Do a simple google search on the Inventions that changed the world, and I bet, you would find ‘Internet’ featuring in every damn list out there. It is the modern wonder. The phenomenon that transformed the world, and propelled the human race into the Information age.

But do you truly know how does it actually work? For the sake of “that last cat video you saw on your Instagram”, follow along and be enlightened.

The birth

It all began as a research exercise when a team of scientists were assigned the task of connecting computers of the US defense’s “Advanced Research Projects Agency” (ARPA) for the smooth exchange of information.

What’s more interesting, they were told to design it in such a way that the communication between the US military officers would continue even in the event of a nuclear attack. So, instead of having a centralized point from where all information could flow, they designed a distributed mesh network of computers, split the data into smaller units called packets, and sends it in all direction possible.

It was the task of every computer in the path to route the packet to the correct destination, and the destination computer would assemble it back to form the original message.

And.. You guessed it right.. It worked !!!

The system became known as the ARPA-NET, and it is now widely regarded as the father of the modern Internet.

The data flow

But hang on, how does the data flow from one end to another? What is the medium? In which form does the data gets transformed? Well, the short answer is, Science.

We all understand that the computers can only understand binary data (the 1’s and 0’s). It can store binary data by magnetizing materials or trapping electrons or burning a reflective surface using lasers.

But the same principles won’t work as is in the transportation of binary data. We need to improvise. And so we did. Over the years, we have mastered several ways to transport binary information.

Using electricity: Electricity (yes, the force that was regarded as the God’s fury upon the world) has come to our rescue more than we can count.

Say we connect two ends with a copper wire, attach a switch at one end and a bulb at another. Now, the sender can turn the switch on, and the bulb at the receiver end will be illuminated, and that can signal 1. To send Zero, the sender turn the switch off.

So far so good. But how can we send multiple 1’s or multiple 0’s simultaneously? To do that, we need to introduce a system of timers. Say we agreed to send one bit per second. So, if the bulb was on for say 3 consecutive seconds, then the sender has sent three 1’s. If the bulb was switched off for 4 consecutive seconds, then the sender has send four 0’s.

Like this we can communicate binary data from one place to another. Sending gigabytes of data at the bit rate of (one bit per second) will take ages to reach to the destination. So, we need to increase what’s called our bandwidth (the maximum transmission capacity of a device).

A different measure of speed is the latency (the amount of time it takes for a single bit to reach to the destination).

All set then, no but hey, wait a second, what kind of wires do we use to send these electrical signals? How far will they be able to carry it? The ones that we use in our offices and homes is called Ethernet cable. It is relatively cheaper but could only carry electrical signals over a few hundred feet. Post that there will be a measurable signal loss. That is precisely the reason why they are only used for a small area network (typically LAN).

To send binary data across oceans and continents, across really long distances, we need a different system of transmission that doesn’t incur signal loss over long distances. In comes Fiber Optics cable and inside it travelling at the speed of 3 * 10⁸ m/s is none other than Light.

Using Light: We know light can travel really fast. It can be sent across long distances in a Fiber Optics cable which is a wire made up of glass designed to reflect light up and down inside it, until it is received at the other end. By sending different light beams at different bounce angle, we can send multiple bits simultaneously, all of them travelling at the speed of light.

The data transmission through fiber optics cable is supremely fast, and it does not incur any signal loss, perfect for sending data across the globe.

But it is very expensive and hard to work with. Only the big players can afford it. Hence, you would still find Ethernet cables in offices and educational institutes.

Here’s a map of hidden submerged network of Fiber Optics Cable which connects the world, and provides Internet worldwide. Quite an astonishing sight to behold, a testimony of our engineering prowess.

All right, so we covered the wires part. But, the world has now something better to offer. The wireless connectivity which lead to Mobile Internet and WiFi, and with that we move into the world of Radio Waves.

Using Radio Waves: The mark of real progress made into any technical field is often established by the measure of how well that technology is faring into the common households or into the hands of the common public. Radio technology has evolved and was brought to the homes of the common public long before the computers. Remember the days of 70s, 80s and even the early 90s, the era before television, when Radio channels were our only electronic source to receive information besides the physical printing press.

But how does a wave carry binary information? The 1’s and 0’s? The answer lies in the two attributes of any wave. Amplitude and Frequency. Simply put, the Amplitude is the height of the wave, and frequency is how close those waves are with each other. By using a technique called modulation (in which we vary either Amplitude and Frequency), we can encode binary information in a wave. They became known by the name Amplitude Modulation (AM) and Frequency Modulation (FM).

But Radio Waves cannot travel long before they get completely jumbled up with other radio waves and disturbances. The information transmitted through them gets lost at long distances. That is the reason why you can never hear your neighboring city’s radio stations.

So, the wireless technology still relies on the wired network for long range data transmission. Your mobile or laptop sends the radio signals to your WiFi router, which then converts the data back into electrical signals or light to transmit through Ethernet or Fiber Optics cables. (Cool, isn’t it?). The internet has gone mobile at-least in the short range :)

The future prototypes are fascinating. One day, we (or our grand-children) will get WiFi from a flying giant balloons or drones, and the world of wires will become a page in history.

The control

Who controls the Internet? Which government or private player controls all these Fiber Optics cables that lay beneath the ocean floors? Well, no single entity private or otherwise controls the entire net. That’s the beauty of it. Every player has the partial control, and cannot claim monopoly or sovereignty over the entire network.

The Internet is partly controlled by three types of companies.

Tier 1 companies: They are the big companies which has the capital and the appetite to build Fiber Optics cable network across the ocean floors to connect Continents and Nations. They use other Tier 1 companies network for free. They don’t have to pay anyone.

Tier 2 companies: Think of them as the wholesalers. They own regional networks. (Typically Nation wide or State Wide). They will have to pay Tier 1 companies to use their network.

Tier 3 companies: Think of them as the retailers. They are the Internet Service Providers (ISPs) from whom we buy our broadband connections. They give Internet to the end users.

Every player small or big, is motivated to have an end to end connectivity otherwise their service will have less buyers because the utility of the Internet is that every device can talk to any other device on the Internet.

Right so, we talked about the birth, the data transmission and type of companies offering the Internet but how does one device find other device on the Internet? How does data which is broken up into Packets gets assembled at the destination computer? The answer lies in the famous Internet Protocol Suite which every device that intends to be on Internet has to implement.

Internet Protocol Suite

Also known as the TCP/IP protocol suite which is a 4 layer architecture. At each layer sits different protocols that aids the transmission of data in a standardized manner.

The discussion on this topic would need a separate dedicated article, so without going into too much details, I will cover two critical protocols (TCP and IP) which plays vital role in the Internet communication.

TCP is the protocol that breaks the data into smaller packets on the sender machine. It then asks the lower layers to broadcast them through the network.

All the packets are not obliged to follow the same route. If the network is congested, then some of the packets can take different routes to reach to the destination. At the destination end, the TCP protocol assembles the packets into correct order in which they were sent, and sends back the acknowledgment to the sender. If any of the packet got lost in the network, the TCP at the sender end will resend it. This protocol is epitome of reliability, a workhorse, caught into this thankless job.

The last piece of the puzzle is to find the destination computer. Like we have a home address so that a delivery man can find us and deliver mails and goods, every computer on the Internet has an address called IP address. It is nothing but a bunch of numbers, decimal to our eyes but binary for the computers (the poor fellow can’t move past that).

The earlier Internet designers had used 32 bit addressing scheme (called IPv4) which could give 4 billion unique IP addresses but the Internet has scaled to much larger proportions than they had dare imagined, and so now we use a new scheme (IPv6) whose addresses are 128 bits of length, that’s enough to have every sand on earth to have its own unique IP address (Wow, that’s a lot).

IP protocol assigns the destination address to every packet that the TCP protocol has given to it, and forwards them ahead. The packets are then given to special computers on the network called Routers. The job of the router is to choose the efficient path to forward the packet towards its destination in the best suitable way possible.

The physical data transmission mediums and the Internet protocol suite helps us cross the Internet Abyss, and enables us to access the Information that we are looking for!!

Footnotes:

See now you know how this cat video is physically transmitted from the the Install-gram servers to your device.

PS: I restrained myself from giving any India centric details for the sake of keeping this article globally appealing. For the Indian Readers, here’s an amazing Quora answer on how India is connected to the Internet.

References:

Internet 101

Radio Waves Diagrams