Controllerless Networks

Maybe I don't fully understand the fundamentals, but there is a question.

There is an option "bandwidth contract" on IAPs.

On what step does it apply?

1. The IAP takes the client traffic normally (the only prioritization on this step is Fair Access and Preferred Access), then cuts it's and sends it further with limited bandwidth.

2. Or does the IAP somehow cut the traffic before the full receiving?

The question is about - what is the goal to restrict the bandwidth?

Is it for proper utilization of internet connection, or is it for proper utilization of the IAP's resources or/and RF?

A bandwidth contract limits client traffic after it is decrypted by the access point at the ip layer.  Fair and preferred access provides more fairness in the AIR, not the ip layer.  You would use a bandwidth contract if you want to limit the effect that types of traffic have on your network.  You would use airtime fairness when you have alot of 802.11ac and 802.11n clients and you suspect that legacy clients are slowing their traffic down.

None of these options really matter if your RF is poor.  The best strategy is to make sure that your RF is good, so that everyone can access the data they need.  If your internet or local bandwidth is very limited, bandwidth contracts and limit the impact of unwanted traffic when bandwidth is limited.