The OSI reference model is layered step by step discussion of how to communication process takes place. There are seven layers in OSI reference model, each are made for its own functions. The OSI model isn’t physical, but it guides the developer to create application or hardware devices.
The seven layers of OSI Reference Model are as follows:
- The top three layers decide how to communicate with each other and with users
- The bottom four layers decide how data is transferred from host to host
These both group are having different functionality. Upper layer with three layer don’t know anything about Network or Network Address or IP Address because that functionality belongs to the bottom four layers.
Now let us see the functionalities of each layers of OSI Reference Model
Application Layer (layer 7):
Application Layer provides user interface to use the application when needed. Actually application layer comes into picture only when it is needed. For example if a user wants to open a file using HTTP/FTP or any protocol, then Application Layer provides interface (for example say Internet Explorer or any Browser). Similarly it provides interface for sending messages, for database, for application services etc.
The Presentation Layer (layer 6):
The function of Presentation Layer is to present the data to Application Layer and also it is responsible for data translation.
It performs the tasks like compression, encryption, decryption, etc
The session Layer (layer 5):
The Session Layer separates the data of one application from another application. It controls the data. The main work of this layer is to provide Dialog Control between devices and node. It Offers simplex, duplex, half duplex and full duplex services.
The Transport Layer (layer 4):
This layer provides end to end data transport services. TCP/IP protocols works at this layer. This layer also provides services like acknowledgement, flow control and sequencing.
The Network Layer (layer 3):
We saw that routers are called layer 3 devices, because they works on Network Layer Functionality. This layer determines all the addresses on the network. Used to transport traffic between the devices connected. All the routing protocols works at this level. Addresses such as IPv4, IPv6, MAC address are known to the layer 3 devices.
The Data Link Layer (layer 2):
This layer provides data transmission and also detect errors or watches the network topology. So Data Link Layer will ensure that a message are delivered to proper device or not, using MAC Address.
It will also convert the messages into bits for physical layer so that physical layer can transmit further. And the message in pieces are called Data Frames. It also contains MAC address of destination as well as of source.
Switches and Bridges are the example that works at layer 2. Hence they are known as layer 2 devices.
The Physical Layer (layer 1):
The Physical Layer of source transmits the data to the destination physical layer in bit format. The data will be in the form of bits (0 or 1). This layer is also used to know the physical links connected to the network devices such as cables, Ethernet cables etc.
Hub is the example which works at layer 1. That is why it is known as Layer 1 device.
So this was all about OSI layer.
0 comments:
Post a Comment