Reassociation Request / Response Frame

Reassociation Request frame can be sent only by the client to access point and is used when the client is already associated to the ESS and wants to associate to another access point.

The follow pictures show the reassociation request frame format and Elements

above the pictures from CWAP

In this logic, the client leaves the coverage area of an access point and needs to associate to another access point offering the same SSID. This roaming station goes through the authentication phase with the new access point, then sends a reassoication request mentioning the old AP MAC address, and finally joins to the new AP, getting a new AID. 

Why not proceed with a simple association request frame?  It is because the logic is that the new access point should contact the old access point and move the parameters for the station from the old AP to the new one. 

A client can be authenticated to server access points, as long as it is associated to only one of them. 

An AP uses the reassociation response frame in response to a reassociation request frame. The reassociation response contains the elements

Above pictures from CWAP

The difference between association frame and re-assoication frame is 

 - With association request/response, the client gets an AID on the local AP

 - WIth reassociation request/response, the client have to move from the old AP to the new AP.