Roaming Capacity Calculator
Work out roam events per second, concurrent roams and RADIUS authentication load, with and without 802.11r fast transition.
Inputs
Roam Events per Second
1.67
Effective Roam Time
50ms
Roams in Flight at Any Instant
0.083
Full RADIUS Authentications per Second
0.08
Roams per AP per Minute
3.33
Step by step
Values used
Mobile clients = 500 clients; Roams per client per hour = 12 roams/h; Full 802.1X roam time = 120 ms; 802.11r fast transition enabled = Yes; Access points = 30 APs
Roaming Capacity
roams per second = clients × roams per hour ÷ 3600; roams in flight = roams per second × roam time (Erlang-style concurrency).
Roam Events per Second
= 1.67
Effective Roam Time
= 50 ms
Roams in Flight at Any Instant
= 0.083
Full RADIUS Authentications per Second
= 0.08
Roams per AP per Minute
= 3.33
How it works
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.
Formula
Roaming Capacity
roams per second = clients × roams per hour ÷ 3600; roams in flight = roams per second × roam time (Erlang-style concurrency).
- effectiveRoamMs
- Capped at 50 ms when 802.11r caches the PMK
- radiusAuthsPerSecond
- Only ~5% of roams need a full EAP exchange under 802.11r
Frequently Asked Questions
How is Roaming Capacity calculated?
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.
Why does Roaming Capacity matter?
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.
What values do I need to enter?
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.