Changeset 481
- Timestamp:
- 04/03/09 03:55:21 (13 years ago)
- File:
-
- 1 edited
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draft-ietf-httpbis/latest-roy/p6-cache.xml
r480 r481 619 619 <t>A "stale" response is one that either has explicit expiry information, or is allowed to 620 620 have heuristic expiry calculated, but is not fresh according to the calculations in 621 <xref target="expiration.model" />. 621 <xref target="expiration.model" />.</t> 622 622 <t>Caches &MUST-NOT; return a stale response if it is prohibited by an explicit 623 623 in-protocol directive (e.g., by a "no-store" or "no-cache" cache directive, a … … 642 642 <section anchor="validation.model" title="Validation Model"> 643 643 <t>When a cache has a stale response that it would like to use, it &SHOULD; first check 644 with the origin server (or possibly an intermediate cache with a fresh response) to see if644 with the origin server (or possibly an intermediate cache) to see if 645 645 it is still usable. This is called "validating" or "revalidating" the stored response.</t> 646 646 <t>HTTP's conditional request mechanism, defined in &conditional;, is used to avoid … … 648 648 response includes one or more "cache validators", such as the field values of an ETag or 649 649 Last-Modified header field, then a validating GET request &SHOULD; be made conditional 650 to those field values. The server checks the conditional request's validator against the 651 current state of the requested resource and, if they match, the server responds with a 304 652 (Not Modified) status code to indicate that the stored response can be refreshed and 653 reused without retransmitting the response payload. If the validator does not match the 654 current state of the requested resource, then the server returns a full response, 655 including payload, so that the request can be satisfied and the stored response supplanted 656 without the need for an additional network round-trip.</t> 657 <t>See <xref target="combining.headers" /> regarding combining cached headers with those in 658 a 304 response.</t> 650 to those field values; a 304 (Not Modified) response status code indicates that the stored 651 response can be updated and reused; see <xref target="combining.headers"/>. 652 <t>If the cache receives a full response (i.e., one with payload), it is used to satisfy the 653 request and replace the stored response.</t> 659 654 <t>If a cache receives a 5xx response while attempting to validate a response, it &MAY; 660 655 either forward this response to the requesting client, or act as if the server failed to 661 respond. In the latter case, it &MAY; return a previously received response unless the656 respond. In the latter case, it &MAY; return a previously stored response unless the 662 657 stored response includes the "must-revalidate" cache directive (see <xref 663 658 target="cache-response-directive" />).</t>
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