Making an Internet From Scratch Charles Jameson explores the remarkable levels of complexity underlying something we all take for granted — The Internet Computer scientists are remarkably good at not telling anyone what they are doing. Even when their inventions are changing the fabric of our society, you probably will not hear about it. For instance, imagine picking up your phone and searching for an image on Google. This is an incredible power that we have forged for ourselves. But how does this actually happen? Where is that picture stored? How does our phone know where to find it? To make things worse, the internet is constantly changing. There are many twists and turns coming up in this story which will profoundly change how the whole world stays connected, but what chance will anyone have to understand them if we don’t know what we already have? So, in this spirit, take this article as a ‘Last week on…’ catchup of sorts in the TV show that is The Internet. And get ready for the rest of the season, because it’s coming thick and fast. Wi-Fi | Our journey starts by pressing ‘Search’ on a phone to look up a picture. The goal is to reach Google with a request for the picture. But first, that request has to get off the phone. Wi-Fi is a system developed by Australian radio-astronomers in the 1990s. Every modern phone contains a small antenna which can send and receive messages across a certain range of frequencies. Our phones are constantly ‘listening’ for announcements, also known as ‘broadcasts’, from a Wireless Access Point (WAP) to let them know that there is a way to access the internet. The WAP listens for replies from phones and talks to each of them over different radio frequencies. IP Packets | It begs the question, what do these ‘messages’ look like? To operate properly, all of these devices need to agree on what order to send information, bit by bit, so that the recipient knows what they are looking at. The exact layout of this information is called the ‘protocol’, and a single
chunk of this information is called a ‘packet’. For example, one of the first things that is sent in a packet is its intended destination, known as the ‘IP address’. 13 servers scattered across the globe, known collectively as the ‘DNS root zone’, control how domain names like ‘google.com’ get turned into IP addresses. Internet Service Providers | Our message then makes its way out to an ‘Internet Service Provider’ (ISP). These companies create sprawling infrastructure networks across entire countries, with the sole task of receiving packets and getting them where they need to go. The inner workings of each ISP are well-kept secrets, but in general, they calculate efficient routes to get packets across their network. Each ISP will also form business relationships with other ISPs to share packets. These relationships are critical to the internet’s success, as otherwise every ISP’s users would be cut off from the rest of the world. It also prevents ISPs from attracting users with ‘exclusive websites’, since all data is shared across all ISPs. Data Centres | Once our message has found its way to an ISP, it hops from country to country to make its way towards a Google data centre. Data centres are huge warehouses full of millions of computers (‘servers’), each handling different requests. These data centres, now more commonly known as ‘the cloud’, store data, process search requests, show you your photos, and more. Data centres across the world are a grand exercise in engineering, networking, and computation. They handle billions of users, trillions of requests, and quadrillions of pieces of data, and require enormous teams of engineers to manage them properly. There And Back Again | Once Google has processed our request for a photo, how does it reply? It retraces the initial packet’s steps! ISPs remember where your packet came from so immediately know where to send the reply. Once this connection is established, Google can finally send the photo to your phone, packet by packet. Of course, there is a lot of complexity being omitted here. How is this conversation kept private? How are all of the packets, which assemble to make up the picture, sent in the right order? There is a more important question... How Did We Get Here? | The most remarkable mechanism here is not any one invention — it is the nature of the endeavour itself. The internal structure of computers provides engineers with extraordinary permission to place blind faith in each other in the pursuit of ever-larger and ever-faster systems.
32
Making An Internet From Scratch
Lent 2021
