mod_qos is a quality of service (QoS) module for the Apache HTTP server implementing control mechanisms that can provide different priority to different requests.

Control mechanisms are available at the following levels: The module can be useful when used in a reverse proxy in order to divide up resources to different webserver.

The first use case shows how mod_qos can avoid service outage of a web server due to slow responses of a single application.

A single client may open many simultaneous TCP connections in order to download different content from the web server.

mod_qos may help to protect an Apache web server against low-bandwidth DoS attacks by enforcing a minimum upload/download throughput a client must generate.