The rapid development of wireless and the advent of fixed mobile convergence have brought deployment of small wireless environment such as femtocell, which can connect Internet or network easily at home and office. Users must be authenticated from the Authentication, Authorization and Accounting (AAA) server to use the Internet or network at home and office. As diameter-based AAA uses TCP/SCTP at the transport, the diameter-based AAA server will have a limit on the number of clients if the interworking of small clients increases. Consequently, the performance will reach its peak and therefore the extension or enlargement of server will be required. This paper proposes an efficient interworking method between diameter-based clients, agent and server upon study of AAA mechanism.