All right.
So welcome back.
In this section we're going to focus on computer networks.
Okay before we go into hacking we first need to understand a few things about computer networks.
So in this section we will cover a few terminologies and things that we need to understand before we
start the hacking process.
So first thing we need to learn is gone.
Computer networks.
So what our computer networks
so we will learn about what the network is and how it works.
So what's the definition of a computer network.
A computer network is nothing but simply a connection or a group of connected devices.
So every device that is connected with each other forms a network.
So it could be there are different types of network.
We will see later what kind of networks there are.
But the basic idea behind networking is that every communicating device or every device that is able
to communicate better with each other forms a network a network could be either physical or wireless
filed simple Wi-Fi as a wireless network.
Similarly there are other networks for example if you have a land or internet connection.
This connection is jus the kind of physical or wired connection and the core idea behind networks is
that in networks their devices are able to communicate or exchange data with each other.
It could be a simple connection like a Bluetooth connection even though this is not able to access the
Internet but still it is able to communicate that with each other.
So a Bluetooth connection is that kind of a network.
So how do we understand network visually.
So let's say you have a few devices.
Let's say you have a mobile phone or a laptop or backstopped P.C. and they're all connected with each
other.
So even if they are not connected to Internet and they're connected with each other two are out there
this still forms a network and this is called a local area network.
Even if there is no Internet connectivity between these two devices there they will still be able to
transmit data from one device to another in the same network.
If they're connected to a SIM Roper.
So I will explain where that outlet is.
Just bear with me.
So it's the same ideas that if they're able to communicate they form a network and this is usually called
a local Asian Network or land in simple terms
the next thing we need to learn is what and Lord
a node is nothing but every communicating device inside the network.
So nodes are defined by their addresses.
So for example if you have Wi-Fi that is a so if you have a mobile that is connected to your Wi-Fi.
And similarly at the same time you have your laptop connected to the Wi-Fi.
These two devices are called nodes and they will have unique addresses.
I will explain what an address is next.
But for the moment just understand that a node is just any connecting device inside your network and
now comes the concept of address.
So we humans are identified by our names but machines do not understand this language.
So in order for machines to be able to communicate with each other they need to know addresses in the
form of numbers.
So an order address is nothing but a simple 32 bit number they are uniquely identifiable and they are
numeric quantities which means that either numbers there could be strings which is a whole different
topic.
These addresses are these numbers helps machines to communicate with each other.
So if the machine does not have a proper address it won't be able to communicate properly.
So when we are talking about addresses who to use need offering to the IP address which is a 32 bit
number.
So you may have seen this kind of numbers for example 1 9 2 1 6 8 0 0 1 and this is called a private
IP address so using this.
So if a writer wants to communicate with your device in the same network it will use your device's IP
address which would be this one.
This is just an example and then associated with addresses is another numeric identifier which is called
a board.
So a port is basically a number that identifies a service funding on the system.
So every communicating device can have multiple services running.
So for example if you have a mobile phone your mobile phone could communicate with for example a YouTube.
Let's say you have a mobile phone and it's running multiple applications.
It is running what it's running a browser.
It's running some other applications in the background that is consuming that is connecting that extending
that over the Internet.
So how do your mobile phone that your daughter knows that rich that is associated with which service
on which application.
So this is done through boards.
So every board on every data that is coming from a specific port is associated with a specific service.
For example if you are read that every internet data that is associated with your browser are with EZ
GDP which is a Hypertext Transfer Protocol will come through board number 80.
And also newly a sixteen bit numbers.
So they range from one to 65000 535.
And one important thing to note about ports is that from board one to first one key ports are 1024 ports
are reserved.
So you should not use them if you are developing a program use or somebody that are higher than this
numbers because they will interfere with the normal functioning of your P.C. so as I already said that
different applications are different services have different port numbers associated with them.
So for example hyper as GDP are a simple tax transfer protocol which is used which was used earlier
for a browsing is associated with port number 80 it still used but it's not very common nowadays.
Most of the Web sites use this as you to be as portable reaches as you were in the same port.
And then there is another protocol called FTB which is used for file transfer
Okay so now you're familiar with networks and nodes and addresses.
So the next thing we need to learn is and what's in the Internet and Internet is nothing but simply
a group of a global connection of group of networks.
So every network that is connected worldwide forms and global network called internet so a form of W
W W on worldwide web is a global network that is usually referred to the Internet.
But this is not the internet.
This is just as part of Internet and the Internet is a very broad network.
Okay so the last thing we will Levin is call a gateway.
So how do we communicate with the Internet devices that are not present inside your own network.
So let's say this is your computer and you want to access a set about a set of what is nothing but a
computer that is running 24/7 and that listens for incoming requests and then accordingly response.
So for example when you access a website Google dot com our Facebook dot com you make a request to this
computer or this server and then the server will respond accordingly.
Let's say you initiate a request from your computer to this P.C. or this server.
So you cannot directly I mean your computer cannot directly communicate with this ever.
Why.
Because this causes a lot of problems in communication.
So what we have what they did was that they developed a concept of called concept called Gateway it
out that.
So every local network has only one entry and exit point through this network.
So as the name indicates it's a gateway.
So only to this gate Rick and your data go outside the network or come to your network.
So let's say this is your local network.
And this is the servers network.
And then if you want to communicate between these two networks all your data must go through this.
There are this gateway in device so you will tend to request that to this one and it will go through
this.
And if the server responds the whole data will pass through this outlet and then come to your P.C..
And this device is called a gateway at outer
okay.
So Mac addresses are addresses that are used for communication inside your own network.
So IP addresses are mostly used for communicating with devices that are not present in your local network
while you make addresses are used for communicating inside because inside your own network you can communicate
with mac addresses.
And remember that when they said that even if you do not have Internet connectivity you can still communicate
inside your own network.
So this is because that then type communication is managed by net MAC addresses.
So even if there is no internet access you can still use these MAC address to communicate with devices
in your own network.
And it stands for media access control.
So MAC address is associated with each hardware interface.
So in your laptop if you have a Wi-Fi card.
So the MAC address will be associated with your Wi-Fi card and it is used in LAN on the MAC address
is a six byte 48 with address.
And it looks something like this for example the for blah blah blah.
So that's it.
These are very basic terminologies.
And in next lecture we will start using our building on top of it.
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And see your next lecture.