OSI Reference model

OSI Reference model

OSI Stands for open system interconnection model,

It was developed by International standards Organization(ISO) in 1984.The OSI model describes seven layers that computer systems use to communicate over a network.

The OSI model helps users and operators of computer networks:

 ■Understand and communicate the process followed by components communicating across a network.

 ■ Determine the required hardware and software to build their network.

 ■  perform troubleshooting ,by identifying which network layer is causing an issue and focusing      

       efforts  on that layer.

There are seven types of OSI reference Model:

1.Physical Layer: 

       ■ It specifies how many No of pin, plug, socket to connect computer.

       ■ Single specification

       ■ It specifies media is guided or unguided.

       ■ Topology (Star, Ring, Bus, mesh)

       ■  HUB and Repeater works on this layer.

       ■  It simply transmit Raw bit data .

       ■   It totally deal with hardware devices.

2.Data Link Layer:

       ■ Framing done at this layer.

       ■  Node to Node error control.

       ■Node to Node flow control.

       ■Bridge and switch device works on this layer.

       ■Physical addressing (MAC ,address size 48BIT)

3.Network Layer:

       ■ logical addressing (IP address size IPV4-32BIT, IPv6128BIT)

       ■  Congestion control.

       ■  Routing 

       ■   Router operation on this layer.

4.Transport Layer:

        ■  Segmentation and Reassembly.

        ■   End to End error control.

        ■    End to End flow control.

        ■    Destination Search.

        ■   TCP(Transmission control protocol)

5.Session Layer:

       ■  Dialogue control

       ■  Token Management.

       ■   log information

6.Presentation  Layer:

       ■ Encryption a

nd Decryption

       ■ Compression and Decompression.

7. Application Layer:

        ■ Email, Telnet, FTP works on this layer.