Intel 1520 manual Caching Http alternates, To cache or not to cache?, Configuring Http cachability

✔Evaluate freshness as follows:

1Use the Expires header test, if applicable, otherwise go to step 2. If the object is stale, revalidate. If it is fresh, check the Cache-Controlheaders.

2Use the Last-Modified / Date header test, if applicable, otherwise go to step 3. If the object is fresh according to the Last-Modified / Date test, check the Cache-Controlheaders for any freshness restrictions.

3Use the absolute freshness limit specified in the Freshness section of the Configure: Cache page. Revalidate if the age is past the freshness limit.

Configuring HTTP cachability

The following HTTP cachability options are available:

✔Cache only documents that have Expires headers

✔Cache only documents that have Expires or Last-Modifiedheaders

✔Do not restrict caching

Caching HTTP alternates

Some Web servers answer requests for the same URL by serving a variety of objects. The content of these objects can vary widely, according to whether a server delivers content for different languages, targets different browsers with different presentation styles, or delivers variable content at different times of the day. Different versions of the same object are termed alternates.

Header information identifies alternates. You can configure the Intel NetStructure Cache Appliance to cache all alternates according to a particular header. For example, if you tell the appliance to vary on the User-Agentheader, the appliance caches all the different user-agent versions of documents it encounters. To configure caching of alternates, see Variable content‚ on page 38.

To cache or not to cache?

Depending on the type of object, you can direct the Intel NetStructure Cache Appliance to cache or not cache an object:

NNTP You can limit article caching to specific news groups. See Blocking particular groups‚ on page 140.

FTP You can configure never-cache rules for specific types of FTP documents by using the command-line interface. See Configuring caching rules‚ on page 79.

HTTP The appliance responds to caching directives from clients and origin servers, as well as configured options in the Manager UI and the command-line interface.

Appendix A Caching Solutions and Performance 119