Hi,
A QoS rule associates a class to a session when it is established. It means that the traffic in both directions will have the same class, since they are part of the same session. Separately from that, traffic is subject to the interface QoS profile when it goes out through that interface. Your 2 interfaces could have different profiles, which means that class 2 on one interface could be guaranteed 15 Mbps, while class 2 on the other interface could be guaranteed 10 Mbps, or any other limit you want to set.
The 15 Mbps guarantee would apply to all class 2 traffic on that interface. I don't know about the exact algorithm used for QoS, but the way I see it is that your class 2 traffic will come out of your interface before any lower priority traffic waiting in a queue to be sent, up to a quota of 15 Mbps. Over that limit, the traffic will not have priority until the next second (or whichever time unit is used internally by the algorithm to calculate bandwidth limit).
I assume here that your class 2 traffic has priority set to high in your QoS profile, versus medium for the rest of the traffic.
Regards,
Benjamin
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