Limit-at exceeds available bandwidth

RouterOS General
1

Hello everyone!
I have a question i can`t find answer neither on forum or wiki.

On QoS i have more than 50 rules and on all i have set limit-at.
The last 2 days i found that my ISP some times have a big reduction from 198Mbps to 173Mbps (SpeedTest).

The question is… What happens if sum of all limit-at is e.g 180Mbps and you have available 150 or less?
It goes priority first as max-limit?

2

The real available bandwidth is not known to the queue system - the uplink just drops packets which exceed the available bandwidth and provides no feedback about that, as no communication channel for such feedback is available. So the queues always act as if the sum of max-limits of the innermost queues was available.