osi model

OSI refers to:

The OSI model, created in 1984 by ISO, explains the process of transmitting data between computers. It is divided into 7 layers that work together. Each layer has specific functions and responsibilities.

1 Physical Layer :

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 the information in the form of bits.

The physical layer is responsible for transmitting individual bits from one node to the next.

function of physical layer :

Bit Transmission: Transmits raw bits over a communication channel.
Physical Connections: Establishes and terminates physical connections between devices.
Data Rate Control: Manages the rate at which data is transmitted.
Signal Encoding: Converts data into signals suitable for the transmission medium.

2 Data link Layer :

The data link layer is responsible for the node-to-node delivery of the message. Its main function is to ensure that data transfer is error-free from one node to another over the physical layer

The data link layer has two sublayers:

LLC (Logical Link Control): It manages communication between devices and handles error checking.
MAC (Media Access Control): It controls how devices access the network and assigns physical addresses.

function of data link layer :

Error Detection and Correction: It checks for errors in the data and corrects them if possible.
Data Framing: It organizes raw data into frames for easier transmission.
Flow Control: It manages the pace of data transmission to prevent overwhelming the receiver.
MAC Addressing: It uses physical addresses to ensure data is sent to the correct device on a network.

3 Network layer :

The Network Layer is responsible for data routing, forwarding, and addressing. It determines the best physical path for data to reach its destination based on network conditions, the priority of service, and other factors. This layer manages logical addressing through IP addresses and handles packet forwarding.

Function of Network Layer :

Routing: Determines the best path for data to travel across the network.
Logical Addressing: Uses IP addresses to identify devices on the network.
Packet Forwarding: Ensures data packets are sent to the correct destination.

4 Transport Layer :

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 a segment. It is responsible for the end-to-end delivery of messages.

Function of Transport Layer :

End-to-End Communication: Ensures complete data transfer between source and destination.
Segmentation and Reassembly: Breaks data into segments for transmission and reassembles them at the destination.
Flow Control: Manages data flow to prevent congestion and ensure efficient transmission.
Error Detection and Correction: Identifies and corrects errors in data transmission.

5 Session Layer :

The Session Layer manages and controls the connections between computers. It establishes, maintains, and terminates communication sessions, ensuring data is properly organized during transmission. It also provides security.

Function of Session Layer :

Session Establishment: Initiates communication sessions between devices.
Session Maintenance: Keeps the session active and manages data exchange during communication.
Session Termination: Ends the session once communication is complete.

6 Presentation Layer :

The Presentation Layer, also known as the syntax layer, is responsible for translating data between the application layer and the network format. It ensures that data sent from the application layer of one system is readable by the application layer of another system. This layer handles data formatting, encryption, and compression, facilitating interoperability between different systems.

Function of Presentation Layer :

Data Translation: Converts data between the application layer and network format.
Data Formatting: Ensures data is in a readable format for different systems.
Encryption: Secures data by converting it into a coded format.
Compression: Reduces the size of data to optimize transmission.

7 Application Layer :

The Application Layer is the topmost layer of the OSI model. It provides network services directly to end-user applications. This layer facilitates communication between software applications and lower layers of the OSI model, ensuring that data is properly packaged and transmitted. It supports various protocols that enable activities such as file transfers, email, and other network software services.

Function of Application Layer :

Network Services: Provides services directly to user applications, such as email, file transfer, and web browsing.
Protocol Support: Supports protocols like HTTP, FTP, SMTP, and others that facilitate communication between applications.
Data Exchange: Manages data exchange between applications and ensures data is properly formatted for transmission.
User Interface: Acts as an interface between the user and the network, allowing users to interact with network services.

OSI MODEL : Open Systems Interconnection Model

Exploring the Seven Layers of the OSI Model

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