What is OSI model ? Explain the Layers of OSI model with diagram .

What is OSI model ? Explain the Layers of OSI model with diagram .

What is OSI model?

The OSI model (Open System Interconnection) model defines a computer networking framework to implement protocols in seven layers. A protocol in the networking terms is a kind of negotiation and rule in between two networking entities.

Layers of OSI model:

Physical layer

The Physical layer is also called as the Layer 1. Here are the basic functionalities of the Physical layer:

·       Responsible for electrical signals, light signal, radio signals etc.

·       Hardware layer of the OSI layer

·       Devices like repeater, hub, cables, ethernet work on this layer

·       Protocols like RS232, ATM, FDDI, Ethernet work on this layer

Data Link layer

The data link layer is also called as the Layer 2 of the OSI model. Here are the basic functionalities of the data link layer:

·       Responsible for encoding and decoding of the electrical signals into bits.

·       Manages data errors from the physical layer

·       Convers electrical signals into frames

·       The data link layer is divided into two sub-layers

o   The Media Access Control (MAC) layer

o   Logical Link Control (LLC) layer.

·       The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it.

·       The LLC layer controls frame synchronization, flow control and error checking.

·       MAC address is a part of the layer 2.

·       Devices like Switch work at this layer

Network Layer

The Network layer is also called as the layer 3 of the OSI model. Here are the basic functionalities of the network layer:

·       Switching and routing technologies work here

·       Creates logical paths between two hosts across the world wide web called as virtual circuits

·       Routes the data packet to destination

·       Routing and forwarding of the data packets.

·       Internetworking, error handling, congestion control and packet sequencing work at this layer

·       Router works at layer three

·       Different network protocols like TCP/ IP, IPX, AppleTalk work at this layer

Transport layer

The Transport  layer is also called as the layer 4 of the OSI model. Here are the basic functionalities of the Transport layer:

·       Responsible for the transparent transfer of data between end systems

·       Responsible for end-to-end error recovery and flow control

·       Responsible for complete data transfer.

·       Protocols like SPX, TCP, UDP work here

Session layer

The Session  layer is also called as the layer 5 of the OSI model. Here are the basic functionalities of the Session layer:

·       Responsible for establishment, management and termination of connections between applications.

·       The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end.

·       It deals with session and connection coordination.

·       Protocols like NFS, NetBios names, RPC, SQL work at this layer.

Presentation layer

The Presentation layer is also called as the layer 6 of the OSI model. Here are the basic functionalities of the presentation layer:

·       Responsible for data representation on your screen

·       Encryption and decryption of the data

·       Data semantics and syntax

·       Layer 6 Presentation examples include encryption, ASCII, EBCDIC, TIFF, GIF, PICT, JPEG, MPEG, MIDI.

Application Layer

The Application layer is also called as the layer 7 of the OSI model. Here are the basic functionalities of the Application layer:

·       Application layer supports application, apps, and end-user processes.

·       Quality of service

·       This layer is responsible for application services for file transfers, e-mail, and other network software services.

·       Protocols like Telnet, FTP, HTTP work on this layer.