this lecture covers the top three layers off the eyes. Always, I model the application. The presentation and the session layers layers seven. Layer six and layer five
the application layer. It is the interface between the user, the human users and the rest off the seven layers. It's an interface between the user and the lower layers off the I saw Asai Modern. That translates and tries to
make it easier for the lower layers toe.
Execute the orders and the requirements given by the user. Tow the network.
The application rail is responsible for the preparation off data for each service. Each service on the Internet requires data to be prepared in a certain format toe appear in a certain way.
For example, the Web browser at lets the data appear in the form off text images and hyperlinks.
Another service, like the file transfer service the FTP, requires later to appear in the form off solid files.
Another service, like the email service, requires data to appear in the form of messages.
The preparation off data for each of these service
is responsibility off the application layer.
The application layer is the goal of the seven layers
perform. End to end communication on both sides between the application layer at the sender and the application layer at the receiver. This is the logical connection that needs to be established between
the sender and the receiver, as if the application Lear here is talking directly to the application layer there as if there were no other layers interfering the end to end communication on both sides. Off the thunder and the receiver is the goal off the seven layers
providing and toe and communication between the application layer here and the application layer. There
is the reason for the existence off these seven years.
The application layers the seventh layer in the eyes. Always I model is the layer where the software application three sites where the program you are dealing with as a user exists and takes from you the data that needs to be sent over the network
and passes toe the lower six layers,
starting from presentation and ending. Tow the physical.
The application layer is the actual layer that sends the requests at the sending process and the actual air that receives the reply at the receiving process. It's the layer that takes the request from the user passes to deliver layers and receives the reply,
arriving from the lower layers
and presenting it to the users in a readable and understandable. For
example, protocols that work at the application layer are the following http hypertext transfer protocol. This is for Web service is
F D P file transfer protocol. This is for transferring files between sources and stations over the Net s MTP. The simple male transfer protocol This is for the mail exchange over the Internet.
Pop three is the post office protocol. SMTP is for exchanging email messages. Among the mail servers. Pop three is for exchanging email between the client and the mail server.
I'm map is instant message access. Protocol is also for exchanging email messages between the client and the mail server.
Pop. Three Allows for downloading email messages I met is only for accessing and reading email messages. Tell nut and as a search protocols are four.
Allowing for remote administration between
decline that exists in a certain machine over the Internet and the server that exists maybe
two or three countries away on the Internet and
the user sitting on the client software
acts as if sitting on the keyboard and the mouse
connected directly to the server machine and can do whatever he likes on the server machine through this stele nut application,
the domain name system or the domain name server that Vienna's is the protocol responsible for resolving the domain names in tow I P addresses and vice versa. It's the protocol that allows for writing www dot yahoo dot com and then
connecting toe a certain machine with the I P edges
corresponding to this domain name server,
the RTP Protocol. The real time protocol is responsible for transferring data that are really time data such as the audio and the video. Really, time transfer
off data has certain requirements for certain data that our delay sensitive and not sensitive to losses in the same way
that they are sensitive today. So the rail time protocol, which is somehow a new protocol, is responsible for transferring data
The presentation layer, or layer number six, is responsible for the common representation off data between any source and any destination.
It is responsible off presenting the data to the application when receiving and receiving the data from the application. When Sunday.
In a certain form that can be
understandable by both the source and the destination. It provides the transformation of data. It supports a standardized application interface at the source side and add the destination side. It is responsible off loading the data syntax.
It's responsible off coding the data
according to a certain syntax that is understandable. Bible to the source and the destination. It is responsible for the encryption at this underside and the decryption at the receiver side off the data being transmitted. It is responsible off the compression at this underside
and the decompression at the receiver side off the data being transmitted
between the source and the destination.
The special layer, or layer number five is
goes about managing the session,
starting by establishing decision in itself, managing the session while it is running and up controlling the session while it is transferring data, and at the end of the session it is responsible off how the session can be terminated safely.
If we look at this diagram, we can see that the social layer sons some data that is
like some data, we or like some sentences we use between each other's as human to start conversation.
If you say to someone, I'd like to send you something and he says, Sounds good. This is a request that is replied by an acknowledgment. This is an establishing to a connection. These two messages are the responsibility off the session layers to transmit. End toa
acknowledge at the beginning of the session
at the end of the session, when you
send your data completely and entirely, you say toe the receiver, thank you, and he acknowledges you by the sentence, you are welcome.
This is closing the session safely and closing the connection safely off course. In between these two messages In between these two diagrams, the session can be stopped and can be restarted and can be resumed at a certain point of time.
The flow of data can be controlled
and can be slowed down and can be set to a faster speed.
All of these functionalities are the responsibility off the session layers. It is responsible off managing the session as a hole from the establishment by some handshaking between the sender and the receiver, till determination by some handshaking and acknowledgement between the same sender and receiver, and
through controlling the session in between. While the data is being transferred between the sender and the receiver off the data,
the social layer makes sure the connection is active during the session and make sure that it is not falling down.
It's this responsible off securing the commission. It is responsible off the synchronization of the dialogue,
the synchronization off the sending and receiving off data. It is responsible off checking for the connection failure if existing during the session,
which leads to losing data and which leads to slowing down the data transfer process. It's responsible for re connection if there is a cut off during the sending off the data or during the data transmission, re connection or resuming the session is the responsibility off the session later.
It's responsible off terminating the communication at the end of the session. After all, the later has bean
received by the receiver.
The special layer defines the note. Communication order and timing, order and timing are the core off the synchronization off the data. Sending
this is the responsibility off the session layer as well.
The three layers, the application, the presentation and the session are very closely connected. They are very related in function to each other.
That's why they form the application layer in the TCP i p. If we have a look at the TCP I P protocol suit, we can say we can see that the application layer the presentation layer the session layer in the eyes. Always I model are all compact
and link it together in one layer in the d c p i p that is called the application layer
in the d. C p i. P. This makes the DCP I P only four layers, not seven layers.
Those three layers are responsible off content for mating are responsible off formatting and representing and preparing the data being sent from the sender to the receiver.
It's preparing for the network. Proofs is preparing for addressing, preparing for routing and preparing for establishing the connection
for the data to be transmitted through they network Claire's that lies down
starting from layer four until the physical layer in the eyes Os. I'm on
by this. We have introduced those important Fleer airs. Thank you