The Background of Networking
The first real networks emerged in the nineteenth century. They were telegraph networks dedicated to routing messages around the world. In technical terms they used a primitive form of message switching.. “Voice telephony” was invented, in 1876, by the Scotsman Alexander Graham Bell. This was, and remains, the major breakthrough in telecommunications. The first automatic switching system was invented soon after in 1879. However, initially the telephone networks were based on manual switching by human operators. By the beginning of the 20th century, automatic switching systems began to be widely deployed. These systems were based on electro-mechanically controlled switches, which continued to be the basic switching technology until well into the 1970s. Voice networks are circuit switched networks. A dedicated path (circuit) is established and maintained between the communicating parties for the duration of the call.
Data networking is a much more recent innovation. The first modems were invented in the late 1950s. Modems took advantage of the telephone networks of the time, but, by current standards, transmission speeds were a very slow 300 bits/sec (compare that with today’s rates of up to 10 gigabits/sec – that’s 10,000,000,000 bits/sec!). At that time the networks were based on analogue transmission technology and used mechanical switches. Two major developments transformed this networking environment. Firstly came the digitisation of the major elements of the telephony networks. Digital transmission, based on Pulse Code Modulation (PCM), was complemented by digital switches controlled by simple computers. Secondly, dedicated switching technology was developed for data communications. Initially two different approaches were adopted for data communications. Circuit switching networks, based on the same principle as the telephone network, were developed in the late 1970’s. This had limited success. The alternative approach, “packet switching” has, until now, been the ubiquitous approach to data switching. Packet switching works on the assumption that data is divisible into discrete elements known as packets. Each packet has the address of its destination on the network and is then routed across the network using this address. The distinction between packet and circuit switching is that there is no dedicated physical path maintained across the network in packet switching.
The digitisation of networking technology has led to dramatic improvements in the capacities of networks. From the modem capacities of the late 1950s capacities have now risen to the point where individual data streams of 10Gbits/sec are possible. The combination of computerised control for switches and digital transmission technology has led to a new generation of networks that are capable of supporting both voice and data services. This will enable new and advanced services to be delivered.
