Which component allows wireless clients to roam between access points and maintain authentication?

The wireless LAN controller (WLC) is responsible for centralized authentication of users and/or computers on a wireless network. When a wireless device is roaming, the WLC is responsible for maintaining the authentication between access points. A basic service set (BSS) is normally served by a single WAP for a single SSID. An extended service is used when two or more WAPs provide coverage for one or more SSIDs. The service set ID (SSID) is a friendly name beaconed to wireless clients so the client can be configured to associate and/or authenticate.