Packet switching is a technology that routes data on computer networks and communication systems. Packet switching was inspired by the cold war: when a communication system was required that could sustain part of it's infrastructure being destroyed (in a nuclear attack for example) and was still capable of functioning and routing data.
Packet switching does this by building a network of independent nodes (locations) with no centralised "heart" (location) routing the data. Before packet switching networks, in the scenario of a nuclear attack: if the central routing location was attacked and destroyed, it would render the network incapable of routing data. The theory of packet switching aimed to remedy this issue.
Packet switching is comprised of two element:
As described above, each node (location on a computer network) works as a switch. It will receive a packet of data, it will then store the packet of data, it will read the packet header routing information, and then it will decide which node to send the packet to. If one node is not functioning, a packet will be returned to the sender, and the sender of the packet will attempt to route the packet "around" that malfunctioning node. Hence, a packet switching network can function independently and with no central "body".
The idea of packet switching was developed (independently of each other) by two individuals at roughly the same time (1960's). The two individuals were:
Packet switching was first displayed (to the public) in a working demonstration at the National Physical Laboratory in 1968. The National Physical Laboratory went on to develop the Mark I computer network; one of the first working examples of a packet switching network. Donald Davies inspired and built the Mark I computer network.
Paul Baran, on the otherhand, inspired computer scientists at ARPA (US defense agency) to develop ARPANET, another packet switching network. ARPANET and the Mark I network at the NPL were launched at a similar time 1969-1970. While the Mark I network evolved to become the Mark II network, this network was eventually disbanded in 1986. ARPANET, on the other hand, would inspire the creation of NSFNET, which eventually transitioned (1990-1995) to become the modern commercial Internet.
Present day (2014), the Internet is the most popular computer system to use packet switching. However, packet switching has been implemented in numerous computer networks and communication systems, such as: CSNET, CYCLADES, JANET and Telenet.