The Internet

by Chris Woodford. Last updated: May 2, 2023.

When you chat to somebody on the Net or send them an e-mail, do you ever stop to think how many different computers you are using in the process? There's the computer on your own desk, of course, and another one at the other end where the other person is sitting, ready to communicate with you. But in between your two machines, making communication between them possible, there are probably about a dozen other computers bridging the gap. Collectively, all the world's linked-up computers are called the Internet. How do they talk to one another? Let's take a closer look!

Photo: What most of us think of as the Internet—Google, eBay, and all the rest of it—is actually the World Wide Web. The Internet is the underlying telecommunication network that makes the Web possible. If you use broadband, your computer is probably connected to the Internet all the time it's on.

What is the Internet?

Global communication is easy now thanks to an intricately linked worldwide computer network that we call the Internet. In less than 20 years, the Internet has expanded to link up around 230 different nations. Even some of the world's poorest developing nations are now connected.

Chart: Countries online: In just over a decade, between 1988 and 2000, virtually every country in the world went online. Although most countries are now "wired," that doesn't mean everyone is online in all those countries, as you can see from the next chart, below. Source: Redrawn by Explainthatstuff.com using data from Figure 1.1 "All online, but a big divide", ITU World Telecommunication Development Report: Access Indicators for the Information Society: Summary, 2003, p.5 (blue bars, 1998–2003) and Percentage of Individuals using the Internet 2000–2021 [XLS spreadsheet format], International Telecommunications Union, December 2022 edition (2010 and 2021, green bars). Please note that the horizontal (year) axis is not linear beyond the blue bars.

Lots of people use the word "Internet" to mean going online. Actually, the "Internet" is nothing more than the basic computer network. Think of it like the telephone network or the network of highways that criss-cross the world. Telephones and highways are networks, just like the Internet. The things you say on the telephone and the traffic that travels down roads run on "top" of the basic network. In much the same way, things like the World Wide Web (the information pages we can browse online), instant messaging chat programs, MP3 music downloading, IPTV (TV streamed over the Internet), and file sharing are all things that run on top of the basic computer network that we call the Internet.

Artwork: "Information superhighway": The Internet is like a global road network on which many different kinds of traffic can travel. Much of it seems one way—from distant computers (servers) into your home—but in reality the traffic is always two-way.

The Internet is a collection of standalone computers (and computer networks in companies, schools, and colleges) all loosely linked together, mostly using the telephone network. The connections between the computers are a mixture of old-fashioned copper cables, fiber-optic cables (which send messages in pulses of light), wireless radio connections (which transmit information by radio. waves), and satellite links.

Chart: Internet use around the world: This chart compares the estimated percentage of households with Internet access for different world regions and economic groupings. For each region or grouping, the lighter bar on the left shows the percentage for 2015, while the darker bar shows 2019. Although there have clearly been dramatic improvements in all regions, there are still great disparities between the "richer" nations and the "poorer" ones. The world average, shown by the black-outlined orange center bars, is still only 57 out of 100 (just over half). Not surprisingly, richer nations are well to the left of the average and poorer ones well to the right. Source: Percentage of Individuals using the Internet 2000–2019 [XLS spreadsheet format], International Telecommunications Union, 2020.

What does the Internet do?

The Internet has one very simple job: to move computerized information (known as data) from one place to another. That's it! The machines that make up the Internet treat all the information they handle in exactly the same way. In this respect, the Internet works a bit like the postal service. Letters are simply passed from one place to another, no matter who they are from or what messages they contain. The job of the mail service is to move letters from place to place, not to worry about why people are writing letters in the first place; the same applies to the Internet.

Just like the mail service, the Internet's simplicity means it can handle many different kinds of information helping people to do many different jobs. It's not specialized to handle emails, Web pages, chat messages, or anything else: all information is handled equally and passed on in exactly the same way. Because the Internet is so simply designed, people can easily use it to run new "applications"—new things that run on top of the basic computer network. That's why, when two European inventors developed Skype, a way of making telephone calls over the Net, they just had to write a program that could turn speech into Internet data and back again. No-one had to rebuild the entire Internet to make Skype possible.

Photo: The Internet is really nothing more than a load of wires—metal wires, fiber-optic cables, and "wireless" wires (radio waves ferrying the same sort of data that wires would carry). Much of the Internet's traffic moves along ethernet networking cables like this one.

How does Internet data move?

Circuit switching

Much of the Internet runs on the ordinary public telephone network—but there's a big difference between how a telephone call works and how the Internet carries data. If you ring a friend, your telephone opens a direct connection (or circuit) between your home and theirs. If you had a big map of the worldwide telephone system (and it would be a really big map!), you could theoretically mark a direct line, running along lots of miles of cable, all the way from your phone to the phone in your friend's house. For as long as you're on the phone, that circuit stays permanently open between your two phones. This way of linking phones together is called circuit switching. In the old days, when you made a call, someone sitting at a "switchboard" (literally, a board made of wood with wires and sockets all over it) pulled wires in and out to make a temporary circuits that connected one home to another. Now the circuit switching is done automatically by an electronic telephone exchange.

If you think about it, circuit switching is a really inefficient way to use a network. All the time you're connected to your friend's house, no-one else can get through to either of you by phone. (Imagine being on your computer, typing an email for an hour or more—and no-one being able to email you while you were doing so.) Suppose you talk very slowly on the phone, leave long gaps of silence, or go off to make a cup of coffee. Even though you're not actually sending information down the line, the circuit is still connected—and still blocking other people from using it.

Packet switching

The Internet could, theoretically, work by circuit switching—and some parts of it still do. If you have a traditional "dialup" connection to the Net (where your computer dials a telephone number to reach your Internet service provider in what's effectively an ordinary phone call), you're using circuit switching to go online. You'll know how maddeningly inefficient this can be. No-one can phone you while you're online; you'll be billed for every second you stay on the Net; and your Net connection will work relatively slowly.

Most data moves over the Internet in a completely different way called packet switching. Suppose you send an email to someone in China. Instead of opening up a long and convoluted circuit between your home and China and sending your email down it all in one go, the email is broken up into tiny pieces called packets. Each one is tagged with its ultimate destination and allowed to travel separately. In theory, all the packets could travel by totally different routes. When they reach their ultimate destination, they are reassembled to make an email again.

Packet switching is much more efficient than circuit switching. You don't have to have a permanent connection between the two places that are communicating, for a start, so you're not blocking an entire chunk of the network each time you send a message. Many people can use the network at the same time and since the packets can flow by many different routes, depending on which ones are quietest or busiest, the whole network is used more evenly—which makes for quicker and more efficient communication all round.

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What are "clients" and "servers"?

There are hundreds of millions of computers on the Net, but they don't all do exactly the same thing. Some of them are like electronic filing cabinets that simply store information and pass it on when requested. These machines are called servers. Machines that hold ordinary documents are called file servers; ones that hold people's mail are called mail servers; and the ones that hold Web pages are Web servers. There are tens of millions of servers on the Internet.

A computer that gets information from a server is called a client. When your computer connects over the Internet to a mail server at your ISP (Internet Service Provider) so you can read your messages, your computer is the client and the ISP computer is the server. There are far more clients on the Internet than servers—billions of them, if you count smartphones!

Artwork: Ordinary computers ("clients"), like the one you're using right now, communicate with more powerful ones ("servers") that hold things like web pages, emails, and so on. This is called client-server computing. Clients can also communicate with other clients. This is called peer-to-peer (P2P) communication.

When two computers on the Internet swap information back and forth on a more-or-less equal basis, they are known as peers. If you use an instant messaging program to chat to a friend, and you start swapping party photos back and forth, you're taking part in what's called peer-to-peer (P2P) communication. In P2P, the machines involved sometimes act as clients and sometimes as servers. For example, if you send a photo to your friend, your computer is the server (supplying the photo) and the friend's computer is the client (accessing the photo). If your friend sends you a photo in return, the two computers swap over roles.

Apart from clients and servers, the Internet is also made up of intermediate computers called routers, whose job is really just to make connections between different systems. If you have several computers at home or school, you probably have a single router that connects them all to the Internet. The router is like the mailbox on the end of your street: it's your single point of entry to the worldwide network.

A brief history of the Internet

Precursors

• 1844: Samuel Morse transmits the first electric telegraph message, eventually making it possible for people to send messages around the world in a matter of minutes.
• 1876: Alexander Graham Bell (and various rivals) develop the telephone.
• 1940: George Stibitz accesses a computer in New York using a teletype (remote terminal) in New Hampshire, connected over a telephone line.
• 1945: Vannevar Bush, a US government scientist, publishes a paper called As We May Think, anticipating the development of the World Wide Web by half a century.
• 1958: Modern modems are developed at Bell Labs. Within a few years, AT&T and Bell begin selling them commercially for use on the public telephone system.

1960s: Preparing for a global network

• 1964: Paul Baran, a researcher at RAND, invents the basic concept of computers communicating by sending "message blocks" (small packets of data); Welsh physicist Donald Davies has a very similar idea and coins the name "packet switching," which sticks.
• 1963: J.C.R. Licklider envisages a network that can link people and user-friendly computers together.
• 1964: Larry Roberts, a US computer scientist, experiments with connecting computers over long distances.
• 1960s: Ted Nelson invents hypertext, a way of linking together separate documents that eventually becomes a key part of the World Wide Web.
• 1966: Inspired by the work of Licklider, Bob Taylor of the US government's Advanced Research Projects Agency (ARPA) hires Larry Roberts to begin developing a national computer network.
• 1969: The ARPANET computer network is launched, initially linking together four scientific institutions in California and Utah.

1970s: The modern Internet appears

• 1971: Ray Tomlinson sends the first email, introducing the @ sign as a way of separating a user's name from the name of the computer where their mail is stored.
• 1973: Bob Metcalfe invents Ethernet, a convenient way of linking computers and peripherals (things like printers) on a local network.
• 1974: Vinton Cerf and Bob Kahn write an influential paper describing how computers linked on a network they called an "internet" could send messages via packet switching, using a protocol (set of formal rules) called TCP (Transmission Control Protocol).
• 1978: TCP is improved by adding the concept of computer addresses (Internet Protocol or IP addresses) to which Internet traffic can be routed. This lays the foundation of TCP/IP, the basis of the modern Internet.
• 1978: Ward Christensen sets up Computerized Bulletin Board System (a forerunner of topic-based Internet forums, groups, and chat rooms) so computer hobbyists can swap information.

1980s: The Internet gives birth to the Web

• 1983: TCP/IP is officially adopted as the standard way in which Internet computers will communicate.
• 1982–1984: DNS (Domain Name System) is developed, allowing people to refer to unfriendly IP addresses (12.34.56.78) with friendly and memorable names (like google.com).
• 1986: The US National Science Foundation (NSF) creates its own network, NSFnet, allowing universities to piggyback onto the ARPANET's growing infrastructure.
• 1988: Finnish computer scientist Jarkko Oikarinen invents IRC (Internet Relay Chat), which allows people to create "rooms" where they can talk about topics in real-time with like-minded online friends.
• 1989: The Peapod grocery store pioneers online grocery shopping and e-commerce.
• 1989: Tim Berners-Lee invents the World Wide Web at CERN, the European particle physics laboratory in Switzerland. It owes a considerable debt to the earlier work of Ted Nelson and Vannevar Bush.

1990s: The Web takes off

• 1993: Marc Andreessen writes Mosaic, the first user-friendly web browser, which later evolves into Netscape and Mozilla.
• 1993: Oliver McBryan develops the World Wide Web Worm, one of the first search engines.
• 1994: People soon find they need help navigating the fast-growing World Wide Web. Brian Pinkerton writes WebCrawler, a more sophisticated search engine and Jerry Yang and David Filo launch Yahoo!, a directory of websites organized in an easy-to-use, tree-like hierarchy.
• 1995: E-commerce properly begins when Jeff Bezos founds Amazon.com and Pierre Omidyar sets up eBay.
• 1996: ICQ becomes the first user-friendly instant messaging (IM) system on the Internet.
• 1997: Jorn Barger publishes the first blog (web-log).
• 1998: Larry Page and Sergey Brin develop a search engine called BackRub that they quickly decide to rename Google.
• 1999: Kevin Ashton conceives the idea that everyday objects, and not just computers, could be part of the Internet. This idea is now known as the Internet of Things.

2000s: Internet and Web for all

• 2003: Virtually every country in the world is now connected to the Internet.
• 2004: Harvard student Mark Zuckerberg revolutionizes social networking with Facebook, an easy-to-use website that connects people with their friends.
• 2006: Jack Dorsey and Evan Williams found Twitter, an even simpler "microblogging" site where people share their thoughts and observations in off-the-cuff, 140-character status messages.
• 2017: Russian president Vladimir Putin approves a plan to create a private alternative to the Internet to counter the historic dominance of the (traditional) Internet by the United States.

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On this website

• BitTorrent
• Broadband
• History of communication
• History of computers
• IPTV
• Modems
• Voice Over Internet Protocol (VOIP) (covers Internet telephony and Skype)
• Wireless Internet
• World Wide Web (WWW)

Books

General overviews

• A History of the Internet and the Digital Future by Johnny Ryan. Reaktion Books, 2013. A wide-ranging look at how Internet technology is changing everything from culture and politics to shopping and war.
• The Master Switch: The Rise and Fall of Information Empires by Tim Wu. Atlantic, 2010. How the open Internet we know and love is threatened by monopolization—amd what we can do about it.
• The Future of the Internet—And How to Stop It by Jonathan Zittrain. Yale University Press, 2008. Why an "open" Internet is better than a "closed" one dominated by proprietary technologies.
• The Internet: A Historical Encyclopedia by Christos Moschovitis, Hilary Poole, Laura Lambert, and Chris Woodford. ABC-Clio, 2005. A comprehensive (though now slightly dated) three-volume guide to the history and impacts of the Internet and the people who made it possible. (I was the author of the second of the three volumes, covering social impacts.)
• Who Controls the Internet? Illusions of a Borderless World by Jack Goldsmith and Tim Wu. Oxford University Press, 2006. Will governments be forced to regulate the Internet as it challenges our traditional conception of a geographically divided world? Quite dated, but still interesting.
• A Brief History of the Future: Origins of the Internet by John Naughton. Phoenix, 2000/2014. Dated, but worth a look for the early history.

Basic technical guides

• The Internet For Dummies by John R. Levine and Margaret Levine Young. Wiley, 2015. The title uses "Internet" in its most general way. This is actually a guide to going online that would most suit older people or those who've barely used a computer before.
• TCP/IP For Dummies by Candace Leiden, Marshall Wilensky. Dummies/Wiley, 2009. One of the simpler introductions to the Internet protocol. However, you might find the light-hearted writing style offputting.

More technical

• TCP/IP Unleashed by Karanjit Siyan, Tim Parker. Sams, 2002. A more serious treatment than the Dummies book.
• TCP/IP Network Administration by Craig Hunt. O'Reilly Media, 2002. A much more detailed guide to TCP/IP for computer networking students and professionals.

Articles

• Think Local About the Digital Divide by Shira Ovide, The New York Times, December 3, 2020. Exploring some practical solutions to Internet inequalities in the United States.
• 'Digital divide' will worsen inequalities, without better global cooperation: UN News, 4 September 2019. The Internet offers unprecedented opportunities, but there's a risk the benefits are moving disproportionately to richer, better-connected nations.
• Net's founding father Dr Larry Roberts dies aged 81: BBC News, 31 December 2018. Looking back on the life and achievements of one of the Internet's inventors.
• Why Russia is Building Its Own Internet by Tracy Staedter. IEEE Spectrum, January 17, 2018. Could Russia really build its own Internet—and why would it want to?
• Bridging a Digital Divide That Leaves Schoolchildren Behind by Cecilia Kang. The New York Times. February 23, 2016. Lack of Internet access is punishing children's education, even in richer nations like the United States.
• Internet access is 'a fundamental right': BBC News, 8 March 2010. Some 80 percent of the world's people think access to the Internet is a fundamental right.
• Superpower: Visualizing the Internet: BBC News, January 2010. What are the world's top websites in search, social networking, retail, and media. Some great interactive graphics.
• Overhaul of net addresses begins: BBC News, 4 February 2008. How the world ran out of IP addresses, prompting the development of IPv6.
• The Tech Lab: Vint Cerf: One of the Internet's founding father's explains how the Internet has developed and where it's going next.

Facts, statistics, and reports

• World Bank: Digital Development: If you're interested in how the world is going online, and how the international community is making efforts to improve Internet access in developing countries, the World Bank is a good place to start your research. You'll find lots of useful reports, facts, charts, and statistics.
• Measuring the Information Society 2018: The latest report from the ITU-T marks an important milestone: more than half the world is now, finally, online.
• Measuring the Information Society 2015: Another recent International Telecommunications Union report, with global and regional analysis of Internet trends (particularly in developing countries), and some discussion of the Internet of Things.
• World Telecommunication/ICT Development Report 2010: Monitoring the WSIS targets: 9th Edition, 2010: A detailed report from the International Telecommunications Union that charts the spread of telephone and Internet technology around the world.
• Internet World Stats: A good collection of tables and charts showing patterns of Internet use around the world.
• Our World in Data: The Internet: Well-digested, well-presented summary of world Internet use.