Open System Interconnection Model
The OSI model was developed by ISO (International Organization of Standardization) in 1984. It divides the entire task into seven smaller manageable tasks. It is a framework that standardizes the network communication system into seven layers.
Upper Layer
Deals with application-related issues.
They are only implemented in software.
Lower layer
Deals with data transport issues.
The data link layer and physical layer are implemented in Hardware and software.
Physical Layer:-
-It transmits raw bits(0s 1s) over physical media.
-It defines hardware specifications.
-It converts digital data into signals.
Data Link Layer:-
-It provides node-to-node data transfer.
-It handles error detection and correction.
-It Manages MAC (Mass Access Control) addresses for device identification.
Network Layer:-
-It Routes data packets across networks.
-It uses IP addressing for local addressing.
-It ensures data reaches the correct destination.
Transport layer:-
-It Manages end-to-end data transfer between devices.
-It Provides error recovery, flow control, and Data segmentation.
-Protocols: TCP (reliable), UDP (faster, no reliability).
Session Layer:-
-It establishes, maintains, and terminates the sessions between applications.
-It handles session recovery in case of interruptions.
Presentation Layer:-
-It formats and encrypts data for the application layer.
-It ensures that data is in a usable format.
-It provides encryption and data compression.
Application Layer:-
-It Interfaces directly with the user applications.
-it provides network services like file transfer (FTP), web browsing (HTTP), and email (SMTP).
Characteristics:-
It acts as a common language for all devices to communicate.
Data is wrapped with instructions at every layer to help it move through the network.
Each layer works on its own, so changes don’t break others.
It allows devices and networks to work together.
It has methods to detect and fix issues.