The web server must provide a clustering capability.

The web server may host applications that display information that cannot be disrupted, such as information that is time-critical or life-threatening. In these cases, a web server that shuts down or ceases to be accessible when there is a failure is not acceptable. In these types of cases, clustering of web servers is used. Clustering of multiple web servers is a common approach to providing fail-safe application availability. To assure application availability, the web server must provide clustering or some form of failover functionality.