Roaming Capacity Calculator
Work out roam events per second, concurrent roams and RADIUS authentication load, with and without 802.11r fast transition.
About Roaming Capacity Calculator
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
Worked example
With the default values below, Roaming Capacity Calculator returns Roam Events per Second of 1.67. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Mobile clientsaccepts 1–200,000 clients
- 500 clients
- Roams per client per houraccepts 0–600 roams/h
- 12 roams/h
- Full 802.1X roam timeaccepts 5–3,000 ms
- 120 ms
- 802.11r fast transition enabled
- Yes
- Access pointsaccepts 1–5,000 APs
- 30 APs
Results
- 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
Step by step
- 1Values used
- 2Roaming Capacity
- 3Roam Events per Second= 1.67
- 4Effective Roam Time= 50 ms
- 5Roams in Flight at Any Instant= 0.083
- 6Full RADIUS Authentications per Second= 0.08
- 7Roams per AP per Minute= 3.33
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
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.