Wireless network can be arranged in one of these three logical configurations-

For the purpose of security these three can be narrowed down to just two: Distributed and Centralized. A distributed architecture, as the name implies, distributes security functions to multiple devices while a centralized architecture collapses security functions into one device. A distributed architecture may consist of standalone “fat” access points, where the AP itself contains all functionality for wireless LAN operation. A distributed architecture may also consist of a controller with “thin” APs when the security functions of the wireless LAN are broken up between multiple devices. For example, if an AP performs encryption, the controller performs authentication, and an external firewall performs access control, this is a distributed system from a security standpoint. A centralized system, on the other hand, places all security functions in a single unit. In the example just given, encryption, authentication, and access control would all be done by a single controller in the centralized architecture. A centralized architecture is always made up of “thin” APs and a central controller. These architectures will be re-visited in each section below to provide comparison and contrast between the capabilities of each.