Possible scenarios
Some possible scenarios are necessary or considered as contexts where it is a good practice to employ QoS in a network firewall. Let's explore two common scenarios.
Controlling hosts' and users' bandwidth usage
When sharing the same WAN connection across more than one host, it is a good idea to keep some control to avoid a single user consuming all the available bandwidth. A simple way to do that is by applying rules that will limit the maximum bandwidth that each user will have available.
Protocol prioritization
With the massive usage of VoIP and other streaming technologies, it is becoming rare to see someone use a PBX extension with a regular voice line. So, it is very important to prioritize packets for these kinds of application. For example, if there are 20 VoIP packets and 1 for HTTP, the firewall may send out 10 VoIP packets, the HTTP packet, and the rest of the VoIP packets. With all sorts of packets passing through our OPNsense...