ATM falls into the category of rooted data and rooted control planes. An application acting as the root would create c_root sockets and counterparts running on leaf nodes would utilize c_leaf sockets. The root application will use WSAJoinLeaf to add new leaf nodes. The corresponding applications on the leaf nodes will have set their c_leaf sockets into listen mode. WSAJoinLeaf with a c_root socket specified will be mapped to the Q.2931 ADDPARTY message. The leaf-initiated join is not supported in ATM UNI 3.1, but will be supported in ATM UNI 4.0. Thus WSAJoinLeaf with a c_leaf socket specified will be mapped to the appropriate ATM UNI 4.0 message.