Work out roam events per second, concurrent roams and RADIUS authentication load, with and without 802.11r fast transition.
Roam events scale linearly with the client population and how much people move. Multiplying the event rate by how long each roam takes gives the number of roams in progress at any instant, which is what the controller and RADIUS server actually have to hold state for. Voice and barcode-scanner traffic breaks above roughly 150 ms of roam time, and a full EAP-TLS exchange on every roam is what pushes past it — 802.11r is the difference between a working warehouse and a silent one.
Roaming Capacity
roams per second = clients × roams per hour ÷ 3600; roams in flight = roams per second × roam time (Erlang-style concurrency).
roams per second = clients × roams per hour ÷ 3600; roams in flight = roams per second × roam time (Erlang-style concurrency). Roam events scale linearly with the client population and how much people move. Multiplying the event rate by how long each roam takes gives the number of roams in progress at any instant, which is what the controller and RADIUS server actually have to hold state for.
Voice and barcode-scanner traffic breaks above roughly 150 ms of roam time, and a full EAP-TLS exchange on every roam is what pushes past it — 802.11r is the difference between a working warehouse and a silent one.
This calculator takes 5 inputs: Mobile clients, Roams per client per hour, Full 802.1X roam time, 802.11r fast transition enabled, Access points. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.