OSI Reference Model

OSI Reference model 

OSI stands for Open System Interconnection.
Developed by ISO in 1984.

It has been developed to categories many processes which take place during data transmission into 7 layers.

Physical Layer

· Use of media to transmit data signal in the form of bits.

· Flow control

· Synchronization

· Devices (Hub, RJ45, BNC, Repeater etc.)

Data Link Layer

· Physical addressing

· Framing

· Flow control

· Link management

· It has 2 sub-layers

o MAC (Media Access Control) – It is responsible to manage the data transmission on the basis of MAC address.

o LLC (Logical Link Control) – it is responsible to check the status of link before data transmission and it also synchronize to nodes.

· Frame filtering.

Network Layer

· Logical addressing (IP Addressing)

· Packet formation

· Packet filtration

· Source to destination data delivery

· Routing for communication between two or more different networks.

Transport Layer

· Port Addressing

· Segmentation

· Process-to-process delivery

· Reliable and unreliable data transmission.

Session Layer

· It divides session for different processes those are executing at the same time.

Presentation Layer

· Encryption and decryption

· Compression and decompression

Application Layer

· www accessing

· File handling

· Running of application software

· Service configuration etc.