NPL network

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The NPL Network or NPL Data Communications Network was a local area computer network operated by a team from the National Physical Laboratory in London that pioneered the concept of packet switching. Following a pilot experiment during 1967, elements of the first version of the network, Mark I, became operational during 1969 then fully operational in 1970, and the Mark II version operated from 1973 until 1986. The NPL network, followed by the wide area ARPANET in the United States, were the first two computer networks that implemented packet switching. The NPL network was designed and directed by Donald Davies.



In 1965, Donald Davies, who was later appointed to head of the NPL Division of Computer Science, proposed a national data network based on packet switching in Proposal for the Development of a National Communications Service for On-line Data Processing. After the proposal was not taken up nationally, during 1966 he headed a team which produced a design for a local network to serve the needs of NPL and prove the feasibility of packet switching. [1] The design was the first to describe the concept of an "Interface computer", today known as a router. [2]

The next year (1967) a written version of the proposal entitled NPL Data Network was presented by Roger Scantlebury at the Symposium on Operating Systems Principles. It described how equipment ( nodes ) used to transmit signals ( packets ) would be connected by electrical links to re-transmit the signals between and to the nodes, and interface computers would be used to link node networks to so-called time-sharing computers and other users. The interface computers would transmit multiplex signals between networks, and nodes would switch transmissions while connected to electrical circuitry functioning at a rate of processing amounting to mega-bits. [3] [4] [5] [6] [7] [8] In Scantlebury's report following the conference, he noted "It would appear that the ideas in the NPL paper at the moment are more advanced than any proposed in the USA". [9] [10] [11] [12] [13]

Packet switching

The first theoretical foundation of packet switching was the work of Paul Baran, in which data was transmitted in small chunks and routed independently by a method similar to store-and-forward techniques between intermediate networking nodes. Davies independently arrived at the same model in 1965 and named it packet switching. [14] [15] He chose the term "packet" after consulting with an NPL linguist because it was capable of being translated into languages other than English without compromise. [16] Packet switching was used to produce an experimental network using a Honeywell 516 node. According to Zakon, NPL under Davies was the earliest organisation that created a packet switching network. [3] [17] [9] [18]

Network development

Following a pilot experiment during 1967, [19] [20] [21] [22] Davies gave the first public presentation of packet switching on 5 August 1968. [23] Elements of the first version of the network, Mark I, became operational during 1969 then fully operational in 1970, and the Mark II version operated from 1973. [3] [4] [24] The NPL team also carried out simulation work on the performance of packet networks, including datagram networks. [25] [26] The local area NPL network and the wide area ARPANET in the United States, were the first two computer networks that implemented packet switching. [27] [28]

The NPL network was later interconnected with other networks, including CYCLADES via the European Informatics Network in 1976. [3] The NPL network used a line speed of 768 kbit/s in 1967. [21] [22] Influenced by this, the proposed line speed for ARPANET was upgraded from 2.4 kbit/s to 50 kbit/s and a similar packet format adopted. [29] [30] [31] In 1976, 12 computers and 75 terminal devices were attached, [32] and more were added. The network remained in operation until 1986, influencing other research in the UK and Europe. [33] [34] Alongside Donald Davies, the NPL team included Derek Barber, Roger Scantlebury, Peter Wilkinson, Keith Bartlett, and Brian Aldous. [35]

Protocol development

The first use of the term 'protocol' in a data-commutation context occurs in a memorandum entitled A Protocol for Use in the NPL Data Communications Network written by Roger Scantlebury and Keith Bartlett in 1967. [36]

NPL was also involved in internetworking research. Davies, Scantlebury and Barber were members of the International Networking Working Group which developed a protocol for internetworking. [37] [38] [39] Connecting existing networks creates a "basic dilemma" since a common host protocol would require restructuring the existing networks. NPL connected with the European Informatics Network (Barber directed the project and Scantlebury led the UK technical contribution) [40] [41] [42] by translating between two different host protocols. While the NPL connection to the Post Office Experimental Packet Switched Service used a common host protocol in both networks. NPL research confirmed establishing a common host protocol would be more reliable and efficient. [43] The EIN protocol would serve to launch the ISO standard. [44]

Modern recognition

NPL sponsors a gallery about "Technology of the Internet" at The National Museum of Computing. [35]

See also

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