In the early days of the telegraph signals could be sent on one line only, say between two cities. To change to another line (to reach a third city or local destination) at the telegraph office, the operator had to listen to the first signal, write it down, and then manually key the Morse signal on the other line. Then, in the telephone age, networks were built up in a star topology, which means that all users are connected to a central switchboard. This prevents buildup of N.N 1/=2 connections which would be necessary to connect N users in a network directly. The voice signal of the Public Switched Telephone Network (PSTN), which is analogue, is used. Today, the task of interconnection is done by hardware, but the two main components of a network remain the: End-user connection; plus The exchange points between the lines. In contrast to the fixed-line age today, mobile and satellite connections replace the copper wires and fibre cables. And in contrast to circuit switching of telephone data networks, packet switching is used instead. This means that the data are split up into packages, labelled with the address of the destination, and sent from node to node. The transmission volume of one cable can be shared, and available bandwidth and delay times of the packets vary with the use of the network. Data networks allow a decentralized topology. Internet Service Providers (ISPs), which give access to the customers, are connected to Internet Backbone Providers (IBPs) which can exchange data directly via a third IBP. The exchange points between the different providers are also called ‘peering’, ‘interconnection’ or ‘transit points’.
Digitalization and Digital Revolution
