Internet… Net … Web … What is it all about ?
During these times of Social Distancing and Virtual Hangs I started to contact a lot of my friends and family via Video Calling Apps on my phone and computer to have a sense of connection and not totally losing my mind :).
Having lots of free time for thinking at home made me question a lot of things that we take for granted on a daily basis. One such call with my friend Sonali Moholkar got us discussing if we can share these thoughts and she asked what I wanted to share. The first thing I could think of was what is the Internet and how it has make it so easy for us to connect to each other and stay Online with the rest of the world. So this is what I will be talking about today.
What is the Internet ?
Believe it or not but the Internet is actually a result of an experiment for the Defence Department research project call ARPANET ( Advanced Research Project Agency Network). In the 1970s Paul Baran was trying to figure out how to build a system of network communication that could survive a nuclear attack. So instead of having a centralized network his idea was to have a Distributed network and break the messages up into blocks and send them as fast as possible. He along with Vint Cerf and Bob Kahn ( fathers of the internet ) built a nationwide experimental packet network and it was a huge success and it is what we today call the Internet.
Who is in charge of the Internet ?
The internet is a fully distributed system and it is made up of a large number of independently operated networks. There is no central control. Think of these operators to be your ISPs( Internet Service Providers) like Comcast Xfinity, AT&T Internet, Verizon Fios etc. The goal of all the operators is to make sure there is end-to-end connectivity of every part of the network given the goal of the NET is that any device can communicate with any other device similar in many ways to what phone calls. Sharing information at this scale without having to be in the same geographical location as the other person is what has made communication and commerce possible at the global scale. This is what has evolved into web and mobile apps. It is what has made connecting, sharing and contacting what it is today.
What are the building blocks of Internet ?
The Internet is basically a giant mesh of cables that connect the continents together. They are fiber optic cables that use light to transport packets of information from source to destination.
When we have 2 devices that need to communicate you can connect them either physically ( using an ethernet cable ) or using Wireless connections ( famously called WiFi ) or Bluetooth .
Imagine you can connect any device to any other device in a mesh network and communicate. That is the internet.
Now the design philosophy or the protocol that the Internet works is very similar to thinking of how a phone number network or mailing address for our houses work. An address on the internet is a number that is unique to that device. For mailing a letter to a particular address you just need to know the address you want it to be sent to and how to write the address properly so that that letter can be carried by the mailing system to the right destination.
Internet Protocol
The addressing system for devices on the internet use the most important protocols of internet communication called the Internet Protocol or IP. The device address is the IP Address.
So when we are visiting a website what we are actually doing under the hood is sending a message to another computer’s (server’s) IP address along with the IP address of origin address that being the address of your device. Now the other computer (server) will receive the request and send its response to the origin address.
Similar to the home address having different parts to it like street address, house number, city, state zip code etc, the IP address also had parts to it. The traditional IP address is 32 bits long with 8 bits for each part of the address. It is called IPv4 designed in 1973 and was widely adapted in the early 80s and 90s. It provides upto 4 billion unique addresses for devices to connect to the internet. But as the number of devices has increased and the popularity of the internet exceeded expectations we needed to come up with more unique addresses quickly. To solve for this a longer IP address format called the IPv6 which uses 128 bits per address is in use. This can provide upto 340 undecillion unique addresses. To explain that number it is more than enough for every grain of sand on the earth to have its own IP address.
Now you might ask, I never used any funny looking numbers to surf the web or communicate with other devices. So think of the IP address like the phone numbers on our contacts list. We associate the contact’s name with the phone number and address etc to associate who it is. The Internet also has something similar to that. Our device uses the DNS or Domain name System to look up domain names and gets the associated IP address for that device, which are similar to your phone contact names. So think of the DNS as a Directory system which acts as an operator to connect your device to the the website’s IP address that you are looking for.
How does the actually communication happen over Internet ?
Ok so now we understand that there are cables and connections to make communication from one device and another possible. How does the data travel from one device to another ? How to do it reliably as well ?
Information on the internet travels in the form of packets. A packet travels from one place to another a lot like how you might get from one place to another on the road. Lots of conditions impact the journey like traffic and road conditions. For Example Google maps reroutes you based on these factors to the same destination.
Now for the packets itself it is similar to contents that you can put into your vehicle and the packet here is filled with digital information. The size of the packets do matter and have limits to the maximum capacity you can send it one packet. So for a larger data file the file is broken down into smaller pieces and then transported using different packets with the same destination IP address. These packets could all take different routes and reach at different times to the destination. Once all the packets are there, they are reassembled into the complete data file.
The traffic managers of the Internet are called routers that keep the packets moving through the networks. The Router keeps track of multiple paths for sending the packets and it chooses the best path to send it.
What if not all the requested data is delivered to the destination ?
For example let's assume you what to listen to a song on youtube. You request the song on the youtube website. Now the internet protocol makes use of the routers to get packets delivered from the youtube server to your device. To make sure that 100% of that song is delivered to your device we have another protocol called the TCP ( Transmission Control Protocol ). Think of TCP as your inventory manager that takes into account all the items delivered and makes sure that everything requested is delivered. If all the deliveries are there then the TCP signs the delivery sheet and we are good. If there are some packets that are missing from the inventory TCP won’t sign and for every incomplete packet it will request to resent it. Once TCP verifies all the packets needed for the song requested are present it will sign off and your song will start playing.
Routers and TCP system are very scalable and can work with any number of devices. Using principles of fault tolerance and redundancy, the more routers we add the more reliable the internet is.
Based on agreed upon standards for how data is sent around the internet billions of systems and devices CONNECT, COMMUNICATE and COLLABORATE in a seamless fashion. Isn’t that just a beautiful system design :).
Closing Words
There are many topics that I left unexplained to simplify what the internet is. In reality there are different protocols for how the web works and how we see content appear on the websites. The internet being completely open also makes it possible for attacks from hackers. For protection we can add layers of security to our packets of data which work with. These are topics for another blog entry. For today I hope you were able to understand the magnificent system called the Internet and how it is very much a physical system that is connecting the entire world literally one network cable system at a time :).
