Roaming in one ESS
Move the client through the same SSID. The network name stays the same, but the active BSSID changes as the client attaches to a different AP.
ESS: Company-WiFi
C
SSID
Company-WiFi
The SSID stays the same across all three APs.
Current BSSID
AA:AA:AA:AA:AA:01
Lobby BSS
Transition
Initial association
The client starts near AP1.