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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7230 (Obsoleted by RFC 9110, RFC 9112) ** Obsolete normative reference: RFC 7231 (Obsoleted by RFC 9110) Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 HTTP Working Group J. Reschke 3 Internet-Draft greenbytes 4 Intended status: Standards Track August 13, 2015 5 Expires: February 14, 2016 7 Hypertext Transfer Protocol (HTTP) Client-Initiated Content-Encoding 8 draft-ietf-httpbis-cice-02 10 Abstract 12 In HTTP, content codings allow for payload encodings such as for 13 compression or integrity checks. In particular, the "gzip" content 14 coding is widely used for payload data sent in response messages. 16 Content codings can be used in request messages as well, however 17 discoverability is not on par with response messages. This document 18 extends the HTTP "Accept-Encoding" header field for use in responses, 19 to indicate the content codings that are supported in requests. 21 Editorial Note (To be removed by RFC Editor before publication) 23 Discussion of this draft takes place on the HTTPBIS working group 24 mailing list (ietf-http-wg@w3.org), which is archived at 25 . 27 Working Group information can be found at 28 and ; 29 source code and issues list for this draft can be found at 30 . 32 The changes in this draft are summarized in Appendix A.5. 34 Status of This Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at http://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on February 14, 2016. 50 Copyright Notice 52 Copyright (c) 2015 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 68 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3 69 3. Using the 'Accept-Encoding' Header Field in Responses . . . . . 3 70 4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 71 5. Deployment Considerations . . . . . . . . . . . . . . . . . . . 5 72 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 73 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 74 7.1. Header Field Registry . . . . . . . . . . . . . . . . . . . 5 75 7.2. Status Code Registry . . . . . . . . . . . . . . . . . . . 6 76 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 77 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 78 8.2. Informative References . . . . . . . . . . . . . . . . . . 6 79 Appendix A. Change Log (to be removed by RFC Editor before 80 publication) . . . . . . . . . . . . . . . . . . . . . 7 81 A.1. Since draft-reschke-http-cice-00 . . . . . . . . . . . . . 7 82 A.2. Since draft-reschke-http-cice-01 . . . . . . . . . . . . . 7 83 A.3. Since draft-reschke-http-cice-02 . . . . . . . . . . . . . 7 84 A.4. Since draft-ietf-httpbis-cice-00 . . . . . . . . . . . . . 7 85 A.5. Since draft-ietf-httpbis-cice-01 . . . . . . . . . . . . . 7 86 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . . 7 88 1. Introduction 90 In HTTP, content codings allow for payload encodings such as for 91 compression or integrity checks ([RFC7231], Section 3.1.2). In 92 particular, the "gzip" content coding is widely used for payload data 93 sent in response messages. 95 Content codings can be used in request messages as well, however 96 discoverability is not on par with response messages. This document 97 extends the HTTP "Accept-Encoding" header field ([RFC7231], Section 98 5.3.4) for use in responses, to indicate the content codings that are 99 supported in requests. It furthermore updates the definition of 100 status code 415 (Unsupported Media Type) ([RFC7231], Section 6.5.13), 101 recommending to include the "Accept-Encoding" header field when 102 appropriate. 104 2. Notational Conventions 106 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 107 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 108 document are to be interpreted as described in [RFC2119]. 110 This document reuses terminology defined in the base HTTP 111 specifications, namely Section 2 of [RFC7230] and Section 3.1.2 of 112 [RFC7231]. 114 3. Using the 'Accept-Encoding' Header Field in Responses 116 Section 5.3.4 of [RFC7231] defines "Accept-Encoding" as a request 117 header field only. 119 This specification expands that definition to allow "Accept-Encoding" 120 as a response header field as well. When present in a response, it 121 indicates what content codings the resource was willing to accept in 122 the associated request. A field value that only contains "identity" 123 implies that no content codings were supported. 125 Note that this information is specific to the associated request; the 126 set of supported encodings might be different for other resources on 127 the same server, and could change over time or depend on other 128 aspects of the request (such as the request method). 130 Section 6.5.13 of [RFC7231] defines status code 415 (Unsupported 131 Media Type) to apply to both media type and content coding related 132 problems. 134 Servers that fail a request due to an unsupported content coding 135 SHOULD respond with a 415 status and SHOULD include an "Accept- 136 Encoding" header field in that response, allowing clients to 137 distinguish between content coding related issues and media type 138 related issues. In order to avoid confusion with media type related 139 problems, servers that fail a request with a 415 status for reasons 140 unrelated to content codings SHOULD NOT include the "Accept-Encoding" 141 header field. 143 It is expected that the most common use of "Accept-Encoding" in 144 responses will have the 415 (Unsupported Media Type) status code, in 145 response to optimistic use of a content coding by clients. However, 146 the header field can also be used to indicate to clients that content 147 codings are supported, to optimize future interactions. For example, 148 a resource might include it in a 2xx response when the request 149 payload was big enough to justify use of a compression coding, but 150 the client failed do so. 152 4. Example 154 A client submits a POST request using the "compress" content coding 155 ([RFC7231], Section 3.1.2.1): 157 POST /edit/ HTTP/1.1 158 Host: example.org 159 Content-Type: application/atom+xml;type=entry 160 Content-Encoding: compress 162 ...compressed payload... 164 The server rejects request because it only allows the "gzip" content 165 coding: 167 HTTP/1.1 415 Unsupported Media Type 168 Date: Fri, 09 May 2014 11:43:53 GMT 169 Accept-Encoding: gzip 170 Content-Length: 68 171 Content-Type: text/plain 173 This resource only supports the "gzip" content coding in requests. 175 ...at which point the client can retry the request with the supported 176 "gzip" content coding. 178 Alternatively, a server that does not support any content codings in 179 requests could answer with: 181 HTTP/1.1 415 Unsupported Media Type 182 Date: Fri, 09 May 2014 11:43:53 GMT 183 Accept-Encoding: identity 184 Content-Length: 61 185 Content-Type: text/plain 187 This resource does not support content codings in requests. 189 5. Deployment Considerations 191 Servers that do not support content codings in requests already are 192 required to fail a request that uses a content coding. Section 193 6.5.13 of [RFC7231] defines the status code 415 (Unsupported Media 194 Type) for this purpose, so the only change needed is to include the 195 "Accept-Encoding" header field with value "identity" in that 196 response. 198 Servers that do support some content codings are required to fail 199 requests with unsupported content codings as well. To be compliant 200 with this specification, servers will need to use the status code 415 201 (Unsupported Media Type) to signal the problem, and will have to 202 include an "Accept-Encoding" header field that enumerates the content 203 codings that are supported. As the set of supported content codings 204 is usually static and small, adding the header field ought to be 205 trivial. 207 6. Security Considerations 209 This specification does not introduce any new security considerations 210 beyond those discussed in Section 9 of [RFC7231]. 212 7. IANA Considerations 214 7.1. Header Field Registry 216 HTTP header fields are registered within the "Message Headers" 217 registry located at 218 , as defined by 219 [BCP90]. 221 This document updates the definition of the "Accept-Encoding" header 222 field, so the "Permanent Message Header Field Names" registry ought 223 to be updated accordingly: 225 +-----------------+----------+----------+---------------------------+ 226 | Header Field | Protocol | Status | Reference | 227 | Name | | | | 228 +-----------------+----------+----------+---------------------------+ 229 | Accept-Encoding | http | standard | [RFC7231], Section 5.3.4, | 230 | | | | and Section 3 of this | 231 | | | | document | 232 +-----------------+----------+----------+---------------------------+ 234 7.2. Status Code Registry 236 HTTP status codes are registered within the "Status Code" registry 237 located at . 239 This document updates the definition of the status code 415 240 (Unsupported Media Type), so the "Status Code" registry ought to be 241 updated accordingly: 243 +-------+------------------+----------------------------------------+ 244 | Value | Description | Reference | 245 +-------+------------------+----------------------------------------+ 246 | 415 | Unsupported | [RFC7231], Section 6.5.13, and | 247 | | Media Type | Section 3 of this document | 248 +-------+------------------+----------------------------------------+ 250 8. References 252 8.1. Normative References 254 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 255 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 256 RFC2119, March 1997, 257 . 259 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 260 Protocol (HTTP/1.1): Message Syntax and Routing", 261 RFC 7230, DOI 10.17487/RFC7230, June 2014, 262 . 264 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 265 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 266 DOI 10.17487/RFC7231, June 2014, 267 . 269 8.2. Informative References 271 [BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration 272 Procedures for Message Header Fields", BCP 90, RFC 3864, 273 September 2004, . 275 Appendix A. Change Log (to be removed by RFC Editor before publication) 277 A.1. Since draft-reschke-http-cice-00 279 Clarified that the information returned in Accept-Encoding is per 280 resource, not per server. 282 Added some deployment considerations. 284 Updated HTTP/1.1 references. 286 A.2. Since draft-reschke-http-cice-01 288 Restrict the scope of A-E from "future requests" to "at the time of 289 this request". 291 Mention use of A-E in responses other than 415. 293 Recommend not to include A-E in a 415 response unless there was 294 actually a problem related to content coding. 296 A.3. Since draft-reschke-http-cice-02 298 First Working Group draft; updated boilerplate accordingly. 300 A.4. Since draft-ietf-httpbis-cice-00 302 Apply editorial improvements suggested by Mark Nottingham. 304 A.5. Since draft-ietf-httpbis-cice-01 306 Clarify that we're also extending the definition of status code 415 307 (so update that IANA registry entry as well). 309 Appendix B. Acknowledgements 311 Thanks go to the members of the and HTTPbis Working Group, namely 312 Amos Jeffries, Mark Nottingham, Pete Resnick, and Ted Hardie. 314 Author's Address 316 Julian F. Reschke 317 greenbytes GmbH 318 Hafenweg 16 319 Muenster, NW 48155 320 Germany 322 EMail: julian.reschke@greenbytes.de 323 URI: http://greenbytes.de/tech/webdav/