RE: Cache control HTTP headers

On Wed, 9 Nov 2005, Leandro Scott R.Z. Jacques wrote:

> And how squid behaves with a pragma: no-cache, it
> doesn't cache the object and a request for that object
> has a TCP_MISS as result or it caches the object then
> a request for it must be validated and has a
> TCP_CLIENT_REFRESH_MISS as result?

Squid doesn't cache objects with either Pragma: no-cache, or
Cache-Control: no-cache, no-store or private.

For compatibility with old HTTP/1.0 applications the following are
recommended on a uncacheable response

   Expires: now (same as Date)
   Pragma: no-cache
   Cache-Control: no-cache, no-store

"Expires: now" has always been a standard method to mark a response as
stale, which in most caches also prevents it from getting cached (no
guarantee however).

"Pragma: no-cache" is understood by most as "not cacheable" even if never
part of any standard.

"Cache-Control: no-cache" is understood by many (RFC2068), but has
slightly different meaning in current standard.

"Cache-Control: no-store" is understood by newer ones (RFC2616).

Regards
Henrik
Received on Wed Nov 09 2005 - 13:31:45 MST