OSI Reference Model

What is OSI Model?

The OSI Model is used to describe networks and network application.

Layers of OSI  Model 

Three are Sever Layers of OSI Model :

OSI Layer Diagram:

  

7)  Application Layer : The application layer provider different services to the application. Example of services provided by this layer are file transfer, electronic messaging e-mail, virtual terminal access and network management.

6) Presentation Layer : The Presentation layer is responsible for protocol conversion, date encryption/decryption, Expanding graphics command and the date compression. This layer makes the communications between two host possible.

5) Session Layer : This layer is responsible for establishing the process-to-process communication between the host in the network. This layer is responsible for establishing and ending the sessions across the network. The interactive login is an example of services provided by this layer in which the connective are re-connected in care of any interruption.

4) Transport Layer : This layer is responsible for end-to-end delivers of messages between the networked hosts. It first divides the streams of data into chunks or packets before transmission and  then the receiving computer re-assembles the packets. It also guarantee error free data delivery without loss or duplications.

3) Network Layer : This layer is responsible for translating the logical network address and names into their physical address ( MAC address). This layer is also responsible for addressing, determining routes for sending and managing network problems such as packet switching, data congestion and routines.

2) Data Link Layer : Data link layer is responsible for controlling the error between adjacent nodes and transfer the frames to other computer via physical layer. Data link layer is used by hubs and switches for their operation.

1) Physical Layer : Physical  Layer is responsible for transmitting row bit stream over the physical cable. The physical layer defines the hardware items such as cables, cards, voltages etc.

How to remember the layer of OSI model?

The easiest way to remember the different layers of OSI Model is to use the mnemonic "All people seem To need Data Processing":

Layer	Name
Mnemonic
7	Application	All
6	Presentation	People
5	Session	Seem
4	Transport	To
3	Network	Need
2	Data Link	Data
1	Physical	Processing