blank.gif (43 bytes)

Church Of The
Swimming Elephant

Search:
14.9.3 Modifications of the Basic Expiration Mechanism Connected: An Internet Encyclopedia
14.9.3 Modifications of the Basic Expiration Mechanism

Up: Connected: An Internet Encyclopedia
Up: Requests For Comments
Up: RFC 2068
Up: 14 Header Field Definitions
Up: 14.9 Cache-Control
Prev: 14.9.2 What May be Stored by Caches
Next: 14.9.4 Cache Revalidation and Reload Controls

14.9.3 Modifications of the Basic Expiration Mechanism

14.9.3 Modifications of the Basic Expiration Mechanism

The expiration time of an entity may be specified by the origin server using the Expires header (see section 14.21). Alternatively, it may be specified using the max-age directive in a response.

If a response includes both an Expires header and a max-age directive, the max-age directive overrides the Expires header, even if the Expires header is more restrictive. This rule allows an origin server to provide, for a given response, a longer expiration time to an HTTP/1.1 (or later) cache than to an HTTP/1.0 cache. This may be useful if certain HTTP/1.0 caches improperly calculate ages or expiration times, perhaps due to desynchronized clocks.

    Note: most older caches, not compliant with this specification, do not implement any Cache-Control directives. An origin server wishing to use a Cache-Control directive that restricts, but does not prevent, caching by an HTTP/1.1-compliant cache may exploit the requirement that the max-age directive overrides the Expires header, and the fact that non-HTTP/1.1-compliant caches do not observe the max-age directive.

Other directives allow an user agent to modify the basic expiration mechanism. These directives may be specified on a request:

max-age
Indicates that the client is willing to accept a response whose age is no greater than the specified time in seconds. Unless max-stale directive is also included, the client is not willing to accept a stale response.

min-fresh
Indicates that the client is willing to accept a response whose freshness lifetime is no less than its current age plus the specified time in seconds. That is, the client wants a response that will still be fresh for at least the specified number of seconds.

max-stale
Indicates that the client is willing to accept a response that has exceeded its expiration time. If max-stale is assigned a value, then the client is willing to accept a response that has exceeded its expiration time by no more than the specified number of seconds. If no value is assigned to max-stale, then the client is willing to accept a stale response of any age.

If a cache returns a stale response, either because of a max-stale directive on a request, or because the cache is configured to override the expiration time of a response, the cache MUST attach a Warning header to the stale response, using Warning 10 (Response is stale).


Next: 14.9.4 Cache Revalidation and Reload Controls

Connected: An Internet Encyclopedia
14.9.3 Modifications of the Basic Expiration Mechanism

Cotse.Net

Protect yourself from cyberstalkers, identity thieves, and those who would snoop on you.
Stop spam from invading your inbox without losing the mail you want. We give you more control over your e-mail than any other service.
Block popups, ads, and malicious scripts while you surf the net through our anonymous proxies.
Participate in Usenet, host your web files, easily send anonymous messages, and more, much more.
All private, all encrypted, all secure, all in an easy to use service, and all for only $5.95 a month!

Service Details

 
.
www.cotse.com
Have you gone to church today?
.
All pages ©1999, 2000, 2001, 2002, 2003 Church of the Swimming Elephant unless otherwise stated
Church of the Swimming Elephant©1999, 2000, 2001, 2002, 2003 Cotse.com.
Cotse.com is a wholly owned subsidiary of Packetderm, LLC.

Packetderm, LLC
210 Park Ave #308
Worcester, MA 01609