Compression
About Compression
The system improves performance by compressing common types of Web and file data such as HTML files, Word documents, and images.
The system determines whether it should compress the data accessed by users by using the following process:
- The system verifies that the accessed data is a compressible type. Compressing many common data types such as such as HTML files, and Word documents is supported.
- If the user is accessing Web data, the system verifies that the user's browser supports compression of the selected data type. The system determines compression supportability based on the browser's user-agent and the accept-encoding header. It supports the compression of all of the standard Web data types if it determines that the user-agent is compatible with Mozilla 5, Internet Explorer 5, or Internet Explorer 6. The system supports only compressing HTML data, however, if it determines that the browser's user-agent is only compatible with Mozilla 4.
- The system verifies that compression is enabled at the system level. You can enable system-level compression through the Maintenance > System > Options page of the admin console.
- The system verifies that compression resource policies or autopolicies are enabled for the selected data type and comes with resource policies that compress data. You may enable these policies or create your own through the following pages of the admin console:
- Users > Resource Policies > Web > Compression.
- Users > Resource Policies > Files > Compression.
You may also create resource profile compression autopolices through the Users > Resource Profiles > Web > Web Applications/Pages page of the admin console.
If all of these conditions are met, the system runs the appropriate resource policy either compresses or does not compress the data accessed by the user based on the configured action.
If all of these conditions are not met, the system does not run the appropriate resource policy and no resource policy items appear in the log files.
The system comes pre-equipped with three resource policies that compress Web and file data. If you are upgrading from a pre-4.2 version of the system software and you previously had compression enabled, these policies are enabled. Otherwise, if you previously had compression disabled, these policies are disabled.
The Web and file resource policies created during the upgrade process specify that the system should compress all supported types of Web and File data, including types that were not compressed by previous versions of the appliance. All data types that were not compressed by previous product versions are marked with an asterisk (*) in the supported data types list below.
The system supports compressing the following types of Web and file data:
- text/plain (.txt)
- text/ascii (.txt)*
- text/html (.html, .htm)
- text/css (.css)
- text/rtf (.rtf)
- text/javascript (.js)
- text/xml (.xml)*
- application/x-javascript (.js)
- application/msword (.doc)
- application/ms-word (.doc)*
- application/vnd.ms-word (.doc)*
- application/msexcel (.xls)*
- application/ms-excel (.xls)*
- application/x-excel (.xls)*
- application/vnd.ms-excel (.xls)*
- application/ms-powerpoint (.ppt)*
- application/vnd.ms-powerpoint (.ppt)*
The data types denoted by an asterisk * were not compressed by pre-4.2 versions of the system software.
Also note that the system does not compress files that you upload-only files that you download from the system.
Additionally, the system supports compressing the following types of files:
- text/html (.html, .htm)
- application/x-javascript (.js)
- text/javascript (.js)
- text/css (.css)
- application/perl (.cgi)
Enabling System-Level Compression
To enable system-level compression:
- Select Maintenance > System > Options.
- Select the Enable gzip compression check box to reduce the amount of data sent to browsers that support HTTP compression. Note that after you enable this option, you must also configure Web and file resource policies specifying which types of data the system should compress.
- Click Save Changes.