A first difference between OSI and TMN management is that OSI has defined a single management architecture whereas TMN defined multiple architectures at different levels of abstraction. In general it may be a good idea to define multiple architectures. This is particularly true in case each architecture elaborates an additional, orthogonal issue. Care should be taken, however, that the relationship between the various architectures remains easy to understand. In the specific example of TMN's functional and physical architecture, this has been the case.
A second difference between TMN and OSI management is that TMN defines a structure for the multiple levels of management responsibility that exist in real networks; OSI management does not provide such structure. The TMN structure is known as the `Logical Layered Architecture'. The advantage of having such a structure, is that understanding and distinguishing the various management responsibilities becomes easier.
A third difference between TMN and OSI management is that, as opposed to OSI, TMN suggests a conceptual separation between the network that is managed (the telecommunication network) and the network that transfers the management information (the Data Communication Network, DCN).