# QoS DSCP AF Class Comparisons

I'm having trouble wrapping my head around DSCP AF Classes and what--all else being equal--gets dropped first.

I understand packets are given a Class, 1-4. The higher the Class number, the higher priority that packet gets. I must assume that higher priority means lower chance of being dropped.

Is this assumption correct: Higher Class = Higher Priority = Lower chance of being dropped?

I also understand that packets are given a drop precedence, 1-3... and in this case the lower the drop precedence, the lower the chance of being dropped.

During congestion, does higher Class traffic have precedence over lower Class traffic, regardless of Drop Priority?

If so, this leads to the absolutely counter-intuitive scenario where, while AF32 is less likely to be dropped than AF13 (32 > 13), AF32 is more likely to be dropped than AF31 (despite 32 > 31)... and that's really throwing me for a loop!

• Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer. Dec 21, 2020 at 0:54