute-URI =
226 absolute-path =
227 authority =
228 comment =
229 field-name =
230 field-value =
231 obs-text =
232 port =
233 query =
234 quoted-string =
235 token =
236 uri-host =
238 2. Message
240 2.1. Message Format
242 All HTTP/1.1 messages consist of a start-line followed by a sequence
243 of octets in a format similar to the Internet Message Format
244 [RFC5322]: zero or more header fields (collectively referred to as
245 the "headers" or the "header section"), an empty line indicating the
246 end of the header section, and an optional message body.
248 HTTP-message = start-line
249 *( header-field CRLF )
250 CRLF
251 [ message-body ]
253 An HTTP message can be either a request from client to server or a
254 response from server to client. Syntactically, the two types of
255 message differ only in the start-line, which is either a request-line
256 (for requests) or a status-line (for responses), and in the algorithm
257 for determining the length of the message body (Section 6).
259 start-line = request-line / status-line
261 In theory, a client could receive requests and a server could receive
262 responses, distinguishing them by their different start-line formats.
263 In practice, servers are implemented to only expect a request (a
264 response is interpreted as an unknown or invalid request method) and
265 clients are implemented to only expect a response.
267 Although HTTP makes use of some protocol elements similar to the
268 Multipurpose Internet Mail Extensions (MIME) [RFC2045], see
269 Appendix B for the differences between HTTP and MIME messages.
271 2.2. HTTP Version
273 HTTP uses a "." numbering scheme to indicate versions
274 of the protocol. This specification defines version "1.1".
275 Section 3.5 of [Semantics] specifies the semantics of HTTP version
276 numbers.
278 The version of an HTTP/1.x message is indicated by an HTTP-version
279 field in the start-line. HTTP-version is case-sensitive.
281 HTTP-version = HTTP-name "/" DIGIT "." DIGIT
282 HTTP-name = %x48.54.54.50 ; "HTTP", case-sensitive
284 When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [RFC1945]
285 or a recipient whose version is unknown, the HTTP/1.1 message is
286 constructed such that it can be interpreted as a valid HTTP/1.0
287 message if all of the newer features are ignored. This specification
288 places recipient-version requirements on some new features so that a
289 conformant sender will only use compatible features until it has
290 determined, through configuration or the receipt of a message, that
291 the recipient supports HTTP/1.1.
293 Intermediaries that process HTTP messages (i.e., all intermediaries
294 other than those acting as tunnels) MUST send their own HTTP-version
295 in forwarded messages. In other words, they are not allowed to
296 blindly forward the start-line without ensuring that the protocol
297 version in that message matches a version to which that intermediary
298 is conformant for both the receiving and sending of messages.
299 Forwarding an HTTP message without rewriting the HTTP-version might
300 result in communication errors when downstream recipients use the
301 message sender's version to determine what features are safe to use
302 for later communication with that sender.
304 A server MAY send an HTTP/1.0 response to an HTTP/1.1 request if it
305 is known or suspected that the client incorrectly implements the HTTP
306 specification and is incapable of correctly processing later version
307 responses, such as when a client fails to parse the version number
308 correctly or when an intermediary is known to blindly forward the
309 HTTP-version even when it doesn't conform to the given minor version
310 of the protocol. Such protocol downgrades SHOULD NOT be performed
311 unless triggered by specific client attributes, such as when one or
312 more of the request header fields (e.g., User-Agent) uniquely match
313 the values sent by a client known to be in error.
315 2.3. Message Parsing
317 The normal procedure for parsing an HTTP message is to read the
318 start-line into a structure, read each header field into a hash table
319 by field name until the empty line, and then use the parsed data to
320 determine if a message body is expected. If a message body has been
321 indicated, then it is read as a stream until an amount of octets
322 equal to the message body length is read or the connection is closed.
324 A recipient MUST parse an HTTP message as a sequence of octets in an
325 encoding that is a superset of US-ASCII [USASCII]. Parsing an HTTP
326 message as a stream of Unicode characters, without regard for the
327 specific encoding, creates security vulnerabilities due to the
328 varying ways that string processing libraries handle invalid
329 multibyte character sequences that contain the octet LF (%x0A).
330 String-based parsers can only be safely used within protocol elements
331 after the element has been extracted from the message, such as within
332 a header field-value after message parsing has delineated the
333 individual fields.
335 Although the line terminator for the start-line and header fields is
336 the sequence CRLF, a recipient MAY recognize a single LF as a line
337 terminator and ignore any preceding CR.
339 Older HTTP/1.0 user agent implementations might send an extra CRLF
340 after a POST request as a workaround for some early server
341 applications that failed to read message body content that was not
342 terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface
343 or follow a request with an extra CRLF. If terminating the request
344 message body with a line-ending is desired, then the user agent MUST
345 count the terminating CRLF octets as part of the message body length.
347 In the interest of robustness, a server that is expecting to receive
348 and parse a request-line SHOULD ignore at least one empty line (CRLF)
349 received prior to the request-line.
351 A sender MUST NOT send whitespace between the start-line and the
352 first header field. A recipient that receives whitespace between the
353 start-line and the first header field MUST either reject the message
354 as invalid or consume each whitespace-preceded line without further
355 processing of it (i.e., ignore the entire line, along with any
356 subsequent lines preceded by whitespace, until a properly formed
357 header field is received or the header section is terminated).
359 The presence of such whitespace in a request might be an attempt to
360 trick a server into ignoring that field or processing the line after
361 it as a new request, either of which might result in a security
362 vulnerability if other implementations within the request chain
363 interpret the same message differently. Likewise, the presence of
364 such whitespace in a response might be ignored by some clients or
365 cause others to cease parsing.
367 When a server listening only for HTTP request messages, or processing
368 what appears from the start-line to be an HTTP request message,
369 receives a sequence of octets that does not match the HTTP-message
370 grammar aside from the robustness exceptions listed above, the server
371 SHOULD respond with a 400 (Bad Request) response.
373 3. Request Line
375 A request-line begins with a method token, followed by a single space
376 (SP), the request-target, another single space (SP), the protocol
377 version, and ends with CRLF.
379 request-line = method SP request-target SP HTTP-version CRLF
381 Although the request-line grammar rule requires that each of the
382 component elements be separated by a single SP octet, recipients MAY
383 instead parse on whitespace-delimited word boundaries and, aside from
384 the CRLF terminator, treat any form of whitespace as the SP separator
385 while ignoring preceding or trailing whitespace; such whitespace
386 includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
387 (%x0C), or bare CR. However, lenient parsing can result in request
388 smuggling security vulnerabilities if there are multiple recipients
389 of the message and each has its own unique interpretation of
390 robustness (see Section 11.2).
392 HTTP does not place a predefined limit on the length of a request-
393 line, as described in Section 3 of [Semantics]. A server that
394 receives a method longer than any that it implements SHOULD respond
395 with a 501 (Not Implemented) status code. A server that receives a
396 request-target longer than any URI it wishes to parse MUST respond
397 with a 414 (URI Too Long) status code (see Section 9.5.15 of
398 [Semantics]).
400 Various ad hoc limitations on request-line length are found in
401 practice. It is RECOMMENDED that all HTTP senders and recipients
402 support, at a minimum, request-line lengths of 8000 octets.
404 3.1. Method
406 The method token indicates the request method to be performed on the
407 target resource. The request method is case-sensitive.
409 method = token
411 The request methods defined by this specification can be found in
412 Section 7 of [Semantics], along with information regarding the HTTP
413 method registry and considerations for defining new methods.
415 3.2. Request Target
417 The request-target identifies the target resource upon which to apply
418 the request. The client derives a request-target from its desired
419 target URI. There are four distinct formats for the request-target,
420 depending on both the method being requested and whether the request
421 is to a proxy.
423 request-target = origin-form
424 / absolute-form
425 / authority-form
426 / asterisk-form
428 No whitespace is allowed in the request-target. Unfortunately, some
429 user agents fail to properly encode or exclude whitespace found in
430 hypertext references, resulting in those disallowed characters being
431 sent as the request-target in a malformed request-line.
433 Recipients of an invalid request-line SHOULD respond with either a
434 400 (Bad Request) error or a 301 (Moved Permanently) redirect with
435 the request-target properly encoded. A recipient SHOULD NOT attempt
436 to autocorrect and then process the request without a redirect, since
437 the invalid request-line might be deliberately crafted to bypass
438 security filters along the request chain.
440 3.2.1. origin-form
442 The most common form of request-target is the origin-form.
444 origin-form = absolute-path [ "?" query ]
446 When making a request directly to an origin server, other than a
447 CONNECT or server-wide OPTIONS request (as detailed below), a client
448 MUST send only the absolute path and query components of the target
449 URI as the request-target. If the target URI's path component is
450 empty, the client MUST send "/" as the path within the origin-form of
451 request-target. A Host header field is also sent, as defined in
452 Section 5.4 of [Semantics].
454 For example, a client wishing to retrieve a representation of the
455 resource identified as
457 http://www.example.org/where?q=now
459 directly from the origin server would open (or reuse) a TCP
460 connection to port 80 of the host "www.example.org" and send the
461 lines:
463 GET /where?q=now HTTP/1.1
464 Host: www.example.org
466 followed by the remainder of the request message.
468 3.2.2. absolute-form
470 When making a request to a proxy, other than a CONNECT or server-wide
471 OPTIONS request (as detailed below), a client MUST send the target
472 URI in absolute-form as the request-target.
474 absolute-form = absolute-URI
476 The proxy is requested to either service that request from a valid
477 cache, if possible, or make the same request on the client's behalf
478 to either the next inbound proxy server or directly to the origin
479 server indicated by the request-target. Requirements on such
480 "forwarding" of messages are defined in Section 5.6 of [Semantics].
482 An example absolute-form of request-line would be:
484 GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
486 To allow for transition to the absolute-form for all requests in some
487 future version of HTTP, a server MUST accept the absolute-form in
488 requests, even though HTTP/1.1 clients will only send them in
489 requests to proxies.
491 3.2.3. authority-form
493 The authority-form of request-target is only used for CONNECT
494 requests (Section 7.3.6 of [Semantics]).
496 authority-form = authority
498 When making a CONNECT request to establish a tunnel through one or
499 more proxies, a client MUST send only the target URI's authority
500 component (excluding any userinfo and its "@" delimiter) as the
501 request-target. For example,
503 CONNECT www.example.com:80 HTTP/1.1
505 3.2.4. asterisk-form
507 The asterisk-form of request-target is only used for a server-wide
508 OPTIONS request (Section 7.3.7 of [Semantics]).
510 asterisk-form = "*"
512 When a client wishes to request OPTIONS for the server as a whole, as
513 opposed to a specific named resource of that server, the client MUST
514 send only "*" (%x2A) as the request-target. For example,
516 OPTIONS * HTTP/1.1
518 If a proxy receives an OPTIONS request with an absolute-form of
519 request-target in which the URI has an empty path and no query
520 component, then the last proxy on the request chain MUST send a
521 request-target of "*" when it forwards the request to the indicated
522 origin server.
524 For example, the request
526 OPTIONS http://www.example.org:8001 HTTP/1.1
528 would be forwarded by the final proxy as
530 OPTIONS * HTTP/1.1
531 Host: www.example.org:8001
533 after connecting to port 8001 of host "www.example.org".
535 3.3. Effective Request URI
537 Since the request-target often contains only part of the user agent's
538 target URI, a server reconstructs the intended target as an effective
539 request URI to properly service the request (Section 5.3 of
540 [Semantics]).
542 If the request-target is in absolute-form, the effective request URI
543 is the same as the request-target. Otherwise, the effective request
544 URI is constructed as follows:
546 If the server's configuration (or outbound gateway) provides a
547 fixed URI scheme, that scheme is used for the effective request
548 URI. Otherwise, if the request is received over a TLS-secured TCP
549 connection, the effective request URI's scheme is "https"; if not,
550 the scheme is "http".
552 If the server's configuration (or outbound gateway) provides a
553 fixed URI authority component, that authority is used for the
554 effective request URI. If not, then if the request-target is in
555 authority-form, the effective request URI's authority component is
556 the same as the request-target. If not, then if a Host header
557 field is supplied with a non-empty field-value, the authority
558 component is the same as the Host field-value. Otherwise, the
559 authority component is assigned the default name configured for
560 the server and, if the connection's incoming TCP port number
561 differs from the default port for the effective request URI's
562 scheme, then a colon (":") and the incoming port number (in
563 decimal form) are appended to the authority component.
565 If the request-target is in authority-form or asterisk-form, the
566 effective request URI's combined path and query component is
567 empty. Otherwise, the combined path and query component is the
568 same as the request-target.
570 The components of the effective request URI, once determined as
571 above, can be combined into absolute-URI form by concatenating the
572 scheme, "://", authority, and combined path and query component.
574 Example 1: the following message received over an insecure TCP
575 connection
577 GET /pub/WWW/TheProject.html HTTP/1.1
578 Host: www.example.org:8080
580 has an effective request URI of
582 http://www.example.org:8080/pub/WWW/TheProject.html
584 Example 2: the following message received over a TLS-secured TCP
585 connection
587 OPTIONS * HTTP/1.1
588 Host: www.example.org
590 has an effective request URI of
592 https://www.example.org
594 Recipients of an HTTP/1.0 request that lacks a Host header field
595 might need to use heuristics (e.g., examination of the URI path for
596 something unique to a particular host) in order to guess the
597 effective request URI's authority component.
599 4. Status Line
601 The first line of a response message is the status-line, consisting
602 of the protocol version, a space (SP), the status code, another
603 space, a possibly empty textual phrase describing the status code,
604 and ending with CRLF.
606 status-line = HTTP-version SP status-code SP reason-phrase CRLF
608 Although the status-line grammar rule requires that each of the
609 component elements be separated by a single SP octet, recipients MAY
610 instead parse on whitespace-delimited word boundaries and, aside from
611 the line terminator, treat any form of whitespace as the SP separator
612 while ignoring preceding or trailing whitespace; such whitespace
613 includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
614 (%x0C), or bare CR. However, lenient parsing can result in response
615 splitting security vulnerabilities if there are multiple recipients
616 of the message and each has its own unique interpretation of
617 robustness (see Section 11.1).
619 The status-code element is a 3-digit integer code describing the
620 result of the server's attempt to understand and satisfy the client's
621 corresponding request. The rest of the response message is to be
622 interpreted in light of the semantics defined for that status code.
623 See Section 9 of [Semantics] for information about the semantics of
624 status codes, including the classes of status code (indicated by the
625 first digit), the status codes defined by this specification,
626 considerations for the definition of new status codes, and the IANA
627 registry.
629 status-code = 3DIGIT
631 The reason-phrase element exists for the sole purpose of providing a
632 textual description associated with the numeric status code, mostly
633 out of deference to earlier Internet application protocols that were
634 more frequently used with interactive text clients. A client SHOULD
635 ignore the reason-phrase content.
637 reason-phrase = *( HTAB / SP / VCHAR / obs-text )
639 5. Header Fields
641 Each header field consists of a case-insensitive field name followed
642 by a colon (":"), optional leading whitespace, the field value, and
643 optional trailing whitespace.
645 header-field = field-name ":" OWS field-value OWS
647 Most HTTP field names and the rules for parsing within field values
648 are defined in Section 4 of [Semantics]. This section covers the
649 generic syntax for header field inclusion within, and extraction
650 from, HTTP/1.1 messages. In addition, the following header fields
651 are defined by this document because they are specific to HTTP/1.1
652 message processing:
654 +-------------------+----------+----------+---------------+
655 | Header Field Name | Protocol | Status | Reference |
656 +-------------------+----------+----------+---------------+
657 | Connection | http | standard | Section 9.1 |
658 | MIME-Version | http | standard | Appendix B.1 |
659 | TE | http | standard | Section 7.4 |
660 | Transfer-Encoding | http | standard | Section 6.1 |
661 | Upgrade | http | standard | Section 9.7 |
662 +-------------------+----------+----------+---------------+
664 Furthermore, the field name "Close" is reserved, since using that
665 name as an HTTP header field might conflict with the "close"
666 connection option of the Connection header field (Section 9.1).
668 +-------------------+----------+----------+------------+
669 | Header Field Name | Protocol | Status | Reference |
670 +-------------------+----------+----------+------------+
671 | Close | http | reserved | Section 5 |
672 +-------------------+----------+----------+------------+
674 5.1. Field Parsing
676 Messages are parsed using a generic algorithm, independent of the
677 individual header field names. The contents within a given field
678 value are not parsed until a later stage of message interpretation
679 (usually after the message's entire header section has been
680 processed).
682 No whitespace is allowed between the header field-name and colon. In
683 the past, differences in the handling of such whitespace have led to
684 security vulnerabilities in request routing and response handling. A
685 server MUST reject any received request message that contains
686 whitespace between a header field-name and colon with a response
687 status code of 400 (Bad Request). A proxy MUST remove any such
688 whitespace from a response message before forwarding the message
689 downstream.
691 A field value might be preceded and/or followed by optional
692 whitespace (OWS); a single SP preceding the field-value is preferred
693 for consistent readability by humans. The field value does not
694 include any leading or trailing whitespace: OWS occurring before the
695 first non-whitespace octet of the field value or after the last non-
696 whitespace octet of the field value ought to be excluded by parsers
697 when extracting the field value from a header field.
699 5.2. Obsolete Line Folding
701 Historically, HTTP header field values could be extended over
702 multiple lines by preceding each extra line with at least one space
703 or horizontal tab (obs-fold). This specification deprecates such
704 line folding except within the message/http media type
705 (Section 10.1).
707 obs-fold = CRLF 1*( SP / HTAB )
708 ; obsolete line folding
710 A sender MUST NOT generate a message that includes line folding
711 (i.e., that has any field-value that contains a match to the obs-fold
712 rule) unless the message is intended for packaging within the
713 message/http media type.
715 A server that receives an obs-fold in a request message that is not
716 within a message/http container MUST either reject the message by
717 sending a 400 (Bad Request), preferably with a representation
718 explaining that obsolete line folding is unacceptable, or replace
719 each received obs-fold with one or more SP octets prior to
720 interpreting the field value or forwarding the message downstream.
722 A proxy or gateway that receives an obs-fold in a response message
723 that is not within a message/http container MUST either discard the
724 message and replace it with a 502 (Bad Gateway) response, preferably
725 with a representation explaining that unacceptable line folding was
726 received, or replace each received obs-fold with one or more SP
727 octets prior to interpreting the field value or forwarding the
728 message downstream.
730 A user agent that receives an obs-fold in a response message that is
731 not within a message/http container MUST replace each received obs-
732 fold with one or more SP octets prior to interpreting the field
733 value.
735 6. Message Body
737 The message body (if any) of an HTTP message is used to carry the
738 payload body of that request or response. The message body is
739 identical to the payload body unless a transfer coding has been
740 applied, as described in Section 6.1.
742 message-body = *OCTET
744 The rules for when a message body is allowed in a message differ for
745 requests and responses.
747 The presence of a message body in a request is signaled by a Content-
748 Length or Transfer-Encoding header field. Request message framing is
749 independent of method semantics, even if the method does not define
750 any use for a message body.
752 The presence of a message body in a response depends on both the
753 request method to which it is responding and the response status code
754 (Section 4). Responses to the HEAD request method (Section 7.3.2 of
755 [Semantics]) never include a message body because the associated
756 response header fields (e.g., Transfer-Encoding, Content-Length,
757 etc.), if present, indicate only what their values would have been if
758 the request method had been GET (Section 7.3.1 of [Semantics]). 2xx
759 (Successful) responses to a CONNECT request method (Section 7.3.6 of
760 [Semantics]) switch to tunnel mode instead of having a message body.
761 All 1xx (Informational), 204 (No Content), and 304 (Not Modified)
762 responses do not include a message body. All other responses do
763 include a message body, although the body might be of zero length.
765 6.1. Transfer-Encoding
767 The Transfer-Encoding header field lists the transfer coding names
768 corresponding to the sequence of transfer codings that have been (or
769 will be) applied to the payload body in order to form the message
770 body. Transfer codings are defined in Section 7.
772 Transfer-Encoding = 1#transfer-coding
774 Transfer-Encoding is analogous to the Content-Transfer-Encoding field
775 of MIME, which was designed to enable safe transport of binary data
776 over a 7-bit transport service ([RFC2045], Section 6). However, safe
777 transport has a different focus for an 8bit-clean transfer protocol.
778 In HTTP's case, Transfer-Encoding is primarily intended to accurately
779 delimit a dynamically generated payload and to distinguish payload
780 encodings that are only applied for transport efficiency or security
781 from those that are characteristics of the selected resource.
783 A recipient MUST be able to parse the chunked transfer coding
784 (Section 7.1) because it plays a crucial role in framing messages
785 when the payload body size is not known in advance. A sender MUST
786 NOT apply chunked more than once to a message body (i.e., chunking an
787 already chunked message is not allowed). If any transfer coding
788 other than chunked is applied to a request payload body, the sender
789 MUST apply chunked as the final transfer coding to ensure that the
790 message is properly framed. If any transfer coding other than
791 chunked is applied to a response payload body, the sender MUST either
792 apply chunked as the final transfer coding or terminate the message
793 by closing the connection.
795 For example,
797 Transfer-Encoding: gzip, chunked
799 indicates that the payload body has been compressed using the gzip
800 coding and then chunked using the chunked coding while forming the
801 message body.
803 Unlike Content-Encoding (Section 6.1.2 of [Semantics]), Transfer-
804 Encoding is a property of the message, not of the representation, and
805 any recipient along the request/response chain MAY decode the
806 received transfer coding(s) or apply additional transfer coding(s) to
807 the message body, assuming that corresponding changes are made to the
808 Transfer-Encoding field-value. Additional information about the
809 encoding parameters can be provided by other header fields not
810 defined by this specification.
812 Transfer-Encoding MAY be sent in a response to a HEAD request or in a
813 304 (Not Modified) response (Section 9.4.5 of [Semantics]) to a GET
814 request, neither of which includes a message body, to indicate that
815 the origin server would have applied a transfer coding to the message
816 body if the request had been an unconditional GET. This indication
817 is not required, however, because any recipient on the response chain
818 (including the origin server) can remove transfer codings when they
819 are not needed.
821 A server MUST NOT send a Transfer-Encoding header field in any
822 response with a status code of 1xx (Informational) or 204 (No
823 Content). A server MUST NOT send a Transfer-Encoding header field in
824 any 2xx (Successful) response to a CONNECT request (Section 7.3.6 of
825 [Semantics]).
827 Transfer-Encoding was added in HTTP/1.1. It is generally assumed
828 that implementations advertising only HTTP/1.0 support will not
829 understand how to process a transfer-encoded payload. A client MUST
830 NOT send a request containing Transfer-Encoding unless it knows the
831 server will handle HTTP/1.1 (or later) requests; such knowledge might
832 be in the form of specific user configuration or by remembering the
833 version of a prior received response. A server MUST NOT send a
834 response containing Transfer-Encoding unless the corresponding
835 request indicates HTTP/1.1 (or later).
837 A server that receives a request message with a transfer coding it
838 does not understand SHOULD respond with 501 (Not Implemented).
840 6.2. Content-Length
842 When a message does not have a Transfer-Encoding header field, a
843 Content-Length header field can provide the anticipated size, as a
844 decimal number of octets, for a potential payload body. For messages
845 that do include a payload body, the Content-Length field-value
846 provides the framing information necessary for determining where the
847 body (and message) ends. For messages that do not include a payload
848 body, the Content-Length indicates the size of the selected
849 representation (Section 6.2.4 of [Semantics]).
851 Note: HTTP's use of Content-Length for message framing differs
852 significantly from the same field's use in MIME, where it is an
853 optional field used only within the "message/external-body" media-
854 type.
856 6.3. Message Body Length
858 The length of a message body is determined by one of the following
859 (in order of precedence):
861 1. Any response to a HEAD request and any response with a 1xx
862 (Informational), 204 (No Content), or 304 (Not Modified) status
863 code is always terminated by the first empty line after the
864 header fields, regardless of the header fields present in the
865 message, and thus cannot contain a message body.
867 2. Any 2xx (Successful) response to a CONNECT request implies that
868 the connection will become a tunnel immediately after the empty
869 line that concludes the header fields. A client MUST ignore any
870 Content-Length or Transfer-Encoding header fields received in
871 such a message.
873 3. If a Transfer-Encoding header field is present and the chunked
874 transfer coding (Section 7.1) is the final encoding, the message
875 body length is determined by reading and decoding the chunked
876 data until the transfer coding indicates the data is complete.
878 If a Transfer-Encoding header field is present in a response and
879 the chunked transfer coding is not the final encoding, the
880 message body length is determined by reading the connection until
881 it is closed by the server. If a Transfer-Encoding header field
882 is present in a request and the chunked transfer coding is not
883 the final encoding, the message body length cannot be determined
884 reliably; the server MUST respond with the 400 (Bad Request)
885 status code and then close the connection.
887 If a message is received with both a Transfer-Encoding and a
888 Content-Length header field, the Transfer-Encoding overrides the
889 Content-Length. Such a message might indicate an attempt to
890 perform request smuggling (Section 11.2) or response splitting
891 (Section 11.1) and ought to be handled as an error. A sender
892 MUST remove the received Content-Length field prior to forwarding
893 such a message downstream.
895 4. If a message is received without Transfer-Encoding and with
896 either multiple Content-Length header fields having differing
897 field-values or a single Content-Length header field having an
898 invalid value, then the message framing is invalid and the
899 recipient MUST treat it as an unrecoverable error. If this is a
900 request message, the server MUST respond with a 400 (Bad Request)
901 status code and then close the connection. If this is a response
902 message received by a proxy, the proxy MUST close the connection
903 to the server, discard the received response, and send a 502 (Bad
904 Gateway) response to the client. If this is a response message
905 received by a user agent, the user agent MUST close the
906 connection to the server and discard the received response.
908 5. If a valid Content-Length header field is present without
909 Transfer-Encoding, its decimal value defines the expected message
910 body length in octets. If the sender closes the connection or
911 the recipient times out before the indicated number of octets are
912 received, the recipient MUST consider the message to be
913 incomplete and close the connection.
915 6. If this is a request message and none of the above are true, then
916 the message body length is zero (no message body is present).
918 7. Otherwise, this is a response message without a declared message
919 body length, so the message body length is determined by the
920 number of octets received prior to the server closing the
921 connection.
923 Since there is no way to distinguish a successfully completed, close-
924 delimited message from a partially received message interrupted by
925 network failure, a server SHOULD generate encoding or length-
926 delimited messages whenever possible. The close-delimiting feature
927 exists primarily for backwards compatibility with HTTP/1.0.
929 A server MAY reject a request that contains a message body but not a
930 Content-Length by responding with 411 (Length Required).
932 Unless a transfer coding other than chunked has been applied, a
933 client that sends a request containing a message body SHOULD use a
934 valid Content-Length header field if the message body length is known
935 in advance, rather than the chunked transfer coding, since some
936 existing services respond to chunked with a 411 (Length Required)
937 status code even though they understand the chunked transfer coding.
938 This is typically because such services are implemented via a gateway
939 that requires a content-length in advance of being called and the
940 server is unable or unwilling to buffer the entire request before
941 processing.
943 A user agent that sends a request containing a message body MUST send
944 a valid Content-Length header field if it does not know the server
945 will handle HTTP/1.1 (or later) requests; such knowledge can be in
946 the form of specific user configuration or by remembering the version
947 of a prior received response.
949 If the final response to the last request on a connection has been
950 completely received and there remains additional data to read, a user
951 agent MAY discard the remaining data or attempt to determine if that
952 data belongs as part of the prior response body, which might be the
953 case if the prior message's Content-Length value is incorrect. A
954 client MUST NOT process, cache, or forward such extra data as a
955 separate response, since such behavior would be vulnerable to cache
956 poisoning.
958 7. Transfer Codings
960 Transfer coding names are used to indicate an encoding transformation
961 that has been, can be, or might need to be applied to a payload body
962 in order to ensure "safe transport" through the network. This
963 differs from a content coding in that the transfer coding is a
964 property of the message rather than a property of the representation
965 that is being transferred.
967 transfer-coding = "chunked" ; Section 7.1
968 / "compress" ; [Semantics], Section 6.1.2.1
969 / "deflate" ; [Semantics], Section 6.1.2.2
970 / "gzip" ; [Semantics], Section 6.1.2.3
971 / transfer-extension
972 transfer-extension = token *( OWS ";" OWS transfer-parameter )
974 Parameters are in the form of a name=value pair.
976 transfer-parameter = token BWS "=" BWS ( token / quoted-string )
978 All transfer-coding names are case-insensitive and ought to be
979 registered within the HTTP Transfer Coding registry, as defined in
980 Section 7.3. They are used in the TE (Section 7.4) and Transfer-
981 Encoding (Section 6.1) header fields.
983 +------------+------------------------------------------+-----------+
984 | Name | Description | Reference |
985 +------------+------------------------------------------+-----------+
986 | chunked | Transfer in a series of chunks | Section 7 |
987 | | | .1 |
988 | compress | UNIX "compress" data format [Welch] | Section 7 |
989 | | | .2 |
990 | deflate | "deflate" compressed data ([RFC1951]) | Section 7 |
991 | | inside the "zlib" data format | .2 |
992 | | ([RFC1950]) | |
993 | gzip | GZIP file format [RFC1952] | Section 7 |
994 | | | .2 |
995 | trailers | (reserved) | Section 7 |
996 | x-compress | Deprecated (alias for compress) | Section 7 |
997 | | | .2 |
998 | x-gzip | Deprecated (alias for gzip) | Section 7 |
999 | | | .2 |
1000 +------------+------------------------------------------+-----------+
1002 Note: the coding name "trailers" is reserved because it would
1003 clash with the use of the keyword "trailers" in the TE header
1004 field (Section 7.4).
1006 7.1. Chunked Transfer Coding
1008 The chunked transfer coding wraps the payload body in order to
1009 transfer it as a series of chunks, each with its own size indicator,
1010 followed by an OPTIONAL trailer containing header fields. Chunked
1011 enables content streams of unknown size to be transferred as a
1012 sequence of length-delimited buffers, which enables the sender to
1013 retain connection persistence and the recipient to know when it has
1014 received the entire message.
1016 chunked-body = *chunk
1017 last-chunk
1018 trailer-part
1019 CRLF
1021 chunk = chunk-size [ chunk-ext ] CRLF
1022 chunk-data CRLF
1023 chunk-size = 1*HEXDIG
1024 last-chunk = 1*("0") [ chunk-ext ] CRLF
1026 chunk-data = 1*OCTET ; a sequence of chunk-size octets
1028 The chunk-size field is a string of hex digits indicating the size of
1029 the chunk-data in octets. The chunked transfer coding is complete
1030 when a chunk with a chunk-size of zero is received, possibly followed
1031 by a trailer, and finally terminated by an empty line.
1033 A recipient MUST be able to parse and decode the chunked transfer
1034 coding.
1036 7.1.1. Chunk Extensions
1038 The chunked encoding allows each chunk to include zero or more chunk
1039 extensions, immediately following the chunk-size, for the sake of
1040 supplying per-chunk metadata (such as a signature or hash), mid-
1041 message control information, or randomization of message body size.
1043 chunk-ext = *( BWS ";" BWS chunk-ext-name
1044 [ BWS "=" BWS chunk-ext-val ] )
1046 chunk-ext-name = token
1047 chunk-ext-val = token / quoted-string
1049 The chunked encoding is specific to each connection and is likely to
1050 be removed or recoded by each recipient (including intermediaries)
1051 before any higher-level application would have a chance to inspect
1052 the extensions. Hence, use of chunk extensions is generally limited
1053 to specialized HTTP services such as "long polling" (where client and
1054 server can have shared expectations regarding the use of chunk
1055 extensions) or for padding within an end-to-end secured connection.
1057 A recipient MUST ignore unrecognized chunk extensions. A server
1058 ought to limit the total length of chunk extensions received in a
1059 request to an amount reasonable for the services provided, in the
1060 same way that it applies length limitations and timeouts for other
1061 parts of a message, and generate an appropriate 4xx (Client Error)
1062 response if that amount is exceeded.
1064 7.1.2. Chunked Trailer Part
1066 A trailer allows the sender to include additional fields at the end
1067 of a chunked message in order to supply metadata that might be
1068 dynamically generated while the message body is sent, such as a
1069 message integrity check, digital signature, or post-processing
1070 status. The trailer fields are identical to header fields, except
1071 they are sent in a chunked trailer instead of the message's header
1072 section.
1074 trailer-part = *( header-field CRLF )
1076 A sender MUST NOT generate a trailer that contains a field necessary
1077 for message framing (e.g., Transfer-Encoding and Content-Length),
1078 routing (e.g., Host), request modifiers (e.g., controls and
1079 conditionals in Section 8 of [Semantics]), authentication (e.g., see
1080 Section 8.5 of [Semantics] and [RFC6265]), response control data
1081 (e.g., see Section 10.1 of [Semantics]), or determining how to
1082 process the payload (e.g., Content-Encoding, Content-Type, Content-
1083 Range, and Trailer).
1085 When a chunked message containing a non-empty trailer is received,
1086 the recipient MAY process the fields (aside from those forbidden
1087 above) as if they were appended to the message's header section. A
1088 recipient MUST ignore (or consider as an error) any fields that are
1089 forbidden to be sent in a trailer, since processing them as if they
1090 were present in the header section might bypass external security
1091 filters.
1093 Unless the request includes a TE header field indicating "trailers"
1094 is acceptable, as described in Section 7.4, a server SHOULD NOT
1095 generate trailer fields that it believes are necessary for the user
1096 agent to receive. Without a TE containing "trailers", the server
1097 ought to assume that the trailer fields might be silently discarded
1098 along the path to the user agent. This requirement allows
1099 intermediaries to forward a de-chunked message to an HTTP/1.0
1100 recipient without buffering the entire response.
1102 When a message includes a message body encoded with the chunked
1103 transfer coding and the sender desires to send metadata in the form
1104 of trailer fields at the end of the message, the sender SHOULD
1105 generate a Trailer header field before the message body to indicate
1106 which fields will be present in the trailers. This allows the
1107 recipient to prepare for receipt of that metadata before it starts
1108 processing the body, which is useful if the message is being streamed
1109 and the recipient wishes to confirm an integrity check on the fly.
1111 7.1.3. Decoding Chunked
1113 A process for decoding the chunked transfer coding can be represented
1114 in pseudo-code as:
1116 length := 0
1117 read chunk-size, chunk-ext (if any), and CRLF
1118 while (chunk-size > 0) {
1119 read chunk-data and CRLF
1120 append chunk-data to decoded-body
1121 length := length + chunk-size
1122 read chunk-size, chunk-ext (if any), and CRLF
1123 }
1124 read trailer field
1125 while (trailer field is not empty) {
1126 if (trailer field is allowed to be sent in a trailer) {
1127 append trailer field to existing header fields
1128 }
1129 read trailer-field
1130 }
1131 Content-Length := length
1132 Remove "chunked" from Transfer-Encoding
1133 Remove Trailer from existing header fields
1135 7.2. Transfer Codings for Compression
1137 The following transfer coding names for compression are defined by
1138 the same algorithm as their corresponding content coding:
1140 compress (and x-compress)
1141 See Section 6.1.2.1 of [Semantics].
1143 deflate
1144 See Section 6.1.2.2 of [Semantics].
1146 gzip (and x-gzip)
1147 See Section 6.1.2.3 of [Semantics].
1149 7.3. Transfer Coding Registry
1151 The "HTTP Transfer Coding Registry" defines the namespace for
1152 transfer coding names. It is maintained at
1153 .
1155 Registrations MUST include the following fields:
1157 o Name
1159 o Description
1161 o Pointer to specification text
1162 Names of transfer codings MUST NOT overlap with names of content
1163 codings (Section 6.1.2 of [Semantics]) unless the encoding
1164 transformation is identical, as is the case for the compression
1165 codings defined in Section 7.2.
1167 The TE header field (Section 7.4) uses a pseudo parameter named "q"
1168 as rank value when multiple transfer codings are acceptable. Future
1169 registrations of transfer codings SHOULD NOT define parameters called
1170 "q" (case-insensitively) in order to avoid ambiguities.
1172 Values to be added to this namespace require IETF Review (see
1173 Section 4.8 of [RFC8126]), and MUST conform to the purpose of
1174 transfer coding defined in this specification.
1176 Use of program names for the identification of encoding formats is
1177 not desirable and is discouraged for future encodings.
1179 7.4. TE
1181 The "TE" header field in a request indicates what transfer codings,
1182 besides chunked, the client is willing to accept in response, and
1183 whether or not the client is willing to accept trailer fields in a
1184 chunked transfer coding.
1186 The TE field-value consists of a comma-separated list of transfer
1187 coding names, each allowing for optional parameters (as described in
1188 Section 7), and/or the keyword "trailers". A client MUST NOT send
1189 the chunked transfer coding name in TE; chunked is always acceptable
1190 for HTTP/1.1 recipients.
1192 TE = #t-codings
1193 t-codings = "trailers" / ( transfer-coding [ t-ranking ] )
1194 t-ranking = OWS ";" OWS "q=" rank
1195 rank = ( "0" [ "." 0*3DIGIT ] )
1196 / ( "1" [ "." 0*3("0") ] )
1198 Three examples of TE use are below.
1200 TE: deflate
1201 TE:
1202 TE: trailers, deflate;q=0.5
1204 The presence of the keyword "trailers" indicates that the client is
1205 willing to accept trailer fields in a chunked transfer coding, as
1206 defined in Section 7.1.2, on behalf of itself and any downstream
1207 clients. For requests from an intermediary, this implies that
1208 either: (a) all downstream clients are willing to accept trailer
1209 fields in the forwarded response; or, (b) the intermediary will
1210 attempt to buffer the response on behalf of downstream recipients.
1211 Note that HTTP/1.1 does not define any means to limit the size of a
1212 chunked response such that an intermediary can be assured of
1213 buffering the entire response.
1215 When multiple transfer codings are acceptable, the client MAY rank
1216 the codings by preference using a case-insensitive "q" parameter
1217 (similar to the qvalues used in content negotiation fields,
1218 Section 8.4.1 of [Semantics]). The rank value is a real number in
1219 the range 0 through 1, where 0.001 is the least preferred and 1 is
1220 the most preferred; a value of 0 means "not acceptable".
1222 If the TE field-value is empty or if no TE field is present, the only
1223 acceptable transfer coding is chunked. A message with no transfer
1224 coding is always acceptable.
1226 Since the TE header field only applies to the immediate connection, a
1227 sender of TE MUST also send a "TE" connection option within the
1228 Connection header field (Section 9.1) in order to prevent the TE
1229 field from being forwarded by intermediaries that do not support its
1230 semantics.
1232 8. Handling Incomplete Messages
1234 A server that receives an incomplete request message, usually due to
1235 a canceled request or a triggered timeout exception, MAY send an
1236 error response prior to closing the connection.
1238 A client that receives an incomplete response message, which can
1239 occur when a connection is closed prematurely or when decoding a
1240 supposedly chunked transfer coding fails, MUST record the message as
1241 incomplete. Cache requirements for incomplete responses are defined
1242 in Section 3 of [Caching].
1244 If a response terminates in the middle of the header section (before
1245 the empty line is received) and the status code might rely on header
1246 fields to convey the full meaning of the response, then the client
1247 cannot assume that meaning has been conveyed; the client might need
1248 to repeat the request in order to determine what action to take next.
1250 A message body that uses the chunked transfer coding is incomplete if
1251 the zero-sized chunk that terminates the encoding has not been
1252 received. A message that uses a valid Content-Length is incomplete
1253 if the size of the message body received (in octets) is less than the
1254 value given by Content-Length. A response that has neither chunked
1255 transfer coding nor Content-Length is terminated by closure of the
1256 connection and, thus, is considered complete regardless of the number
1257 of message body octets received, provided that the header section was
1258 received intact.
1260 9. Connection Management
1262 HTTP messaging is independent of the underlying transport- or
1263 session-layer connection protocol(s). HTTP only presumes a reliable
1264 transport with in-order delivery of requests and the corresponding
1265 in-order delivery of responses. The mapping of HTTP request and
1266 response structures onto the data units of an underlying transport
1267 protocol is outside the scope of this specification.
1269 As described in Section 5.2 of [Semantics], the specific connection
1270 protocols to be used for an HTTP interaction are determined by client
1271 configuration and the target URI. For example, the "http" URI scheme
1272 (Section 2.5.1 of [Semantics]) indicates a default connection of TCP
1273 over IP, with a default TCP port of 80, but the client might be
1274 configured to use a proxy via some other connection, port, or
1275 protocol.
1277 HTTP implementations are expected to engage in connection management,
1278 which includes maintaining the state of current connections,
1279 establishing a new connection or reusing an existing connection,
1280 processing messages received on a connection, detecting connection
1281 failures, and closing each connection. Most clients maintain
1282 multiple connections in parallel, including more than one connection
1283 per server endpoint. Most servers are designed to maintain thousands
1284 of concurrent connections, while controlling request queues to enable
1285 fair use and detect denial-of-service attacks.
1287 9.1. Connection
1289 The "Connection" header field allows the sender to indicate desired
1290 control options for the current connection. In order to avoid
1291 confusing downstream recipients, a proxy or gateway MUST remove or
1292 replace any received connection options before forwarding the
1293 message.
1295 When a header field aside from Connection is used to supply control
1296 information for or about the current connection, the sender MUST list
1297 the corresponding field-name within the Connection header field. A
1298 proxy or gateway MUST parse a received Connection header field before
1299 a message is forwarded and, for each connection-option in this field,
1300 remove any header field(s) from the message with the same name as the
1301 connection-option, and then remove the Connection header field itself
1302 (or replace it with the intermediary's own connection options for the
1303 forwarded message).
1305 Hence, the Connection header field provides a declarative way of
1306 distinguishing header fields that are only intended for the immediate
1307 recipient ("hop-by-hop") from those fields that are intended for all
1308 recipients on the chain ("end-to-end"), enabling the message to be
1309 self-descriptive and allowing future connection-specific extensions
1310 to be deployed without fear that they will be blindly forwarded by
1311 older intermediaries.
1313 The Connection header field's value has the following grammar:
1315 Connection = 1#connection-option
1316 connection-option = token
1318 Connection options are case-insensitive.
1320 A sender MUST NOT send a connection option corresponding to a header
1321 field that is intended for all recipients of the payload. For
1322 example, Cache-Control is never appropriate as a connection option
1323 (Section 5.2 of [Caching]).
1325 The connection options do not always correspond to a header field
1326 present in the message, since a connection-specific header field
1327 might not be needed if there are no parameters associated with a
1328 connection option. In contrast, a connection-specific header field
1329 that is received without a corresponding connection option usually
1330 indicates that the field has been improperly forwarded by an
1331 intermediary and ought to be ignored by the recipient.
1333 When defining new connection options, specification authors ought to
1334 survey existing header field names and ensure that the new connection
1335 option does not share the same name as an already deployed header
1336 field. Defining a new connection option essentially reserves that
1337 potential field-name for carrying additional information related to
1338 the connection option, since it would be unwise for senders to use
1339 that field-name for anything else.
1341 The "close" connection option is defined for a sender to signal that
1342 this connection will be closed after completion of the response. For
1343 example,
1345 Connection: close
1347 in either the request or the response header fields indicates that
1348 the sender is going to close the connection after the current
1349 request/response is complete (Section 9.6).
1351 A client that does not support persistent connections MUST send the
1352 "close" connection option in every request message.
1354 A server that does not support persistent connections MUST send the
1355 "close" connection option in every response message that does not
1356 have a 1xx (Informational) status code.
1358 9.2. Establishment
1360 It is beyond the scope of this specification to describe how
1361 connections are established via various transport- or session-layer
1362 protocols. Each connection applies to only one transport link.
1364 9.3. Persistence
1366 HTTP/1.1 defaults to the use of "persistent connections", allowing
1367 multiple requests and responses to be carried over a single
1368 connection. The "close" connection option is used to signal that a
1369 connection will not persist after the current request/response. HTTP
1370 implementations SHOULD support persistent connections.
1372 A recipient determines whether a connection is persistent or not
1373 based on the most recently received message's protocol version and
1374 Connection header field (if any):
1376 o If the "close" connection option is present, the connection will
1377 not persist after the current response; else,
1379 o If the received protocol is HTTP/1.1 (or later), the connection
1380 will persist after the current response; else,
1382 o If the received protocol is HTTP/1.0, the "keep-alive" connection
1383 option is present, either the recipient is not a proxy or the
1384 message is a response, and the recipient wishes to honor the
1385 HTTP/1.0 "keep-alive" mechanism, the connection will persist after
1386 the current response; otherwise,
1388 o The connection will close after the current response.
1390 A client MAY send additional requests on a persistent connection
1391 until it sends or receives a "close" connection option or receives an
1392 HTTP/1.0 response without a "keep-alive" connection option.
1394 In order to remain persistent, all messages on a connection need to
1395 have a self-defined message length (i.e., one not defined by closure
1396 of the connection), as described in Section 6. A server MUST read
1397 the entire request message body or close the connection after sending
1398 its response, since otherwise the remaining data on a persistent
1399 connection would be misinterpreted as the next request. Likewise, a
1400 client MUST read the entire response message body if it intends to
1401 reuse the same connection for a subsequent request.
1403 A proxy server MUST NOT maintain a persistent connection with an
1404 HTTP/1.0 client (see Section 19.7.1 of [RFC2068] for information and
1405 discussion of the problems with the Keep-Alive header field
1406 implemented by many HTTP/1.0 clients).
1408 See Appendix C.1.2 for more information on backwards compatibility
1409 with HTTP/1.0 clients.
1411 9.3.1. Retrying Requests
1413 Connections can be closed at any time, with or without intention.
1414 Implementations ought to anticipate the need to recover from
1415 asynchronous close events.
1417 When an inbound connection is closed prematurely, a client MAY open a
1418 new connection and automatically retransmit an aborted sequence of
1419 requests if all of those requests have idempotent methods
1420 (Section 7.2.2 of [Semantics]). A proxy MUST NOT automatically retry
1421 non-idempotent requests.
1423 A user agent MUST NOT automatically retry a request with a non-
1424 idempotent method unless it has some means to know that the request
1425 semantics are actually idempotent, regardless of the method, or some
1426 means to detect that the original request was never applied. For
1427 example, a user agent that knows (through design or configuration)
1428 that a POST request to a given resource is safe can repeat that
1429 request automatically. Likewise, a user agent designed specifically
1430 to operate on a version control repository might be able to recover
1431 from partial failure conditions by checking the target resource
1432 revision(s) after a failed connection, reverting or fixing any
1433 changes that were partially applied, and then automatically retrying
1434 the requests that failed.
1436 A client SHOULD NOT automatically retry a failed automatic retry.
1438 9.3.2. Pipelining
1440 A client that supports persistent connections MAY "pipeline" its
1441 requests (i.e., send multiple requests without waiting for each
1442 response). A server MAY process a sequence of pipelined requests in
1443 parallel if they all have safe methods (Section 7.2.1 of
1444 [Semantics]), but it MUST send the corresponding responses in the
1445 same order that the requests were received.
1447 A client that pipelines requests SHOULD retry unanswered requests if
1448 the connection closes before it receives all of the corresponding
1449 responses. When retrying pipelined requests after a failed
1450 connection (a connection not explicitly closed by the server in its
1451 last complete response), a client MUST NOT pipeline immediately after
1452 connection establishment, since the first remaining request in the
1453 prior pipeline might have caused an error response that can be lost
1454 again if multiple requests are sent on a prematurely closed
1455 connection (see the TCP reset problem described in Section 9.6).
1457 Idempotent methods (Section 7.2.2 of [Semantics]) are significant to
1458 pipelining because they can be automatically retried after a
1459 connection failure. A user agent SHOULD NOT pipeline requests after
1460 a non-idempotent method, until the final response status code for
1461 that method has been received, unless the user agent has a means to
1462 detect and recover from partial failure conditions involving the
1463 pipelined sequence.
1465 An intermediary that receives pipelined requests MAY pipeline those
1466 requests when forwarding them inbound, since it can rely on the
1467 outbound user agent(s) to determine what requests can be safely
1468 pipelined. If the inbound connection fails before receiving a
1469 response, the pipelining intermediary MAY attempt to retry a sequence
1470 of requests that have yet to receive a response if the requests all
1471 have idempotent methods; otherwise, the pipelining intermediary
1472 SHOULD forward any received responses and then close the
1473 corresponding outbound connection(s) so that the outbound user
1474 agent(s) can recover accordingly.
1476 9.4. Concurrency
1478 A client ought to limit the number of simultaneous open connections
1479 that it maintains to a given server.
1481 Previous revisions of HTTP gave a specific number of connections as a
1482 ceiling, but this was found to be impractical for many applications.
1483 As a result, this specification does not mandate a particular maximum
1484 number of connections but, instead, encourages clients to be
1485 conservative when opening multiple connections.
1487 Multiple connections are typically used to avoid the "head-of-line
1488 blocking" problem, wherein a request that takes significant server-
1489 side processing and/or has a large payload blocks subsequent requests
1490 on the same connection. However, each connection consumes server
1491 resources. Furthermore, using multiple connections can cause
1492 undesirable side effects in congested networks.
1494 Note that a server might reject traffic that it deems abusive or
1495 characteristic of a denial-of-service attack, such as an excessive
1496 number of open connections from a single client.
1498 9.5. Failures and Timeouts
1500 Servers will usually have some timeout value beyond which they will
1501 no longer maintain an inactive connection. Proxy servers might make
1502 this a higher value since it is likely that the client will be making
1503 more connections through the same proxy server. The use of
1504 persistent connections places no requirements on the length (or
1505 existence) of this timeout for either the client or the server.
1507 A client or server that wishes to time out SHOULD issue a graceful
1508 close on the connection. Implementations SHOULD constantly monitor
1509 open connections for a received closure signal and respond to it as
1510 appropriate, since prompt closure of both sides of a connection
1511 enables allocated system resources to be reclaimed.
1513 A client, server, or proxy MAY close the transport connection at any
1514 time. For example, a client might have started to send a new request
1515 at the same time that the server has decided to close the "idle"
1516 connection. From the server's point of view, the connection is being
1517 closed while it was idle, but from the client's point of view, a
1518 request is in progress.
1520 A server SHOULD sustain persistent connections, when possible, and
1521 allow the underlying transport's flow-control mechanisms to resolve
1522 temporary overloads, rather than terminate connections with the
1523 expectation that clients will retry. The latter technique can
1524 exacerbate network congestion.
1526 A client sending a message body SHOULD monitor the network connection
1527 for an error response while it is transmitting the request. If the
1528 client sees a response that indicates the server does not wish to
1529 receive the message body and is closing the connection, the client
1530 SHOULD immediately cease transmitting the body and close its side of
1531 the connection.
1533 9.6. Tear-down
1535 The Connection header field (Section 9.1) provides a "close"
1536 connection option that a sender SHOULD send when it wishes to close
1537 the connection after the current request/response pair.
1539 A client that sends a "close" connection option MUST NOT send further
1540 requests on that connection (after the one containing "close") and
1541 MUST close the connection after reading the final response message
1542 corresponding to this request.
1544 A server that receives a "close" connection option MUST initiate a
1545 close of the connection (see below) after it sends the final response
1546 to the request that contained "close". The server SHOULD send a
1547 "close" connection option in its final response on that connection.
1548 The server MUST NOT process any further requests received on that
1549 connection.
1551 A server that sends a "close" connection option MUST initiate a close
1552 of the connection (see below) after it sends the response containing
1553 "close". The server MUST NOT process any further requests received
1554 on that connection.
1556 A client that receives a "close" connection option MUST cease sending
1557 requests on that connection and close the connection after reading
1558 the response message containing the "close"; if additional pipelined
1559 requests had been sent on the connection, the client SHOULD NOT
1560 assume that they will be processed by the server.
1562 If a server performs an immediate close of a TCP connection, there is
1563 a significant risk that the client will not be able to read the last
1564 HTTP response. If the server receives additional data from the
1565 client on a fully closed connection, such as another request that was
1566 sent by the client before receiving the server's response, the
1567 server's TCP stack will send a reset packet to the client;
1568 unfortunately, the reset packet might erase the client's
1569 unacknowledged input buffers before they can be read and interpreted
1570 by the client's HTTP parser.
1572 To avoid the TCP reset problem, servers typically close a connection
1573 in stages. First, the server performs a half-close by closing only
1574 the write side of the read/write connection. The server then
1575 continues to read from the connection until it receives a
1576 corresponding close by the client, or until the server is reasonably
1577 certain that its own TCP stack has received the client's
1578 acknowledgement of the packet(s) containing the server's last
1579 response. Finally, the server fully closes the connection.
1581 It is unknown whether the reset problem is exclusive to TCP or might
1582 also be found in other transport connection protocols.
1584 9.7. Upgrade
1586 The "Upgrade" header field is intended to provide a simple mechanism
1587 for transitioning from HTTP/1.1 to some other protocol on the same
1588 connection. A client MAY send a list of protocols in the Upgrade
1589 header field of a request to invite the server to switch to one or
1590 more of those protocols, in order of descending preference, before
1591 sending the final response. A server MAY ignore a received Upgrade
1592 header field if it wishes to continue using the current protocol on
1593 that connection. Upgrade cannot be used to insist on a protocol
1594 change.
1596 Upgrade = 1#protocol
1598 protocol = protocol-name ["/" protocol-version]
1599 protocol-name = token
1600 protocol-version = token
1602 A server that sends a 101 (Switching Protocols) response MUST send an
1603 Upgrade header field to indicate the new protocol(s) to which the
1604 connection is being switched; if multiple protocol layers are being
1605 switched, the sender MUST list the protocols in layer-ascending
1606 order. A server MUST NOT switch to a protocol that was not indicated
1607 by the client in the corresponding request's Upgrade header field. A
1608 server MAY choose to ignore the order of preference indicated by the
1609 client and select the new protocol(s) based on other factors, such as
1610 the nature of the request or the current load on the server.
1612 A server that sends a 426 (Upgrade Required) response MUST send an
1613 Upgrade header field to indicate the acceptable protocols, in order
1614 of descending preference.
1616 A server MAY send an Upgrade header field in any other response to
1617 advertise that it implements support for upgrading to the listed
1618 protocols, in order of descending preference, when appropriate for a
1619 future request.
1621 The following is a hypothetical example sent by a client:
1623 GET /hello.txt HTTP/1.1
1624 Host: www.example.com
1625 Connection: upgrade
1626 Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
1628 The capabilities and nature of the application-level communication
1629 after the protocol change is entirely dependent upon the new
1630 protocol(s) chosen. However, immediately after sending the 101
1631 (Switching Protocols) response, the server is expected to continue
1632 responding to the original request as if it had received its
1633 equivalent within the new protocol (i.e., the server still has an
1634 outstanding request to satisfy after the protocol has been changed,
1635 and is expected to do so without requiring the request to be
1636 repeated).
1638 For example, if the Upgrade header field is received in a GET request
1639 and the server decides to switch protocols, it first responds with a
1640 101 (Switching Protocols) message in HTTP/1.1 and then immediately
1641 follows that with the new protocol's equivalent of a response to a
1642 GET on the target resource. This allows a connection to be upgraded
1643 to protocols with the same semantics as HTTP without the latency cost
1644 of an additional round trip. A server MUST NOT switch protocols
1645 unless the received message semantics can be honored by the new
1646 protocol; an OPTIONS request can be honored by any protocol.
1648 The following is an example response to the above hypothetical
1649 request:
1651 HTTP/1.1 101 Switching Protocols
1652 Connection: upgrade
1653 Upgrade: HTTP/2.0
1655 [... data stream switches to HTTP/2.0 with an appropriate response
1656 (as defined by new protocol) to the "GET /hello.txt" request ...]
1658 When Upgrade is sent, the sender MUST also send a Connection header
1659 field (Section 9.1) that contains an "upgrade" connection option, in
1660 order to prevent Upgrade from being accidentally forwarded by
1661 intermediaries that might not implement the listed protocols. A
1662 server MUST ignore an Upgrade header field that is received in an
1663 HTTP/1.0 request.
1665 A client cannot begin using an upgraded protocol on the connection
1666 until it has completely sent the request message (i.e., the client
1667 can't change the protocol it is sending in the middle of a message).
1668 If a server receives both an Upgrade and an Expect header field with
1669 the "100-continue" expectation (Section 8.1.1 of [Semantics]), the
1670 server MUST send a 100 (Continue) response before sending a 101
1671 (Switching Protocols) response.
1673 The Upgrade header field only applies to switching protocols on top
1674 of the existing connection; it cannot be used to switch the
1675 underlying connection (transport) protocol, nor to switch the
1676 existing communication to a different connection. For those
1677 purposes, it is more appropriate to use a 3xx (Redirection) response
1678 (Section 9.4 of [Semantics]).
1680 9.7.1. Upgrade Protocol Names
1682 This specification only defines the protocol name "HTTP" for use by
1683 the family of Hypertext Transfer Protocols, as defined by the HTTP
1684 version rules of Section 3.5 of [Semantics] and future updates to
1685 this specification. Additional protocol names ought to be registered
1686 using the registration procedure defined in Section 9.7.2.
1688 +------+-------------------+--------------------+-------------------+
1689 | Name | Description | Expected Version | Reference |
1690 | | | Tokens | |
1691 +------+-------------------+--------------------+-------------------+
1692 | HTTP | Hypertext | any DIGIT.DIGIT | Section 3.5 of |
1693 | | Transfer Protocol | (e.g, "2.0") | [Semantics] |
1694 +------+-------------------+--------------------+-------------------+
1696 9.7.2. Upgrade Token Registry
1698 The "Hypertext Transfer Protocol (HTTP) Upgrade Token Registry"
1699 defines the namespace for protocol-name tokens used to identify
1700 protocols in the Upgrade header field. The registry is maintained at
1701 .
1703 Each registered protocol name is associated with contact information
1704 and an optional set of specifications that details how the connection
1705 will be processed after it has been upgraded.
1707 Registrations happen on a "First Come First Served" basis (see
1708 Section 4.4 of [RFC8126]) and are subject to the following rules:
1710 1. A protocol-name token, once registered, stays registered forever.
1712 2. The registration MUST name a responsible party for the
1713 registration.
1715 3. The registration MUST name a point of contact.
1717 4. The registration MAY name a set of specifications associated with
1718 that token. Such specifications need not be publicly available.
1720 5. The registration SHOULD name a set of expected "protocol-version"
1721 tokens associated with that token at the time of registration.
1723 6. The responsible party MAY change the registration at any time.
1724 The IANA will keep a record of all such changes, and make them
1725 available upon request.
1727 7. The IESG MAY reassign responsibility for a protocol token. This
1728 will normally only be used in the case when a responsible party
1729 cannot be contacted.
1731 10. Enclosing Messages as Data
1732 10.1. Media Type message/http
1734 The message/http media type can be used to enclose a single HTTP
1735 request or response message, provided that it obeys the MIME
1736 restrictions for all "message" types regarding line length and
1737 encodings.
1739 Type name: message
1741 Subtype name: http
1743 Required parameters: N/A
1745 Optional parameters: version, msgtype
1747 version: The HTTP-version number of the enclosed message (e.g.,
1748 "1.1"). If not present, the version can be determined from the
1749 first line of the body.
1751 msgtype: The message type -- "request" or "response". If not
1752 present, the type can be determined from the first line of the
1753 body.
1755 Encoding considerations: only "7bit", "8bit", or "binary" are
1756 permitted
1758 Security considerations: see Section 11
1760 Interoperability considerations: N/A
1762 Published specification: This specification (see Section 10.1).
1764 Applications that use this media type: N/A
1766 Fragment identifier considerations: N/A
1768 Additional information:
1770 Magic number(s): N/A
1772 Deprecated alias names for this type: N/A
1774 File extension(s): N/A
1776 Macintosh file type code(s): N/A
1778 Person and email address to contact for further information:
1779 See Authors' Addresses section.
1781 Intended usage: COMMON
1783 Restrictions on usage: N/A
1785 Author: See Authors' Addresses section.
1787 Change controller: IESG
1789 10.2. Media Type application/http
1791 The application/http media type can be used to enclose a pipeline of
1792 one or more HTTP request or response messages (not intermixed).
1794 Type name: application
1796 Subtype name: http
1798 Required parameters: N/A
1800 Optional parameters: version, msgtype
1802 version: The HTTP-version number of the enclosed messages (e.g.,
1803 "1.1"). If not present, the version can be determined from the
1804 first line of the body.
1806 msgtype: The message type -- "request" or "response". If not
1807 present, the type can be determined from the first line of the
1808 body.
1810 Encoding considerations: HTTP messages enclosed by this type are in
1811 "binary" format; use of an appropriate Content-Transfer-Encoding
1812 is required when transmitted via email.
1814 Security considerations: see Section 11
1816 Interoperability considerations: N/A
1818 Published specification: This specification (see Section 10.2).
1820 Applications that use this media type: N/A
1822 Fragment identifier considerations: N/A
1824 Additional information:
1826 Deprecated alias names for this type: N/A
1828 Magic number(s): N/A
1829 File extension(s): N/A
1831 Macintosh file type code(s): N/A
1833 Person and email address to contact for further information:
1834 See Authors' Addresses section.
1836 Intended usage: COMMON
1838 Restrictions on usage: N/A
1840 Author: See Authors' Addresses section.
1842 Change controller: IESG
1844 11. Security Considerations
1846 This section is meant to inform developers, information providers,
1847 and users of known security considerations relevant to HTTP message
1848 syntax, parsing, and routing. Security considerations about HTTP
1849 semantics and payloads are addressed in [Semantics].
1851 11.1. Response Splitting
1853 Response splitting (a.k.a, CRLF injection) is a common technique,
1854 used in various attacks on Web usage, that exploits the line-based
1855 nature of HTTP message framing and the ordered association of
1856 requests to responses on persistent connections [Klein]. This
1857 technique can be particularly damaging when the requests pass through
1858 a shared cache.
1860 Response splitting exploits a vulnerability in servers (usually
1861 within an application server) where an attacker can send encoded data
1862 within some parameter of the request that is later decoded and echoed
1863 within any of the response header fields of the response. If the
1864 decoded data is crafted to look like the response has ended and a
1865 subsequent response has begun, the response has been split and the
1866 content within the apparent second response is controlled by the
1867 attacker. The attacker can then make any other request on the same
1868 persistent connection and trick the recipients (including
1869 intermediaries) into believing that the second half of the split is
1870 an authoritative answer to the second request.
1872 For example, a parameter within the request-target might be read by
1873 an application server and reused within a redirect, resulting in the
1874 same parameter being echoed in the Location header field of the
1875 response. If the parameter is decoded by the application and not
1876 properly encoded when placed in the response field, the attacker can
1877 send encoded CRLF octets and other content that will make the
1878 application's single response look like two or more responses.
1880 A common defense against response splitting is to filter requests for
1881 data that looks like encoded CR and LF (e.g., "%0D" and "%0A").
1882 However, that assumes the application server is only performing URI
1883 decoding, rather than more obscure data transformations like charset
1884 transcoding, XML entity translation, base64 decoding, sprintf
1885 reformatting, etc. A more effective mitigation is to prevent
1886 anything other than the server's core protocol libraries from sending
1887 a CR or LF within the header section, which means restricting the
1888 output of header fields to APIs that filter for bad octets and not
1889 allowing application servers to write directly to the protocol
1890 stream.
1892 11.2. Request Smuggling
1894 Request smuggling ([Linhart]) is a technique that exploits
1895 differences in protocol parsing among various recipients to hide
1896 additional requests (which might otherwise be blocked or disabled by
1897 policy) within an apparently harmless request. Like response
1898 splitting, request smuggling can lead to a variety of attacks on HTTP
1899 usage.
1901 This specification has introduced new requirements on request
1902 parsing, particularly with regard to message framing in Section 6.3,
1903 to reduce the effectiveness of request smuggling.
1905 11.3. Message Integrity
1907 HTTP does not define a specific mechanism for ensuring message
1908 integrity, instead relying on the error-detection ability of
1909 underlying transport protocols and the use of length or chunk-
1910 delimited framing to detect completeness. Additional integrity
1911 mechanisms, such as hash functions or digital signatures applied to
1912 the content, can be selectively added to messages via extensible
1913 metadata header fields. Historically, the lack of a single integrity
1914 mechanism has been justified by the informal nature of most HTTP
1915 communication. However, the prevalence of HTTP as an information
1916 access mechanism has resulted in its increasing use within
1917 environments where verification of message integrity is crucial.
1919 User agents are encouraged to implement configurable means for
1920 detecting and reporting failures of message integrity such that those
1921 means can be enabled within environments for which integrity is
1922 necessary. For example, a browser being used to view medical history
1923 or drug interaction information needs to indicate to the user when
1924 such information is detected by the protocol to be incomplete,
1925 expired, or corrupted during transfer. Such mechanisms might be
1926 selectively enabled via user agent extensions or the presence of
1927 message integrity metadata in a response. At a minimum, user agents
1928 ought to provide some indication that allows a user to distinguish
1929 between a complete and incomplete response message (Section 8) when
1930 such verification is desired.
1932 11.4. Message Confidentiality
1934 HTTP relies on underlying transport protocols to provide message
1935 confidentiality when that is desired. HTTP has been specifically
1936 designed to be independent of the transport protocol, such that it
1937 can be used over many different forms of encrypted connection, with
1938 the selection of such transports being identified by the choice of
1939 URI scheme or within user agent configuration.
1941 The "https" scheme can be used to identify resources that require a
1942 confidential connection, as described in Section 2.5.2 of
1943 [Semantics].
1945 12. IANA Considerations
1947 The change controller for the following registrations is: "IETF
1948 (iesg@ietf.org) - Internet Engineering Task Force".
1950 12.1. Header Field Registration
1952 Please update the "Message Headers" registry of "Permanent Message
1953 Header Field Names" at with the header field names listed in the two tables of
1955 Section 5.
1957 12.2. Media Type Registration
1959 Please update the "Media Types" registry at
1960 with the registration
1961 information in Section 10.1 and Section 10.2 for the media types
1962 "message/http" and "application/http", respectively.
1964 12.3. Transfer Coding Registration
1966 Please update the "HTTP Transfer Coding Registry" at
1967 with the
1968 registration procedure of Section 7.3 and the content coding names
1969 summarized in the table of Section 7.
1971 12.4. Upgrade Token Registration
1973 Please update the "Hypertext Transfer Protocol (HTTP) Upgrade Token
1974 Registry" at
1975 with the registration procedure of Section 9.7.2 and the upgrade
1976 token names summarized in the table of Section 9.7.1.
1978 13. References
1980 13.1. Normative References
1982 [Caching] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
1983 Ed., "HTTP Caching", draft-ietf-httpbis-cache-02 (work in
1984 progress), July 2018.
1986 [RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Format
1987 Specification version 3.3", RFC 1950,
1988 DOI 10.17487/RFC1950, May 1996,
1989 .
1991 [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
1992 version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996,
1993 .
1995 [RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and G.
1996 Randers-Pehrson, "GZIP file format specification version
1997 4.3", RFC 1952, DOI 10.17487/RFC1952, May 1996,
1998 .
2000 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
2001 Requirement Levels", BCP 14, RFC 2119,
2002 DOI 10.17487/RFC2119, March 1997,
2003 .
2005 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
2006 Resource Identifier (URI): Generic Syntax", STD 66,
2007 RFC 3986, DOI 10.17487/RFC3986, January 2005,
2008 .
2010 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
2011 Specifications: ABNF", STD 68, RFC 5234,
2012 DOI 10.17487/RFC5234, January 2008,
2013 .
2015 [Semantics]
2016 Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
2017 Ed., "HTTP Semantics", draft-ietf-httpbis-semantics-02
2018 (work in progress), July 2018.
2020 [USASCII] American National Standards Institute, "Coded Character
2021 Set -- 7-bit American Standard Code for Information
2022 Interchange", ANSI X3.4, 1986.
2024 [Welch] Welch, T., "A Technique for High-Performance Data
2025 Compression", IEEE Computer 17(6), June 1984.
2027 13.2. Informative References
2029 [Err4667] RFC Errata, Erratum ID 4667, RFC 7230,
2030 .
2032 [Klein] Klein, A., "Divide and Conquer - HTTP Response Splitting,
2033 Web Cache Poisoning Attacks, and Related Topics", March
2034 2004, .
2037 [Linhart] Linhart, C., Klein, A., Heled, R., and S. Orrin, "HTTP
2038 Request Smuggling", June 2005,
2039 .
2041 [RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext
2042 Transfer Protocol -- HTTP/1.0", RFC 1945,
2043 DOI 10.17487/RFC1945, May 1996,
2044 .
2046 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2047 Extensions (MIME) Part One: Format of Internet Message
2048 Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
2049 .
2051 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2052 Extensions (MIME) Part Two: Media Types", RFC 2046,
2053 DOI 10.17487/RFC2046, November 1996,
2054 .
2056 [RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2057 Extensions (MIME) Part Five: Conformance Criteria and
2058 Examples", RFC 2049, DOI 10.17487/RFC2049, November 1996,
2059 .
2061 [RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T.
2062 Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
2063 RFC 2068, DOI 10.17487/RFC2068, January 1997,
2064 .
2066 [RFC2557] Palme, F., Hopmann, A., Shelness, N., and E. Stefferud,
2067 "MIME Encapsulation of Aggregate Documents, such as HTML
2068 (MHTML)", RFC 2557, DOI 10.17487/RFC2557, March 1999,
2069 .
2071 [RFC5322] Resnick, P., "Internet Message Format", RFC 5322,
2072 DOI 10.17487/RFC5322, October 2008,
2073 .
2075 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
2076 DOI 10.17487/RFC6265, April 2011,
2077 .
2079 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
2080 Protocol (HTTP/1.1): Message Syntax and Routing",
2081 RFC 7230, DOI 10.17487/RFC7230, June 2014,
2082 .
2084 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
2085 Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
2086 DOI 10.17487/RFC7231, June 2014,
2087 .
2089 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
2090 Writing an IANA Considerations Section in RFCs", BCP 26,
2091 RFC 8126, DOI 10.17487/RFC8126, June 2017,
2092 .
2094 Appendix A. Collected ABNF
2096 In the collected ABNF below, list rules are expanded as per
2097 Section 11 of [Semantics].
2099 BWS =
2101 Connection = *( "," OWS ) connection-option *( OWS "," [ OWS
2102 connection-option ] )
2104 HTTP-message = start-line *( header-field CRLF ) CRLF [ message-body
2105 ]
2106 HTTP-name = %x48.54.54.50 ; HTTP
2107 HTTP-version = HTTP-name "/" DIGIT "." DIGIT
2109 OWS =
2111 RWS =
2113 TE = [ ( "," / t-codings ) *( OWS "," [ OWS t-codings ] ) ]
2114 Transfer-Encoding = *( "," OWS ) transfer-coding *( OWS "," [ OWS
2115 transfer-coding ] )
2117 Upgrade = *( "," OWS ) protocol *( OWS "," [ OWS protocol ] )
2119 absolute-URI =
2120 absolute-form = absolute-URI
2121 absolute-path =
2122 asterisk-form = "*"
2123 authority =
2124 authority-form = authority
2126 chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
2127 chunk-data = 1*OCTET
2128 chunk-ext = *( BWS ";" BWS chunk-ext-name [ BWS "=" BWS chunk-ext-val
2129 ] )
2130 chunk-ext-name = token
2131 chunk-ext-val = token / quoted-string
2132 chunk-size = 1*HEXDIG
2133 chunked-body = *chunk last-chunk trailer-part CRLF
2134 comment =
2135 connection-option = token
2137 field-name =
2138 field-value =
2140 header-field = field-name ":" OWS field-value OWS
2141 last-chunk = 1*"0" [ chunk-ext ] CRLF
2143 message-body = *OCTET
2144 method = token
2146 obs-fold = CRLF 1*( SP / HTAB )
2147 obs-text =
2148 origin-form = absolute-path [ "?" query ]
2150 port =
2151 protocol = protocol-name [ "/" protocol-version ]
2152 protocol-name = token
2153 protocol-version = token
2155 query =
2156 quoted-string =
2158 rank = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] )
2159 reason-phrase = *( HTAB / SP / VCHAR / obs-text )
2160 request-line = method SP request-target SP HTTP-version CRLF
2161 request-target = origin-form / absolute-form / authority-form /
2162 asterisk-form
2164 start-line = request-line / status-line
2165 status-code = 3DIGIT
2166 status-line = HTTP-version SP status-code SP reason-phrase CRLF
2168 t-codings = "trailers" / ( transfer-coding [ t-ranking ] )
2169 t-ranking = OWS ";" OWS "q=" rank
2170 token =
2171 trailer-part = *( header-field CRLF )
2172 transfer-coding = "chunked" / "compress" / "deflate" / "gzip" /
2173 transfer-extension
2174 transfer-extension = token *( OWS ";" OWS transfer-parameter )
2175 transfer-parameter = token BWS "=" BWS ( token / quoted-string )
2177 uri-host =
2179 Appendix B. Differences between HTTP and MIME
2181 HTTP/1.1 uses many of the constructs defined for the Internet Message
2182 Format [RFC5322] and the Multipurpose Internet Mail Extensions (MIME)
2183 [RFC2045] to allow a message body to be transmitted in an open
2184 variety of representations and with extensible header fields.
2185 However, RFC 2045 is focused only on email; applications of HTTP have
2186 many characteristics that differ from email; hence, HTTP has features
2187 that differ from MIME. These differences were carefully chosen to
2188 optimize performance over binary connections, to allow greater
2189 freedom in the use of new media types, to make date comparisons
2190 easier, and to acknowledge the practice of some early HTTP servers
2191 and clients.
2193 This appendix describes specific areas where HTTP differs from MIME.
2194 Proxies and gateways to and from strict MIME environments need to be
2195 aware of these differences and provide the appropriate conversions
2196 where necessary.
2198 B.1. MIME-Version
2200 HTTP is not a MIME-compliant protocol. However, messages can include
2201 a single MIME-Version header field to indicate what version of the
2202 MIME protocol was used to construct the message. Use of the MIME-
2203 Version header field indicates that the message is in full
2204 conformance with the MIME protocol (as defined in [RFC2045]).
2205 Senders are responsible for ensuring full conformance (where
2206 possible) when exporting HTTP messages to strict MIME environments.
2208 B.2. Conversion to Canonical Form
2210 MIME requires that an Internet mail body part be converted to
2211 canonical form prior to being transferred, as described in Section 4
2212 of [RFC2049]. Section 6.1.1.2 of [Semantics] describes the forms
2213 allowed for subtypes of the "text" media type when transmitted over
2214 HTTP. [RFC2046] requires that content with a type of "text"
2215 represent line breaks as CRLF and forbids the use of CR or LF outside
2216 of line break sequences. HTTP allows CRLF, bare CR, and bare LF to
2217 indicate a line break within text content.
2219 A proxy or gateway from HTTP to a strict MIME environment ought to
2220 translate all line breaks within text media types to the RFC 2049
2221 canonical form of CRLF. Note, however, this might be complicated by
2222 the presence of a Content-Encoding and by the fact that HTTP allows
2223 the use of some charsets that do not use octets 13 and 10 to
2224 represent CR and LF, respectively.
2226 Conversion will break any cryptographic checksums applied to the
2227 original content unless the original content is already in canonical
2228 form. Therefore, the canonical form is recommended for any content
2229 that uses such checksums in HTTP.
2231 B.3. Conversion of Date Formats
2233 HTTP/1.1 uses a restricted set of date formats (Section 10.1.1.1 of
2234 [Semantics]) to simplify the process of date comparison. Proxies and
2235 gateways from other protocols ought to ensure that any Date header
2236 field present in a message conforms to one of the HTTP/1.1 formats
2237 and rewrite the date if necessary.
2239 B.4. Conversion of Content-Encoding
2241 MIME does not include any concept equivalent to HTTP/1.1's Content-
2242 Encoding header field. Since this acts as a modifier on the media
2243 type, proxies and gateways from HTTP to MIME-compliant protocols
2244 ought to either change the value of the Content-Type header field or
2245 decode the representation before forwarding the message. (Some
2246 experimental applications of Content-Type for Internet mail have used
2247 a media-type parameter of ";conversions=" to perform
2248 a function equivalent to Content-Encoding. However, this parameter
2249 is not part of the MIME standards).
2251 B.5. Conversion of Content-Transfer-Encoding
2253 HTTP does not use the Content-Transfer-Encoding field of MIME.
2254 Proxies and gateways from MIME-compliant protocols to HTTP need to
2255 remove any Content-Transfer-Encoding prior to delivering the response
2256 message to an HTTP client.
2258 Proxies and gateways from HTTP to MIME-compliant protocols are
2259 responsible for ensuring that the message is in the correct format
2260 and encoding for safe transport on that protocol, where "safe
2261 transport" is defined by the limitations of the protocol being used.
2262 Such a proxy or gateway ought to transform and label the data with an
2263 appropriate Content-Transfer-Encoding if doing so will improve the
2264 likelihood of safe transport over the destination protocol.
2266 B.6. MHTML and Line Length Limitations
2268 HTTP implementations that share code with MHTML [RFC2557]
2269 implementations need to be aware of MIME line length limitations.
2270 Since HTTP does not have this limitation, HTTP does not fold long
2271 lines. MHTML messages being transported by HTTP follow all
2272 conventions of MHTML, including line length limitations and folding,
2273 canonicalization, etc., since HTTP transfers message-bodies as
2274 payload and, aside from the "multipart/byteranges" type
2275 (Section 6.3.4 of [Semantics]), does not interpret the content or any
2276 MIME header lines that might be contained therein.
2278 Appendix C. HTTP Version History
2280 HTTP has been in use since 1990. The first version, later referred
2281 to as HTTP/0.9, was a simple protocol for hypertext data transfer
2282 across the Internet, using only a single request method (GET) and no
2283 metadata. HTTP/1.0, as defined by [RFC1945], added a range of
2284 request methods and MIME-like messaging, allowing for metadata to be
2285 transferred and modifiers placed on the request/response semantics.
2286 However, HTTP/1.0 did not sufficiently take into consideration the
2287 effects of hierarchical proxies, caching, the need for persistent
2288 connections, or name-based virtual hosts. The proliferation of
2289 incompletely implemented applications calling themselves "HTTP/1.0"
2290 further necessitated a protocol version change in order for two
2291 communicating applications to determine each other's true
2292 capabilities.
2294 HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent
2295 requirements that enable reliable implementations, adding only those
2296 features that can either be safely ignored by an HTTP/1.0 recipient
2297 or only be sent when communicating with a party advertising
2298 conformance with HTTP/1.1.
2300 HTTP/1.1 has been designed to make supporting previous versions easy.
2301 A general-purpose HTTP/1.1 server ought to be able to understand any
2302 valid request in the format of HTTP/1.0, responding appropriately
2303 with an HTTP/1.1 message that only uses features understood (or
2304 safely ignored) by HTTP/1.0 clients. Likewise, an HTTP/1.1 client
2305 can be expected to understand any valid HTTP/1.0 response.
2307 Since HTTP/0.9 did not support header fields in a request, there is
2308 no mechanism for it to support name-based virtual hosts (selection of
2309 resource by inspection of the Host header field). Any server that
2310 implements name-based virtual hosts ought to disable support for
2311 HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact,
2312 badly constructed HTTP/1.x requests caused by a client failing to
2313 properly encode the request-target.
2315 C.1. Changes from HTTP/1.0
2317 This section summarizes major differences between versions HTTP/1.0
2318 and HTTP/1.1.
2320 C.1.1. Multihomed Web Servers
2322 The requirements that clients and servers support the Host header
2323 field (Section 5.4 of [Semantics]), report an error if it is missing
2324 from an HTTP/1.1 request, and accept absolute URIs (Section 3.2) are
2325 among the most important changes defined by HTTP/1.1.
2327 Older HTTP/1.0 clients assumed a one-to-one relationship of IP
2328 addresses and servers; there was no other established mechanism for
2329 distinguishing the intended server of a request than the IP address
2330 to which that request was directed. The Host header field was
2331 introduced during the development of HTTP/1.1 and, though it was
2332 quickly implemented by most HTTP/1.0 browsers, additional
2333 requirements were placed on all HTTP/1.1 requests in order to ensure
2334 complete adoption. At the time of this writing, most HTTP-based
2335 services are dependent upon the Host header field for targeting
2336 requests.
2338 C.1.2. Keep-Alive Connections
2340 In HTTP/1.0, each connection is established by the client prior to
2341 the request and closed by the server after sending the response.
2342 However, some implementations implement the explicitly negotiated
2343 ("Keep-Alive") version of persistent connections described in
2344 Section 19.7.1 of [RFC2068].
2346 Some clients and servers might wish to be compatible with these
2347 previous approaches to persistent connections, by explicitly
2348 negotiating for them with a "Connection: keep-alive" request header
2349 field. However, some experimental implementations of HTTP/1.0
2350 persistent connections are faulty; for example, if an HTTP/1.0 proxy
2351 server doesn't understand Connection, it will erroneously forward
2352 that header field to the next inbound server, which would result in a
2353 hung connection.
2355 One attempted solution was the introduction of a Proxy-Connection
2356 header field, targeted specifically at proxies. In practice, this
2357 was also unworkable, because proxies are often deployed in multiple
2358 layers, bringing about the same problem discussed above.
2360 As a result, clients are encouraged not to send the Proxy-Connection
2361 header field in any requests.
2363 Clients are also encouraged to consider the use of Connection: keep-
2364 alive in requests carefully; while they can enable persistent
2365 connections with HTTP/1.0 servers, clients using them will need to
2366 monitor the connection for "hung" requests (which indicate that the
2367 client ought stop sending the header field), and this mechanism ought
2368 not be used by clients at all when a proxy is being used.
2370 C.1.3. Introduction of Transfer-Encoding
2372 HTTP/1.1 introduces the Transfer-Encoding header field (Section 6.1).
2373 Transfer codings need to be decoded prior to forwarding an HTTP
2374 message over a MIME-compliant protocol.
2376 C.2. Changes from RFC 7230
2378 Most of the sections introducing HTTP's design goals, history,
2379 architecture, conformance criteria, protocol versioning, URIs,
2380 message routing, and header field values have been moved to
2381 [Semantics]. This document has been reduced to just the messaging
2382 syntax and connection management requirements specific to HTTP/1.1.
2384 Furthermore:
2386 In the ABNF for chunked extensions, re-introduce (bad) whitespace
2387 around ";" and "=". Whitespace was removed in [RFC7230], but later
2388 this change was found to break existing implementations (see
2389 [Err4667]). (Section 7.1.1)
2391 Disallow transfer coding parameters called "q" in order to avoid
2392 conflicts with the use of ranks in the TE header field.
2393 (Section 7.3)
2395 Appendix D. Change Log
2397 This section is to be removed before publishing as an RFC.
2399 D.1. Between RFC7230 and draft 00
2401 The changes were purely editorial:
2403 o Change boilerplate and abstract to indicate the "draft" status,
2404 and update references to ancestor specifications.
2406 o Adjust historical notes.
2408 o Update links to sibling specifications.
2410 o Replace sections listing changes from RFC 2616 by new empty
2411 sections referring to RFC 723x.
2413 o Remove acknowledgements specific to RFC 723x.
2415 o Move "Acknowledgements" to the very end and make them unnumbered.
2417 D.2. Since draft-ietf-httpbis-messaging-00
2419 The changes in this draft are editorial, with respect to HTTP as a
2420 whole, to move all core HTTP semantics into [Semantics]:
2422 o Moved introduction, architecture, conformance, and ABNF extensions
2423 from RFC 7230 (Messaging) to semantics [Semantics].
2425 o Moved discussion of MIME differences from RFC 7231 (Semantics) to
2426 Appendix B since they mostly cover transforming 1.1 messages.
2428 o Moved all extensibility tips, registration procedures, and
2429 registry tables from the IANA considerations to normative
2430 sections, reducing the IANA considerations to just instructions
2431 that will be removed prior to publication as an RFC.
2433 D.3. Since draft-ietf-httpbis-messaging-01
2435 o Cite RFC 8126 instead of RFC 5226 ()
2438 o Resolved erratum 4779, no change needed here
2439 (,
2440 )
2442 o In Section 7, fixed prose claiming transfer parameters allow bare
2443 names (,
2444 )
2446 o Resolved erratum 4225, no change needed here
2447 (,
2448 )
2450 o Replace "response code" with "response status code"
2451 (,
2452 )
2454 o In Section 9.3, clarify statement about HTTP/1.0 keep-alive
2455 (,
2456 )
2458 o In Section 7.1.1, re-introduce (bad) whitespace around ";" and "="
2459 (,
2460 , )
2463 o In Section 7.3, state that transfer codings should not use
2464 parameters named "q" (, )
2467 o In Section 7, mark coding name "trailers" as reserved in the IANA
2468 registry ()
2470 Index
2472 A
2473 absolute-form (of request-target) 10
2474 application/http Media Type 39
2475 asterisk-form (of request-target) 11
2476 authority-form (of request-target) 11
2478 C
2479 Connection header field 28, 33
2480 Content-Length header field 18
2481 Content-Transfer-Encoding header field 49
2482 chunked (Coding Format) 17, 19
2483 chunked (transfer coding) 22
2484 close 28, 33
2485 compress (transfer coding) 25
2487 D
2488 deflate (transfer coding) 25
2490 E
2491 effective request URI 12
2493 G
2494 Grammar
2495 absolute-form 9-10
2496 ALPHA 5
2497 asterisk-form 9, 11
2498 authority-form 9, 11
2499 chunk 22
2500 chunk-data 22
2501 chunk-ext 22-23
2502 chunk-ext-name 23
2503 chunk-ext-val 23
2504 chunk-size 22
2505 chunked-body 22-23
2506 Connection 29
2507 connection-option 29
2508 CR 5
2509 CRLF 5
2510 CTL 5
2511 DIGIT 5
2512 DQUOTE 5
2513 field-name 14
2514 field-value 14
2515 header-field 14, 23
2516 HEXDIG 5
2517 HTAB 5
2518 HTTP-message 6
2519 HTTP-name 6
2520 HTTP-version 6
2521 last-chunk 22
2522 LF 5
2523 message-body 16
2524 method 9
2525 obs-fold 15
2526 OCTET 5
2527 origin-form 9-10
2528 rank 26
2529 reason-phrase 14
2530 request-line 8
2531 request-target 9
2532 SP 5
2533 start-line 6
2534 status-code 14
2535 status-line 13
2536 t-codings 26
2537 t-ranking 26
2538 TE 26
2539 trailer-part 22-23
2540 transfer-coding 21
2541 Transfer-Encoding 17
2542 transfer-extension 21
2543 transfer-parameter 21
2544 Upgrade 35
2545 VCHAR 5
2546 gzip (transfer coding) 25
2548 H
2549 header field 6
2550 header section 6
2551 headers 6
2553 M
2554 MIME-Version header field 48
2555 Media Type
2556 application/http 39
2557 message/http 38
2558 message/http Media Type 38
2559 method 9
2561 O
2562 origin-form (of request-target) 10
2564 R
2565 request-target 9
2567 T
2568 TE header field 26
2569 Transfer-Encoding header field 17
2571 U
2572 Upgrade header field 34
2574 X
2575 x-compress (transfer coding) 25
2576 x-gzip (transfer coding) 25
2578 Acknowledgments
2580 See Appendix "Acknowledgments" of [Semantics].
2582 Authors' Addresses
2584 Roy T. Fielding (editor)
2585 Adobe
2586 345 Park Ave
2587 San Jose, CA 95110
2588 USA
2590 EMail: fielding@gbiv.com
2591 URI: https://roy.gbiv.com/
2593 Mark Nottingham (editor)
2594 Fastly
2596 EMail: mnot@mnot.net
2597 URI: https://www.mnot.net/
2599 Julian F. Reschke (editor)
2600 greenbytes GmbH
2601 Hafenweg 16
2602 Muenster, NW 48155
2603 Germany
2605 EMail: julian.reschke@greenbytes.de
2606 URI: https://greenbytes.de/tech/webdav/