How does the internet work?
The data center which can be thousands of miles away from you has your video stored inside it.
how does this data reach your mobile phone or a laptop?
An easy way to achieve this goal would be with use of satellites.
From the data center, a signal could be sent to the satellite via an antenna,
and then from the satellite a signal could be sent to your mobile phone
via another antenna near to you.
However, this way of transmitting signals is not a good idea.
Let's see why.
The satellite is parked nearly 22,000 miles above the earth's equator,
so in order for the data transmission to be successful,
the data would have to travel a total distance of 44,000 miles.
Such a long distance of travel causes a significant delay in receiving the signal.
More specifically it causes huge latency which is unacceptable
for most internet applications
so if this video does not reach you via a satellite then
how does it actually get to you?
Well it is done with the help of a complicated
network of optical fiber cables,
which connect between the data center and your device.
Your phone could be connected to the internet via cellular data or any Wi-Fi router,
but ultimately at some point your phone will be connected
to this network of optical fiber cables
We saw at the beginning that the video you are currently watching
is stored inside a data center.
To be more specific, it is stored in a solid-state device within the data center.
This SSD acts as the internal memory of a server.
The server is simply a powerful computer whose job is to provide you the video or
other stored content when you request it.
Now the challenge is how to transfer the data stored
in the data center specifically to your device via the
complex network of optical fiber cables.
Let's see how this is done.
Before proceeding further we should first understand an important concept
which is the concept of an IP address.
Every device that is connected to the Internet
whether it is a server a computer or a mobile phone is identified uniquely by a
string of numbers known as an IP address.
You can consider the IP address similar
to your home address that is the address, that uniquely identifies your home.
Any letter sent to you reaches you precisely because of your home address.
Similarly in the internet world an IP address acts as a shipping address
through which all information reaches its destination.
Your internet service provider will decide the IP address of your device and you are able to see what
IP address your ISP has given to your mobile phone or laptop.
The server in the data center also has an IP address.
The server stores a website so you can access any website just by knowing the
server's IP address. However, it is difficult for a person to remember so
many IP addresses.
So to solve this problem domain names like
youtube.com, facebook.com etc are used which correspond to IP addresses
which are easier for us to remember than the long sequence of numbers
Another thing to notice here is that a server has the capability of storing several websites
and if the server consists of multiple websites all the websites cannot be
accessed with the server's IP address.
In such cases additional pieces of
information, host headers are used to uniquely identify the website.
However, for the giant web sites like Facebook.com or YouTube.com the entire data
center infrastructure will be dedicated to the storage of the particular website.
To access the internet we always use domain names instead of the complex IP address numbers.
From where does the internet get IP addresses corresponding to our domain name requests.
Well, for this purpose the internet uses a huge phone book known as DNS.
If you know a person's name, but don't know their telephone number
you can simply look it up in a phone book.
The DNS server provides the same service to the internet.
Your internet service provider or other organizations can manage the DNS server.
Let's have a recap of the whole operation.
You enter the domain name,
the browser sends a request to the DNS server to get the corresponding IP address.
After getting the IP address,
your browser simply forwards the request to the data center,
more specifically to the respective server.
Once the server gets a request to access a particular website the data flow starts.
The data is transferred in digital format via optical fiber cables,
more specifically in the form of light pulses.
These light pulses sometimes have
to travel thousands of miles via the optical fiber cable to reach their destination.
During their journey they often have to go through tough terrains
such as hilly areas or under the sea.
There are a few global companies who lay
and maintain these optical cable networks.
These visuals show how the laying of optical fiber cables is done with the help of a ship.
A plow is dropped deep into the sea from the ship,
and this plow creates a trench on the seabed and to which places the optical fiber cable.
In fact, this complex optical cable
network is the backbone of the Internet.
These optical fiber cables carrying the
light are stretched across the seabed to your doorstep where they are connected to a router.
The router converts these light signals
to electrical signals.
An Ethernet cable is then used to
transmit the electrical signals to your laptop.
However if you are accessing the Internet using cellular data,
from the optical cable the signal has to be sent to a cell tower
and from the cell tower the signal
reaches your cell phone in the form of electromagnetic waves.
Since the Internet is a global network it has become important to have an
organization to manage things like IP address assignment, domain name registration etc
this is all managed by an institution called ICANN located in the USA.
One amazing thing about the internet is its efficiency in
transmitting data when compared with cellular and landline communication technologies.
This video you are watching from the Google Data Center is sent to
you in the form of a huge collection of zeros and ones.
What makes the data transfer in the internet efficient is the way in which these zeros and ones
are chopped up into small chunks known as packets and transmitted.
Let's assume these streams of zeros and ones are divided into different packets by the
server where each packet consists of six bits.
Along with the bits of the video each packet also consists of the sequence
number and the IP addresses of the server and your phone.
With this information the packets are routed towards your phone.
It's not necessary that all packets are routed through the same path and each packet independently
takes the best route available at that time.
Upon reaching your phone the packets are reassembled according to their sequence number.
If it is the case that any packets fail to reach your phone and acknowledgement
is sent from your phone to resend the lost packets.
Now compare this with a postal network
with a good infrastructure, but the customers do not follow the basic rules
regarding the destination addresses.
In this scenario letters won't be able to
reach the correct destination.
Similarly in the internet we use something called protocols for the
management of this complex flow of data packets.
The protocols set the rules for
data packet conversion, attachment of the source and destination addresses to each packet
and the rules for routers etc for different applications the protocols
used are different.
more specifically about the amazing journey of data packets
from the data center to your mobile phone.
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