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PO outlines its plans for Packet-Switching Network:
Proposals for establishing a packet-switching data transmission network on an experimental basis have now been outlined by Professor J. H. H. Merriman, the Post Office Corporation’s Board Member for Technology. The project, which will be known as the experimental packet-switching service (EPSS), is seen as a joint venture between computer users, manufacturers and the Post Office. It will form part of studies by the Post Office into the development of networks using digital data transmission techniques, in contrast to the analogue technique currently used. Referring to the advantages of packet-switching, Prof Merriman said: “In particular, overall economic advantage is claimed by allowing a large number of low capacity connections to a multi-access computer to be replaced by a single high-capacity connection. “To achieve this will involve both the Post Office and users in additional investment, but the experiment will permit both to assess the overall cost benefits of packet working. In addition, packet working provides improved error performance and enables a terminal working at a particular data rate to communicate with another working at a different data rate”. As the basis of the new service, the Post Office is to set up three packet-switching exchanges (PSEs) which will be interconnected by circuits operating at 48K bits per second. It is currently planned to establish these exchanges in London, Manchester and Glasgow, although Birmingham, Bristol Leeds and Edinburgh are possible alternatives, depending on the location of those taking part in the experiment. (CW 21/09/1972 p21)
PO network to be tested by users:
The important experiment into the feasibility of setting up a national packet switched data transmission network in the UK will start at the end of 1974 and about a dozen organisations have already committed themselves, in principle at least, to take an active part in the evaluation. Last week the Post Office sent out a manual outlining the facilities and requirements of the service to about 100 groups, including large companies, bureaux, manufacturers and universities, together with a ‘letter of intent’ which must be signed by anyone wishing to become a user of the EPSS (Experimental Packet Switched Service). One of the first companies to sign up was British Olivetti, whose DP product manager, Lance English, described the Post Office’s attitude towards open involvement of users from an early stage as ‘an enormous step forward’. Other users who have committed themselves in principle, if not formally as yet, are understood to include BOAC, Edinburgh Regional Computing Centre, Scicon, Data Dynamics, Univac and CRC Information. Although he is aware that there are many difficulties to be ironed out during the experiment, such as the important question of how users will be charged for using the service, Mr English feels that the EPSS ‘makes sense because we must be approaching the limits of the number of data paths available on physical media and packet switching seems to make optimum use of physical resources. This is because in a packet switched network data is transferred in discrete packages preceded by a ‘header’, which includes the address of where the data is to be transmitted and ended by a ‘tail’ containing error checking information. Once entered into the system, the packet reaches its destination via routeing its packet switching exchanges (PSEs) which means that a two-way dedicated line need not be connected between transmission points as with existing circuit switching systems. (CW 1/2/1973 p1)
PDP-11 at the heart of new ‘bleep’ PO service:
At the heart of a new Post Office service which will enable people to be contacted via small radio receivers activated by a telephone call is a 28K byte Digital Equipment PDP-11 at the Reading trunk telephone exchange. Each user of the service will have a portable receiver which will emit a high-pitched ‘bleep-bleep’ signal when a unique 10-digit code is dialled over the public telephone network. At present the service is based at Reading and covers about 500 square miles of the Thames Valley. The PDP-11 is used to check that the 10-digit code is valid and then initiates the relevant radio signal to be transmitted to the paging equipment. The caller is also informed by a recorded message that the paging request has been accepted. In the trial scheme, two signals are transmitted. The first, which lasts for 2.7 seconds, will cause all available receivers to switch on and decode the signal and only those which respond to the first signal will be available for the second tone, which is transmitted for .0.8 seconds. There is a unique combination of tone pairs for each receiver so that only the relevant device will emit a bleep. The user of the service can then take some pre-determined action, such as telephoning the office or home. Future plans for the service, which the Post Office hope will eventually be nationwide, include providing three different types of ‘bleep’ to provide more action options for the user. (CW 25/1/1973 p5)
UK link to ARPA in use by June:
This may have been the start of the Internet in the UK:
The experimental data link between the UK and the Advanced Research Project Research Agency's ARPA network in the US is expected to start operation by June when an Interface Message Processor, IMP, for front-ending the UK side of the operation, is scheduled to become operational at London University Institute of Computer Science. The IMP unit, supplied by ARPA, will eventually be linked in the experiment with the institute's Digital Equipment PDP-9 machine, and to London University’s Control Data 6600 and the IBM 370/195 at the Science Research Council’s Rutherford Laboratory at Chilton. In the experiments, data will be transmitted by high-speed line to a seismic experimental centre in Norway equipped with an IBM 360/44 and then by satellite to the Seismic Analysis Centre, near Washington, DC, which is linked directly to the ARPA network. The UK end of the experiment is being funded largely by the National Physical Laboratory. The IMP is being supplied free of charge, ARPA itself is supplying over £20,000 of computer time, and the Post Office is not going to charge for the use of the direct line to Norway during the first year of operation. The project, which will bring US computing power to the UK ‘within weeks’ of the IMP becoming operational, makes no commitment to provide anyone with computer service, but the NPL obviously have a vested interest in the scheme as they are subsidising it to the tune of about £5,000. (CW 15/2/1973 p2)
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