Configuring Http Freshness Options; Caching Http Alternates - HP P4535A - Web Cache Server Appliance Administrator's Manual

Chapter 3
Traffic Server applies
document might be considered fresh, but if its age is greater than its

Configuring HTTP freshness options

You can configure the following freshness guidelines for Traffic Server:
How often to revalidate (when to consider objects stale). See
Whether to cache documents without freshness information. See
page 14.
The upper boundary used to determine if the Last-Modified /Date freshness limit is too long.
The absolute freshness lifetime used to estimate the freshness of documents without
headers.
Modified
In the
cache.config
at specific times. Refer to
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
by first checking the
Evaluate freshness as follows:
1. Use the
Expires
it is fresh, check the
2. Use the
Last-Modified
according to the
restrictions.
3. Use 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
Cache only documents that have
Do not restrict caching

Caching HTTP alternates

Some origin servers answer requests to the same URL with 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 called alternates.
servability criteria after HTTP freshness criteria. For example, a
Cache-Control
file, you can configure Traffic Server to revalidate objects from specific origin servers
cache.config‚ on page
headers. Evaluate the freshness of objects with
Expires
header, and then checking
Expires
header test, if applicable, otherwise go to step 2. If the object is stale, revalidate. If
headers.
Cache-Control
/ header test, if applicable, otherwise go to step 3. If the object is fresh
Date
/
Last-Modified Date
headers
Expires
or
Expires
max-age
Configuring HTTP revalidation‚ on page
Configuring HTTP cachability‚ on
162.
Cache-Control
test, check the
Cache-Control
headers
Last-Modified
Web Proxy Caching
, it is not served.
or
Expires Last-
headers
Expires
headers.
headers for any freshness
14.
14