| nua_client_methods_t | Methods for client request |
| nua_client_request | Each handle has a queue of client-side requests; if a request is pending, a new request from API is added to the queue |
| nua_dialog_usage | Base structure for dialog usage |
| nua_handle_preferences | NUA preferences |
| nua_handle_s | NUA handle |
| nua_server_request | Server side transaction |
| nua_session_usage | Session-related state |
| nua_usage_class | Virtual function pointer table for dialog usage |
| register_usage | REGISTER usage, aka nua_registration_t |