Tim Newcomb* explains how the internet works, now that its foundation stone, the ARPANET, has just turned 50.
Fifty years ago, the Advanced Research Projects Agency Network (ARPANET), went live as a packet-switching network and the first to implement the TCP/IP protocols that have become the technical backbone of the internet.
But what does that all mean and just what are the steps involved in even some of the basic functions of enjoying the internet?
Dr Cecilia Aragon, Director of the Human-Centred Data Science Lab at the University of Washington in Seattle, explains the steps.
“A great analogy,” she says, “is it is like a telephone network for data instead of voice.”
“Every piece of information you get, when you download an article from the server, there is another human on the other end producing that information.”
“It is broken into packets and sent over wires and made visible on the computer of the person who is reading it.”
Aragon says the step-by-step process of doing something as basic as reading an article on the internet is really not that simple.
Everything starts with a computer, a device already designed to take bits of zeroes and ones and convert them into pixels on a screen, so humans can understand the information.
From there, once that computer launches an operating system, a browser runs on top of that operating system.
The browser serves as a special program designed to collect packets and make connections to other computers to get information.
“The browser sets up a connection between you and somebody else, some other server somewhere else in the world,” Aragon says.
How the internet works
Let’s call this Step One.
To start, your browser sends a request to read the article you’re engrossed in right now via your Internet Service Provider (ISP) that can connect to the internet.
That message included your browser sending a request, with your computer’s Internet Protocol (IP) address, to the server holding all the information from this website, basically saying “I’m interested, send me that collection of packets.”
You may have known the Domain Name Server (DNS) of the internet site you wanted to get information from, but computers think much more in black and white.
That’s where Step Two comes into play, as your browser turns the DNS into an IP address of this website’s server.
Then, Step Three, where your browser requests a Transmission Control Protocol (TCP) connection with the server, basically a permission to send messages happens.
A quick Step Four allows the server to respond to the request by saying “sure, we can send that along” – known as a 200 OK message – or a “sorry, we don’t have those bits any longer,” commonly rendered as a “404 Document Not Found”.
With the conversation started and the request accepted, the really interesting Step Five comes into play, establishing a Hypertext Transfer Protocol (HTTP) that will create levels of packets of information (an FTP server, in contrast, uses the file transfer protocol, another popular protocol that dictates the framework that servers use to operate as part of the internet).
Every packet contains a header of bits of info that tell servers and browsers where the packet needs to go and its purpose.
“It gets very complicated, very quickly,” Aragon says.
“You can think of a packet as a piece of information stored as a series of high and low voltage, essentially binary because all information can be represented in binary form.”
Then comes the really fun part, Step Six, as the packets of information must travel by that TCP protocol.
These TCP packets – collections of bits placed essentially into the digital version of a complex envelope – get transmitted across wires, cables or WiFi in the form of low-volt and high-volt data.
The packets, using the IP address so they know where to go, move from router to router, across cables, fibre optic cables, phone lines and WiFi until they run through however many routers are needed to arrive at your physical location, always moving at the speed of light and generally traversing the world.
Sometimes the packets hit heavily congested areas along the way and must change course and sometimes they can find a direct route back to you.
Every router knows only what it needs to know.
The first router may not know the final destination of the packets of information, but it knows part of the way.
The subsequent router knows the next place it needs to go, and so on until the packets get back to you.
Once the requested packets arrive, Step Seven kicks into place, allowing the browser to convert all those words and images from the packets back into a humanly readable article.
“Some may get lost and be re-sent, but that goes through a number of routers back and forth until it gets back to your ISP and then your ISP sends the packets back to the router through WiFi to a port on your computer and then your browser, which is listening for those packets, takes the data and displays them in a form you as a human can understand,” Aragon says.
“And that is incredibly oversimplified.”
The internet’s uncertain future
The future of the internet isn’t necessarily all good news.
All those internet cables and radio frequencies?
They can be throttled so that information can move at various speeds, hence that whole net neutrality discussion.
Servers can also control how quickly they respond to requests for packets and sometimes websites go down because there is a physical limitation of how many high and low voltage signals a server can sent out at one time.
With physical wires and radio frequencies and their bandwidth limitations, Aragon says we are already now starting to run into some physical limitations.
Even IP addresses, which can account for something in the range of four billion addresses, have met an issue because of the eight billion network-connected devices.
Even at 50 years old, the internet sure looks young compared with what’s coming.
* Tim Newcomb is a freelance journalist. He tweets at @tdnewcomb. His website is timnewcomb.wordpress.com.
This article first appeared at www.popularmechanics.com
