Network management systems which administer actual network resources are developed based on a software system called network management platforms. Network management platforms provide major functions defined in TMN and interfaces to develop network management systems. Our research designs and implements a network management platform suitable to the TMN environment of today and tomorrow. This platform increases the efficiency in handling management information by completely separating Managed Object class information from instance information. In addition, the performance of the platform is significantly improved through a multi-structured MIT and a multi-staged arrangement of the execution of CMIS services. Furthermore, our platform allows a new MIB to be added to the managed system in run-time, solving the problem of having to recompile and restart the network management system. In our research, we develop a new concept of Class Level Filtering, which yields relatively high performance as the MIT becomes larger.