15.1.1 Network Configurations

First we have to consider some network elements in order to configure an information transmission system. A transmission medium must exist between an information server and the client as shown in Figure 15.1. This medium does not merely mean cables for wiring or air for propagating radio signals. It includes various components such as transmission and switching devices. Optical transmission and multiplexing functions such as SDH systems provide broadband services. Moreover, switching and cross-connect systems such as ATM and add and drop multiplexer (ADM) contribute to the reduction of network cost for carriers and consequently to a reduction in the charges made to customers. Figure 15.2 gives an example of an actual network configuration where computers transmit and receive information. An access network connects the customer premises with a carrier building. An access system and a router are included in this network. The information delivered to the carrier building is transferred to a transmission and switching system, and it travels over a long-distance network. Domestic and international networks...