Common authentication and authorization (AA) between networks having disparate access technologies may enable a seamless user transition between the networks. A set of AA credentials from a user attempting to gain access to one of the networks may be received, and a subscriber database of another of the networks may be used to verify the set of AA credentials. A communication protocol common to the networks may be used. Additionally, the user may employ a single set of authentication and authorization (AA) credentials, usable over multiple communication protocol layers. Further, a user may perform a single authentication and authorization (AA) operation when roaming across two or more networks by gathering user's key material during an AA challenge and reply session at a data link layer. The gathered material may be used for an AA challenge at an upper network layer or another network as the user transitions between networks.