Hello everyone in this video. We will be talking about
the networking fundamentals. Now, we
are getting started with OSI and tcp/ip models
information.
The tcp/ip model is a framework for organizing and
communicating data across networks. It
consists of four layers. First one
is the link layer.
This layer handles the physical connection between devices on
the same network these responsible for transmitting data
over the physical link between devices
and handles issues such as
error checking and floor control.
And the second one is the internet layer. This
layer is responsible for routing data
between devices on different networks. It does
this by using IP addresses to
identify devices and reading data through
intermediate devices such as routers as
needed.
And in the transport layer, this layer is responsible
for ensuring that data is delivered reliably from
one device to another it.
Does this by providing error checking
floor control and other mechanism to ensure
that the data is delivered correctly?
And in the application layer, it is
responsible for providing the interface
between the network and the applications that
use it. It is responsible for defining how
applications communicate with the network and with
each other.
The tcp/ip model is often referred to
as the Internet Protocol Suite because it
defines the protocols that are used to transmit data
over the internet.
These protocols include TCP which means
transmission control protocol, which is
responsible for Reliable data transmission and
IP which means Internet Protocol.
Which is responsible for routing data
between Networks.
They also model is a framework for understanding how
communication occurs between different devices
on a network. It divides the process of
communication into seven layers Each of which performs
a specific set of functions.
These are the layers first one physical
layer.
The physical layer is responsible for the
transmission of row of data bits over a communication
Channel. It deals with the physical characteristics
of the transmission medium.
such as the type of cable or wireless connection
being used
It also defines the electrical mechanical and functional
characteristics of the interfaces between
the devices.
And the second one data link layer, the
data link layer is responsible for
providing reliable communication between devices over
a single link of the network.
Does despite dividing the data into frames
adding a header and a trailer
to each frame to identify the start
and end of the frame and providing
error detection and correction.
The data link layer is also responsible for establishing
and maintaining a link between
devices known as a logical link control.
and in the network layer
It is responsible for routing data between devices on
the network. It does this by adding a heater
to each data packet that contains the
destination address and reading information.
The network layer is also responsible
for establishing and maintaining logical connections
between devices known as
virtual circuits.
And in the transport layer, the
transport layer is responsible for providing and
to end communication between devices. It adds
a heater to each data packet that
contains information about the source and destination devices
and the seconds of the packets
the transport layer also provides error
recovery flow control and congestion
control to ensure that the data
is delivered reliably and efficiently and
in the session layer, the session layer
is responsible for establishing maintaining and
terminating sessions between devices.
A session is a logical connection between two devices that
allows them to exchange data in a structured
manner. The session layer is also responsible
for providing synchronization and checkpointing
or services to hello for
recovery from failures decision layer
is also responsible for providing synchronization and
checkpointing services to allow for
recovery from failures.
And the presentation layer is responsible for the representation
of data in a format that can
be understood by both the sender and
the receiver.
It does this by providing encoding and decoding
of data as well as compression and
decompression of data.
The presentation layer is also responsible for encryption and
decryption of data to provide secure
communication.
In the application layer, the application layer is the
highest layer of the OSI model and is
responsible for providing the interface between
the network and the applications that use it.
It defines the protocols and standards that
applications use to communicate with
each other and with the network.
It also provide services such as file transfer email
and virtual terminal access.
The outside model is a useful way of understanding how
communication occurs between devices on a
network but it is important to note that it
is a logical model and doesn't necessarily correspond
to the physical implementation of a
network.
In practice many devices and systems combine
the functions of multiple layers into
a single device or software component.
If you wonder how a network packet travels in the
usai model, we can explain this in this
way. When a device on a network wants to send
data to another device. It breaks. The
data down into smaller units called packets.
Each packet contains the data to be transmitted as
well as a heater that contains information about
the packet such as the source and
destination addresses and the sequence number of
the packet.
As the packet there was through the network. It passes
through each of the seven layers of the YSI model
in turn.
At each layer the packet is modified in
some way to enable it to be transmitted over
the network.
Here is how a packet travels through the
OSI model.
At the physical layer, the packet is transformed into
a series of bits that can
be transmitted over the physical medium of the network.
This may involve encoding the bits in
a particular way to ensure that they can be transmitted to
reliably
such as using postcode modulation.
Or PCM or such as type of cable
or wireless connection being used.
And in the data link layer, the packet
is divided into smaller units called frames Each
of which contains a heater
and a trailer.
The application layer is the topmost layer of the OSI model
and it represents the interface between the
application and network. Then an application
wants to send a network packet. It constructs the
packet and hands it off to the next layer
down in this stack.
The presentation layer is responsible for
formatting and encoding the data being transmitted
as well as for providing that data
compression and encryption services.
When I picked is handed down from the application layer the
presentation layer may add its own
Header information to the packet depending on
the protocol being used and the
session layer is responsible for
establishing maintaining and terminating connections
between devices.
It does this by exchanging control messages
between devices to establish and terminate
sessions.
As well as by providing floor control and error
Recovery Services.
The transport layer is responsible for establishing and
maintaining and-to-end connections between devices
as well as for providing variable data
transfer services to the application
layer when I packet is handed down from
the session layer the transport layer may add its
own heater information to the packet depending on
the protocol being used and the network layer
is responsible for routing packets through the
network today your destination.
Does this by adding a network layer heater to
the packet which contains information about source and destination
addresses of the packet?
The data link layer is responsible for moving packets
between devices on the same network segment.
It does this by adding a data link header to
the packet which contains information about source
and destination devices on the network segment.
The physical layer is responsible for transmitting the
packet over the actual physical link between devices this
involves converting the packet
into a series of electrical sinus or pulses.
Which are transmitted over the link?
Once the packet has been transmitted over the physical link.
It is received by the destination device and goes to
a similar process in reverse.
Starting at the physical layer and working its way
up through the layers of the SI model until its
delivered to the destination application.
Let's talk about encapsulation process based on OSI
model.
Encapsulation is the process of adding heater
information to data as it travels to
a network and is an important aspect of
how data is transmitted and received over
a network according to the other side model.
There are some model is a framework for understanding how
data is transmitted over a network and consists of
seven layers each with its
own specific role and function here is a
step-by-step description of the encapsulation process
on each layer of the assign model.
First one is the application layer and a
device sends data over a network it first adds
an application layer header to the data this header
contains information about the source and
destination devices as well as error checking
data.
And in the presentation layers, the device
adds a presentation layer header to
the data this heater contains information about
the formatting and encoding of the
data as well as error checking data.
In decision layer the device then adds a
session layer header to the data this heater
contains information about the connection between the
source and destination devices as well
as error checking data.
And in the transport layer after the
session layer heater is added the device adds a
transport layer header to the data.
Is hey there contains information about the reliability and
Order of the data as well as
error checking data in the network layer. The
device adds a network layer header to
the data which contains the address of destination device
as well as error checking data.
And in the data link layer after
the network layer heater is added the device
adds a data link layer header and filter
due to the data this contain
information about source and destination devices
as well as error checking data.
In physical layer, finally the device adds a
physical layer heater and footer to the data
and this information is about physical
transmission of the data such as the type of
cables or connectors use it the data rate
and to signalic method.
Once all of the headers have been added the data
is fully encapsulated and ready to be
transmitted over the network when the
data reach its destination the capsulation process
begins and the heaters are stripped of
one layer at a time starting with the
top layer which means that the application layer
and working it's way down to the physical layer.
Now we will explain the capsulation process based
on OSI model the capsulation also
known as the process of unwrapping or
stripping of the layers of a packet.
As it travels through a network is an
important aspect of how data is transmitted and
received over a network according to the OSI model
to understand the decapsulation process. It's
helpful to consider. How data is
transmitted over the network when a device sends
data or a network. It wraps the data
in a series of eaters and Footers that
contain information about source and destination devices.
As well as error checking data each layer
of the RSI model adds its
own header or footer to the data as
it travels through the network when the data
reach its destination the capsulation process begins
the device receiving the data strips of
the headers and Footers one
layer at a time.
This process allows the receiving device to extracted
original data and pass it on to the
appropriate application for processing.
Here is a detailed step by step description of
the decoupcellation process on each layer of
the website model and we will begin with the
physical layer.
In the physical layer when the data reach
the physical layer the device receiving the data
removes on the physical layer header and footer
which contain information about the
physical transmission of the data such as the
type of cables or connectors use it the
data rate and the signaling method.
In the data link layer.
After the physical layer heater and footer are
remote the device removes the data link
layer and footer.
Which contain information about source and destination devices
as well as error checking data?
In the network layer the device that removes the network
layer header.
Which contains the address of the destination device?
In the transport layer after the network
layer is removed the device you're most
transport layer heater which contains information
about reliability and Order of
the data as well as error checking
data.
And when it comes to session layers
the device then removes the session layer
header.
Next the device you most presentation layer
header contains information about the formatting
and encoding of the data.
In the application layer, finally the device
removes the application layer header which
contains information about the source and destination
devices.
Now, let me tell you about some common protocols and
ports.
In a typical network data flows between devices such as
computer servers and routers using a
set of protocols and ports.
Protocols are the sets of rules that Define how
devices communicate with each other over a
network. They specify the format and structure
of the data being transmitted as well
as procedures and rules for exchanging data.
Ports are logical connections on a
device that allow it to communicate with other
devices on the network. There are many different protocols
and port numbers that are commonly used
in Networks.
Some examples are here.
First one is the TCP which means transmission control
protocol.
This is a transport layer protocol that
provides reliable and to end communication
between devices.
It is commonly used for applications that require
guaranteed delivery of data such as
web processing and file transfer.
And the second one is UDP,
which means user datagram protocol.
This is also a transport layer protocol, but
it is connectionless and doesn't guarantee
the delivery of data.
It is often used for real-time applications such
as video streaming and online gaming
where it is important more where
it is more important to receive
data in a timely manner than to
ensure that all data is delivered.
At the next one is http.
Which means hypertext transfer protocol this is
an application layer protocol that is
used to transmit hypertext documents such as
web page over the internet.
Is commonly used on Port 80. The other
one is https, which means HTTP
secure.
This is a secure version of HTTP that is
used to transmit data over a secure connection.
And it is commonly used on Port for
three.
And the next one is FTP, which means
file transfer protocol.
This is an application layer protocol. Also
that is used to transfer files between
devices or network. It is commonly used
on Port 21.
And the last one is SSH which means
secure shaft.
This is a network protocol that is used to set
your remote command line login sessions and other
types of network connections and it
is commonly used on Port 22. These
are just a few examples of the many
protocols and port numbers that are used in
Networks.
There are many others and specific protocols and ports
that are used can depend on the specific
needs and requirements of the network.
Now I will talk about the three-way handshake.
Three way handshake is a process that is used
to establish a transport connection between the two
devices on a network.
It involves the exchange of three messages between
the devices as follows.
Here is device a sense a scene
message to device P indicating that it
wants to establish a connection.
Then device P receives the scene message and
sends a thin egg synchronize acknowledge
message back to the device a
acknowledging the request and indicating
that it is also ready to establish a
connection.
Device a receives the syntax
message and sends an egg message
which means acknowledge message back to
the device B acknowledging result of
the syntax message and completing the three
way handshake.
Once the trivia handshake is completed. The devices can
begin exchanging data over the established connection.
The connection remains open until one of the devices sends
a fin message which means punish message
to the other indicating that it wants
to close the connection.
The other device responds with an act
message and the connection is closed.
here is a sample of network traffic that shows the
TCP three way handshake in this example device
a with the IP address 1
9 2 1 6
8 1 10
initiates the three-way handshake by sanding message
to device p
the message includes a sequence number.
A sequence number of hundred 100 which
is a value that is used to track track.
The order of the data being transmitted. The
ACT field is set to zero since this
is the first message in the three way handshake.
Then device be response with a synec message acknowledging
the request and indicating that it
is also ready to establish a connection.
The message includes a sequence number of 200 and
the Egg field is set to 101
acknowledging the
same message from device a and lastly device
a response with an X message
acknowledging recite of the scene act
message and completing the three way
handshake the message includes a sequence
number of 101 and
the heck field is set to 201.
Acknowledging the sin act message from device B
wants the three way handshake is complete the
devices can begin exchanging data
over the established connection the connection remains open
until one of the devices sends a
thin message to the other.
Now we have finished the section 1 move on to the next
we will talk about basics of Wireshark. See you
on the next video.