Priority queuing (PRIQ) is a queuing policy that divides traffic into different priority levels. At an abstract level, it is essentially the same as the priority queue you may have learned about when studying data structures in computer science. Items are being pushed into the queue; when an item is pulled from the queue, it is always the highest priority item. This continues until the queue is empty.
Implementations of priority queuing differ in the number of levels, but in pfSense, there are seven levels, with seven being the highest priority. This is a flat hierarchy of priority levels. On each interface, priority queues are scanned for packets in descending order of priority. The highest priority queue is scanned first, ...
