How Does The Internet Work?

Category: Reference

We all take the Internet for granted, using it as naturally as we use electricity or city water. But when you peek under the hood to see what’s really going on out there “in the cloud,” you’ll find an elegantly simple yet infinitely complex system. Read on for a layman's explanation of how it all works...

What Happens When You Click?

I once heard a presentation by one of IBM's top sales reps. He said when people asked him "How do computers work?" he always told them "Just great!" The Internet is a similar story, but I think AskBob readers, since they are smarter and better looking than the average Internet user, should have a better understanding of what happens when you click a link or send an email.

“Internet” stands for “interconnected networks" because it's really a network of networks. The computers in your office are connected in a local network. That network is connected to another network operated by your Internet Service Provider (ISP). The ISPs network is connected to other ISPs’ networks. Those networks may be comprised of many different types of computers. That’s the hardware or physical view of the Internet.

How The Internet Works

A variety of physical media can be used to make the connections: Ethernet cable, telephone or power transmission lines, radio signals (satellite or wifi), and beams of visible light (fiber optics) are all the same to the Internet. The key thing is that a medium be capable of transmitting information according to the protocols of the Internet.

A protocol, on or off the Internet, is a set of rules for doing something. There are fire drill protocols; CPR protocols; dinner-at-the-White-House protocols, and the Internet Protocol. The last is the “IP” in the acronym, “TCP/IP.”

IP determines where data goes and how it travels; TCP makes sure it gets there quickly and intact. The Internet Protocol is the set of rules followed to deliver data from point A to point B on the Internet based on the destination machine’s IP address. TCP stands for Transmission Control Protocol; it is the set of rules followed to ensure fast, error-checked transmission of data between two points on the Internet.

IP Addresses and the Domain Name System

An IP address such as 69.167.177.104 is similar to the address written on a postcard. Applying the rules of the Internet Protocol to an IP address should get data from the sending (host) machine to the one with that IP address. These addressing and routing rules are found in the Domain Name System (DNS).

The core of the DNS is a huge, two-column table of domain names and IP addresses. When you type “askbobrankin.com” into your browser’s address bar, here is what happens:

The browser sends “askbobrankin.com” to a DNS server along with a request: “What’s the IP address that corresponds to ‘askbobrankin.com?’” The DNS server consults its table and sends the answer, if it has one. If the DNS server can’t find the answer, it sends the request to a higher-level DNS server that has more names and addresses. The request keeps getting kicked up to a higher level DNS server until the answer is found, if it exists. In the whole wide world, there are only 13 “root” DNS servers that know every name and address pair; most DNS requests are resolved (successfully answered) at much lower levels.

When your browser receives the correct IP address, it sends a request for Web content to that address using the HTTP or HTTPS protocol. (The latter specifies that certain security measures be taken to protect the privacy of communications; see below). When the Web server at that IP address gets the request, it collects the requested data and sends it back to the requesting browser’s IP address.

So let me clear up a misconception (or at least a misnomer) here. You don’t really “go to” a Web page, and likewise, there are no “site visitors.” Web pages come to you in response to your browser's requests, just as packages come to you from Amazon in response to your purchase orders. To use the physical mail analogy, it's like sending a postcard from New York to Paris, asking for a picture of the Eiffel Tower. Someone in Paris receives that request, and sends back a postcard with the photo. You've gotten the photo of the Eiffel Tower, but you never actually visited Paris.

A Web page may consist of thousands or millions of bytes of data. They don’t all arrive at once in one huge package. The data your browser requests is broken up into blocks of 1,000 to 1,500 bytes. Each block is packaged with header and footer information that specify where it’s going, what larger body of data it comes from, and where it fits in the jigsaw puzzle of blocks that will have to be re-assembled at the destination address.

Data blocks rarely follow each other in single file over the same path from a server to the machine that requested them. Instead, each packet of data is sent along the path of least resistance (fastest speed) by each router that handles it on its way back to you. So that postcard in my analogy would actually be torn into bits, each labelled with the destination address, and then re-assembled upon arrival.

The illusion that you are visiting a website in Paris, London or Rome is created by software. Or if you prefer, magic. Clarke's Third Law states: "Any sufficiently advanced technology is indistinguishable from magic."

What About Security?

In theory, any data travelling across the Internet can be seen by persons who have access to the computers or routers in the local network or Internet backbone. On a public wifi connection, you are even more exposed, because everything you can see in your web browser or email program is also visible to others on the same wifi network. In practical terms, that means everyone in the same coffee shop, airport lounge, library or hotel.

The answer is encryption. When the web address shown in your browser says HTTPS instead of HTTP, that means your data is encrypted before hitting the Internet. To anyone who might be "sniffing" it will appear as a random jumble of numbers and letters.

The HTTPS protocol combines HTTP with a security protocol called TLS/SSL. Actually, TLS (Transport Layer Security) is a modern, more secure replacement for SSL (Secure Sockets Layer), but both are commonly used and so appear together. Using digital certificates and public key encryption technology, TLS/SSL first authenticates the destination server, verifying that it is indeed “askbobrankin.com” and not a malware-spewing imposter. Then an encrypted “tunnel” is created between the destination server and the requesting host machine, through which data is exchanged safe from eavesdropping. The math involved is mind-bogglingly complex, but that need not concern mere mortals.

All the extra activity of authentication, encryption and decryption of data adds overhead to an Internet communication stream and the machines on each end. The Web may seem a bit slower but the added security and privacy are more than worth the sacrifice.

I hope that give you a better idea of what's happening under the hood and in the cloud, while you surf the Web, chat with friends and exchange emails. Your thoughts on this topic are welcome. Post your comment or question below...

 
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Most recent comments on "How Does The Internet Work?"

(See all 22 comments for this article.)

Posted by:

Michael
27 Jun 2014

What's the difference between the Internet and the WWW? With an internet connection can parts of the Internet which are outside of the WWW be accessed? With a browser?


Posted by:

Tony
27 Jun 2014

I second Cheryl's comment and am particularly impressed by her 97 year old mum with whom I share an interest in learning for as long as I remain upright.

For me your detailed explanation of the internet was TMI (too much information) and also I think your comment that your subscribers are good looking is a generalisation if not an exaggeration :)


Posted by:

Daniel
27 Jun 2014

Excellent. I would guess that part of the internet protocols is that the machines all agree to speak the same language. That way they understand each other just like we understand each other better when we speak the same language.

My question regards a quote: "Data blocks rarely follow each other in single file over the same path...." Does this change when using HTTPS and or a VPN?

My reason is trying to understand why my solutins to a problem worked. One of our banks will not allow a secure connection unless I turn off one of our ISP's at the router. My guess has been that the bank was recognizing some of the data packets was coming from two different ISP's. My solutions was to install a switch that allows me to disconnect one of the ISP's from the router and then reconnect when we're finished with that bank. Of course, if we were to upgrade our router to have connection tracking.


Posted by:

tom mcdonald
27 Jun 2014

Thanks Bob,
A great and clear explanation. I'm going to save this so when my grandchildren ask me how does the Internet work I'll give them a copy of this article!
Tom


Posted by:

RandiO
27 Jun 2014

I had always thought of the internet as the "Muhammed going to the Mountain" concept: Now you are telling me that it is more of a "Mountain coming to the Muhammed" corollary, which seems so inefficient. I will never again tell someone to "Go and Google it"! Argh!
Your next tutorial should educate us, the pretty people, on GoogleNow voice/speech recognition (in 52 languages) before I get that all screwed up at its current early stages!


Posted by:

Rochelle
27 Jun 2014

Great, Bob! would you consider making a diagram of this, maybe 2 related diagrams, so we can have it handy? I would like to present it in a talk to my computer users' club.


Posted by:

David
27 Jun 2014

OK, now explain how those packets get created, how the routers decide which is the best path, and how my computer puts them all into the proper order. Then explain how people write the code for all of this, and how the routers can do it all in 4.2psec while listening to everyone else. I can program a little bit, but I think magic is an apt description. Or perhaps Dr. Forbin is in a room somewhere.


Posted by:

Peter Ballantyne
27 Jun 2014

Bob, I have been using the Internet since it first started, and I kinda know, in a general sort of way, how it all works. But that is the best straightforward and easy to understand presentation of it all that I have ever read. As I read your article it reminded me all over again of the incredible thing we all now take for granted so easily. Many thanks.


Posted by:

Janet Slivinski
27 Jun 2014

That sure is a great article. I am not sure how much of it will stay in my brain but while I was reading it I thought I understood most of it or just some of it. Thanks for all you do.
Jan
PS I am not too good with the computer.


Posted by:

Jim
28 Jun 2014

Thanks, Bob, very useful. I am also curious about how the internet is administered and financed. Who does the design, development, management, quality control, and who pays them/how are they paid?


Posted by:

Nancy
28 Jun 2014

Bob, this was so helpful to read. Thanks for explaining it in such a simple, concise way.


Posted by:

Lloyd
28 Jun 2014

What a great explanation of such a complicated subject. Please ignore negative comments and follow through as asked by David.


Posted by:

intelligencia
28 Jun 2014

@Tony

Lighten Up a Bit!

Mr. Rankin always provides us with things that are not "TMI" in my book as there are plenty of us who enjoy any and all information given (as we absorb how the Internet works)!
This only works for our own edification and enlightenment on whatever topic Mr. Rankin chooses to share with us.

Also: I happen to be good-looking . . . And?

i


Posted by:

Gail
29 Jun 2014

Your answers are always so informational, interesting and fun to read. That's why I've been reading your articles for over 10 years. Thanks!


Posted by:

Kathi
30 Jun 2014

So where are the 13 ROOT servers and who controls them?

EDITOR'S NOTE: See http://www.lmgtfy.com/?q=where+are+the+13+ROOT+servers+and+who+controls+them :-)


Posted by:

David
30 Jun 2014

Tony said, "your comment that your subscribers are good looking is a generalisation if not an exaggeration :)"

That is certainly not the case for all of us. :)


Posted by:

Thorsteinn
01 Jul 2014

Thanks Bob, very interesting
Thorsteinn


Posted by:

Don
04 Jul 2014

Hi Bob, thanks for a good article. But I'm a little disappointed because I think you stopped just short of discussing the info that people like me really don't understand and are really curious about, once they know it exists.
DNS servers. Where are they, how many? And more importantly, who decides all that? Can anyone have a DNS server? and especially the root DNS servers. Who decided who would have them and where they would be?
I went to that cute little link you set up in someone else's question, and the first article I read said there are NOT 13 - its more like 130, and they are all over the world. Who authorized that? Who owns them? Who maintains them?
Is all this controlled by the US government or the defense department?
And perhaps most important of all, the same article I read said there is really only 1 master server that controls all the root servers. My god, that must ben the most important machine in the history of mankind!
Where is that and who owns and controls it? If it got nuked would that mean the internet would be dead, perhaps forever? I'll stop, because this is beginning to scare me.
Don


Posted by:

Mary Ann
13 Jul 2014

Bob, can you discuss VPNs in more detail? I'm interested in Hotspot Shield VPN which allows users to access foreign TV programs or blocked TV programs like AlJazeera English. Someone on a blog mentioned that his computer is set for the UK and can watch BBC, ITN, Sky, etc.

I am not clear about how to set up and use a VPN.

Thanks.


Posted by:

Butch Kemper
13 Jul 2014

The Domain Name Service system is simply complex :) I think Bob's description is good start to explain a complex system constructed from simple components.

The IANA is global coordinator of the DNS root. A complete explanation of the DNS root system is here: with lots of additional pages. The information contained on this website is very technical and cryptic but is helpful.

The 13 root servers are administered by 13 separate organizations and through the magic of IP Multicast protocol, each organization will duplicate their server at multiple strategic locations in the Internet. See the map at for more information.

A very good description of the DNS system can be found at which will answer many of Don's questions.

Butch


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