One of four priorities can be enforced for a QoS class: real-time, high, medium, and low. Traffic matching a QoS policy rule is assigned the QoS class associated with that rule, and the firewall treats the matching traffic based on the QoS class priority. Packets in the outgoing traffic flow are queued based on their priority until the network is ready to process the packets. Priority queuing allows you to ensure that important traffic, applications, and users take precedence. Real-time priority is typically used for applications that are particularly sensitive to latency, such as voice and video applications.