Rapid developments in computer and information technology continue to expose new requirements for switched data services, e.g. teletext, electronic funds transfer, electronic mail. The features of packet switching make it attractive for many of these new services, and many countries, including the UK, now operate or plan to introduce public packet-switched data networks. But packet switching is a relatively new art, particularly in the realm of public-switched networks, and is itself developing rapidly, driven both by the increasing demand for switched data services and by advances in semiconductor technology. It tends therefore to be the preserve of a relatively small band of specialists. This paper reviews the principles, origins and evolution of packet switching, with particular reference to public-switched networks. The picture emerges of well laid foundations and the prospect of rapid expansion in public packet-switched networks throughout the world. The development of large switches, such as those being developed at BTRL, will play an important part in this.
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