Intel 1520 manual Configuring Http freshness options, Configuring Http revalidation

✔The min-freshfield, sent by clients, is an acceptable freshness tolerance. The client wants the object to be at least this fresh. If a cached document does not remain fresh at least this long in the future, it is revalidated.

✔The max-stalefield, sent by clients, permits the appliance to serve stale documents provided they are not too old. Some browsers might be willing to take stale documents in exchange for improved performance, especially during periods of poor Internet availability.

The appliance applies Cache-Controlservability criteria after HTTP freshness criteria. For example, a document might be considered fresh, but if its age is greater than its max-age, it is not served.

Configuring HTTP freshness options

You can configure the following freshness guidelines for the Intel NetStructure Cache Appliance:

✔How often to revalidate (when to consider objects stale). See Configuring HTTP revalidation below.

✔Whether to cache documents without freshness information. See Configuring HTTP cachability below.

✔Whether to use an upper boundary to determine if the Last-Modified / Date freshness limit is too long.

✔What absolute freshness lifetime to use when estimating the freshness of documents without Expires or Last-Modifiedheaders.

See Freshness‚ on page 36 for instructions.

Configuring HTTP revalidation

The following HTTP revalidation options are available:

✔Always revalidate (everything is considered stale).

✔Never revalidate (everything is considered fresh).

✔Revalidate all objects without Expires headers. Evaluate the freshness of objects with Expires headers by first checking the Expires header, and then checking Cache-Controlheaders.

118Intel NetStructure Cache Appliance Administrator’s Guide