Networks

What to expect

This chapter discusses the history of computer networks, from the ARPANET to the present day.

“It seems reasonable to envision, for a time 10 or 15 years hence, a ‘thinking center’ that will incorporate the functions of present-day libraries together with anticipated advances in information storage and retrieval. The picture readily enlarges itself into a network of such centers, connected to one another by wide-band communication lines and to individual users by leased-wire services. In such a system, the speed of the computers would be balanced, and the cost of the gigantic memories and the sophisticated programs would be divided by the number of users.”

Joseph Licklider, 1960

TL;DR.

In this chapter we looked back at the creation of the internet and then the world-wide-web. We learned that in the 1960s, computers in university campuses like ULCA were joined together in a Local Area Network (LAN). Then in 1969 the first Wide Area Network (WAN) was created between UCLA and Stanford, as part of the ARPANET project. This network was made possible by the design of Interface Message Processors known as IMPs, which can be considered the first routers because they joined two LANs together to make a WAN. The principle of abstraction can be seen in the ARPANET design: the IMPS take care of networking so the computers don’t have to.

These early routers implemented packet switching, the process of breaking up data into chunks and routing it across a network, the packets potentially taking different routes, to be re-assembled at the other end, which differs from circuit switching used in traditional telephone networks. This is a key strength of the ARPANET, allowing it to grow quickly and perform reliably.

To make the newly-networked computers useful, ARPA’s visionary director during the 1970s, Joseph Licklider also drove development of time-sharing, the principle of allowing multiple programs to run on one computer, which is a key feature of all modern operating systems.

In 1983 the ARPANET adopted a set of standard protocols created by Vint Cerf called TCP/IP. Protocols are rules of communication that enable very different computers to communicate. Protocols are arranged in layers with each layer performing a single job. At the top is the application layer where email sits, and later, websites displayed by the browser. Throughout the 80s the internet was mostly used by universities and the military, using text-only services like email, FTP and Usenet. Home users arrived on the internet in the early 90s thanks to the first commercial ISPs including AOL and Compuserve.

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Tim Berners-Lee invented HTML in the 80s and combined this with TCP/IP to create the World Wide Web (WWW) which was made freely available in 1993. This technology allows a browser to download and display pages from a web server anywhere in the world. The WWW has grown rapidly since then and as a result around 59% of the world’s population is now online.

It’s important to draw a clear distinction between the internet: a global network of networks, the cables, satellite links, switches and routers that join computers together, and the world wide web: the collection of websites, apps and services that make use of the internet to do useful things.

In the next chapter we will look at some of the implications of the internet and the WWW, including threats such as SQL Injection and malware, and developments such as cloud computing.

References

Refs for Networks…

[130] The Sputnik Surprise, DARPA website link

[131] Memo to the Intergalactic Computer Network, Kurzweil link

[132]  https://www.wired.com/2012/04/epicenter-isoc-famers-qa-cerf/

[133] Coding In Paradise: Original Program Announcement for Mother of All Demos

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[134] https://home.cern/news/opinion/computing/open-internet-and-web

[135] Courtesy of William Lau (Lau 2017, ibid)

[136] “Hacking the Curriculum”, Livingstone & Saeed, John Catt Educational Ltd, 2017.

[137] NCCE Resources, KS4 Networks, Lesson 5 Activity http://ncce.io/netw-5-a5-w

[138] NCCE Resources, KS4 Networks, Lesson 3 Activity http://ncce.io/netw-3-a3-w