to Network System Modeling -- Layer Structures -- Node Structures -- Modeling Vertical and Horizontal Partitions -- Management and Traffic Systems -- Applying AMLn.The book describes a method for creating models of telecom systems. The method is intended for practicing network architects and designers. This method emphasizes modeling the (very complex) functional structure of networks in a way that is independent of any hardware and software design methodology. The method also allows designers to express their model in two main views: a generic view and a system view that takes protocols and network configuration issues into account. The idea is to retain a stable view (the generic) in the context of constant changes and large variations within the system view. The expected benefits are large savings in telecom systems development and maintenance. The terminology is domain unique, i.e., based on de-facto telecom terminology. All concepts that are used in modeling are well defined. The purpose of using a telecom-oriented terminology instead of industry-standard methods for software and protocol design (e.g., UML and SDL) is to be able to create models that are expressive and intelligible for network architects and designers. Models are created as graphical models that show the functional and physical structure of networks at different levels of details. Information on properties, including behavior is attached to the models. A fairly small set of symbols is used in modeling.