I have been really interested in how the internet works and what those internal things happen after we search for things till we get a response so I have explored a bit about the OSI Model of Computer network and learned too many things in detail that how the internet works what are the different protocoal there in different layers . I have written the brief about it and all the layers of it by showing that
OSI MODEL
Application Layer (Layer 7) :
At the very top of the OSI Reference Model stack of layers, we find the Application layer which is implemented by the network applications. These applications produce the data, which has to be transferred over the network. This layer also serves as a window for the application services to access the network and for displaying the received information to the user.
Example: Application – Browsers, Skype Messenger, etc.
Presentation Layer (Layer 6):
The presentation layer is also called the Translation layer. The data from the application layer is extracted here and manipulated as per the required format to transmit over the network. The functions of the presentation layer are :
Translation: For example, ASCII to EBCDIC. Encryption/ Decryption: Data encryption translates the data into another form or code. The encrypted data is known as the ciphertext and the decrypted data is known as plain text. A key value is used for encrypting as well as decrypting data. Compression: Reduces the number of bits that need to be transmitted on the network.
Session Layer (Layer 5) :
This layer is responsible for the establishment of connection, maintenance of sessions, authentication, and also ensures security. This layer adds session after authentication of the user. basically it makes your application aware about your information
Transport Layer (Layer 4) :
The transport layer provides services to the application layer and takes services from the network layer. The data in the transport layer is referred to as Segments. It is responsible for the End to End Delivery of the complete message. The transport layer also provides the acknowledgement of the successful data transmission and re-transmits the data if an error is found.
At sender’s side: Transport layer receives the formatted data from the upper layers, performs Segmentation, and also implements Flow & Error control to ensure proper data transmission. It also adds Source and Destination port numbers in its header and forwards the segmented data to the Network Layer.
It has some of the protocols to send the data through internet and it also takes data from network layer and make the application layer aware about it.
Network Layer (Layer 3) :
The network layer works for the transmission of data from one host to the other located in different networks. It also takes care of packet routing i.e. selection of the shortest path to transmit the packet, from the number of routes available. The sender & receiver’s IP addresses are placed in the header by the network layer.
The functions of the Network layer are :
Routing: The network layer protocols determine which route is suitable from source to destination. This function of the network layer is known as routing. Logical Addressing: In order to identify each device on internetwork uniquely, the network layer defines an addressing scheme. The sender & receiver’s IP addresses are placed in the header by the network layer. Such an address distinguishes each device uniquely and universally.
Data Link Layer (DLL) (Layer 2) :
The data link layer is responsible for the node-to-node delivery of the message. The main function of this layer is to make sure data transfer is error-free from one node to another, over the physical layer. When a packet arrives in a network, it is the responsibility of the DLL to transmit it to the Host using its MAC address. The data Link Layer is divided into two sublayers:
Logical Link Control (LLC) Media Access Control (MAC)
Physical Layer (Layer 1) :
The lowest layer of the OSI reference model is the physical layer. It is responsible for the actual physical connection between the devices. The physical layer contains information in the form of bits. It is responsible for transmitting individual bits from one node to the next. When receiving data, this layer will get the signal received and convert it into 0s and 1s and send them to the Data Link layer, which will put the frame back together.
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