Apache Cookbook, 2nd Edition

11.3. Tuning KeepAlive Settings

Problem

You want to tune the keepalive-related directives to the best possible setting for your Web site.

Solution

Turn on the KeepAlive setting, and set the related directives to sensible values:

KeepAlive On
MaxKeepAliveRequests 0
KeepAliveTimeout 15

Discussion

The default behavior of HTTP is for each document to be requested over a new connection. This causes a lot of time to be spent opening and closing connections. KeepAlive allows multiple requests to be made over a single connection, thus reducing the time spent establishing socket connections. This, in turn, speeds up the load time for clients requesting content from your site.

In addition to turning keepalive on using the KeepAlive directive, there are two directives that allow you to adjust the way that it is done.

The first of these, MaxKeepAliveRequests, indicates how many keepalive requests should be permitted over a single connection. There is no reason to have this number set low. The default value for this directive is 100, and this seems to work pretty well for most sites. Setting this value to 0 means that an unlimited number of requests will be permitted over a single connection. This might allow users to load all of their content from your site over a single connection, depending on the value of KeepAliveTimeout and how quickly they went through the site.

KeepAliveTimeout indicates how long a particular connection will be held open when no further requests are received. The optimal setting ...