Administrator's Guide - Kerio Software Archive

9.5 HTTP cache
other objects can be stored into the cache unless there is more free space on the disk
(made by further cleaning or by manual removal).
2. If the maximum cache size set is larger than the free space on the corresponding
disk, the cache is not initialized and the following error is recorded in the Error log
(see chapter 22.8).
Max HTTP object size
maximal size of the object that can be stored in cache.
With respect to statistics, the highest number of requests are for small objects (i.e. HTML
pages, images, etc.). Big sized objects, such as archives (that are usually downloaded at
once), would require too much memory in the cache.
Cache Options
Advanced options where cache behavior can be defined.
• Continue aborted download — tick this option to enable automatic download of
objects that have been aborted by the user (using the Stop button in a browser).
Users often abort downloads for slow pages. If any user attempts to open the
same page again, the page will be available in the cache and downloads will be
much faster.
• Cache responses ’302 Redirect’ — this option accelerates connection to redirected
web pages.
Under usual circumstances, 302 Redirect responses are not cached. HTTP
protocol’s return code 302 stands for temporary redirection — such redirection
can be canceled any time or the target URL can change. If user applies the cached
response to open a web page, the client can be redirected to an obsolete or invalid
URL.
• Use server supplied Time-To-Live — objects will be cached for time specified by
the Web server from which they are downloaded. If TTL is not specified by the
server, the default TTL will be used (see the HTTP protocol TTL item).
Warning:
Some web servers may attempt to bypass the cache by too
short/long TTL.
• Ignore server Cache-Control directive — Kerio Control will ignore directives for
cache control of web pages.
Pages often include a directive that the page will not be saved into the cache.
This directive page may be misused for example to bypass the cache. Enable the
Ignore server Cache-Control directive option to make Kerio Control accept only
no-store and private directives.
Note: Kerio Control examines HTTP header directives of responses, not Web
pages.
• Always validate file in cache — with each query Kerio Control will check the
server for updates of objects stored in the cache (regardless of whether the client
demands this).
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