How do the Internet and World Wide Web work?

What's the science behind how the internet actually works?
13 March 2018

Interview with 

Dr Noa Zilberman - Cambridge University


Many of us use the internet everyday, but what actually is it, and how does it work? Tim Revell put this to Noa Zilberman from Cambridge University...

Noa - The internet is a global system that connects all computer networks.

Tim - What does that mean practically? The computer network’s quite abstract but everyone knows how to use the internet at the moment so what are they actually doing when they click on the computer and they access the internet?

Noa - You can think of the internet as the postal delivery service for computers. Let’s say that you have a message that you want to send to someone. You’ve got your application, your software, that is running and is writing this message.

Tim - So this is a bit like email?

Noa - It might be an email, it might be that you are trying to watch some online movie. It might be that you are accessing a website like the Naked Scientists and you want to listen to this podcast, so what you need to do first is to write this message. This message is then handed from your application to the operating system. So, as I mentioned earlier, it might be Windows, it might be Linux, it might be a Mac, it doesn’t matter. But this operating system is the one in charge of taking this message and delivering it the hardware, to the component in your computer that knows how to transmit the message into the network.

Tim - What happens next? Where does the message then go?

Noa - Each computer that is connected to the internet has an IP address - an Internet Protocol address - which is just like your home address, so you have your home address and you have the postcode. If you are trying to access the Naked Scientists website, you know what is the name of the website - you know it’s the Naked Scientists but you don’t know what is the IP address.

To this end, what happens is you need to access a certain service that provides this address to you and it is called DNS - the Domain Name Service. You give it a name and it provides an IP address just like looking up a postcode. You know the address of someone but you don’t know what is the postcode.

In the same manner you get the IP address and the software writes its own message and delivers it to the network. Within the network there are multiple network devices that know how to route the message according to the IP address that is on it.

Tim - This is like I then post my letter through the internet and along the way there are little nodes or, in this analogy, you could match them as people who deliver post. And they then just pass the message onto the next person and, eventually, it gets to the Naked Scientists Website or the person I’m trying to email. Is that about right?

Noa - That’s exactly right. You have your own internet service provider, the one you connect to from home. They take your message and they are the first ones to deliver it to the next network, and the next network, until you get to the last network, the one that might be the BBC network. The BBC knows how to take the message and deliver it to the specific computer.

Tim - So this is how a message from this studio in Cambridge can make it all the way across the world. There’s obviously a big difference between sending a small message, just in terms of the size, and if I’m watching something and streaming something from the BBC website there’s just a huge difference in the amount of data. How do you send such a big package; can the postal delivery system deal with that?

Noa - You simply chop it into smaller messages - that’s it. There is what is called a maximum transmission unit that you can send from a computer into the network.

Tim - Going back to the original internet, how did that differ from today? Nowadays, we can send these massive packages by splitting them up, would we have been able to have sent Game of Thrones through the internet 30/40 years ago when these things were starting off?

Noa - You could have sent it but then you would have waited for ages and ages until it would have arrived. If you are thinking back to the beginning of the internet, which was the “uppernet” in 1969. At the beginning there were only four computers connected to that in UCLA, Stanford, UCSB, and University of Utah. The first message that was sent was just a single word “login.” They sent the letter “l” and everything was fine. They sent the letter “o” and everything was fine. They send the letter “g” and it crashed.

Tim - Well that seems like it wasn’t quite as good then as it is today?

Noa - Yes. The internet today is about 10 thousand times to 100 thousand times faster than the network then and, obviously, more reliable.

Tim - Looking forwards, what can we imagine from the internet in 10, 20 or even 30 years time?

Noa - Thinking about 10, 20 and 30 years time is crazy long in terms of the internet. We can already see new technologies coming in like the Internet of Things (IoT), where almost everything is connected. You already heard probably about your fridge letting you know when you ran out of milk. But you can also see more technological trends such as the integration of computing and storage and networks together. Things that you use to do on the computer are now moving to the network and visa versa. But you can also assume that everything will be much faster, though we can’t be much faster than the speed of light.


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