We take the Internet for granted now, but it is not that long ago that it did not exist at all. Disabled from birth with spina bifida, Adrian Stokes, OBE was one of the people who helped build it: a celebrated “Internet pioneer”. He was, for example, responsible for setting up the first email service in the UK and so the first transatlantic email system, as well as providing the service linking other universities in the UK to the network making it work as a network of networks in different countries.
He worked on ARPANET, the precursor to the Internet. It was a research project funded by the US department of defence exploring the future of communication networks. Up to that point there were global networks but they were based on what is called circuit switching. Think of an old fashioned telephone exchange, Each person had a direct line – an electrical circuit – connecting them to the operator. When you talked to the operator and asked to talk to someone over the phone, the operator would plug a wire that connected your line to theirs, making a new direct circuit from you to them. When you talked, your voice was converted to an analogue signal (a changing electrical signal) which passed down that wire – along the circuit. Transatlantic telephone cables even allowed circuits, so phone calls, to be set up between countries. Early computers connected to each other, sending data over phone lines in this way by converting them into sounds.
ARPANET worked differently to a circuit-based system. It was a packet switched network. It worked by treating data sent over a network as binary, just as the computer itself does internally. This contrasted with the analogue system then used to send sound over early phones. Importantly, the binary data being sent was divided up into fixed size groups of bits called packets. Each packet was then sent separately over the network. In this system there is no fixed circuit from source to destination that the data travels down, just lots of different computers connected to each other, On receiving packets of data each computer or node of the network passes it on to another until eventually it arrives at the target computer. A key advantage to this is that each of those packets can go by a different route, travelling between different computers. They can even arrive out of order, The data no longer travels along a single circuit. The packets are put back together (in the right order) on reaching the destination, reconstructing the original so that the fact it was ever split up is invisible to the person receiving the data. Extra information is added to the packets beyond the actual data to make the system work: such as a destination address to indicate where it is going to and the number of the packet so the order can be reconstructed if they do arrive out of order. Managing the packets and their journey to the destination is done by software implementing a protocol (a set of communication rules agreed between the computers on the network, that allows them to interpret the streams of bits arriving from other computers).
So ARPANET consisted of a series of computers that acted as nodes of the network. Each had to be programmed with software to run the protocol, passing packets on in their journey to the destination and pulling the original data out and reconstructing it if that computer was their destination. UCL were working with the ARPANET team, exploring how to make it work across continents, so had to program one of their computers to make it an ARPANET node. Once done it could connect to the ARPANET via a satellite link in Norway.
At first, the ARPANET was set up as a way just to access data on other computers as though it was on your own local computer. However, other services could be provided on top of the basic protocols. It just amounts to writing code for your node’s computer to turn data into packets and interpret the data in packets arriving in the way needed for the new application. For example, a way to access files on other computers as though they were on yours were added. Much, much later of course code to allow communication through a web page service was written and the world wide web was born to sit on top of the Internet.
This was one of the jobs Adrian Stokes did. He wrote code for the UCL computers that could treat packets of data as email messages rather than just files. Users could write messages and send them to people on other computers on ARPANET without them needing to know where they actually were. It was the first UK email service.
Once UCL had a link to the ARPANET, they could also extend ARPANET. One of Adrian’s other jobs was in managing onward links around the UK, creating a UK ARPANET network. Researchers in other UK universities could set up their own computers as ARPANET nodes (write and run the software on their computer) and then connect their computers to the UCL one. Networks their computers were linked to could then also connect to the ARPANET. In doing so they created a UK ARPANET network but one that was also connected to the full ARPANET via the UCL computer. It meant, for example, that anyone on the ARPANET in the US could (with permission as UCL added password protection to their node – the first on the ARPANET!) access the powerful IBM System 360/195 computer at the Rutherford and Appleton Labs in Oxfordshire. ARPANET became a transatlantic network of connected networks. Any of those UK universities could also then connect to any computer anywhere on the ARPANET. Their packets just went to the UCL one and then to the US via the satellite link, before being forwarded onwards to other US computers. If these UK university computers had the programs for the file transfer or email services, for example, then they could seamlessly use them to access files anywhere else or send messages to anyone else connected to the ARPANET anywhere.
ARPANET ultimately turned into what we now call the Internet. No single person invented the Internet, it was a massive team effort with lots of people involved each responsible for getting some part of it to work. Those like Adrian who played a critical part in making it work, however, have been recognised as “Internet pioneers”: those who can justifiably claim they were part of the team that invented the Internet, and transformed all our lives as a result.
– Paul Curzon, Queen Mary University of London
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