Layered structure approach to network architecture

The needs and principles of network architecture, which consist of the network functional architecture and three kinds of system architectures, are described. The network functional architecture is studied first and then mapped onto system architectures. Network functions are segmented into the transport and intelligent layers so that functional and technological changes can be introduced into the network quickly with a minimum impact on the rest of the network. System architectures refer to actual implementation and are divided into networks, node, and software system architectures. Primary matters of concern in each architecture are discussed