Osi Reference Model

Basic Concept of OSI Reference Model

OSI (Open Systems Interconnection) is a reference model for how applications communicate over a network which focuses on providing a visual design of how each communications layer is built on top of each other.
The seven layers of functions are provided by a combination of applications, operating systems, network card device drivers, networking hardware, and protocols that enable a system to transmit a signal over a network through various physical mediums.

Layer7- Application layer

This layer enables the user or software to interact with the application or network whenever the user elects to read messages, transfer files or perform other network-related tasks. Web browsers and other internet-connected apps like MS-Teams and Zoom uses Layer 7 protocols.

Layer6- Presentation layer

This layer translates or formates data from the application layer based on the semantic or syntax the application accepts. It also handles encryption and decryption that the application layer requires.

Layer5- Session layer

This layer connects, coordinates and terminates conversations between applications. Managing the session involves synchronization of user tasks and dailogue control. Login name recognition and security functions take place at this layer.

Layer4- Transport layer

It is responsible for transferring data across a network and provides error-checking mechanisms and data flow controls. It determines how much data to send where it gets sent and at what rate.

Layer3- Network layer

It determines how data are transferred between network devices, routes packets according to unique network device addresses and provides flow and congestion control to prevent network resource depletion.

Layer2- Data-link layer

It defines procedures for operating the communication links. It handles problems that occur as a result of bit transmission errors.

Layer1- Physical layer

It defines physical means of sending data over network devices. It determines how physical connections to the network are set up and how bits are represented into predictable signals as they’re transmitted either electrically, optically, or via radio waves.