Roaming Decision Simulator
Walk a client past several APs and watch when it scans, roams or clings to a weak AP. Change the roam trigger and hysteresis, switch 802.11k, v and r on and off, and see sticky clients, a coverage gap and ping-pong.
How to use this tool controls and what to look for
Choose a route and a client, press Play, and watch when the client scans, roams, or clings to a weak AP.
Controls to change
- Route: choose Corridor, 4 APs, Office loop, 5 APs, Corridor with a coverage gap, or Standing between two APs.
- Client: choose a Typical phone, a Sticky laptop or an Eager client.
- Roam trigger: set the signal level at which the client starts looking for a better AP.
- Hysteresis (how much better): set how much stronger the new AP must be.
- 802.11k neighbour reports (network and client): switch 802.11k, 802.11v and 802.11r on and off.
- Security: compare Personal (PSK) with Enterprise (802.1X, PEAP).
- ▶ Play: walk the route, or drag the slider beside it to any point.
What to look for
- The client decides when to roam, not the AP. A low roam trigger makes it sticky.
- A hysteresis that is too small makes the client ping-pong between two APs when standing between them.
- 802.11v suggestions help only clients that follow them. 802.11k cuts the time spent scanning.
- With 802.1X, 802.11r shortens each roam a lot. Check the time cut off while roaming.
About this tool
When does a Wi-Fi client roam, and why does it sometimes cling to a weak AP or bounce between two? Walk a client along a corridor, around an office, through a concrete lobby with poor coverage or back and forth between two APs, and watch the signal from every AP, the roam trigger and the hysteresis gap as it goes. Try a typical phone, a sticky laptop or an eager client, change their settings, and switch 802.11k neighbour reports, 802.11v BSS transition management and 802.11r fast transition on and off. Every scan and roam is listed with the frames exchanged and how long the client was cut off.
What you'll learn
- Why the client, not the AP, decides when to roam, and what the roam trigger and hysteresis do
- How a sticky client happens, and how 802.11v suggestions help clients that follow them
- Why a hysteresis that is too small makes a client ping-pong between two APs
- What 802.11k saves when scanning, and how much 802.11r shortens each roam with 802.1X
Common questions
Who decides when a Wi-Fi client roams?
The client. IEEE 802.11 defines the frames for scanning, reassociating and suggesting a move, but not when a client should roam. Each vendor chooses its own roam trigger, hysteresis and scan timing, which is why phones and laptops on the same network behave so differently.
What is roaming hysteresis?
The margin by which another AP must be stronger before the client moves, for example 8 dB. It stops the client flipping back and forth between two APs of similar strength. Too large a margin, together with a low roam trigger, makes a sticky client.
Does 802.11v force a client to roam?
No. With BSS transition management the AP can suggest a better AP, but the client decides whether to follow it. Many clients do; some laptops ignore suggestions and stay put.
Free for private and educational use. This interactive model is a simplified teaching aid and may contain mistakes. It is provided as is, without warranty. Use it to understand the concepts, not as a substitute for a site survey, vendor documentation or professional design advice.