- From: Henrik Nordstrom <henrik@henriknordstrom.net>
- Date: Thu, 25 Jun 2009 03:51:17 +0200
- To: Jamie Lokier <jamie@shareable.org>
- Cc: Bil Corry <bil@corry.biz>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
tor 2009-06-25 klockan 01:17 +0100 skrev Jamie Lokier: > > RFC2616? > > No, because it does not cover all browsers and proxies. > Only those conforming to RFC2616. > > It probably doesn't even cover most proxies. When did Squid get > HTTP/1.1 support? It hasn't even come there yet (almost there now). But has understood Cache-Control since about a decade or so... > If the Expires is older than Date, I see why the proxy can't cache, > but why do think it permits caching in browsers? Expires older than Date has nothing to do with browser vs proxy. Just HTTP/1.0 vs 1.1. It's a safety precaution if you should ever encounter a HTTP/1.0 client cache (user-agent or proxy) who don't know about Cache-Control. For anything reasonably modern Cache-Control max-age takes priority over Expires. > Is the common advice to include "Pragma: no-cache" unnecessary? These days yes. And was in fact never really needed provided you expired the content... > There's also the Microsoft ones, post-check and pre-check: > > The post-check and pre-check cache-control extensions are defined as follows: > > * post-check > > o Defines an interval in seconds after which an entity must be > checked for freshness. The check may happen after the user > is shown the resource but ensures that on the next roundtrip > the cached copy will be up-to-date. > > * pre-check > > o Defines an interval in seconds after which an entity must > be checked for freshness prior to showing the user the > resource. Sounds similar to some other cache-control headers proposed by mnot some year ago.. > I'm not quite sure how these differ from max-age, but they presumably do. post-check is about adding a bit of fuzziness to the process, doing cache validation asynchronous from client request, showing the client the cached copy while performing a cache validation in the background. but I don't get how pre-check differs from max-age... > Some advice on disabling caching includes these. I think that's just "because they exists in MSIE so we better set them to something..." but I don't know. Haven't studied MSIE handling of pre/post-check.. Regards Henrik
Received on Thursday, 25 June 2009 01:52:00 UTC