Enabling data compression on an IBM HTTP Server

Answer

The Apache mod_deflate module can be used to improve response time in environments that have low bandwidth and high latency. The Apache mod_deflate module compresses output from your server before the data is sent to the client over the network. You can set the compression level to 3 or 6 to improve response time.

About the operating system versions
These instructions work for both Windows and AIX. The only difference is in how you start and stop the server. Refer to your IBM HTTP Server product documentation for more information.

Typically, the IBM HTTP Server on Windows is installed as a Windows Service, which you can start by using the NET START "<ServiceName>" command. The ServiceName parameter can vary depending on the version of IBM HTTP Server that you have installed. Alternatively, you can start the service from the Services graphical user interface by clicking Start > All Programs > Administrative Tools > Services then right-clicking on the IBM HTTP Server service and selecting Start.

Because it is possible to install the IBM HTTP Server without using a service in Windows, you can also use the following command to start the server on Windows:

    <HTTPServer_installdir>\bin\apache.exe -k start

Before you begin
The mod_deflate module is only available in Apache server version 2.0 and higher.
To verify the server version, use the apachectl -V command.

Procedure
1. Stop the server by running the following command: apachectl stop
2. Create a backup copy of httpd.conf.
3. Open httpd.conf in a text editor.
4. Change the KeepAliveTimeout 10 line to KeepAliveTimeout 60.
Changing the KeepAliveTimeout is useful in high latency environments or in environments with geographically distributed users. A higher KeepAliveTimeout value can prevent timeouts due to slow network traffic.
5. Uncomment the LoadModule deflate_module modules/mod_deflate.so line. If you cannot find the LoadModule deflate_module modules/mod_deflate.so line, in the # Dynamic Shared Object (DSO) Support section, immediately after the # LoadModule foo_module modules/mod_foo.so comment, add the line for the module.
6. Locate the section in the file for adding filters. Immediately under the #AddOutputFilter INCLUDES .shtml comment, add the following lines:

AddOutputFilterByType DEFLATE text/html text/plain text/xml

BrowserMatch ^Mozilla/4 gzip-only-text/html
BrowserMatch ^Mozilla/4\.0[678] no-gzip
BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
#Highest 9 - Lowest 1
DeflateCompressionLevel 3

The compression level is now set to 3, which provides minimal CPU usage and a decent benefit from the compression. You can also set the compression level to 6, which provides even more compression benefit with a small CPU overhead.