LEAP is Cisco's implementation of 802.1x. The RADIUS authentication is the method Cisco picked to implement. There is no set method spelled out in 802.1x for authentication (i.e. RADIUS, TACACS, KERBEROS, etc.) The 802.1x protocol was placed to support port based security on switches. The newer draft standard will be an extension of the 802.1x within the 802.11 protocol suite. (In a nut shell: LEAP is 802.1x for Cisco wireless)