| Individual Submission | J. Snell |
| Internet-Draft | March 28, 2011 |
| Intended status: Informational | |
| Expires: September 29, 2011 |
This specification defines an HTTP header that can be used by a client to request that certain behaviors be implemented by a server while processing a request.¶
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This specification defines a new HTTP header that can be used by a client to request that certain behaviors be implemented by a server while processing a request.¶
The Prefer request-header is used to indicate that particular server behaviors are preferred by the client, but not required for successful completion of the request. Prefer is similar in nature to the Expect header defined by [RFC2616] with the exception that servers are allowed to ignore stated preferences.¶
Prefer = "Prefer" ":" 1#preference
preference = "return-no-content" |
"return-content" |
"return-status" |
preference-extension
preference-extension = token [ "=" ( token | quoted-string )
*prefer-params ]
prefer-params = ";" token [ "=" ( token | quoted-string ) ]
This header is defined with an extensible syntax to allow for future values included in the Registry of Preferences (Section 8.1)). A server that does not recognize or is unable to comply with particular preference values in the Prefer header of a request MUST ignore those values and MUST NOT stop processing or signal an error.¶
Comparison of preference values is case-insensitive for unquoted tokens and is case-sensitive for quoted-string preference-extensions.¶
An HTTP proxy MAY choose to honor a preference even if the origin server does not. The Prefer request-header MUST be forwarded by the proxy if the request is forwarded.¶
Note that the application of a preference by the server MAY affect the caching characteristics of the response.¶
The Preference-Applied response header MAY be included in the response message to indicate which Prefer request header values were honored by the server and applied to the request.¶
Preference-Applied = "Preference-Applied" ":" 1#preference
The "return-accepted" token indicates that the client prefers that the server respond with a 202 Accepted response indicating that the request has been accepted for processing.¶
The "return-content" token indicates that the client prefers that the server include an entity representing the current state of the resource in the response to a successful request.¶
The "return-no-content" token indicates that the client prefers that the server not include an entity in the response to a successful request. Typically, such responses would use the 204 No Content status code as defined in Section 10.2.5 of [RFC2616], but other status codes can be used as appropriate.¶
The "return-status" token indicates that the client prefers that the server include an entity describing the status of the request in the response to a successful request.¶
The 'Prefer' and 'Preference-Applied' headers should be added to the permanent registry (see [RFC3864]).¶
Header field name: Prefer
Applicable Protocol: HTTP
Status:
Author/Change controller: IETF
Specification document: this specification
Header field name: Preference-Applied
Applicable Protocol: HTTP
Status:
Author/Change controller: IETF
Specification document: this specification
This registry is maintained by IANA and initially contains the values: "return-accepted", "return-content", "return-no-content" and "return-status". New assignments are subjects to IESG approval, as outlined in [RFC2434]. Requests should be made by email to IANA, which will then forward the request to the IESG, requesting approval. The request should use the following template:¶