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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 May 30, 2015 5 Expires: December 1, 2015 7 Hypertext Transfer Protocol (HTTP) Client-Initiated Content-Encoding 8 draft-ietf-httpbis-cice-01 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 that content codings 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.4. 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 December 1, 2015. 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 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 75 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 76 8.2. Informative References . . . . . . . . . . . . . . . . . . 6 77 Appendix A. Change Log (to be removed by RFC Editor before 78 publication) . . . . . . . . . . . . . . . . . . . . . 6 79 A.1. Since draft-reschke-http-cice-00 . . . . . . . . . . . . . 6 80 A.2. Since draft-reschke-http-cice-01 . . . . . . . . . . . . . 6 81 A.3. Since draft-reschke-http-cice-02 . . . . . . . . . . . . . 6 82 A.4. Since draft-ietf-httpbis-cice-00 . . . . . . . . . . . . . 7 83 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . . 7 85 1. Introduction 87 In HTTP, content codings allow for payload encodings such as for 88 compression or integrity checks ([RFC7231], Section 3.1.2). In 89 particular, the "gzip" content coding is widely used for payload data 90 sent in response messages. 92 Content codings can be used in request messages as well, however 93 discoverability is not on par with response messages. This document 94 extends the HTTP "Accept-Encoding" header field ([RFC7231], Section 95 5.3.4) for use in responses, to indicate that content codings are 96 supported in requests. 98 2. Notational Conventions 100 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 101 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 102 document are to be interpreted as described in [RFC2119]. 104 This document reuses terminology defined in the base HTTP 105 specifications, namely Section 2 of [RFC7230] and Section 3.1.2 of 106 [RFC7231]. 108 3. Using the 'Accept-Encoding' Header Field in Responses 110 Section 5.3.4 of [RFC7231] defines "Accept-Encoding" as a request 111 header field only. 113 This specification expands that definition to allow "Accept-Encoding" 114 as a response header field as well. When present in a response, it 115 indicates what content codings the resource was willing to accept in 116 the associated request. A field value that only contains "identity" 117 implies that no content codings were supported. 119 Note that this information is specific to the associated request; the 120 set of supported encodings might be different for other resources on 121 the same server, and could change over time or depend on other 122 aspects of the request (such as the request method). 124 Section 6.5.13 of [RFC7231] defines status code 415 (Unsupported 125 Media Type) to apply to both media type and content coding related 126 problems. 128 Servers that fail a request due to an unsupported content coding 129 SHOULD respond with a 415 status and SHOULD include an "Accept- 130 Encoding" header field in that response, allowing clients to 131 distinguish between content coding related issues and media type 132 related issues. In order to avoid confusion with media type related 133 problems, servers that fail a request with a 415 status for reasons 134 unrelated to content codings SHOULD NOT include the "Accept-Encoding" 135 header field. 137 It is expected that the most common use of "Accept-Encoding" in 138 responses will have the 415 (Unsupported Media Type) status code, in 139 response to optimistic use of a content coding by clients. However, 140 the header field can also be used to indicate to clients that content 141 codings are supported, to optimize future interactions. For example, 142 a resource might include it in a 2xx response when the request 143 payload was big enough to justify use of a compression coding, but 144 the client failed do so. 146 4. Example 148 A client submits a POST request using the "compress" content coding 149 ([RFC7231], Section 3.1.2.1): 151 POST /edit/ HTTP/1.1 152 Host: example.org 153 Content-Type: application/atom+xml;type=entry 154 Content-Encoding: compress 156 ...compressed payload... 158 The server rejects request because it only allows the "gzip" content 159 coding: 161 HTTP/1.1 415 Unsupported Media Type 162 Date: Fri, 09 May 2014 11:43:53 GMT 163 Accept-Encoding: gzip 164 Content-Length: 68 165 Content-Type: text/plain 167 This resource only supports the "gzip" content coding in requests. 169 ...at which point the client can retry the request with the supported 170 "gzip" content coding. 172 Alternatively, a server that does not support any content codings in 173 requests could answer with: 175 HTTP/1.1 415 Unsupported Media Type 176 Date: Fri, 09 May 2014 11:43:53 GMT 177 Accept-Encoding: identity 178 Content-Length: 61 179 Content-Type: text/plain 180 This resource does not support content codings in requests. 182 5. Deployment Considerations 184 Servers that do not support content codings in requests already are 185 required to fail a request that does use a content coding. Section 186 6.5.13 of [RFC7231] recommends using the status code 415 (Unsupported 187 Media Type), so the only change needed is to include the "Accept- 188 Encoding" header field with value "identity" in that response. 190 Servers that do support some content codings are required to fail 191 requests with unsupported content codings as well. To be compliant 192 with this specification, servers will need to use the status code 415 193 (Unsupported Media Type) to signal the problem, and will have to 194 include an "Accept-Encoding" header field that enumerates the content 195 codings that are supported. As the set of supported content codings 196 is usually static and small, adding the header field ought to be 197 trivial. 199 6. Security Considerations 201 This specification does not introduce any new security considerations 202 beyond those discussed in Section 9 of [RFC7231]. 204 7. IANA Considerations 206 HTTP header fields are registered within the "Message Headers" 207 registry located at 208 , as defined by 209 [BCP90]. 211 This document updates the definition of the "Accept-Encoding" header 212 field, so the "Permanent Message Header Field Names" registry shall 213 be updated accordingly: 215 +-----------------+----------+----------+---------------------------+ 216 | Header Field | Protocol | Status | Reference | 217 | Name | | | | 218 +-----------------+----------+----------+---------------------------+ 219 | Accept-Encoding | http | standard | [RFC7231], Section 5.3.4, | 220 | | | | and Section 3 of this | 221 | | | | document | 222 +-----------------+----------+----------+---------------------------+ 224 8. References 225 8.1. Normative References 227 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 228 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 229 RFC2119, March 1997, 230 . 232 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 233 Protocol (HTTP/1.1): Message Syntax and Routing", 234 RFC 7230, DOI 10.17487/RFC7230, June 2014, 235 . 237 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 238 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 239 DOI 10.17487/RFC7231, June 2014, 240 . 242 8.2. Informative References 244 [BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration 245 Procedures for Message Header Fields", BCP 90, RFC 3864, 246 September 2004, . 248 Appendix A. Change Log (to be removed by RFC Editor before publication) 250 A.1. Since draft-reschke-http-cice-00 252 Clarified that the information returned in Accept-Encoding is per 253 resource, not per server. 255 Added some deployment considerations. 257 Updated HTTP/1.1 references. 259 A.2. Since draft-reschke-http-cice-01 261 Restrict the scope of A-E from "future requests" to "at the time of 262 this request". 264 Mention use of A-E in responses other than 415. 266 Recommend not to include A-E in a 415 response unless there was 267 actually a problem related to content coding. 269 A.3. Since draft-reschke-http-cice-02 271 First Working Group draft; updated boilerplate accordingly. 273 A.4. Since draft-ietf-httpbis-cice-00 275 Apply editorial improvements suggested by Mark Nottingham. 277 Appendix B. Acknowledgements 279 Thanks go to the members of the and HTTPbis Working Group, namely 280 Amos Jeffries, Mark Nottingham, and Ted Hardie. 282 Author's Address 284 Julian F. Reschke 285 greenbytes GmbH 286 Hafenweg 16 287 Muenster, NW 48155 288 Germany 290 EMail: julian.reschke@greenbytes.de 291 URI: http://greenbytes.de/tech/webdav/