OSI and TCP-IP models are the most commonly used networking models. OSI model was designed by ISO (International organization for standardization) for explaining the function of the communication model. It describes how network application communicates on different computers. Moreover, it provides information on how packets get send and received. These protocols are useful for sending the packets.

OSI layer model
OSI layers

What is OSI Model

OSI Model has seven layers with each having different functions for transferring the packets. It always starts with the last layer.

layers of OSI model
Layers

Lower Layers of OSI Models

1) Physical layer: This layer deals with the hardware part, It describes how connectors, cables and NIC (Network interface cards) send and receive bits. It describes how bits move from one device to another. 

2) Data Link Layer: It defines that in which format data will be transfer in a network. It put the packet in a frame and that packet contains header and trailer that enable the device to communicate. A header contains source and destination MAC address and Trailer contains a frame sequence field which checks transmission error.

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The data link layer is further divided into two parts:

  • a) Logical link control: Helpful in error detection and flows control.
  • b) Media access control: Important in hardware addressing and for controlling the access method.

3) Network layer: It describes the path for data. The device has a different IP address from which we can address the hosts.

4) Transport layer: The layer transmits data from protocols including TCP and UDP. It cuts large packets in small chunks and also used for data recovery and flow control.

Upper Layers of OSI Models

5) Session layer: It maintains a connection and also responsible for controlling sessions and ports. It defines the connection between the two systems.

6) Presentation layer: It ensures that data is in a usable format and also take care of where data encryption and compression will occur.

7) Application layer: It is the layer which interacts with the user GUI. Here application can access the network services.

All the layers have different protocols for working which help them to work properly.

What is the TCP-IP Model?

TCP/IP model was established in 1970 for public networking by DARPA (Defense advance research project agency) which is similar to the OSI model. It gives guidelines for designing and implementing protocols and has four layers.

TCP-IP layer model
TCP-IP layer

Now we will see the comparison between OSI and TCP/IP layers

OSI and TCP-IP models
OSI vs TCP-IP Models

As we can see TCP/IP model has fewer layer than the OSI layer. Application, presentation and session layer in OSI is equal to the Application layer in the TCP/IP model and data link and the physical layer are equal to the network layer.

Description of layers of TCP/IP

1) Link layer: It deals with the hardware and physical part. It defines a protocol to deliver data across the physical network.

2) Internet layer: It defines a protocol for the logical transmission of packets over the network.

3) Transport layer: It defines a protocol for setting up a level of transmission service for the application. This is responsible for the error-free transmission of data.

4) Application layer: It defines node to node application communication through different protocols. It also provides services to the application to run on the computer.

Difference between OSI and TCP-IP models

There is some more difference in the OSI and TCP-IP models. In the OSI model, the transport layer guarantees the delivery of packets and it is connection-oriented while in TCP/IP model, the transport layer does not guarantee about delivery of packets. Additionally, it is connection-oriented as well as connectionless oriented. 

OSI model follows the vertical approach but TCP/IP model follow the horizontal approach. Protocols are hidden in the OSI model and In TCP replacing protocol is not easy.

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