Professor Nigel Linge FROM PACKET SWITCHING TO THE CLOUD Telecommunication engineers have always drawn a picture of a cloud to represent a network. Today, however, the cloud has taken on a new meaning, where IT becomes a utility, accessed and used in exactly the same on-demand way as we connect to the National Grid for electricity. Yet, only 50 years ago, this vision of universal access to an all- encompassing and powerful network would have been seen as nothing more than fanciful science fiction. he first electronic, digital, network - a figure that represented a concept of packet switching in which stored-program computer 230% increase on the previous year. data is assembled into a short se- was built in 1948 and This clear and growing demand for quence of data bits (a packet) which heralded the dawning of data services resulted in the GPO com- includes an address to tell the network a new age. missioning in July 1970 an experi- where the data is to be sent, error de- T mental, manual call-set-up, data net- tection to allow the receiver to confirm DATA COMMUNICATIONS 1 work that used modems operating at that the contents of the packet are cor- These early computers were large, 48,000bit/s (48kbit/s). rect and a source address to facilitate cumbersome and expensive machines However, computer communica- a reply. and inevitably a need arose for a com- tions is different to voice communi- Since each packet is self-contained, munication system that would allow cations not only in its form but also any number of them can be transmit- shared remote access to them. its nature. Whereas a voice call has a ted over the same physical network, An obvious candidate for such a clearly defined beginning and end with one after the other, with each poten- system was the national telephone a reasonably continuous transfer of in- tially representing a totally different network but that had been designed formation in between, remote access and separate communication. In the and optimised for the transmission of to a computer is a much more sporadic USA these concepts were taken for- the human voice and not the digital bi- form of communication. Therefore ty- ward by the Advanced Research Proj- nary digits used by computers. Conse- ing up a telephone line continuously ect Agency (ARPA), which, under the quently, the Modulator/Demodulator between a user and computer is an un- guidance of Larry Roberts, developed or modem was designed to convert the necessary waste of resources because, its ARPAnet network for linking com- computer's data bits into signals that for much of the time, no data is being puters in North America. The first could be accepted and transmitted by sent. four computers were connected to the the telephone network. The Datel Mo- An alternative approach was need- ARPAnet in December 1969 and by dem No. 1A became available within ed and both Donald Davies at the Na- 1970 the network was extended inter- the UK in 1964 and was capable of tional Physical Laboratory (NPL) in nationally with a satellite link to the transmitting data at a rate of 200 bits the UK and Paul Baron at the RAND Goonhilly earth station in Cornwall per second (bit/s). Corporation in the USA were working and from there via undersea cable to By March 1969, the GPO reported on precisely that. In the mid-1960s the NORSAR seismic research facility that 3,334 modems were in use on its they both independently invented the in Kjeller, Norway. Meanwhile back #% !!" !! 9ROXPH3DUW #$%!&'()*+,!'-!#$%!.*/#.#(#%!'-!#%,%0'11(*.0+#.'*/!2)'-%//.'*+,/ in the UK, Donald Davies and his team built the NPL Data Communication Network, which became operational in July 1971 as the world's first packet switching local area network. Connecting the UK to ARPAnet was achieved on 25 July 1973 when, under the direction of Professor Peter Kirstein of University College London, the first data packets were exchanged between University College London and the Information Sciences Institute in Cali- fornia. Whilst this connection used a satellite link operating at 9.6kbit/s, it was actually routed via Kjeller in Nor- The cloud has seen IT become a utility, accessed way where a new earth station had and used in exactly the same on-demand way as we been commissioned that removed the connect to the National Grid for electricity. necessity to use Goonhilly. On the 14 November 1973 the first full public demonstration of ARPAnet in the UK networks called X.75. published their Transmission Control was provided by Professor Kirstein The X.75-based International Protocol and Internet Protocol (TCP/ when he delivered a lecture to the In- Packet Switch Stream (IPSS) Service IP) suite. On 1 January 1983, ARPA- stitution of Electrical Engineers. Also opened in 1978 with an international net adopted TCP/IP as its standard in 1973, Robert Metcalfe was work- exchange located in London and links protocols and in 1991 the ARPAnet ing at Xerox PARC when he invented to data networks in the USA, Canada, morphed into the Internet. a local area packet-switched network Japan and into Europe via Euronet. On called Ethernet. Standardised as IEEE 20 August 1981 the UK, X.25-based, HOME AND OFFICE 802.3 in 1983 and IEEE 802.11 (WiFi) Packet Switch Stream (PSS) service COMPUTING in 1999, Ethernet has become the was opened with switching exchanges These early data networks were used dominant local area network technol- designed using the Telenet TP4000 by companies for business processing ogy with a multi-billion dollar global processors and built by Plessey Con- applications and by the research com- market. trols (Poole). By 1983 customers were munity for remote access to mainframe The work on packet switching at offered a fully digital interface with the computing services. The concept of the NPL and ARPA naturally drew the launch by British Telecommunications using a network for information re- attention of the Post Office which, in (formerly Post Office Telecommunica- trieval purposes as we do today began 1977 establish its trial Experimental tions) of the KiloStream (64kbit/s) and to emerge with the launch of Viewdata Packet Switching Service network. MegaStream (2Mbit/s) services. In services. Post Office Telecommuni- This network comprised three packet 1984 KiloStream was expanded to pro- cations launched the world's first pub- switching exchanges, designed us- vide International KiloStream facilitat- lic Viewdata service called Prestel in ing the Ferranti Argus 700E proces- ed by links provided through satellite March 1979. Customers were able to sor, located in London, Manchester earth stations at Goonhilly in Cornwall use their television sets, linked via a (actually Dial House in Salford) and or Madley in Herefordshire. telephone, to access a central Informa- Glasgow with interconnecting links The development of X.25 was tion Retrieval Centre where data was running at 48kbit/s. Needless to say driven by the telecommunications organised into a series of information that at this time several other coun- companies (telcos) that were seeking pages. Prestel proved very successful tries were developing their own public to establish national public data net- with 80,000 user terminals connected data networks which created an in- works. However, telcos had a phi- by 1988 generating a total of 9.1 mil- centive to harmonise their respective losophy that the network service must lion accesses per week for pages of- designs towards a common network be inherently reliable which led to fered by 1,300 information providers. interface. Consequently, the Interna- the criticism that X.25 was inefficient One of the most popular services was tional Telegraph and Telephone Con- and too complex. A different school Prestel Travel and gateways offered sultative Committee, now the Inter- of thought in network design was access to a broader range of services national Telecommunications Union, emerging from the USA, not driven that included personal banking, train established Study Group VII for the by telcos but by computer scientists. timetables, stocks and shares trading, development of standards relating Their view was that the data network education and even a basic form of to data communications services. In did not need to be inherently reliable email called Prestel Mailbox, which March 1976 it published its Orange providing that the computers using the was launched on 15 October 1984. books which included the specifica- service could detect and correct any Using the television as an access ter- tion of a standard for packet-switched packet errors that occurred in trans- minal for Prestel was logical because wide area networks called X.25 and mission. This work culminated in in the late 1970s domestic customers a standard for interconnecting such 1974 when Vinton Cerf and Bob Kahn simply did not have a computer in !9ROXPH3DUW !! "!! #& THE INTERNET AND ACCESS way beyond the means of a domestic TO THE INTERNET customer. This led Cliff Stanford to The next important advance came in propose a new form of business that March 1989 when Sir Tim Berners- would act as the intermediary be- Lee published his now iconic paper tween the domestic user and the Inter- entitled, "Information Management: A net. He bought leased line access to Proposal" [1], in which he proposed the Internet and then charged custom- an integration of hypertext with the ers a monthly subscription for which Internet to create what he termed the they could have dial-up access via his WorldWideWeb. Information coded company to the Internet. Demon In- as hypertext could be transmitted over ternet therefore became the UK's first the Internet using the hypertext trans- Internet Service Provider when it was By 1970 the network was extended fer protocol (http) and displayed on launched on 1 June 1992.